Effects of two different incision phacoemulsification on corneal astigmatism

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Lu Huo

2014-12-01

Full Text Available AIM:To compare the effect of different incision in corneal astigmatism after phacoemulsification. METHODS: Totally 88 cases(122 eyeswith pure cataract were randomly divided into two groups. Forty cases(60 eyeswere clarity corneal incision in group A, and 48 cases(62 eyeswere sclera tunnel incision in group B. Mean corneal astigmatism, surgically induced astigmatism(SIA, uncorrected visual acuity(UCVAand best correct vision acuity(BCVAwere observed in pre- and post-operation at 1d; 1wk; 1mo.RESULTS: The mean astigmatism had statistically significant difference between two groups at 1d; 1wk; 1mo after operation(PPP>0.05. UCVA≥0.5 and BCVA≥0.8 had statistically significant difference at 1d; 1wk(PP>0.05.CONCLUSION: Phacoemulsification with scleral tunnel incision remove combined intraocular lens(IOLimplantation has small changes to corneal astigmatism. By selecting personalized corneal incision according to the corneal topography might be more beneficial.

Developmental changes in anterior corneal astigmatism in Tohono O'odham Native American infants and children.

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Harvey, Erin M; Miller, Joseph M; Schwiegerling, Jim; Sherrill, Duane; Messer, Dawn H; Dobson, Velma

2013-04-01

ABSTRACT Purpose: To describe change in corneal astigmatism in infants and children of a Native American tribe with a high prevalence of astigmatism. Longitudinal measurements of corneal astigmatism were obtained in 960 Tohono O'odham children aged 6 months to <8 years. Change in corneal astigmatism (magnitude (clinical notation), J0, J45) across age in children with high astigmatism (≥2 diopter (D) corneal astigmatism) or low/no astigmatism (<2 D corneal astigmatism) at their baseline measurement was assessed. Regression analyses indicated that early in development (6 months to <3 years), astigmatism magnitude decreased in the high astigmatism group (0.37 D/year) and remained stable in the low/no astigmatism group. In later development (3 to <8 years), astigmatism decreased in the high (0.11 D/year) and low/no astigmatism groups (0.03 D/year). In 52 children who had data at all three of the youngest ages (6 months to <1 year, 1 to <2 years, 2 to <3 years) astigmatism decreased after infancy in those with high astigmatism (p = 0.021), and then remained stable from age 1-2 years, whereas astigmatism was stable from infancy through age 1 year and increased from age 1-2 years in the low/no astigmatism group (p = 0.026). J0 results were similar, but results on J45 yielded no significant effects. The greatest change occurred in highly astigmatic infants and toddlers (0.37 D/year). By age 3 years, change was minimal and not clinically significant. Changes observed were due primarily to change in the J0 component of astigmatism.

Longitudinal change and stability of refractive, keratometric, and internal astigmatism in childhood.

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Harvey, Erin M; Miller, Joseph M; Twelker, J Daniel; Sherrill, Duane L

2014-12-16

To assess longitudinal change in refractive, keratometric, and internal astigmatism in a sample of students from a population with a high prevalence of with-the-rule (WTR) astigmatism and to determine the optical origins of changes in refractive astigmatism. A retrospective analysis of longitudinal measurements of right eye refractive and keratometric astigmatism in Tohono O'odham Native American children was conducted. Changes in refractive and keratometric astigmatism per year were compared in a younger cohort (n = 1594, 3 to O'odham children. Copyright 2015 The Association for Research in Vision and Ophthalmology, Inc.

Association between mode of delivery and astigmatism in preschool children.

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Liu, Fengyang; Yang, Xubo; Tang, Angcang; Liu, Longqian

2018-03-01

To determine whether mode of delivery has any impact on astigmatism. This case-control study was performed in the Department of Ophthalmology in 2015. Exposure was mode of delivery [vaginal delivery (VD) or caesarean section (CS), which here included both elective and emergency CS]. Outcome was astigmatism (≥2.5 D), which was determined by cycloplegic refraction. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were computed to assess the associations between mode of delivery and astigmatism from logistic regression models. Of the 659 children studied here (341 boys; mean age, 4.37 years), 440 were born by CS and 219 by VD. The incidence of severe astigmatism (≥2.5 D) in the CS and VD groups was 22.06% and 13.24%, respectively. Children delivered by CS had a 77.9% higher risk of severe astigmatism compared with vaginally delivered children (OR = 1.779; 95% CI, 1.121 to 2.824). After dividing CS into elective CS and emergency CS, children delivered by elective CS had an 87.3% increased risk of severe astigmatism (OR = 1.873; 95% CI, 1.157 to 3.032), but children delivered by emergency CS did not differ from vaginally delivered children. In addition, the children whose mothers had histories of breastfeeding had a 44.6% lower risk of severe astigmatism than children whose mother did not breastfeed them (OR = 0.554, 95% CI, 0.335-0.914). Birth by CS, especially elective CS, increases the risk of severe astigmatism (≥2.50 D) in childhood. © 2017 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Spherical equivalent refractive error in preschool children from a population with a high prevalence of astigmatism.

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Dobson, Velma; Harvey, Erin M; Miller, Joseph M

2007-02-01

To describe spherical equivalent (sph eq) refractive errors in preschool members of a Native American tribe with a high prevalence of astigmatism. Cycloplegic autorefraction measurements were obtained for 819 three- and four-year-old Tohono O'odham children, with follow-up measurements in 146 after 4 to 8 years. Mean sph eq was significantly more hyperopic in the astigmatic group than in the non-astigmatic group (1.24 vs. 0.87 D). At follow-up, prevalence of hyperopic sph eq and hyperopic astigmatism had significantly decreased, and prevalence of emmetropic/myopic sph eq and myopic astigmatism had significantly increased. The decrease in mean sph eq was similar in astigmats and non-astigmats. Astigmatism did not change over time. Most preschool children in this highly astigmatic population are hyperopic, with astigmats showing higher mean hyperopic sph eq than non-astigmats. Astigmats and non-astigmats show a similar decrease in amount of hyperopic sph eq over follow-up of 4 to 8 years.

Accuracy of the Spot and Plusoptix photoscreeners for detection of astigmatism.

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Crescioni, Mabel; Miller, Joseph M; Harvey, Erin M

2015-10-01

To evaluate the accuracy of the Spot (V2.0.16) and Plusoptix S12 (ROC4, V6.1.4.0) photoscreeners in detecting astigmatism meeting AAPOS referral criteria in students from a population with high prevalence of astigmatism. Students attending grades 3-8 on the Tohono O'odham reservation were examined. Screening was attempted with both the Spot and Plusoptix photoscreeners. Results were compared to cycloplegic refraction. Screening attempts providing no estimate of refractive error were considered fail/refer. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for detection of refractive errors were determined using AAPOS referral criteria and receiver operating characteristic area under the curve (ROC AUC) analysis was conducted for measures of astigmatism. Agreement between screening and cycloplegic refraction measurements of astigmatism, spherical equivalent, and anisometropia were assessed using t tests and correlation analyses. A total of 209 students were included. Of the total, 116 (55%) met examination-positive criteria based on cycloplegic refraction, with 105 of those (90%) meeting the criterion for astigmatism. Measurements success rates were 97% for Spot and 54% for Plusoptix. Comparing the Spot and the Plusoptix, sensitivity was 96% versus 100%, specificity was 87% versus 61%, PPV was 90% versus 76%, and NPV was 94% versus 100% for detection of refractive error. Both screeners overestimated astigmatism by 1/3 D to 2/3 D. AUC for astigmatism was 0.97 for Spot and 0.83 for Plusoptix. In this highly astigmatic population, the Spot and the Plusoptix had similar sensitivity, but the Spot had better specificity and measurement success rates. Compared with results from study samples with lower rates of astigmatism, our results highlight the need to assess the ability of screening instruments to detect individual types of refractive errors. Copyright © 2015 American Association for Pediatric Ophthalmology and Strabismus

Defocus and twofold astigmatism correction in HAADF-STEM

International Nuclear Information System (INIS)

Rudnaya, M.E.; Van den Broek, W.; Doornbos, R.M.P.; Mattheij, R.M.M.; Maubach, J.M.L.

2011-01-01

A new simultaneous autofocus and twofold astigmatism correction method is proposed for High Angle Annular Dark Field Scanning Transmission Electron Microscopy (HAADF-STEM). The method makes use of a modification of image variance, which has already been used before as an image quality measure for different types of microscopy, but its use is often justified on heuristic grounds. In this paper we show numerically that the variance reaches its maximum at Scherzer defocus and zero astigmatism. In order to find this maximum a simultaneous optimization of three parameters (focus, x- and y-stigmators) is necessary. This is implemented and tested on a FEI Tecnai F20. It successfully finds the optimal defocus and astigmatism with time and accuracy, compared to a human operator. -- Research highlights: → A new simultaneous defocus and astigmatism correction method is proposed. → The method does not depend on the image Fourier transform. → The method does not require amorphous area of the sample. → The method is tested numerically as well, as for the real-world application.

A STUDY ON CORNEAL ASTIGMATISM IN PTERYGIUM CASES BEFORE AND AFTER SURGERY

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Kalanchiarani S

2018-02-01

Full Text Available BACKGROUND Pterygium is a common degenerative condition seen in the Indian subcontinent. One of the indications for pterygium excision is visual impairment due to astigmatism. Several mechanisms have been suggested to explain the induced astigmatism – a pooling of the tear film at the leading edge of the pterygium, b mechanical traction exerted by the pterygium on cornea. Hence this study was done retrospectively to assess the effect of pterygium excision on the induced astigmatism. MATERIALS AND METHODS Records of patients operated for primary ocular pterygium by pterygium excision with primary conjunctival closure/ conjunctival autograft in the age group 18 - 70 years over a 1-year period were analysed retrospectively. Pre-operative and post-operative follow up records of day 1 and 1 st month were analysed for changes in corneal curvature and astigmatism using the recorded Automated Refractometry and Keratometry readings. RESULTS Out of the 44 cases analysed retrospectively as 2 groups – pterygium excision with primary conjunctival closure and pterygium excision with conjunctival autograft, majority of them were found to be females (70%, and between 40 - 50 years (90%. Most of the pterygium cases were found to be nasal, and commonly in the right eye and also that the amount of astigmatism increased with the grading of pterygium (p<.000. The most common type of astigmatism noted was “with the rule” astigmatism (75%. The percentage of “against the rule” and oblique astigmatism were 9% & 15% respectively. The decrease in the mean astigmatism after surgery was found to be statistically significant. The difference in t value between the preoperative and one-month postoperative corneal astigmatism was 2.5 D (p<.018. Steepening of both horizontal and vertical meridian was found in conjunctival autograft cases, but in simple closure cases steepening was found only in the vertical meridian. CONCLUSION To conclude, pterygium leads to a

Self-Compensation of Astigmatism in Mode-Cleaners for Advanced Interferometers

Energy Technology Data Exchange (ETDEWEB)

Barriga, P; Zhao Chunnong; Ju Li; Blair, David G [School of Physics, University of Western Australia, Crawley, WA6009 (Australia)

2006-03-02

Using a conventional mode-cleaner with the output beam taken through a diagonal mirror it is impossible to achieve a non-astigmatic output. The geometrical astigmatism of triangular mode-cleaners for gravitational wave detectors can be self-compensated by thermally induced astigmatism in the mirrors substrates. We present results from finite element modelling of the temperature distribution of the suspended mode-cleaner mirrors and the associated beam profiles. We use these results to demonstrate and present a self-compensated mode-cleaner design. We show that the total astigmatism of the output beam can be reduced to 5x10{sup -3} for {+-}10% variation of input power about a nominal value when using the end mirror of the cavity as output coupler.

Correction of low corneal astigmatism in cataract surgery.

Science.gov (United States)

Leon, Pia; Pastore, Marco Rocco; Zanei, Andrea; Umari, Ingrid; Messai, Meriem; Negro, Corrado; Tognetto, Daniele

2015-01-01

To evaluate and compare aspheric toric intraocular lens (IOL) implantation and aspheric monofocal IOL implantation with limbal relaxing incisions (LRI) to manage low corneal astigmatism (1.0-2.0 D) in cataract surgery. A prospective randomized comparative clinical study was performed. There were randomly recruited 102 eyes (102 patients) with cataracts associated with corneal astigmatism and divided into two groups. The first group received toric IOL implantation and the second one monofocal IOL implantation with peripheral corneal relaxing incisions. Outcomes considered were: visual acuity, postoperative residual astigmatism, endothelial cell count, the need for spectacles, and patient satisfaction. To determine the postoperative toric axis, all patients who underwent the toric IOL implantation were further evaluated using an OPD Scan III (Nidek Co, Japan). Follow-up lasted 6mo. The mean uncorrected distance visual acuity (UCVA) and the best corrected visual acuity (BCVA) demonstrated statistically significant improvement after surgery in both groups. At the end of the follow-up the UCVA was statistically better in the patients with toric IOL implants compared to those patients who underwent implantation of monofocal IOL plus LRI. The mean residual refractive astigmatism was of 0.4 D for the toric IOL group and 1.1 D for the LRI group (P<0.01). No difference was observed in the postoperative endothelial cell count between the two groups. The two surgical procedures demonstrated a significant decrease in refractive astigmatism. Toric IOL implantation was more effective and predictable compared to the limbal relaxing incision.

Comparative study of Epi-LASIK and LASIK for myopic astigmatism

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Jiao Chen

2013-11-01

Full Text Available AIM: To analyze the effects of epipolis laser in situ keratomileusis(Epi-LASIKand laser in situ keratomileusis(LASIKfor treatment of myopic astigmatism. METHODS: For treatment of myopic astigmatism, 32 patients(64 eyestreated by Epi-LASIK and 63 patients(126 eyesreceived LASIK. By their degree of astigmatism, the eyes were divided into Group Ⅰ(-0.25～-2.75DC and Group Ⅱ(-3.0～-5.0DC. During the 6-month follow-up, the early effects of the two operations were observed and compared in terms of uncorrected visual acuity(UCVA, best corrected visual acuity(BCVA, residual astigmatism, corneal healing, intraocular pressure(IOP, corneal topography. RESULTS: In Group Ⅱ, UCVA better than 20/20 was achieved in 87.5% of the eyes subjected to Epi-LASIK and in 63.3% of the eyes subjected to LASIK, with significant difference between them(χ2=4.055, Pt=2.672, Pt=2.234, PCONCLUSION: For treatment of high astigmatism(≥-3.00D, Epi-LASIK is more effective and predictive than LASIK.

Prevalence of corneal astigmatism before cataract surgery in northeast China

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Zuo-Feng Guo

2016-05-01

Full Text Available AIM:To analyze the prevalence and presentation patterns of corneal astigmatism in cataract surgery candidates of Shenyang in northeast China.METHODS:A retrospective survey was used to study the corneal astigmatism which were measured by intraocular lens(IOLMaster optical biometer before cataract surgery between Jan. 1st, 2014 and Dec. 31st, 2014. Descriptive statistics of corneal astigmatism data were analyzed.RESULTS:The keratometric data from 4 543 eyes from 3 821 patients with a mean age of 66.36±10.38y(SD. In 10.50% of eyes, corneal astigmatism was between 0.5 diopters(Dor less; in 30.05% of eyes, it was 0.5-1.0 D; in 23.60%, it was 1.0-1.5 D; in 13.19%, it was 1.5-2.0 D; in 7.68%, it was 2.0-2.5 D; in 6.41%, it was 2.5-3.0 D; in 8.58%, it was 3.0 D or higher. With-the-rule astigmatism was found in 27.69% of eyes, while against-the-rule was found in 53.84% of eyes.CONCLUSION:About 59.46% of eyes in this study had preoperative corneal astigmatism equal to or above 1.0 D. Findings indicated more surgical techniques or toric intraocular lenses to meet the potential demand of the cataract surgery candidates.

Characteristics of astigmatism in Black South African high school ...

African Journals Online (AJOL)

Abstract. Background: Astigmatism impairs vision at various distances and causes symptoms of asthenopia which negatively impacts reading efficiency. Objective: The aim of conducting this study was to determine the prevalence and distribution of astigmatism and its relation- ship to gender, age, school grade levels and ...

Preoperative corneal astigmatism among adult patients with cataract in Northern Nigeria

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Mohammed Isyaku

2014-01-01

Full Text Available The prevalence and nature of corneal astigmatism among patients with cataract has not been well-documented in the resident African population. This retrospective study was undertaken to investigate preexisting corneal astigmatism in adult patients with cataract. We analyzed keratometric readings acquired by manual Javal-Schiotz keratometry before surgery between January 1, 2011 and December 31, 2011. There were 3,169 patients (3286 eyes aged between 16 and 110 years involved with a Male to female ratio of 1.4:1. Mean keratometry in diopters was K1 = 43.99 and K2 = 43.80. Mean corneal astigmatism was 1.16 diopter and a majority (45.92% of eyes had astigmatism between 1.00 and 1.99 diopters. Two-thirds of the eyes (66.9% in this study had preoperative corneal astigmatism equal to or above 1.00 diopter. Findings will help local cataract surgeons to estimate the potential demand for toric intraocular lenses.

Correction of low corneal astigmatism in cataract surgery

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Pia Leon

2015-08-01

Full Text Available AIM: To evaluate and compare aspheric toric intraocular lens (IOL implantation and aspheric monofocal IOL implantation with limbal relaxing incisions (LRI to manage low corneal astigmatism (1.0-2.0 D in cataract surgery.METHODS:A prospective randomized comparative clinical study was performed. There were randomly recruited 102 eyes (102 patients with cataracts associated with corneal astigmatism and divided into two groups. The first group received toric IOL implantation and the second one monofocal IOL implantation with peripheral corneal relaxing incisions. Outcomes considered were:visual acuity, postoperative residual astigmatism, endothelial cell count, the need for spectacles, and patient satisfaction. To determine the postoperative toric axis, all patients who underwent the toric IOL implantation were further evaluated using an OPD Scan III (Nidek Co, Japan. Follow-up lasted 6mo.RESULTS: The mean uncorrected distance visual acuity (UCVA and the best corrected visual acuity (BCVA demonstrated statistically significant improvement after surgery in both groups. At the end of the follow-up the UCVA was statistically better in the patients with toric IOL implants compared to those patients who underwent implantation of monofocal IOL plus LRI. The mean residual refractive astigmatism was of 0.4 D for the toric IOL group and 1.1 D for the LRI group (P<0.01. No difference was observed in the postoperative endothelial cell count between the two groups.CONCLUSION: The two surgical procedures demonstrated a significant decrease in refractive astigmatism. Toric IOL implantation was more effective and predictable compared to the limbal relaxing incision.

Astigmatism and Amblyopia among Native American Children (AANAC): design and methods.

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Miller, J M; Dobson, V M; Harvey, E M; Sherrill, D L

2000-09-01

The overall goal of the AANAC study is to improve detection of astigmatism and prevention of amblyopia in populations with a high prevalence of astigmatism. To meet this goal, the study will evaluate four methods of screening for astigmatism in preschool children and will assess both the short-term and long-term benefits of early correction of astigmatism in improving acuity and preventing amblyopia. This paper presents an overview of the design and methodology of the AANAC study. Subjects are members of the Tohono O'Odham Nation, a Native American tribe with a high prevalence of astigmatism. Preschool-age children who attend Head Start are screened with four tools: the Marco Nidek KM-500 autokeratometer, the MTI photoscreener, the Nikon Retinomax K-Plus autorefractor, and the Lea Symbols acuity chart. Sensitivity and specificity for detection of significant astigmatism, as measured by a technique that uses both cycloplegic retinoscopy and cycloplegic autorefraction, is determined for each of the four screening tools. Presence of amblyopia is evaluated by measurement of best-corrected recognition acuity and acuity for orthogonal gratings. Spectacles are provided to all 3-year-old children with > or =2.00 diopters (D) of astigmatism and all 4- and 5-year-old children with > or =1.50 D of astigmatism. Persistence of amblyopia after glasses wearing is evaluated by follow-up measurement of best-corrected recognition acuity and acuity for orthogonal gratings, conducted 2-5 months after glasses are prescribed. Long-term effectiveness of early screening and glasses prescription is evaluated through measurement of recognition acuity in two groups of first-grade children: one group who participated in the Head Start program before the intensive vision screening program was initiated, and a second group who participated in the study's Head Start vision screening program.

Pattern of astigmatism in a clinical setting in Maldives

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Sanjay Marasini

2016-01-01

Conclusion: In conclusion, this study inferred that among patients with relatively higher magnitude of astigmatism attending to the clinics in Maldives, younger patients are affected more, which could possibly link to the environment, genetics and nutrition. The probable association between nutrition and astigmatism needs to be investigated to fill the gap in literature.

Does correcting astigmatism with toric lenses improve driving performance?

Science.gov (United States)

Cox, Daniel J; Banton, Thomas; Record, Steven; Grabman, Jesse H; Hawkins, Ronald J

2015-04-01

Driving is a vision-based activity of daily living that impacts safety. Because visual disruption can compromise driving safety, contact lens wearers with astigmatism may pose a driving safety risk if they experience residual blur from spherical lenses that do not correct their astigmatism or if they experience blur from toric lenses that rotate excessively. Given that toric lens stabilization systems are continually improving, this preliminary study tested the hypothesis that astigmats wearing toric contact lenses, compared with spherical lenses, would exhibit better overall driving performance and driving-specific visual abilities. A within-subject, single-blind, crossover, randomized design was used to evaluate driving performance in 11 young adults with astigmatism (-0.75 to -1.75 diopters cylinder). Each participant drove a highly immersive, virtual reality driving simulator (210 degrees field of view) with (1) no correction, (2) spherical contact lens correction (ACUVUE MOIST), and (3) toric contact lens correction (ACUVUE MOIST for Astigmatism). Tactical driving skills such as steering, speed management, and braking, as well as operational driving abilities such as visual acuity, contrast sensitivity, and foot and arm reaction time, were quantified. There was a main effect for type of correction on driving performance (p = 0.05). Correction with toric lenses resulted in significantly safer tactical driving performance than no correction (p driving safety from no correction (p = 0.118). Operational tests differentiated corrected from uncorrected performance for both spherical (p = 0.008) and toric (p = 0.011) lenses, but they were not sensitive enough to differentiate toric from spherical lens conditions. Given previous research showing that deficits in these tactical skills are predictive of future real-world collisions, these preliminary data suggest that correcting low to moderate astigmatism with toric lenses may be important to driving safety. Their

Separation of the effects of astigmatic figure error from misalignments using Nodal Aberration Theory (NAT).

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Schmid, Tobias; Rolland, Jannick P; Rakich, Andrew; Thompson, Kevin P

2010-08-02

We present the nodal aberration field response of Ritchey-Chrétien telescopes to a combination of optical component misalignments and astigmatic figure error on the primary mirror. It is shown that both astigmatic figure error and secondary mirror misalignments lead to binodal astigmatism, but that each type has unique, characteristic locations for the astigmatic nodes. Specifically, the characteristic node locations in the presence of astigmatic figure error (at the pupil) in an otherwise aligned telescope exhibit symmetry with respect to the field center, i.e. the midpoint between the astigmatic nodes remains at the field center. For the case of secondary mirror misalignments, one of the astigmatic nodes remains nearly at the field center (in a coma compensated state) as presented in Optics Express 18, 5282-5288 (2010), while the second astigmatic node moves away from the field center. This distinction leads directly to alignment methods that preserve the dynamic range of the active wavefront compensation component.

A genome-wide association study of corneal astigmatism: The CREAM Consortium

OpenAIRE

Shah, Rupal L.; Li, Qing; Zhao, Wanting; Tedja, Milly S.; Tideman, J. Willem L.; Khawaja, Anthony P.; Fan, Qiao; Yazar, Seyhan; Williams, Katie M.; Verhoeven, Virginie J.M.; Xie, Jing; Wang, Ya Xing; Hess, Moritz; Nickels, Stefan; Lackner, Karl J.

2018-01-01

Purpose To identify genes and genetic markers associated with corneal astigmatism. Methods: A meta-analysis of genome-wide association studies (GWASs) of corneal astigmatism undertaken for 14 European ancestry (n=22,250) and 8 Asian ancestry (n=9,120) cohorts was performed by the Consortium for Refractive Error and Myopia. Cases were defined as having >0.75 diopters of corneal astigmatism. Subsequent gene-based and gene-set analyses of the meta-analyzed results of European ancestry cohorts we...

A genome-wide association study of corneal astigmatism: The CREAM Consortium

OpenAIRE

Shah, Rupal L.; Li, Qing; Zhao, Wanting; Tedja, Milly S.; Tideman, J. Willem L.; Khawaja, Anthony P.; Fan, Qiao; Yazar, Seyhan; Williams, Katie M.; Verhoeven, Virginie J.M.; Xie, Jing; Wang, Ya Xing; Hess, Moritz; Nickels, Stefan; Lackner, Karl J.

2018-01-01

Purpose To identify genes and genetic markers associated with corneal astigmatism. Methods A meta-analysis of genome-wide association studies (GWASs) of corneal astigmatism undertaken for 14 European ancestry (n=22,250) and 8 Asian ancestry (n=9,120) cohorts was performed by the Consortium for Refractive Error and Myopia. Cases were defined as having >0.75 diopters of corneal astigmatism. Subsequent gene-based and gene-set analyses of the meta-analyzed results of European ancestry cohorts wer...

A genome-wide association study of corneal astigmatism: The CREAM Consortium.

OpenAIRE

Shah, Rupal L; Li, Qing; Zhao, Wanting; Tedja, Milly S; Tideman, J Willem L; Khawaja, Anthony P; Fan, Qiao; Yazar, Seyhan; Williams, Katie M; Verhoeven, Virginie J M; Xie, Jing; Wang, Ya Xing; Hess, Moritz; Nickels, Stefan; Lackner, Karl J

2018-01-01

Purpose To identify genes and genetic markers associated with corneal astigmatism. Methods A meta-analysis of genome-wide association studies (GWASs) of corneal astigmatism undertaken for 14 European ancestry (n=22,250) and 8 Asian ancestry (n=9,120) cohorts was performed by the Consortium for Refractive Error and Myopia. Cases were defined as having >0.75 diopters of corneal astigmatism. Subsequent gene-based and gene-set analyses of the meta-analyzed results of European ancestry...

A genome-wide association study of corneal astigmatism : The CREAM Consortium

OpenAIRE

Shah, Rupal L.; Li, Qing; Zhao, Wanting; Tedja, Milly S.; Tideman, J. Willem L.; Khawaja, Anthony P.; Fan, Qiao; Yazar, Seyhan; Williams, Katie M.; Verhoeven, Virginie J.M.; Xie, Jing; Wang, Ya Xing; Hess, Moritz; Nickels, Stefan; Lackner, Karl J.

2018-01-01

Purpose: To identify genes and genetic markers associated with corneal astigmatism. Methods: A meta-analysis of genome-wide association studies (GWASs) of corneal astigmatism undertaken for 14 European ancestry (n=22,250) and 8 Asian ancestry (n=9,120) cohorts was performed by the Consortium for Refractive Error and Myopia. Cases were defined as having >0.75 diopters of corneal astigmatism. Subsequent gene-based and gene-set analyses of the meta-analyzed results of European ancestry cohor...

A genome-wide association study of corneal astigmatism:The CREAM consortium

OpenAIRE

Shah, Rupal L.; Li, Qing; Zhao, Wanting; Tedja, Milly S.; Tideman, J. Willem L.; Khawaja, Anthony P.; Fan, Qiao; Yazar, Seyhan; Williams, Katie M.; Verhoeven, Virginie J.M.; Xie, Jing; Wang, Ya Xing; Hess, Moritz; Nickels, Stefan; Lackner, Karl J.

2018-01-01

Purpose: To identify genes and genetic markers associated with corneal astigmatism. Methods: A meta-analysis of genome-wide association studies (GWASs) of corneal astigmatism undertaken for 14 European ancestry (n=22,250) and 8 Asian ancestry (n=9,120) cohorts was performed by the Consortium for Refractive Error and Myopia. Cases were defined as having >0.75 diopters of corneal astigmatism. Subsequent gene-based and gene-set analyses of the meta-analyzed results of European ancestry cohort...

Influence of different phacoemulsification incision on postoperative corneal astigmatism for cataract patients

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Zhao-Rong Zeng

2014-05-01

Full Text Available AIM: To compare the effect of different phacoemulsification incision on postoperative corneal astigmatism for cataract patients. METHODS: The cataract patients were selected in our hospital. The patients were divided into control group(corneal limbus opposite curved scleral tunnel incision groupand observation group(above the top of cornea or temporal transparent corneal incision grouprandomly. At 1wk; 1 and 3mo after surgery, the change of corneal astigmatism and vision of the patients in two groups were compared and analyzed. RESULTS:Compared with control group, 1wk; 1 and 3mo after surgery, the average corneal astigmatism and surgically induced corneal astigmatism of the patients in observation group were decreased significantly. The visual acuity and corrected visual acuity were increased significantly. There was statistically significant(PPCONCLUSION: Center distance and small incision corneal phacoemulsification can reduce postoperative astigmatism and improve postoperative visual acuity for cataract patients. It provides guarantee for further strengthen the clinical treated effect for cataract patients.

Astigmatism and myopia in Tohono O'odham Native American children.

Science.gov (United States)

Twelker, J Daniel; Miller, Joseph M; Sherrill, Duane L; Harvey, Erin M

2013-11-01

To describe change in spherical equivalent (M) in a longitudinal sample of Tohono O'odham students ages 3 to 18 years and to test the hypothesis that astigmatism creates complex cues to emmetropization, resulting in increased change in M in the direction of increasing myopia and increased occurrence of myopia. Subjects were 777 Tohono O'odham Native American children on whom cycloplegic right eye autorefraction was measured on at least two study encounters between ages 3 and 18 years (first encounter prior to age 5.5 years, final encounter ≥3 years later). Regression lines were fit to individual subjects' longitudinal M data to estimate rate of change in M (regression slope, D/yr). Regression was also used to predict if a subject would be myopic (≤-0.75 D M) by age 18 years. Analysis of covariance was used to assess the relation between M slope and magnitude of baseline M and astigmatism. Chi-square analyses were used to assess the relation between predicted myopia onset and magnitude of baseline M and astigmatism. Mean M slope was significantly more negative for hyperopes (M ≥ +2.00) than for myopes (M ≤ -0.75) or for subjects neither hyperopic nor myopic (NHM, M > -0.75 and < +2.00), but there was no significant difference between the myopic and NHM groups. Chi-square analysis indicated that final myopia status varied across level of baseline astigmatism. Subjects with high astigmatism were more likely to be predicted to have significant myopia by age 18 years. The association between greater shift in M towards myopia with age in subjects who were hyperopic at baseline is consistent with continued emmetropization in the school years. Results regarding predicted myopia development imply that degradation of image quality due to refractive astigmatism creates complex cues to emmetropization, resulting in increased occurrence of myopia.

Optical analysis for simplified astigmatic correction of non-imaging focusing heliostat

Energy Technology Data Exchange (ETDEWEB)

Chong, K.K. [Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Off Jalan Genting Kelang, Setapak, 53300 Kuala Lumpur (Malaysia)

2010-08-15

In the previous work, non-imaging focusing heliostat that consists of m x n facet mirrors can carry out continuous astigmatic correction during sun-tracking with the use of only (m + n - 2) controllers. For this paper, a simplified astigmatic correction of non-imaging focusing heliostat is proposed for reducing the number of controllers from (m + n - 2) to only two. Furthermore, a detailed optical analysis of the new proposal has been carried out and the simulated result has shown that the two-controller system can perform comparably well in astigmatic correction with a much simpler and more cost effective design. (author)

Alpins and thibos vectorial astigmatism analyses: proposal of a linear regression model between methods

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Giuliano de Oliveira Freitas

2013-10-01

Full Text Available PURPOSE: To determine linear regression models between Alpins descriptive indices and Thibos astigmatic power vectors (APV, assessing the validity and strength of such correlations. METHODS: This case series prospectively assessed 62 eyes of 31 consecutive cataract patients with preoperative corneal astigmatism between 0.75 and 2.50 diopters in both eyes. Patients were randomly assorted among two phacoemulsification groups: one assigned to receive AcrySof®Toric intraocular lens (IOL in both eyes and another assigned to have AcrySof Natural IOL associated with limbal relaxing incisions, also in both eyes. All patients were reevaluated postoperatively at 6 months, when refractive astigmatism analysis was performed using both Alpins and Thibos methods. The ratio between Thibos postoperative APV and preoperative APV (APVratio and its linear regression to Alpins percentage of success of astigmatic surgery, percentage of astigmatism corrected and percentage of astigmatism reduction at the intended axis were assessed. RESULTS: Significant negative correlation between the ratio of post- and preoperative Thibos APVratio and Alpins percentage of success (%Success was found (Spearman's ρ=-0.93; linear regression is given by the following equation: %Success = (-APVratio + 1.00x100. CONCLUSION: The linear regression we found between APVratio and %Success permits a validated mathematical inference concerning the overall success of astigmatic surgery.

Association between anterior corneal astigmatism and posterior corneal astigmatism across age groups: a cross-sectional analysis

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Vijay Shetty

2017-11-01

Full Text Available AIM: To assess the anterior corneal astigmatism(ACAand posterior corneal astigmatism(PCApatterns across various age groups. We also evaluated the association between magnitudes and axes of the ACA and PCA across these age groups. METHODS: The present study was a cross-sectional analysis of clinical data of 381 eyes. We converted the clinical astigmatic notation to vector notation for analysis of ACA and PCA. We estimated the correlation between magnitude and axes of the ACA and PCA in the whole population and in four age groups(5-19, 20-39, 40-59, and ≥ 60y. We used random effects linear regression models for estimating the association between the magnitudes of ACA and PCA.RESULTS: The mean of the magnitude of the ACA(3.59Dand the PCA(0.50Dwas highest in children(5 to 9y. Overall, the magnitude of the ACA ranged from 0D to 10.0 Diopters(Dand the magnitude of the PCA ranged from 0 to 3.5 D. There was a significant correlation between the ACA and the PCA in the younger age group(r=0.85, PP=0.03with each unit increase in the ACA, the increase was the smallest in this age group.CONCLUSION: It will be prudent to measure the both the magnitude and axis of the PCA, particularly in those above 60y rather than rely on rule-of-thumb calculations based on ACA parameters for IOL power calculation.

Correction of High Astigmatism after Penetrating Keratoplasty with Toric Multifocal Intraocular Lens Implantation

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Raffaele Nuzzi

2017-07-01

Full Text Available After penetrating keratoplasty (PK, high astigmatism is often induced, being frequently about 4–6 dpt. According to the entity and typology of astigmatism, different methods of correction can be used. Selective suture removal, relaxing incisions, wedge resections, compression sutures, photorefractive keratectomy, and laser-assisted in situ keratomileusis can reduce corneal astigmatism and ametropia, but meanwhile they can cause a reduction in the corneal integrity and cause an over- or undercorrection. In case of moderate-to-high regular astigmatisms, the authors propose a toric multifocal intraocular lens (IOL implantation to preserve the corneal integrity (especially in PK after herpetic corneal leukoma keratitis. We evaluated a 45-year-old patient who at the age of 30 was subjected to PK in his left eye due to corneal leukoma herpetic keratitis, which led to high astigmatism (7.50 dpt cyl. 5°. The patient was subjected to phacoemulsification and customized toric multifocal IOL implantation in his left eye. The correction of PK-induced residual astigmatism with a toric IOL implantation is an excellent choice but has to be evaluated in relation to patient age, corneal integrity, longevity graft, and surgical risk. It seems to be a well-tolerated therapeutic choice and with good results.

The astigmatism factor for semiconductor injection lasers

International Nuclear Information System (INIS)

Zhao Yiguang; Guo Changzhi

1988-03-01

The relations between the astigmatism factor and the waveguide structure, working conditions etc. were accurately calculated, using a method for deriving a self-consistent solution of the optical field equation and the carrier diffusion equation. Various theoretical models regarding the spontaneous emission factor were analyzed and compared. The results show that there is a difference between astigmatism factors of semiconductor lasers with different waveguide structures. W. Streifer's results, for a model having an invariable distribution of the complex refractive index, are larger by a factor of 6 to 80 than the accurate calculated value. K. Petermann's theory regarding the spontaneous emission factor is more appropriate than other theories. (author). 19 refs, 6 figs

Prevalence of corneal astigmatism in Tohono O'odham Native American children 6 months to 8 years of age.

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Harvey, Erin M; Dobson, Velma; Miller, Joseph M; Schwiegerling, Jim; Clifford-Donaldson, Candice E; Green, Tina K; Messer, Dawn H

2011-06-21

To describe the prevalence of corneal astigmatism in infants and young children who are members of a Native American tribe with a high prevalence of refractive astigmatism. The prevalence of corneal astigmatism was assessed by obtaining infant keratometer (IK4) measurements from 1235 Tohono O'odham children, aged 6 months to 8 years. The prevalence of corneal astigmatism >2.00 D was lower in the 1- to <2-year-old age group when compared with all other age groups, except the 6- to <7-year-old group. The magnitude of mean corneal astigmatism was significantly lower in the 1- to <2-year age group than in the 5- to <6-, 6- to <7-, and 7- to <8-year age groups. Corneal astigmatism was with-the-rule (WTR) in 91.4% of astigmatic children (≥1.00 D). The prevalence and mean amount of corneal astigmatism were higher than reported in non-Native American populations. Mean astigmatism increased from 1.43 D in 1-year-olds to nearly 2.00 D by school age.

[Interlamellar sectoral keratoplasty in the surgical correction of astigmatism].

Science.gov (United States)

Frolov, M A; Beliaev, V S; Dushin, N V; Kravchinina, V V; Barashkov, V I; Gonchar, P A

1996-01-01

A new original method of interlamellar sectorial keratoplasty is proposed for surgical correction of astigmatism. Eleven operations were carried out in 8 patients (11 eyes) with astigmatism of 4 to 7.0 diopters. Vision acuity without correction was 0.6 to 1.0 in 5 patients (7 eyes, 63.6%). In 2 patients (2 eyes, 18.2%) vision acuity without correction was 0.3 to 0.5 diopters, and in 2 more patients (2 eyes, 18.2%) it was from 0.1 to 0.3 diopters, that is, equal to the maximal vision acuity with the optimal correction. The refraction effect stabilized in 3-4 months. The highest refraction effect attained was 7.0 diopters. The patients were followed up for 3 months to 4 years. Clinical analysis of the operations confirmed the efficacy and reliability of the method and stability of refraction. Interlamellar sectorial keratoplasty is recommended for surgical correction of astigmatism.

Optical treatment of amblyopia in astigmatic children: the sensitive period for successful treatment.

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Harvey, Erin M; Dobson, Velma; Clifford-Donaldson, Candice E; Miller, Joseph M

2007-12-01

To compare the effectiveness of eyeglass treatment of astigmatism-related amblyopia in children younger than 8 years (range, 4.75-7.99 years) versus children 8 years of age and older (range, 8.00-13.53 years) over short (6-week) and long (1-year) treatment intervals. Prospective, interventional, comparative case-control study. Four hundred forty-six nonastigmatic (right and left eye, or =1.00 D) Native American (Tohono O'odham) children in kindergarten or grades 1 through 6. Eyeglass correction of refractive error, prescribed for full-time wear, in astigmatic children. Amount of change in mean right-eye best-corrected letter visual acuity for treated astigmatic children versus untreated, age-matched nonastigmatic children after short (6-week) and long (1-year) treatment intervals. Astigmatic children had significantly reduced mean best-corrected visual acuity at baseline compared to nonastigmatic children. Astigmats showed significantly greater improvement in mean best-corrected visual acuity (0.08 logarithm of the minimum angle of resolution [logMAR] unit; approximately 1 line), than the nonastigmatic children (0.01 logMAR unit) over the 6-week treatment interval. No additional treatment effect was observed between 6 weeks and 1 year. Treatment effectiveness was not dependent on age group ( or =8 years) and was not influenced by previous eyeglass treatment. Despite significant improvement, mean best-corrected visual acuity in astigmatic children remained significantly poorer than in nonastigmatic children after 1 year of eyeglass treatment, even when analyses were limited to results from highly compliant children. Sustained eyeglass correction results in significant improvement in best-corrected visual acuity in astigmatic children, including those previously believed to be beyond the sensitive period for successful treatment.

Assessment of refractive astigmatism and simulated therapeutic refractive surgery strategies in coma-like-aberrations-dominant corneal optics.

Science.gov (United States)

Zhou, Wen; Stojanovic, Aleksandar; Utheim, Tor Paaske

2016-01-01

The aim of the study is to raise the awareness of the influence of coma-like higher-order aberrations (HOAs) on power and orientation of refractive astigmatism (RA) and to explore how to account for that influence in the planning of topography-guided refractive surgery in eyes with coma-like-aberrations-dominant corneal optics. Eleven eyes with coma-like-aberrations-dominant corneal optics and with low lenticular astigmatism (LA) were selected for astigmatism analysis and for treatment simulations with topography-guided custom ablation. Vector analysis was used to evaluate the contribution of coma-like corneal HOAs to RA. Two different strategies were used for simulated treatments aiming to regularize irregular corneal optics: With both strategies correction of anterior corneal surface irregularities (corneal HOAs) were intended. Correction of total corneal astigmatism (TCA) and RA was intended as well with strategies 1 and 2, respectively. Axis of discrepant astigmatism (RA minus TCA minus LA) correlated strongly with axis of coma. Vertical coma influenced RA by canceling the effect of the with-the-rule astigmatism and increasing the effect of the against-the-rule astigmatism. After simulated correction of anterior corneal HOAs along with TCA and RA (strategies 1 and 2), only a small amount of anterior corneal astigmatism (ACA) and no TCA remained after strategy 1, while considerable amount of ACA and TCA remained after strategy 2. Coma-like corneal aberrations seem to contribute a considerable astigmatic component to RA in eyes with coma-like-aberrations dominant corneal optics. If topography-guided ablation is programmed to correct the corneal HOAs and RA, the astigmatic component caused by the coma-like corneal HOAs will be treated twice and will result in induced astigmatism. Disregarding RA and treating TCA along with the corneal HOAs is recommended instead.

[Clinical analysis of real-time iris recognition guided LASIK with femtosecond laser flap creation for myopic astigmatism].

Science.gov (United States)

Jie, Li-ming; Wang, Qian; Zheng, Lin

2013-08-01

To assess the safety, efficacy, stability and changes in cylindrical degree and axis after real-time iris recognition guided LASIK with femtosecond laser flap creation for the correction of myopic astigmatism. Retrospective case series. This observational case study comprised 136 patients (249 eyes) with myopic astigmatism in a 6-month trial. Patients were divided into 3 groups according to the pre-operative cylindrical degree: Group 1, -0.75 to -1.25 D, 106 eyes;Group 2, -1.50 to -2.25 D, 89 eyes and Group 3, -2.50 to -5.00 D, 54 eyes. They were also grouped by pre-operative astigmatism axis:Group A, with the rule astigmatism (WTRA), 156 eyes; Group B, against the rule astigmatism (ATRA), 64 eyes;Group C, oblique axis astigmatism, 29 eyes. After femtosecond laser flap created, real-time iris recognized excimer ablation was performed. The naked visual acuity, the best-corrected visual acuity, the degree and axis of astigmatism were analyzed and compared at 1, 3 and 6 months postoperatively. Static iris recognition detected that eye cyclotorsional misalignment was 2.37° ± 2.16°, dynamic iris recognition detected that the intraoperative cyclotorsional misalignment range was 0-4.3°. Six months after operation, the naked visual acuity was 0.5 or better in 100% cases. No eye lost ≥ 1 line of best spectacle-corrected visual acuity (BSCVA). Six months after operation, the naked vision of 227 eyes surpassed the BSCVA, and 87 eyes gained 1 line of BSCVA. The degree of astigmatism decreased from (-1.72 ± 0.77) D (pre-operation) to (-0.29 ± 0.25) D (post-operation). Six months after operation, WTRA from 157 eyes (pre-operation) decreased to 43 eyes (post-operation), ATRA from 63 eyes (pre-operation) decreased to 28 eyes (post-operation), oblique astigmatism increased from 29 eyes to 34 eyes and 144 eyes became non-astigmatism. The real-time iris recognition guided LASIK with femtosecond laser flap creation can compensate deviation from eye cyclotorsion, decrease

Applicability of supervised discriminant analysis models to analyze astigmatism clinical trial data

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Sedghipour MR

2012-09-01

Full Text Available Mohammad Reza Sedghipour,1 Homayoun Sadeghi-Bazargani2,31Nikoukari Ophthalmology University Hospital, Tabriz, Iran; 2Department of Statistics and Epidemiology, Neuroscience Research Center, Tabriz University of Medical Sciences, Tabriz, Iran; 3Department of Public Health Sciences, Karolinska Institute, Stockholm, SwedenBackground: In astigmatism clinical trials where more complex measurements are common, especially in nonrandomized small sized clinical trials, there is a demand for the development and application of newer statistical methods.Methods: The source data belonged to a project on astigmatism treatment. Data were used regarding a total of 296 eyes undergoing different astigmatism treatment modalities: wavefront-guided photorefractive keratectomy, cross-cylinder photorefractive keratectomy, and monotoric (single photorefractive keratectomy. Astigmatism analysis was primarily done using the Alpins method. Prior to fitting partial least squares regression discriminant analysis, a preliminary principal component analysis was done for data overview. Through fitting the partial least squares regression discriminant analysis statistical method, various model validity and predictability measures were assessed.Results: The model found the patients treated by the wavefront method to be different from the two other treatments both in baseline and outcome measures. Also, the model found that patients treated with the cross-cylinder method versus the single method didn't appear to be different from each other. This analysis provided an opportunity to compare the three methods while including a substantial number of baseline and outcome variables.Conclusion: Partial least squares regression discriminant analysis had applicability for the statistical analysis of astigmatism clinical trials and it may be used as an adjunct or alternative analysis method in small sized clinical trials.Keywords: astigmatism, regression, partial least squares regression

Prevalence of high astigmatism, eyeglass wear, and poor visual acuity among Native American grade school children.

Science.gov (United States)

Harvey, Erin M; Dobson, Velma; Miller, Joseph M

2006-04-01

The purpose of this study was to examine the prevalence of astigmatism and poor visual acuity and rate of eyeglass wear in grade school children who are members of a Native American tribe reported to have a high prevalence of large amounts of astigmatism. Vision screening was conducted on 1,327 first through eighth grade children attending school on the Tohono O'odham Reservation. Noncycloplegic autorefraction was conducted on the right and left eye of each child using the Nikon Retinomax K+ autorefractor, and monocular recognition acuity was tested using ETDRS logarithm of the minimum angle of resolution (logMAR) letter charts. Tohono O'odham children had a high prevalence of high astigmatism (42% had > or = 1.00 D in the right or left eye) and the axis of astigmatism was uniformly with-the-rule. However, only a small percentage of children arrived at the vision screening wearing glasses, and the prevalence of poor visual acuity (20/40 or worse in either eye) was high (35%). There was a significant relation between amount of astigmatism and uncorrected visual acuity with each additional diopter of astigmatism resulting in an additional 1 logMAR line reduction in visual acuity. Uncorrected astigmatism and poor visual acuity are prevalent among Tohono O'odham children. The results highlight the importance of improving glasses-wearing compliance, determining barriers to receiving eye care, and initiating public education programs regarding the importance of early identification and correction of astigmatism in Tohono O'odham children.

Assessment and statistics of surgically induced astigmatism.

Science.gov (United States)

Naeser, Kristian

2008-05-01

The aim of the thesis was to develop methods for assessment of surgically induced astigmatism (SIA) in individual eyes, and in groups of eyes. The thesis is based on 12 peer-reviewed publications, published over a period of 16 years. In these publications older and contemporary literature was reviewed(1). A new method (the polar system) for analysis of SIA was developed. Multivariate statistical analysis of refractive data was described(2-4). Clinical validation studies were performed. The description of a cylinder surface with polar values and differential geometry was compared. The main results were: refractive data in the form of sphere, cylinder and axis may define an individual patient or data set, but are unsuited for mathematical and statistical analyses(1). The polar value system converts net astigmatisms to orthonormal components in dioptric space. A polar value is the difference in meridional power between two orthogonal meridians(5,6). Any pair of polar values, separated by an arch of 45 degrees, characterizes a net astigmatism completely(7). The two polar values represent the net curvital and net torsional power over the chosen meridian(8). The spherical component is described by the spherical equivalent power. Several clinical studies demonstrated the efficiency of multivariate statistical analysis of refractive data(4,9-11). Polar values and formal differential geometry describe astigmatic surfaces with similar concepts and mathematical functions(8). Other contemporary methods, such as Long's power matrix, Holladay's and Alpins' methods, Zernike(12) and Fourier analyses(8), are correlated to the polar value system. In conclusion, analysis of SIA should be performed with polar values or other contemporary component systems. The study was supported by Statens Sundhedsvidenskabeligt Forskningsråd, Cykelhandler P. Th. Rasmussen og Hustrus Mindelegat, Hotelejer Carl Larsen og Hustru Nicoline Larsens Mindelegat, Landsforeningen til Vaern om Synet

Applicability of supervised discriminant analysis models to analyze astigmatism clinical trial data.

Science.gov (United States)

Sedghipour, Mohammad Reza; Sadeghi-Bazargani, Homayoun

2012-01-01

In astigmatism clinical trials where more complex measurements are common, especially in nonrandomized small sized clinical trials, there is a demand for the development and application of newer statistical methods. The source data belonged to a project on astigmatism treatment. Data were used regarding a total of 296 eyes undergoing different astigmatism treatment modalities: wavefront-guided photorefractive keratectomy, cross-cylinder photorefractive keratectomy, and monotoric (single) photorefractive keratectomy. Astigmatism analysis was primarily done using the Alpins method. Prior to fitting partial least squares regression discriminant analysis, a preliminary principal component analysis was done for data overview. Through fitting the partial least squares regression discriminant analysis statistical method, various model validity and predictability measures were assessed. The model found the patients treated by the wavefront method to be different from the two other treatments both in baseline and outcome measures. Also, the model found that patients treated with the cross-cylinder method versus the single method didn't appear to be different from each other. This analysis provided an opportunity to compare the three methods while including a substantial number of baseline and outcome variables. Partial least squares regression discriminant analysis had applicability for the statistical analysis of astigmatism clinical trials and it may be used as an adjunct or alternative analysis method in small sized clinical trials.

Intrastromal Corneal Ring Segments for Astigmatism Correction after Deep Anterior Lamellar Keratoplasty

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Júlio C. D. Arantes

2017-01-01

Full Text Available Background. To evaluate the change in corneal astigmatism after intrastromal corneal ring segment (ICRS implantation in keratoconus patients with previous deep anterior lamellar keratoplasty (DALK. Design was a longitudinal, retrospective, interventional study. The study included 25 eyes of 24 patients with keratoconus who had DALK performed at least two years prior to ICRS implantation. All patients had a clear corneal graft with up to 8.00 D of corneal astigmatism and intolerance to contact lenses. The studied parameters were age, sex, corrected distance visual acuity (CDVA, maximum keratometry (K1, minimum keratometry (K2, spherical equivalent, and astigmatism. There was a statistically significant decrease in the postintervention analysis as follows: 3.5 D reduction in K1 (p<0.001; 1.53 D in K2 (p=0.005; and 2.52 D (p<0.001 in the average K. The spherical equivalent reduced from −3.67 D (±2.74 to −0.71 D (±2.35 (p<0.001. The topographic astigmatism reduced from 3.87 D preoperatively to 1.90 D postoperatively (p<0.001. The CDVA improved from 0.33 (±0.10 to 0.20 (±0.09, p<0.001. ICRS implantation is a useful option for the correction of astigmatism after DALK as it yields significant visual, topographic, and refractive results.

Sequential selective same-day suture removal in the management of post-keratoplasty astigmatism.

Science.gov (United States)

Fares, U; Mokashi, A A; Elalfy, M S; Dua, H S

2013-09-01

In a previous study, we proposed that corneal topography performed 30-40 min after the initial suture removal can identify the next set of sutures requiring removal, for the treatment of post-keratoplasty astigmatism. The aim of this study was to evaluate the effect of removing subsequent sets of sutures at the same sitting. 10/0 nylon interrupted sutures were placed, to secure the graft-host junction, at the time of keratoplasty. Topography was performed using Pentacam (Oculus) before suture removal. The sutures to be removed in the steep semi-meridians were identified and removed at the slit-lamp biomicroscope. Topography was repeated 30-40 min post suture removal, the new steep semi-meridians determined, and the next set of sutures to be removed were identified and removed accordingly. Topography was repeated 4-6 weeks later and the magnitude of topographic astigmatism was recorded. A paired-samples t-test was used to evaluate the impact of selective suture removal on reducing the magnitude of topographic and refractive astigmatism. Twenty eyes of 20 patients underwent sequential selective same-day suture removal (SSSS) after corneal transplantation. This study showed that the topographic astigmatism decreased by about 46.7% (3.68 D) and the refractive astigmatism decreased by about 37.7% (2.61 D) following SSSS. Vector calculations also show a significant reduction of both topographic and refractive astigmatism (P<0.001). SSSS may help patients to achieve satisfactory vision more quickly and reduce the number of follow-up visits required post keratoplasty.

Photorefractive keratectomy for post-penetrating keratoplasty myopia and astigmatism.

Science.gov (United States)

Bilgihan, K; Ozdek, S C; Akata, F; Hasanreisoğlu, B

2000-11-01

To determine the safety, effectiveness, and predictability of photorefractive keratectomy (PRK) for the correction of myopia and astigmatism after penetrating keratoplasty. Gazi University, Medical School, Department of Ophthalmology, Ankara, Turkey. Photorefractive keratectomy was performed in 16 eyes of 16 patients with postkeratoplasty myopia and astigmatism who were unable to wear glasses due to anisometropia and were contact lens intolerant. They were examined for uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and corneal transplant integrity before and after surgery. The mean follow-up after PRK was 26.0 months +/- 15.7 (SD) (range 12 to 63 months). The mean preoperative spherical equivalent refraction of -4.47 +/- 1.39 diopters (D) was -3.39 +/- 1.84 D (P >.05) at the last postoperative visit and the mean preoperative cylinder of -5.62 +/- 2.88 D was -3.23 +/- 1.70 D (P <.05); refractive regression correlated with the amount of ablation performed. The BSCVA decreased in 3 eyes (18.8%), and the UCVA decreased in 2 (12.5%). Six eyes (37.5%) had grade 2 to 3 haze, which resolved spontaneously in 4 eyes within a relatively long time but caused a decrease in BSCVA in 2 (12.5%). Two of the eyes (12.5%) had a rejection episode after PRK and were successfully treated with topical steroids. Photorefractive keratectomy to correct postkeratoplasty myopia and astigmatism appears to be less effective and less predictable than PRK for naturally occurring myopia and astigmatism. Corneal haze and refractive regression are more prevalent, and patient satisfaction is not good.

Plasma channels during filamentation of a femtosecond laser pulse with wavefront astigmatism in air

Energy Technology Data Exchange (ETDEWEB)

Dergachev, A A; Kandidov, V P; Shlenov, S A [Lomonosov Moscow State University, Faculty of Physics, Moscow (Russian Federation); Ionin, A A; Mokrousova, D V; Seleznev, L V; Sinitsyn, D V; Sunchugasheva, E S; Shustikova, A P [P N Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2014-12-31

We have demonstrated experimentally and numerically the possibility of controlling parameters of plasma channels formed during filamentation of a femtosecond laser pulse by introducing astigmatism in the laser beam wavefront. It is found that weak astigmatism increases the length of the plasma channel in comparison with the case of aberration-free focusing and that strong astigmatism can cause splitting of the plasma channel into two channels located one after another on the filament axis. (interaction of laser radiation with matter. laser plasma)

Changes in falling risk depending on induced axis directions of astigmatism on static posture

OpenAIRE

Kim, Sang-Yeob; Moon, Byeong-Yeon; Cho, Hyun Gug

2015-01-01

[Purpose] To assess the changes in falling risk depending on the induced axis direction of astigmatism using cylindrical lenses in a static posture. [Subjects and Methods] Twenty subjects (10 males, 10 females; mean age, 23.4 ? 2.70?years) fully corrected by subjective refraction participated. To induce myopic simple astigmatism conditions, cylindrical lenses of +0.50, +1.00, +1.50, +2.00, +3.00, +4.00, and +5.00 D were used. The direction of astigmatic axes were induced under five conditions...

Excimer laser correction of hyperopia, hyperopic and mixed astigmatism: past, present, and future.

Science.gov (United States)

Lukenda, Adrian; Martinović, Zeljka Karaman; Kalauz, Miro

2012-06-01

The broad acceptance of "spot scanning" or "flying spot" excimer lasers in the last decade has enabled the domination of corneal ablative laser surgery over other refractive surgical procedures for the correction of hyperopia, hyperopic and mixed astigmatism. This review outlines the most important reasons why the ablative laser correction of hyperopia, hyperopic and mixed astigmatism for many years lagged behind that of myopia. Most of today's scanning laser systems, used in the LASIK and PRK procedures, can safely and effectively perform low, moderate and high hyperopic and hyperopic astigmatic corrections. The introduction of these laser platforms has also significantly improved the long term refractive stability of hyperopic treatments. In the future, further improvements in femtosecond and nanosecond technology, eye-tracker systems, and the development of new customized algorithms, such as the ray-tracing method, could additionally increase the upper limit for the safe and predictable corneal ablative laser correction ofhyperopia, hyperopic and mixed astigmatism.

Effect of Mitomycin C on Myopic versus Astigmatic Photorefractive Keratectomy

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Ashwag A. Almosa

2017-01-01

Full Text Available Purpose. Long-term mitomycin C (MMC effects on photorefractive keratectomy (PRK were compared in simple myopic and astigmatic patients. Methods. In this observational cohort study, subjects were selected based on preoperative and postoperative data collected from medical records; they were divided into simple myopia with/without MMC and myopic astigmatism with/without MMC groups. Haze, uncorrected visual acuity (UCVA, best-corrected visual acuity (BCVA, subjective refraction, and K-reading were evaluated at 1-, 3-, 6-, and 12-month follow-ups. Results. One hundred fifty-nine eyes of 80 subjects (34 women and 46 men; mean age, 26.81 ± 7.74 years; range, 18–53 years; spherical powers, −0.50 to −8.00 DS; and cylindrical powers, −0.25 to −5.00 DC were enrolled. One year postoperatively, the simple myopia with/without MMC groups showed no difference in UCVA (P=0.187, BCVA (P=0.163, or spherical equivalent (P=0.163 and a significant difference (P=0.0495 in K-reading; the haze formation difference was nonsignificant (P=0.056. Astigmatic groups with/without MMC showed a significant difference in K-reading (P<0.0001. MMC groups had less haze formation (P<0.0001. Conclusion. PRK with intraoperative MMC application showed excellent visual outcomes. MMC’s effect on astigmatic patients was significantly better with acceptable safety and minimal side effects.

Astigmatism and biometric optic components of diode laser-treated threshold retinopathy of prematurity at 9 years of age

Science.gov (United States)

Yang, C-S; Wang, A-G; Shih, Y-F; Hsu, W-M

2013-01-01

Purpose To assess the prevalence of astigmatism and its relationship with biometric optic components in preterm school children with diode laser-treated threshold retinopathy of prematurity (ROP). Methods A prospective, cross-sectional study in which cycloplegic keratometry, refraction, and ultrasound biometric measurement of optic components were performed on 24 consecutive preterm children with diode laser-treated threshold ROP at the age of 9 years. The study results were compared with data on 1021 age-matched full-term control children from a national survey. Results The laser-treated eyes had a mean astigmatism of 3.47 D, with a mean spherical equivalent of −4.49 D. Of the 46 eyes studied, 98% of eyes showed astigmatism ≥0.5 D and 50% had high astigmatism (>3.0 D). Most astigmatic eyes (97.7%) showed with-the-rule astigmatism, with the mean plus cylinder axis at 89.30o. Further correlation analysis showed the astigmatism in refraction was highly correlated with the corneal astigmatism (r=0.921, P<0.001) and the vertical corneal curvature (r=0.405, P=0.005). There was significantly steeper vertical corneal curvature (P=0.003) and flatter horizontal corneal curvature (P=0.031) in eyes with laser-treated ROP when compared with age-matched full-term controls. The eyes with laser-treated ROP also show significantly thicker lens (3.93 mm) and shallower anterior chamber depth (ACD; 2.92 mm) than full-term controls (P<0.001). Conclusions There is significantly higher prevalence and greater magnitude of astigmatism in eyes with laser-treated threshold ROP compared with full-term controls. The steeper vertical corneal curvature component contributes to the increased astigmatism in eyes with laser-treated ROP. PMID:23222565

Convergence Insufficiency, Accommodative Insufficiency, Visual Symptoms, and Astigmatism in Tohono O'odham Students.

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Davis, Amy L; Harvey, Erin M; Twelker, J Daniel; Miller, Joseph M; Leonard-Green, Tina; Campus, Irene

2016-01-01

Purpose. To determine rate of convergence insufficiency (CI) and accommodative insufficiency (AI) and assess the relation between CI, AI, visual symptoms, and astigmatism in school-age children. Methods. 3rd-8th-grade students completed the Convergence Insufficiency Symptom Survey (CISS) and binocular vision testing with correction if prescribed. Students were categorized by astigmatism magnitude (no/low: <1.00 D, moderate: 1.00 D to <3.00 D, and high: ≥3.00 D), presence/absence of clinical signs of CI and AI, and presence of symptoms. Analyses determine rate of clinical CI and AI and symptomatic CI and AI and assessed the relation between CI, AI, visual symptoms, and astigmatism. Results. In the sample of 484 students (11.67 ± 1.81 years of age), rate of symptomatic CI was 6.2% and symptomatic AI 18.2%. AI was more common in students with CI than without CI. Students with AI only (p = 0.02) and with CI and AI (p = 0.001) had higher symptom scores than students with neither CI nor AI. Moderate and high astigmats were not at increased risk for CI or AI. Conclusions. With-the-rule astigmats are not at increased risk for CI or AI. High comorbidity rates of CI and AI and higher symptoms scores with AI suggest that research is needed to determine symptomatology specific to CI.

ANALYSIS OF CORNEAL ASTIGMATISM BEFORE AND AFTER PTERYGIUM SURGERY- A PROSPECTIVE STUDY IN PATIENTS ATTENDING KIMS, HUBLI

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Y. B. Bajantri

2017-10-01

Full Text Available BACKGROUND Pterygium is a very common degenerative condition seen in Indian subcontinent. It is a wing-shaped fibrovascular encroaching up on the cornea from either sides. The prevalence rate is 5.2%. Pterygium is known to affect refractive astigmatism. The induced astigmatism may become significant to cause visual distortion, even though the pterygium remains distant from visual axis induced astigmatism maybe either “with-the-rule” or “against-the-rule.” The aim of the study is to- 1. Compare preoperative with postoperative astigmatism in case of pterygium. 2. Assess the amount of astigmatism in case of pterygia of different lengths measured from the limbus over the cornea. MATERIALS AND METHODS The study included 70 eyes of 70 patients with primary pterygium. Preoperative evaluation included pterygium size, visual acuity, keratometry and refraction with subjective correction. Patients included in the study were divided into three groups based on length of pterygium encroaching on cornea (1 to 2 mm, 2 to 3 mm, >3 mm. Each eye underwent bare sclera pterygium excision. Postoperative visual acuity, keratometry and refraction were evaluated on 1st day, at the end of 1st week, 4 th week and 9th week. The pre and postoperative results were compared and analysed. RESULTS An average of all 70 cases with mean pterygium length 3.2 mm had a mean keratometry astigmatism of 1.84 ± 0.89D preoperatively and 0.514 ± 0.52D postoperatively indicating a reduction of pterygium-induced corneal astigmatism by 1.45 ± 0.77D (p value <0.0001, which was statistically significant. CONCLUSION Pterygium-induced corneal astigmatism is directly proportional to the size of the pterygium. Thus, early surgical excision reduces the corneal astigmatism, and hence, improves the visual acuity.

LASIK versus photorefractive keratectomy for high myopic (> 3 diopter) astigmatism.

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Katz, Toam; Wagenfeld, Lars; Galambos, Peter; Darrelmann, Benedikt Große; Richard, Gisbert; Linke, Stephan Johannes

2013-12-01

To compare the efficacy, safety, predictability, and vector analysis indices of LASIK and photorefractive keratectomy (PRK) for correction of high cylinder of greater than 3 diopters (D) in myopic eyes. The efficacy, safety, and predictability of LASIK or PRK performed in 114 consecutive randomly selected myopic eyes with an astigmatism of greater than 3 D were retrospectively analyzed at the 2- to 6-month follow-up visits. Vector analysis of the cylindrical correction was compared between the treatment groups. A total of 57 eyes receiving PRK and 57 eyes receiving LASIK of 114 refractive surgery candidates were enrolled in the study. No statistically significant difference in efficacy [efficacy index = 0.76 (±0.32) for PRK vs 0.74 (±0.19) for LASIK (P = .82)], safety [safety index = 1.10 (±0.26) for PRK vs 1.01 (±0.17) for LASIK (P = .121)], or predictability [achieved astigmatism PRK- and 54% of LASIK-treated eyes, and PRK- and 89% of LASIK-treated eyes (P = .218)] was demonstrated. Using Alpins vector analysis, the surgically induced astigmatism and difference vector were not significantly different between the surgery methods, whereas the correction index showed a slight and significant advantage of LASIK over PRK (1.25 for PRK and 1.06 for LASIK, P LASIK and PRK are comparably safe, effective, and predictable procedures for excimer laser correction of high astigmatism of greater than 3 D in myopic eyes. Predictability of the correction of the cylindrical component is lower than that of the spherical equivalent. Copyright 2013, SLACK Incorporated.

Comparison of the Keratometric Corneal Astigmatic Power after Phacoemulsification: Clear Temporal Corneal Incision versus Superior Scleral Tunnel Incision

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Yongqi He

2009-01-01

Full Text Available Objective. This is prospective randomized control trial to compare the mean keratometric corneal astigmatism diopter power (not surgical induced astigmatism among preop and one-month and three-month postop phacoemulcification of either a clear temporal corneal incision or a superior scleral tunnel Incision, using only keratometric astigmatic power reading to evaluate the difference between the two cataract surgery incisions. Methods. 120 patients (134 eyes underwent phacoemulcification were randomly assigned to two groups: Group A, the clear temporal corneal incision group, and Group B, the superior scleral tunnel incision group. SPSS11.5 Software was used for statistical analysis to compare the postsurgical changes of cornea astigmatism on keratometry. Results. The changes of corneal astigmatic diopter in Groups A and B after 3 month postop from keratometric reading were 1.04 + 0.76 and 0.94 + 0.27, respectively (=.84>.05, which showed no statistic significance difference. Conclusion. The incision through either temporal clear cornea or superior scleral tunnel in phacoemulcification shows no statistic difference in astigmatism change on keratometry 3-month postop.

Two-year results of femtosecond assisted LASIK versus PRK for different severity of astigmatism.

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Miraftab, Mohammad; Hashemi, Hassan; Asgari, Soheila

2018-03-01

To compare two-year results of femtosecond laser assisted LASIK (femto-LASIK) and photorefractive keratectomy (PRK) in terms of astigmatism correction in patients with less than 2.0 diopters (D) of spherical error and more than 2.0 D of cylinder error. In this retrospective study, data were extracted from 100 patient charts. The two study groups were matched by age, gender, and baseline uncorrected distance visual acuity (UDVA) and refractive astigmatism (RA). Preoperative astigmatism was categorized as mild: 2.00 to LASIK and PRK groups was respectively -3.15 ± 0.94 D (-7.00 to -2.00 D) and -3.29 ± 0.95 D (-6.25 to -2.00 D) at baseline ( P  = 0.284), and -0.61 ± 0.40 D and -0.62 ± 0.60 D one year after surgery ( P  = 0.674), but significantly lower in the femto-LASIK group (-0.61 ± 0.39 vs. -0.83 ± 0.56 D, P  = 0.021) at 2 years when the rate of residual astigmatism more than 1.0 D was 6.3% in the femto-LASIK and 19.6% in the PRK group ( P  = 0.046). Mean UDVA in the femto-LASIK group (0.02 ± 0.05 logMAR) was better than the PRK group (0.06 ± 0.10 logMAR) ( P  = 0.025). Mean corrected distance visual acuity (CDVA) was not significantly different between groups (0.01 ± 0.03 vs. 0.01 ± 0.04 logMAR, P  = 0.714). Both groups had 1-4 Snellen lines CDVA improvement. The three subgroups of baseline astigmatism did not differ significantly in terms of residual astigmatism (all P  > 0.05). However, in subgroups with ≥4.00 D cylinder, there was less astigmatic regression at 1 year in the femto-LASIK group (0.28 ± 0.43 D) than the PRK group (0.54 ± 0.68 D) ( P  = 0.007). Our results pointed to better two-year results with femto-LASIK in the treatment of different degrees of astigmatism. UDVA improvement was superior with femto-LASIK, but the two methods did not significantly differ in terms of CDVA improvement.

Clinical research on keratoconus and subclinical keratoconus in patients with astigmatism examined by Pentacam

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Yang An

2016-03-01

Full Text Available AIM: To study the keratoconus(KCNand subclinical KCN in patients with astigmatism ≥2D by Pentacam anterior segment analyzer. METHODS: Two hundred and one eyes in 107 patients with astigmatism ≥2D were included in this study. All patients underwent optometry, visual acuity, corrected visual acuity, slit lamp biomicroscopy, fundus examination, traditional corneal topography and examination with Pentacam. Changes of several parameters were observed including K1(horizontal central curvature within the scope with diameter of 3mm, K2(vertical central curvature within the scope with diameter of 3mm; Kmax(the maximum anterior corneal refractive power, corneal astigmatism(CYL, MinPachy(the thickness at the thinnest area of cornea, index of surface variation(ISV, index of vertical asymmetry(IVA, keratoconus index(KI, height of anterior corneal surface(AEand height of posterior corneal surface(PE, etc. ROC curve was made. Cutoff value and the sensitive index of each group were compared. Mann-Whitney U test was used for analysis of several parameters obtained from Pentacam. ROC curve was analyzed to determine the best diagnosis cutoff value. RESULTS: Mean age of the study population was 25.7±6.6 years old. Kmax, IVA, KI, AE and PE of the clinical and subclinical group were significantly higher than those of the astigmatism group, while the thickness at the thinnest area of cornea in clinical and subclinical group was lower than that of the astigmatism group(PCONCLUSION: The current study shows that subjects with 2D or more of astigmatism, even some of them have normal vision, should undergo corneal topography screening. Pentacam may provide more accurate information about anterior and posterior corneal anatomy especially for the height of posterior corneal surface, which plays an important role in screening of subclinical KCN.

Anisometropia prevalence in a highly astigmatic school-aged population.

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Dobson, Velma; Harvey, Erin M; Miller, Joseph M; Clifford-Donaldson, Candice E

2008-07-01

To describe prevalence of anisometropia, defined in terms of both sphere and cylinder, examined cross-sectionally, in school-aged members of a Native American tribe with a high prevalence of astigmatism. Cycloplegic autorefraction measurements, confirmed by retinoscopy and, when possible, by subjective refraction were obtained from 1041 Tohono O'odham children, 4 to 13 years of age. Astigmatism > or =1.00 diopter (D) was present in one or both eyes of 462 children (44.4%). Anisometropia > or =1.00 D spherical equivalent (SE) was found in 70 children (6.7%), and anisometropia > or =1.00 D cylinder was found in 156 children (15.0%). Prevalence of anisometropia did not vary significantly with age or gender. Overall prevalence of significant anisometropia was 18.1% for a difference between eyes > or =1.00 D SE or cylinder. Vector analysis of between-eye differences showed a prevalence of significant anisometropia of 25.3% for one type of vector notation (difference between eyes > or =1.00 D for M and/or > or =0.50 D for J0 or J45), and 16.2% for a second type of vector notation (between-eye vector dioptric difference > or =1.41). Prevalence of SE anisometropia is similar to that reported for other school-aged populations. However, prevalence of astigmatic anisometropia is higher than that reported for other school-aged populations.

Assessment of corneal astigmatism following frown and straight incision forms in sutureless manual small incision cataract surgery

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Amedo AO

2016-04-01

Full Text Available Angela Ofeibea Amedo, Kwadwo Amoah, Nana Yaa Koomson, David Ben Kumah, Eugene Appenteng Osae Department of Optometry and Visual Science, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana Abstract: To investigate which of two tunnel incision forms (frown versus straight in sutureless manual small incision cataract surgery creates more corneal astigmatism. Sixty eyes of 60 patients who had consented to undergo cataract surgery and to partake in this study were followed from baseline through >12-week postoperative period. Values of preoperative and postoperative corneal astigmatism for the 60 eyes, measured with a Bausch and Lomb keratometer, were extracted from the patients’ cataract surgery records. Residual astigmatism was computed as the difference between preoperative and postoperative keratometry readings. Visual acuity was assessed during the preoperative period and at each postoperative visit with a Snellen chart at 6 m. Fifty eyes of 50 patients were successfully followed-up on. Overall, the mean residual astigmatism was 0.75±0.12 diopters. The differences in mean residual astigmatism between the two different incision groups were statistically significant (t [48]=6.33, P<0.05; frown incision group recorded 1.00±0.12 diopters, whereas the straight incision group recorded 0.50±0.12 diopters. No significant difference was observed between male and female groups (t [48]=0.24, P>0.05. Residual corneal astigmatism in the frown incision group was significantly higher than in the straight incision group. Fisher’s exact test did not reveal a significant association between incision forms and visual acuity during the entire postoperative period (P>0.05. Keywords: cataract, residual corneal astigmatism, frown incision, straight incision

Unilateral Posterior Polymorphous Corneal Dystrophy Presented as Anisometropic Astigmatism: 3 Case Reports

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Hyun Sun Jeon

2017-04-01

Full Text Available Background: Posterior polymorphous corneal dystrophy (PPCD is typically considered bilateral and asymptomatic. However, few case reports on patients with unilateral PPCD with asymmetric refractive error have mentioned anisometropic amblyopia development. In support of this, we report 3 cases of unilateral PPCD that presented as anisometropic astigmatism. Visual prognosis related to amblyopia development is discussed. Case Presentation: All 3 patients had a band lesion in the affected eye and a difference of at least 1.5 diopters in cylindrical refractive error between their eyes. The affected eye had a greater amount of astigmatism in all cases. Two patients (Cases 1 and 2 also had amblyopia in the affected eye. Case 1 was a 25-year-old male with a unilateral PPCD diagnosis and a band lesion involving the visual axis. Case 2 was an 11-year-old boy diagnosed with unilateral PPCD. The boy was treated with occlusion and atropine therapy over a 2-year period. Case 3 was a 4-year-old girl diagnosed with unilateral PPCD. The girl had a 30-month history of corrective spectacle use and had no amblyopia. In all cases, the corneal endothelial cell count was lower in the affected eye than in the unaffected contralateral eye. Conclusions: Practitioners should closely monitor patients with unilateral PPCD for astigmatic anisometropia and amblyopia development. Visual prognosis for patients with unilateral PPCD may be related to lesion position, age at diagnosis, astigmatism severity, and early-childhood corrective spectacle use.

A novel nomogram for the treatment of astigmatism with femtosecond-laser arcuate incisions at the time of cataract surgery.

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Baharozian, Connor J; Song, Christian; Hatch, Kathryn M; Talamo, Jonathan H

2017-01-01

The purpose of this study was to determine an arcuate incision (AI) nomogram to treat astigmatism during femtosecond laser-assisted cataract surgery. This is a retrospective, cohort study. Femtosecond laser (FSL)-assisted transepithelial AIs were created at a 9.0 mm optical zone, 80% depth, centered on the limbus. We modified the manual Donnenfeld limbal relaxing incision nomogram to 70% for with-the-rule (WTR), 80% for oblique (OBL), and 100% for against-the-rule (ATR) astigmatism. The correction index (CI) equaled AI-induced astigmatism/target-induced astigmatism. Measures included preoperative keratometric corneal cylinder (Pre Kcyl), postoperative Kcyl (Post Kcyl), and postoperative residual refractive astigmatism (Post RRA). Mean Pre Kcyl and 1-2 months Post RRA in 161 eyes of 116 patients were 0.626±0.417 diopters (D) (range 0.5-2 D), and 0.495±0.400 D (range 0-1.5 D), respectively. Mean absolute astigmatic changes (Pre Kcyl-Post Kcyl) without accounting for axis change in the WTR, ATR, and OBL groups were 0.165±0.383 D ( P <0.001), 0.374±0.536 D ( P <0.001), and 0.253±0.416 D ( P =0.02), respectively. Mean absolute astigmatic changes using RRA as the postoperative measurement (Pre Kcyl-Post RRA) without accounting for axis change were 0.440±0.461 D ( P <0.001), 0.238±0.571 D ( P <0.05), 0.154±0.450 ( P =0.111) in WTR, ATR, and OBL groups, respectively. CIs for WTR, ATR, and OBL were 0.53, 1.01, and 0.95, respectively. There were no intraoperative or postoperative complications related to the AIs. Transepithelial FSL-AIs using the modified Donnenfeld nomogram show potential for management of mild to moderate corneal astigmatism. An increase in the magnitude or reduction of the optical zone size for the treatment of WTR and ATR astigmatism for this nomogram may further improve refractive accuracy.

Genome-wide meta-analysis of five Asian cohorts identifies PDGFRA as a susceptibility locus for corneal astigmatism.

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Qiao Fan

2011-12-01

Full Text Available Corneal astigmatism refers to refractive abnormalities and irregularities in the curvature of the cornea, and this interferes with light being accurately focused at a single point in the eye. This ametropic condition is highly prevalent, influences visual acuity, and is a highly heritable trait. There is currently a paucity of research in the genetic etiology of corneal astigmatism. Here we report the results from five genome-wide association studies of corneal astigmatism across three Asian populations, with an initial discovery set of 4,254 Chinese and Malay individuals consisting of 2,249 cases and 2,005 controls. Replication was obtained from three surveys comprising of 2,139 Indians, an additional 929 Chinese children, and an independent 397 Chinese family trios. Variants in PDGFRA on chromosome 4q12 (lead SNP: rs7677751, allelic odds ratio = 1.26 (95% CI: 1.16-1.36, P(meta = 7.87×10(-9 were identified to be significantly associated with corneal astigmatism, exhibiting consistent effect sizes across all five cohorts. This highlights the potential role of variants in PDGFRA in the genetic etiology of corneal astigmatism across diverse Asian populations.

Characteristics of astigmatism in Black South African high school ...

African Journals Online (AJOL)

Keywords: Astigmatism prevalence, school children, South Africa. ... ception and symptoms.3 The high school population is of interest given that they ..... Malaysia. Asian. 7-15. 4634. ≤−0.75 15.7. Paudel te al45. Vietnam. Asian. 12-15. 2238.

A novel nomogram for the treatment of astigmatism with femtosecond-laser arcuate incisions at the time of cataract surgery

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Baharozian CJ

2017-10-01

Full Text Available Connor J Baharozian,1 Christian Song,2,3 Kathryn M Hatch,2,3 Jonathan H Talamo2,3 1Boston University School of Medicine, 2Massachusetts Eye and Ear Infirmary, 3Department of Ophthalmology, Harvard Medical School, Boston, MA, USA Purpose: The purpose of this study was to determine an arcuate incision (AI nomogram to treat astigmatism during femtosecond laser-assisted cataract surgery. Methods: This is a retrospective, cohort study. Femtosecond laser (FSL-assisted transepithelial AIs were created at a 9.0 mm optical zone, 80% depth, centered on the limbus. We modified the manual Donnenfeld limbal relaxing incision nomogram to 70% for with-the-rule (WTR, 80% for oblique (OBL, and 100% for against-the-rule (ATR astigmatism. The correction index (CI equaled AI-induced astigmatism/target-induced astigmatism. Measures included preoperative keratometric corneal cylinder (Pre Kcyl, postoperative Kcyl (Post Kcyl, and postoperative residual refractive astigmatism (Post RRA. Results: Mean Pre Kcyl and 1–2 months Post RRA in 161 eyes of 116 patients were 0.626±0.417 diopters (D (range 0.5–2 D, and 0.495±0.400 D (range 0–1.5 D, respectively. Mean absolute astigmatic changes (Pre Kcyl–Post Kcyl without accounting for axis change in the WTR, ATR, and OBL groups were 0.165±0.383 D (P<0.001, 0.374±0.536 D (P<0.001, and 0.253±0.416 D (P=0.02, respectively. Mean absolute astigmatic changes using RRA as the postoperative measurement (Pre Kcyl–Post RRA without accounting for axis change were 0.440±0.461 D (P<0.001, 0.238±0.571 D (P<0.05, 0.154±0.450 (P=0.111 in WTR, ATR, and OBL groups, respectively. CIs for WTR, ATR, and OBL were 0.53, 1.01, and 0.95, respectively. There were no intraoperative or postoperative complications related to the AIs.Conclusion: Transepithelial FSL-AIs using the modified Donnenfeld nomogram show potential for management of mild to moderate corneal astigmatism. An increase in the magnitude or reduction of the optical zone

The effects of lateral head tilt on ocular astigmatic axis

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Hamid Fesharaki

2014-01-01

Conclusion: Any minimal angle of head tilt may cause erroneous measurement of astigmatic axis and should be avoided during refraction. One cannot rely on the compensatory function of ocular counter-torsion during the refraction.

Vector analysis of low to moderate astigmatism with small incision lenticule extraction (SMILE): results of a 1-year follow-up.

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Zhang, Jiamei; Wang, Yan; Wu, Wenjing; Xu, Lulu; Li, Xiaojing; Dou, Rui

2015-01-24

To evaluate the refractive outcomes for the correction of low to moderate astigmatism up to 1 year following small incision lenticule extraction (SMILE) surgery. This retrospective study enrolled 98 eyes from 98 patients who underwent SMILE surgery for the correction of myopia and astigmatism. Only right eyes were included in this study to avoid the bias of orientation errors. The vector method was used to analyze the outcomes of astigmatism at 1 month, 6 months and 12 months after the procedure, including the double-angle plots, correction index (CI), index of success (IOS), angle of error (AofE) and magnitude of error (MofE). The effectiveness, safety, stability and predictability were also investigated during the 12-month follow-up. The preoperative cylinder ranged from -2.75 D to -0.25 D (average of -0.90±0.68 D), and the mean postoperative cylinder values were -0.24±0.29 D, -0.24±0.29 D, and -0.20±0.27 D at 1 month, 6 months, and 12 months, respectively. The mean astigmatism in vector form was -0.14 D×27.19° at 1 month, -0.13 D×27.29° at 6 months, and -0.10 D×28.63° at 12 months after surgery. The CI was 1.00±0.32 and IOS was 0.29±0.44 at the 12-month follow-up. Significant negative correlations were found between the CI and absolute target induced astigmatism (TIA) value, and positive correlations were found between the IOS and absolute AofE value (Psafe in correcting low to moderate astigmatism, and stable refractive outcomes were observed at the long-term follow-up. The undercorrection of astigmatism could possibly be influenced by attempted astigmatism correction preoperatively, the axis rotation during the surgery or wound healing postoperatively. This study suggested that nomograms should be adjusted in correcting astigmatism with SMILE surgery.

Changes in higher order aberrations after wavefront guided FS-LASIK for myopia combined with moderate to high astigmatism

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Cang-Yu Guan

2018-02-01

Full Text Available AIM: To assess the changes in higher order aberrations after wavefront guided femtosecond laser assisted laser in situ keratomileusis(FS-LASIKfor moderate to high astigmatism. METHODS: Eighty-eight eyes of 50 myopia patients with moderate to high astigmatism were included in this prospective study. There were 51 eyes with moderate astigmatism(≥-1.50D and RESULTS: At the 3mo after operation, the mean UDVA of all eyes was above 20/20, better than before operation(PP=0.36and no eyes lost ≥2 lines of CDVA. Mean astigmstism of 85 eyes(97%was reduced below -1.00D, mean astigmatism of 70 eyes(80%was reduced below -0.50D(PPP=0.078, 0.065. The spherical aberration, secondary astigmatism and the HOA root mean square(RMSincreased from 0.19±0.06, 0.05±0.02 and 0.42±0.12, preoperatively to 0.32±0.17, 0.26±0.08 and 0.78±0.28(PCONCLUSION: Wavefront-guided FS-LASIK is a safe and effective option for the patients with moderate to high astigmstism although parts of HOAs increased.

Comparison of the Effect of Cycloplegia on Astigmatism Measurements in a Pediatric Amblyopic Population: A Prospective Study.

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Goyal, Sunali; Phillips, Paul H; Rettiganti, Mallikarjuna; Gossett, Jeffrey M; Lowery, R Scott

2018-06-18

To study the effect of cycloplegia on astigmatism measurements in pediatric patients with amblyopia. This was a prospective comparative clinical study. Participants 4 to 17 years old were recruited from the patient population at the Arkansas Children's Hospital eye clinic after informed consent was obtained. Autorefractor measurements were used to obtain values of refractive error in amblyopic and non-amblyopic patients before and after cycloplegia. The groups were subdivided into myopia and hyperopia and with and without underlying amblyopia. The refractive error was expressed as sphere, cylinder, axis of astigmatism, and spherical equivalent. The treatment effect was summarized as the mean difference (95% confidence interval) for each outcome. No statistically significant difference was found on the axis and power of astigmatism before and after cycloplegia in the patients with amblyopia (P = .28 and .99, respectively). Non-cycloplegic autorefraction measurements may be considered safe for refining astigmatism power and axis in pediatric patients with amblyopia. [J Pediatr Ophthalmol Strabismus. 201X; XX(X):XXXX.]. Copyright 2018, SLACK Incorporated.

Vision of low astigmats through thick and thin lathe-cut soft contact lenses.

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Cho, P; Woo, G C

2001-01-01

Distance and near visual acuity of 13 low astigmats were determined in a double-masked experiment through thick and thin (centre thickness 0.12 mm and 0.06 mm, respectively) spherical lathe-cut soft lenses. For each lens type, distance and near LogMAR VA and over-refraction were assessed with different logMAR VA charts. For 70% of the subjects, the residual astigmatism was significantly lower than the refractive astigmatism with thicker lenses. No statistically significant differences in the distance and near logMAR VA was found between the two lens types using any of the charts used, though, in general, logMAR VA obtained through the thicker lens was better than logMAR VA through the thinner lens. The variabilities in distance and near logMAR VA between the two lens types increased with decreased contrast. The variabilities in distance logMAR VA were greater with Chinese charts than with English charts, and LogMAR VA with Chinese charts were significantly worse for both lens types. Based on the results of this study, we concluded that thicker spherical lathe-cut soft lenses provide better vision in low astigmats. The Snellen acuity test is inadequate for vision assessment of soft contact lens wearers. When a patient wearing thin soft contact lenses complains of poor vision in spite of 6/6 or 6/5 Snellen acuity, changing to thicker lenses may be considered.

Two-year results of femtosecond assisted LASIK versus PRK for different severity of astigmatism

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Mohammad Miraftab; Hassan Hashemi; Soheila Asgari

2018-01-01

Purpose: To compare two-year results of femtosecond laser assisted LASIK (femto-LASIK) and photorefractive keratectomy (PRK) in terms of astigmatism correction in patients with less than 2.0 diopters (D) of spherical error and more than 2.0 D of cylinder error. Methods: In this retrospective study, data were extracted from 100 patient charts. The two study groups were matched by age, gender, and baseline uncorrected distance visual acuity (UDVA) and refractive astigmatism (RA). Preoperativ...

Optical treatment reduces amblyopia in astigmatic children who receive spectacles before kindergarten.

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Dobson, Velma; Clifford-Donaldson, Candice E; Green, Tina K; Miller, Joseph M; Harvey, Erin M

2009-05-01

To examine the effect of spectacle correction of astigmatism during preschool on best-corrected recognition visual acuity (VA), grating VA, and meridional amblyopia (difference between acuity for vertical versus horizontal gratings) once the children reach kindergarten. Comparative case series. Seventy-three astigmatic (right eye > or =1.50 diopters [D] cylinder) Native American (Tohono O'odham) children 5 to 7 years of age. All had with-the-rule astigmatism. In 28 children, the astigmatism was simple myopic, compound myopic, or mixed (M/MA), and in 45 children, it was simple or compound hyperopic (HA). Thirty-nine children (Treated Group) had spectacle correction of refractive error, prescribed for full-time wear, in preschool (0.8-2.4 years before testing). Thirty-four children (Untreated Group) had no prior correction. Comparison of Treated versus Untreated Groups for mean best-corrected right-eye recognition VA, measured with the Early Treatment Diabetic Retinopathy Study (ETDRS) chart and the Lea Symbols chart, for grating VA, measured with modified Teller acuity card stimuli, and for meridional amblyopia, based on grating acuity results. Mean ETDRS VA was significantly better in the Treated Group (20/37) than in the Untreated Group (20/48; P<0.003), but the difference between mean Lea Symbols VA in the Treated Group (20/33) and in the Untreated Group (20/38) was not significant. No significant Treated versus Untreated Group differences were found for either vertical or horizontal grating acuity. Meridional amblyopia differed between the M/MA group, which showed better acuity for vertical than for horizontal gratings, and the HA group, which showed better acuity for horizontal than for vertical gratings. However, in neither the M/MA group nor the HA group was there a significant difference in magnitude of meridional amblyopia in the Treated versus the Untreated Group. Spectacle correction during the preschool years results in a significant improvement in best

Long-term outcomes of wedge resection at the limbus for high irregular corneal astigmatism after repaired corneal laceration

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Jun Du

2016-06-01

Full Text Available AIM: To evaluate the clinical value of wedge resection at corneal limbus in patients with traumatic corneal scarring and high irregular astigmatism. METHODS: Patients with traumatic corneal astigmatism received wedge resection at least 6mo after suture removal from corneal wound. The uncorrected distance visual acuities (UCVA and best corrected distance visual acuities (BCVA, pre- and post-operation astigmatism, spherical equivalent (SE, safety and complications were evaluated. RESULTS: Ten eyes (10 patients were enrolled in this study. Mean follow-up time after wedge resection was 37.8±15.4mo (range, 20-61mo. The mean UCVA improved from +1.07±0.55 logMAR to +0.43±0.22 logMAR (P=0.000 and the mean BCVA from +0.50±0.30 logMAR to +0.15±0.17 logMAR (P=0.000. The mean astigmatism power measured by retinoscopy was -2.03±2.27 D postoperatively and -2.83±4.52 D preoperatively (P=0.310. The mean SE was -0.74±1.61 D postoperatively and -0.64±1.89 D preoperatively (P=0.601. Two cases developed mild pannus near the sutures. No corneal perforation, infectious keratitis or wound gape occurred. CONCLUSION: Corneal-scleral limbal wedge resection with compression suture is a safe, effective treatment for poor patients with high irregular corneal astigmatism after corneal-scleral penetrating injury. Retinoscopy can prove particularly useful for high irregular corneal astigmatism when other measurements are not amenable.

Comparison of clinical outcomes between limbal relaxing incisions and toric intraocular lenses in eyes with astigmatic corneas

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Giuliano de Oliveira Freitas

2014-01-01

Full Text Available Objective: To compare refractive and vectorial outcomes of limbal relaxing incisions (LRI versus toric intraocular lenses (IOL in the treatment of preexisting corneal astigmatism at the time of phacoemulsification. Methods: This longitudinal observational case series assessed 62 eyes of 31 consecutive cataract patients with preoperative corneal astigmatism between 0.75 and 2.50 diopters in both eyes. Patients were randomly assorted in two groups: one assigned to receive AcrySof Toric™ IOL in both eyes, and another one assigned to have AcrySof Natural™ IOL associated with LRI, also in both eyes. All patients were re-evaluated, postoperatively, at 1, 3 and 6 months, when refractive astigmatism analysis was performed using vectorial methods proposed by Thibos. Variability of outcomes within each group and between groups were assessed and compared. Results: Manifest refractive cylinder, in diopters (D, as means ± standard deviation, in the LRI group for 1-month, 3-month and 6-month re-evalutions were respectively -0.66 ± 0.30; -0.70 ± 0.21 and -0.74 ± 0.26 when compared to -0.58 ± 0.24; -0.63 ± 0.20, and -0.62 ± 0.17 in the toric IOL group. (p value ≥ 0.06. Vectorial analysis evidenced greater astigmatism reduction in the toric IOL group in the 6th postoperative month, when postoperative mean astigmatic power vector was 0.31 D, when compared to 0.37 D in the LRI group (p value = 0.00. Conclusions: A trend of slightly better refractive outcomes favoring toric IOL group was seen, although such a trend was not statistically significant. Vectorial analysis, however, suggests that the use of toric IOL may constitute a more advantageous approach in the treatment of pre-existing corneal astigmatism, simultaneously with phacoemulsification.

Vector analysis of high (≥3 diopters) astigmatism correction using small-incision lenticule extraction and laser in situ keratomileusis.

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Chan, Tommy C Y; Wang, Yan; Ng, Alex L K; Zhang, Jiamei; Yu, Marco C Y; Jhanji, Vishal; Cheng, George P M

2018-06-13

To compare the astigmatic correction in high myopic astigmatism between small-incision lenticule extraction and laser in situ keratomileusis (LASIK) using vector analysis. Hong Kong Laser Eye Center, Hong Kong. Retrospective case series. Patients who had correction of myopic astigmatism of 3.0 diopters (D) or more and had either small-incision lenticule extraction or femtosecond laser-assisted LASIK were included. Only the left eye was included for analysis. Visual and refractive results were presented and compared between groups. The study comprised 105 patients (40 eyes in the small-incision lenticule extraction group and 65 eyes in the femtosecond laser-assisted LASIK group.) The mean preoperative manifest cylinder was -3.42 D ± 0.55 (SD) in the small-incision lenticule extraction group and -3.47 ± 0.49 D in the LASIK group (P = .655). At 3 months, there was no significant between-group difference in uncorrected distance visual acuity (P = .915) and manifest spherical equivalent (P = .145). Ninety percent and 95.4% of eyes were within ± 0.5 D of the attempted cylindrical correction for the small-incision lenticule extraction and LASIK group, respectively (P = .423). Vector analysis showed comparable target-induced astigmatism (P = .709), surgically induced astigmatism vector (P = .449), difference vector (P = .335), and magnitude of error (P = .413) between groups. The absolute angle of error was 1.88 ± 2.25 degrees in the small-incision lenticule extraction group and 1.37 ± 1.58 degrees in the LASIK group (P = .217). Small-incision lenticule extraction offered astigmatic correction comparable to LASIK in eyes with high myopic astigmatism. Copyright © 2018 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Customized toric intraocular lens implantation for correction of extreme corneal astigmatism due to corneal scarring

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R Bassily

2010-03-01

Full Text Available R Bassily, J LuckOphthalmology Department, Royal United Hospital, Combe Park, Bath, UKAbstract: A 76-year-old woman presented with decreased visual function due to cataract formation. Twenty-five years prior she developed right sided corneal ulceration that left her with 10.8 diopters (D of irregular astigmatism at 71.8° (steep axis. Her uncorrected visual acuity was 6/24 and could only ever wear a balanced lens due to the high cylindrical error. Cataract surgery was planned with a custom designed toric intraocular lens (IOL with +16.0 D sphere inserted via a wound at the steep axis of corneal astigmatism. Postoperative refraction was -0.75/+1.50 × 177° with a visual acuity of 6/9 that has remained unchanged at six-week follow-up with no IOL rotation. This case demonstrates the value of high power toric IOLs for the correction of pathological corneal astigmatism.Keywords: intraocular lens, corneal ulceration, visual acuity, scarring

Application of the fractional Fourier transformation to digital holography recorded by an elliptical, astigmatic Gaussian beam.

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Nicolas, F; Coëtmellec, S; Brunel, M; Allano, D; Lebrun, D; Janssen, A J E M

2005-11-01

The authors have studied the diffraction pattern produced by a particle field illuminated by an elliptic and astigmatic Gaussian beam. They demonstrate that the bidimensional fractional Fourier transformation is a mathematically suitable tool to analyse the diffraction pattern generated not only by a collimated plane wave [J. Opt. Soc. Am A 19, 1537 (2002)], but also by an elliptic and astigmatic Gaussian beam when two different fractional orders are considered. Simulations and experimental results are presented.

Astigmatism compensation in mode-cleaner cavities for the next generation of gravitational wave interferometric detectors

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Barriga, Pablo J. [School of Physics, University of Western Australia, Crawley, WA 6009 (Australia)]. E-mail: pbarriga@cyllene.uwa.edu.au; Zhao Chunnong [School of Physics, University of Western Australia, Crawley, WA 6009 (Australia); Blair, David G. [School of Physics, University of Western Australia, Crawley, WA 6009 (Australia)

2005-06-06

Interferometric gravitational wave detectors use triangular ring cavities to filter spatial and frequency instabilities from the input laser beam. The next generation of interferometric detectors will use high laser power and greatly increased circulating power inside the cavities. The increased power inside the cavities increases thermal effects in their mirrors. The triangular configuration of conventional mode-cleaners creates an intrinsic astigmatism that can be corrected by using the thermal effects to advantage. In this Letter we show that an astigmatism free output beam can be created if the design parameters are correctly chosen.

Astigmatism compensation in mode-cleaner cavities for the next generation of gravitational wave interferometric detectors

International Nuclear Information System (INIS)

Barriga, Pablo J.; Zhao Chunnong; Blair, David G.

2005-01-01

Interferometric gravitational wave detectors use triangular ring cavities to filter spatial and frequency instabilities from the input laser beam. The next generation of interferometric detectors will use high laser power and greatly increased circulating power inside the cavities. The increased power inside the cavities increases thermal effects in their mirrors. The triangular configuration of conventional mode-cleaners creates an intrinsic astigmatism that can be corrected by using the thermal effects to advantage. In this Letter we show that an astigmatism free output beam can be created if the design parameters are correctly chosen

A COMPARATIVE STUDY OF THE AMOUNT OF ASTIGMATISM FOLLOWING CONVENTIONAL EXTRACAPSULAR CATARACT EXTRACTION AND MANUAL SMALL INCISION CATARACT SURGERY

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Rajkumari Bigyabati

2016-06-01

Full Text Available BACKGROUND Cataract is the principal cause of avoidable blindness in India and throughout the world. Surgical removal of the cataractous lens remains the only effective treatment for management of cataract blindness. The success of cataract surgery is determined by best and earliest visual recovery. But the occurrence of postoperative astigmatism has become a major hurdle in achieving this goal. AIMS The study was designed to compare the amount of astigmatism following conventional extracapsular cataract extraction (ECCE and manual small incision cataract surgery (SICS. MATERIALS AND METHODS The study was carried out in 100 eyes of 75 patients aged between 50 and 80 years admitted for cataract surgery. Out of these, 50 eyes were operated by conventional extracapsular cataract extraction and 50 eyes by manual small incision cataract surgery. The patients were followed up at 2 nd , 4 th , 6 th and 8 th weeks. At each follow-up visual acuity, refraction and acceptance and keratometry were recorded and the findings analysed for astigmatism. RESULTS In the current study, the mean (SD astigmatism developed at the end of the 2 nd , 4 th and 6 th of follow-up was significantly lower in the SICS group as compared to the ECCE group (P<0.000. At the end of 8 weeks of follow-up, the mean (SD astigmatism of the SICS group was 0.64±0.56 D as compared to the mean (SD of the ECCE group of 1.39±86 D and the difference was found to be significant (p<0.014. CONCLUSION The current study concludes that manual small incision cataract surgery is a better technique to control postoperative astigmatism than conventional extracapsular cataract extraction.

Validity of autorefractor based screening method for irregular astigmatism compared to the corneal topography- a cross sectional study

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Alicia Galindo-Ferreiro

2017-09-01

Full Text Available AIM: To present a method of screening for irregular astigmatism with an autorefractor and its determinants compared to corneal topography. METHODS: This cross-sectional validity study was conducted in 2013 at an eye hospital in Spain. A tabletop autorefractor (test 1 was used to measure the refractive status of the anterior surface of the cornea at two corneal meridians of each eye. Then corneal topography (test 2 and Bogan’s classification was used to group eyes into those with regular or no astigmatism (GRI and irregular astigmatism (GRII. Test 1 provided a single absolute value for the greatest cylinder difference (Vr. The receiver operating characteristic (ROC were plotted for the Vr values measured by test 1 for GRI and GRII eyes. On the basis a Vr value of 1.25 D as cut off, sensitivity, specificity were also calculated. RESULTS: The study sample was comprised of 260 eyes (135 patients. The prevalence of irregular astigmatism was 42% [95% confidence interval (CI: 36, 48]. Based on test 2, there were 151 eyes in GRI and 109 eyes in GRII. The median Vr was 0.75 D (25% quartile, 0.5 D for GRI and 1.75 D (25% quartile, 1.25 D for GRII. The area under curve was 0.171 for GRI and 0.83 for GRII. The sensitivity of test I was 78.1% and the specificity was 76.1%. CONCLUSION: A conventional autorefractor can be effective as a first level screening method to detect irregular corneal astigmatism in places where corneal topography facilities are not available.

Matched population comparison of visual outcomes and patient satisfaction between 3 modalities for the correction of low to moderate myopic astigmatism

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Ganesh S

2017-07-01

Full Text Available Sri Ganesh, Sheetal Brar, Archana Pawar Phacorefractive Department, Nethradhama Superspeciality Eye Hospital, Bengaluru, Karnataka, India Purpose: To compare toric implantable collamer lens (T-ICL, femto-LASIK, and ReLEx SMILE for the treatment of low to moderate myopic astigmatism in terms of long-term visual and refractive outcomes and predictability of astigmatic correction.Materials and methods: The study included 30 eyes from 30 patients between the age groups of 21 and 40 years, undergoing bilateral surgery with any of the three procedures – T-ICL, femto-LASIK, or ReLEx SMILE – for correction of myopic astigmatism within the range of −3 to −8 D spherical equivalent (SE, with a minimum astigmatism of −0.75 D. Patients were followed up at day 1, 1 month, 6 months, and 1 year.Results: At 1 year, the mean cylinder reduced to −0.21±0.28, −0.17±0.36, and −0.22±0.28 D in the T-ICL, femto-LASIK, and ReLEx SMILE group, respectively. The predictability of astigmatism correction was comparable, with no statistically significant difference between the 3 groups (P>0.05. A total of 97% of eyes in ReLEx SMILE achieved a uncorrected distance visual acuity of 20/20 or better, compared to T-ICL (93% and FS-LASIK (90%. However, gain in lines of corrected distant visual acuity (CDVA was maximum in T-ICL group (60%. Four eyes in the femto-LASIK group had loss of CDVA by one line. Three eyes required exchange due to high vault and rotation of the T-ICL, which did not affect the final outcome.Conclusion: All 3 modalities were effective for myopic astigmatism at the end of 1 year. Quality of vision and patient satisfaction with T-ICL and ReLEx SMILE were similar and better than FS-LASIK. However, slight chances of postoperative rotation and exchange exist with T-ICL, which warrant thorough preoperative planning. Keywords: toric implantable collamer lens, femtosecond LASIK, ReLEx SMILE, myopic astigmatism

Astigmatic single photon emission computed tomography imaging with a displaced center of rotation

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Wang, H.; Smith, M.F.; Stone, C.D.; Jaszczak, R.J.

1998-01-01

A filtered backprojection algorithm is developed for single photon emission computed tomography (SPECT) imaging with an astigmatic collimator having a displaced center of rotation. The astigmatic collimator has two perpendicular focal lines, one that is parallel to the axis of rotation of the gamma camera and one that is perpendicular to this axis. Using SPECT simulations of projection data from a hot rod phantom and point source arrays, it is found that a lack of incorporation of the mechanical shift in the reconstruction algorithm causes errors and artifacts in reconstructed SPECT images. The collimator and acquisition parameters in the astigmatic reconstruction formula, which include focal lengths, radius of rotation, and mechanical shifts, are often partly unknown and can be determined using the projections of a point source at various projection angles. The accurate determination of these parameters by a least squares fitting technique using projection data from numerically simulated SPECT acquisitions is studied. These studies show that the accuracy of parameter determination is improved as the distance between the point source and the axis of rotation of the gamma camera is increased. The focal length to the focal line perpendicular to the axis of rotation is determined more accurately than the focal length to the focal line parallel to this axis. copyright 1998 American Association of Physicists in Medicine

Higher-order aberrations and best-corrected visual acuity in Native American children with a high prevalence of astigmatism.

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Miller, Joseph M; Harvey, Erin M; Schwiegerling, Jim

2015-08-01

To determine whether higher-order aberrations (HOAs) in children from a highly astigmatic population differ from population norms and whether HOAs are associated with astigmatism and reduced best-corrected visual acuity. Subjects were 218 Tohono O'odham Native American children 5-9 years of age. Noncycloplegic HOA measurements were obtained with a handheld Shack-Hartmann sensor (SHS). Signed (z06s to z14s) and unsigned (z06u to z14u) wavefront aberration Zernike coefficients Z(3,-3) to Z(4,4) were rescaled for a 4 mm diameter pupil and compared to adult population norms. Cycloplegic refraction and best-corrected logMAR letter visual acuity (BCVA) were also measured. Regression analyses assessed the contribution of astigmatism (J0) and HOAs to BCVA. The mean root-mean-square (RMS) HOA of 0.191 ± 0.072 μm was significantly greater than population norms (0.100 ± 0.044 μm). All unsigned HOA coefficients (z06u to z14u) and all signed coefficients except z09s, z10s, and z11s were significantly larger than population norms. Decreased BCVA was associated with astigmatism (J0) and spherical aberration (z12u) but not RMS coma, with the effect of J0 about 4 times as great as z12u. Tohono O'odham children show elevated HOAs compared to population norms. Astigmatism and unsigned spherical aberration are associated with decreased acuity, but the effects of spherical aberration are minimal and not clinically significant. Copyright © 2015 American Association for Pediatric Ophthalmology and Strabismus. Published by Elsevier Inc. All rights reserved.

Evaluation of iris recognition system for wavefront-guided laser in situ keratomileusis for myopic astigmatism.

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Ghosh, Sudipta; Couper, Terry A; Lamoureux, Ecosse; Jhanji, Vishal; Taylor, Hugh R; Vajpayee, Rasik B

2008-02-01

To evaluate the visual and refractive outcomes of wavefront-guided laser in situ keratomileusis (LASIK) using an iris recognition system for the correction of myopic astigmatism. Centre for Eye Research Australia, Melbourne Excimer Laser Research Group, and Royal Victorian Eye and Ear Hospital, East Melbourne, Victoria, Australia. A comparative analysis of wavefront-guided LASIK was performed with an iris recognition system (iris recognition group) and without iris recognition (control group). The main parameters were uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity, amount of residual cylinder, manifest spherical equivalent (SE), and the index of success using the Alpins method of astigmatism analysis 1 and 3 months postoperatively. A P value less than 0.05 was considered statistically significant. Preoperatively, the mean SE was -4.32 diopters (D) +/- 1.59 (SD) in the iris recognition group (100 eyes) and -4.55 +/- 1.87 D in the control group (98 eyes) (P = .84). At 3 months, the mean SE was -0.05 +/- 0.21 D and -0.20 +/- 0.40 D, respectively (P = .001), and an SE within +/-0.50 D of emmetropia was achieved in 92.0% and 85.7% of eyes, respectively (P = .07). At 3 months, the UCVA was 20/20 or better in 90.0% and 76.5% of eyes, respectively. A statistically significant difference in the amount of astigmatic correction was seen between the 2 groups (P = .00 and P = .01 at 1 and 3 months, respectively). The index of success was 98.0% in the iris recognition group and 81.6% in the control group (P = .03). Iris recognition software may achieve better visual and refractive outcomes in wavefront-guided LASIK for myopic astigmatism.

The effect of static cyclotorsion compensation on refractive and visual outcomes using the Schwind Amaris laser platform for the correction of high astigmatism.

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Aslanides, Ioannis M; Toliou, Georgia; Padroni, Sara; Arba Mosquera, Samuel; Kolli, Sai

2011-06-01

To compare the refractive and visual outcomes using the Schwind Amaris excimer laser in patients with high astigmatism (>1D) with and without the static cyclotorsion compensation (SCC) algorithm available with this new laser platform. 70 consecutive eyes with ≥1D astigmatism were randomized to treatment with compensation of static cyclotorsion (SCC group- 35 eyes) or not (control group- 35 eyes). A previously validated optimized aspheric ablation algorithm profile was used in every case. All patients underwent LASIK with a microkeratome cut flap. The SCC and control group did not differ preoperatively, in terms of refractive error, magnitude of astigmatism or in terms of cardinal or oblique astigmatism. Following treatment, average deviation from target was SEq +0.16D, SD±0.52 D, range -0.98 D to +1.71 D in the SCC group compared to +0.46 D, SD±0.61 D, range -0.25 D to +2.35 D in the control group, which was statistically significant (p<0.05). Following treatment, average astigmatism was 0.24 D (SD±0.28 D, range -1.01 D to 0.00 D) in the SCC group compared to 0.46 D (SD±0.42 D, range -1.80 D to 0.00 D) in the control group, which was highly statistically significant (p<0.005). There was no statistical difference in the postoperative uncorrected vision when the aspheric algorithm was used although there was a trend to increased number of lines gained in the SCC group. This study shows that static cyclotorsion is accurately compensated for by the Schwind Amaris laser platform. The compensation of static cyclotorsion in patients with moderate astigmatism produces a significant improvement in refractive and astigmatic outcomes than when not compensated. Copyright © 2011 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

Efficacy and safety of cross-cylinder photorefractive keratectomy versus single method in medium-high astigmatism: a randomized clinical trial.

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Sedghipour, Mohammad R; Lotfi, Afshin; Sadeghilar, Ayaz; Banan, Saeeid

2012-09-07

BACKGROUND: To compare efficacy and safety of photorefractive keratectomy (PRK) by cross-cylinder with single methods in medium-high astigmatism. DESIGN: Randomized clinical trial study PARTICIPANTS: Fifty patients with medium-high compound myopic astigmatism were enrolled between September 2007 and September 2008. METHODS: PRK was performed on 100 eyes of 50 patients with compound myopic astigmatism. Each patient underwent PRK by cross-cylinder approach in one eye and single method on the contralateral eye. Vector analysis was used to assess astigmatic results. MAIN OUTCOME MEASURES: Improvement of visual acuity (snelen chart), refraction, aberrometry. RESULTS: Uncorrected visual acuity (UCCA) equal to 20/40 or better after six months, was achieved in 98% of eyes in the cross-cylinder method versus 96% in single method.. Mean preoperative spherical equivalent(SE) was -5.2 ±2.1 D in the cross-cylinder method versus -5.1 ±0.5 D in the single method. At six months, the mean SE was - 0.5±0.4 D and -0.6±0.3 D, respectively. Mean IOS was 0.4±0.3 in the cross-cylinder group and 0.4±0.4 in the single group. Mean postoperative absolute change in total root-mean-square higher order aberrations in the cross-cylinder group and single group were 0.16 pm and 0.17 pm, respectively. Any of the mentioned differences didn't appear to be statistically significant. CONCLUSIONS: Both PRK methods appeared to be safe and effective in correcting medium-high astigmatism. © 2012 The Author. Clinical and Experimental Ophthalmology © 2012 Royal Australian and New Zealand College of Ophthalmologists.

Results of Intraoperative Manual Cyclotorsion Compensation for Myopic Astigmatism in Patients Undergoing Small Incision Lenticule Extraction (SMILE).

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Ganesh, Sri; Brar, Sheetal; Pawar, Archana

2017-08-01

To study the safety, efficacy, and outcomes of manual cyclotorsion compensation in small incision lenticule extraction (SMILE) for myopic astigmatism. Eligible patients with myopia from -1.00 to -10.00 diopters (D) spherical equivalent with a minimum astigmatism of 0.75 D undergoing SMILE were included. Intraoperative cyclotorsion compensation was performed by gently rotating the cone and aligning the 0° to 180° limbal marks with the horizontal axis of the reticule of the right eye piece of the microscope of the femtosecond laser after activating the suction. In this study, 81 left eyes from 81 patients were analyzed for vector analysis of astigmatism. The mean cyclotorsion was 5.64° ± 2.55° (range: 2° to 12°). No significant differences were found for surgically induced astigmatism, difference vector, angle of error (AE), correction index, magnitude of error, index of success (IOS), and flattening index between 2 weeks and 3 months postoperatively (P > .05). The eyes were categorized into low (≤ 1.50 D, n = 37) and high (> 1.50 D, n = 44) cylinder groups. At 3 months, intergroup analysis showed a comparable correction index of 0.97 for the low and 0.93 for the high cylinder groups, suggesting a slight undercorrection of 3% and 7%, respectively (P = .14). However, the AE and IOS were significantly lower in the high compared to the low cylinder group (P = .032 and .024 for AE and IOS, respectively), suggesting better alignment of the treatment in the high cylinder group. However, the mean uncorrected distance visual acuity of both groups was comparable (P = .21), suggesting good visual outcomes in the low cylinder group despite a less favorable IOS. Manual compensation may be a safe, feasible, and effective approach to refine the results of astigmatism with SMILE, especially in higher degrees of cylinders. [J Refract Surg. 2017;33(8):506-512.]. Copyright 2017, SLACK Incorporated.

Visual performance in cataract patients with low levels of postoperative astigmatism: full correction versus spherical equivalent correction

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Lehmann RP

2012-03-01

Full Text Available Robert P Lehmann1, Diane M Houtman21Lehmann Eye Center, Nacogdoches, TX, 2Alcon Research Ltd, Fort Worth, TX, USAPurpose: To evaluate whether visual performance could be improved in pseudophakic subjects by correcting low levels of postoperative astigmatism.Methods: An exploratory, noninterventional study was conducted using subjects who had been implanted with an aspheric intraocular lens and had 0.5–0.75 diopter postoperative astigmatism. Monocular visual performance using full correction was compared with visual performance using spherical equivalent correction. Testing consisted of high- and low-contrast visual acuity, contrast sensitivity, and reading acuity and speed using the Radner Reading Charts.Results: Thirty-eight of 40 subjects completed testing. Visual acuities at three contrast levels (100%, 25%, and 9% were significantly better using full correction than when using spherical equivalent correction (all P < 0.001. For contrast sensitivity testing under photopic, mesopic, and mesopic with glare conditions, only one out of twelve outcomes demonstrated a significant improvement with full correction compared with spherical equivalent correction (at six cycles per degree under mesopic without glare conditions, P = 0.046. Mean reading speed was numerically faster with full correction across all print sizes, reaching statistical significance at logarithm of the reading acuity determination (logRAD 0.2, 0.7, and 1.1 (P , 0.05. Statistically significant differences also favored full correction in logRAD score (P = 0.0376, corrected maximum reading speed (P < 0.001, and logarithm of the minimum angle of resolution/logRAD ratio (P < 0.001.Conclusions: In this study of pseudophakic subjects with low levels of postoperative astigmatism, full correction yielded significantly better reading performance and high- and low-contrast visual acuity than spherical equivalent correction, suggesting that cataractous patients may benefit from surgical

The effects of induced oblique astigmatism on symptoms and reading performance while viewing a computer screen.

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Rosenfield, Mark; Hue, Jennifer E; Huang, Rae R; Bababekova, Yuliya

2012-03-01

Computer vision syndrome (CVS) is a complex of eye and vision problems related to computer use which has been reported in up to 90% of computer users. Ocular symptoms may include asthenopia, accommodative and vergence difficulties and dry eye. Previous studies have reported that uncorrected astigmatism may have a significant impact on symptoms of CVS. However, its effect on task performance is unclear. This study recorded symptoms after a 10 min period of reading from a computer monitor either through the habitual distance refractive correction or with a supplementary -1.00 or -2.00D oblique cylinder added over these lenses in 12 young, visually-normal subjects. Additionally, the distance correction condition was repeated to assess the repeatability of the symptom questionnaire. Subjects' reading speed and accuracy were monitored during the course of the 10 min trial. There was no significant difference in reading rate or the number of errors between the three astigmatic conditions. However, a significant change in symptoms was reported with the median total symptom scores for the 0, 1 and 2D astigmatic conditions being 2.0, 6.5 and 40.0, respectively (p computer operation. Ophthalmic & Physiological Optics © 2011 The College of Optometrists.

Management of moderate and severe corneal astigmatism with AcrySof® toric intraocular lens implantation - Our experience.

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Farooqui, Javed Hussain; Koul, Archana; Dutta, Ranjan; Shroff, Noshir Minoo

2015-01-01

Visual performance following toric intraocular lens implantation for cataract with moderate and severe astigmatism. Cataract services, Shroff Eye Centre, New Delhi, India. Case series. This prospective study included 64 eyes of 40 patients with more than 1.50 dioptre (D) of pre-existing corneal astigmatism undergoing phacoemulsification with implantation of the AcrySof® toric IntraOcular Lens (IOL). The unaided visual acuity (UCVA), best corrected visual acuity (BCVA), residual refractive sphere and refractive cylinders were evaluated. Toric IOL axis and alignment error was measured by slit lamp method and Adobe Photoshop (version 7) method. Patient satisfaction was evaluated using a satisfaction questionnaire at 3 months. The mean residual refractive astigmatism was 0.57 D at the final follow-up of 3 months. Mean alignment error was 3.44 degrees (SD = 2.60) by slit lamp method and 3.88 degrees (SD = 2.86) by Photoshop method. Forty-six (71.9%) eyes showed misalignment of 5 degrees or less, and 60 (93.8%) eyes showed misalignment of 10 degrees or less. The mean log MAR UCVA at 1st post-op day was 0.172 (SD = 0.02), on 7th post-op day was 0.138 (SD = 0.11), and on 30th post-op day was 0.081 (SD = 0.11). The mean log MAR BCVA at three months was -0.04 (SD = 0.76). We believe that implantation of AcrySof® toric IOL is an effective, safe and predictable method to correct high amounts of corneal astigmatism during cataract surgery.

Optimization of nonimaging focusing heliostat in dynamic correction of astigmatism for a wide range of incident angles.

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Chong, Kok-Keong

2010-05-15

To overcome astigmatism has always been a great challenge in designing a heliostat capable of focusing the sunlight on a small receiver throughout the year. In this Letter, a nonimaging focusing heliostat with a dynamic adjustment of facet mirrors in a group manner has been analyzed for optimizing the astigmatic correction in a wide range of incident angles. This what is to the author's knowledge a new heliostat is not only designed to serve the purpose of concentrating sunlight to several hundreds of suns, but also to significantly reduce the variation of the solar flux distribution with the incident angle.

Partial null astigmatism-compensated interferometry for a concave freeform Zernike mirror

Science.gov (United States)

Dou, Yimeng; Yuan, Qun; Gao, Zhishan; Yin, Huimin; Chen, Lu; Yao, Yanxia; Cheng, Jinlong

2018-06-01

Partial null interferometry without using any null optics is proposed to measure a concave freeform Zernike mirror. Oblique incidence on the freeform mirror is used to compensate for astigmatism as the main component in its figure, and to constrain the divergence of the test beam as well. The phase demodulated from the partial nulled interferograms is divided into low-frequency phase and high-frequency phase by Zernike polynomial fitting. The low-frequency surface figure error of the freeform mirror represented by the coefficients of Zernike polynomials is reconstructed from the low-frequency phase, applying the reverse optimization reconstruction technology in the accurate model of the interferometric system. The high-frequency surface figure error of the freeform mirror is retrieved from the high-frequency phase adopting back propagating technology, according to the updated model in which the low-frequency surface figure error has been superimposed on the sag of the freeform mirror. Simulations verified that this method is capable of testing a wide variety of astigmatism-dominated freeform mirrors due to the high dynamic range. The experimental result using our proposed method for a concave freeform Zernike mirror is consistent with the null test result employing the computer-generated hologram.

Two-year results of femtosecond assisted LASIK versus PRK for different severity of astigmatism

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Mohammad Miraftab

2018-03-01

Conclusions: Our results pointed to better two-year results with femto-LASIK in the treatment of different degrees of astigmatism. UDVA improvement was superior with femto-LASIK, but the two methods did not significantly differ in terms of CDVA improvement.

Designing Fresnel microlenses for focusing astigmatic multi-Gaussian beams by using fractional order Fourier transforms

International Nuclear Information System (INIS)

Patino, A; Durand, P-E; Fogret, E; Pellat-Finet, P

2011-01-01

According to a scalar theory of diffraction, light propagation can be expressed by two-dimensional fractional order Fourier transforms. Since the fractional Fourier transform of a chirp function is a Dirac distribution, focusing a light beam is optically achieved by using a diffractive screen whose transmission function is a two-dimensional chirp function. This property is applied to designing Fresnel microlenses, and the orders of the involved Fourier fractional transforms depend on diffraction distances as well as on emitter and receiver radii of curvature. If the emitter is astigmatic (with two principal radii of curvature), the diffraction phenomenon involves two one-dimensional fractional Fourier transforms whose orders are different. This degree of freedom allows us to design microlenses that can focus astigmatic Gaussian beams, as produced by a line-shaped laser diode source.

Effect of arcuate keratomy on decreasing astigmatism in IOL implantation after intracapsular cataract extraction

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Zhong-Yu Xu

2014-07-01

Full Text Available AIM: To study an approach to visual acuity correction after intracapsular cataract extraction by phase-II intraocular lens implantation through the individualized arcuate keratotomy. METHODS: For demonstration, 48 postoperative patients(50 eyesreceiving the intracapsular cataract extraction were gathered up. Each patient received a scleral tunnel major incision along the radial line of the maximum corneal refractive power determined by a cornea curvimeter, and a arcuate keratotomy was made opposite to the major one; through the major incision an iris-claw intraocular lens is implanted. Each patient was measured for their corneal astigmatism and uncorrected visual acuity before and after the surgery.RESULTS: The results suggested the average corneal astigmatism before the surgery and that 3d, 1, 3, 6 and 12mo after the surgery as +3.18±0.68, -1.56±0.73, +0.87±0.51, +1.21±0.70, +1.33±0.68 and +1.48±0.48 respectively. The uncorrected visual acuities 3d, 1, 3, 6 and 12mo after the surgery are 0.5±0.38, 0.56±0.23, 0.55±0.24, 0.52±0.28 and 0.51±0.25 respectively. CONCLUSION: Phase-II intraocular lens implantation witharcuate keratotomy is helpful to improve the postoperative visual acuity and reduce preoperative corneal astigmatism after the intracapsular cataract extraction aphakic eyes, It is also a low-cost surgery, and easy to perform, with minor surgical injuries, particularly available for surgical visual acuity correction of the aphakic eye receiving intracapsular cataract extraction.

Lower- and higher-order aberrations predicted by an optomechanical model of arcuate keratotomy for astigmatism.

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Navarro, Rafael; Palos, Fernando; Lanchares, Elena; Calvo, Begoña; Cristóbal, José A

2009-01-01

To develop a realistic model of the optomechanical behavior of the cornea after curved relaxing incisions to simulate the induced astigmatic change and predict the optical aberrations produced by the incisions. ICMA Consejo Superior de Investigaciones Científicas and Universidad de Zaragoza, Zaragoza, Spain. A 3-dimensional finite element model of the anterior hemisphere of the ocular surface was used. The corneal tissue was modeled as a quasi-incompressible, anisotropic hyperelastic constitutive behavior strongly dependent on the physiological collagen fibril distribution. Similar behaviors were assigned to the limbus and sclera. With this model, some corneal incisions were computer simulated after the Lindstrom nomogram. The resulting geometry of the biomechanical simulation was analyzed in the optical zone, and finite ray tracing was performed to compute refractive power and higher-order aberrations (HOAs). The finite-element simulation provided new geometry of the corneal surfaces, from which elevation topographies were obtained. The surgically induced astigmatism (SIA) of the simulated incisions according to the Lindstrom nomogram was computed by finite ray tracing. However, paraxial computations would yield slightly different results (undercorrection of astigmatism). In addition, arcuate incisions would induce significant amounts of HOAs. Finite-element models, together with finite ray-tracing computations, yielded realistic simulations of the biomechanical and optical changes induced by relaxing incisions. The model reproduced the SIA indicated by the Lindstrom nomogram for the simulated incisions and predicted a significant increase in optical aberrations induced by arcuate keratotomy.

LASIK for myopia and astigmatism using the SCHWIND AMARIS excimer laser: an international multicenter trial.

Science.gov (United States)

Arbelaez, Maria Clara; Aslanides, Ioannis M; Barraquer, Carmen; Carones, Francesco; Feuermannova, Alena; Neuhann, Tobias; Rozsival, Pavel

2010-02-01

To assess the efficacy, predictability, and safety of LASIK for the surgical correction of low to moderate myopia with astigmatism using the SCHWIND AMARIS excimer laser. Six international study sites enrolled 358 eyes with a manifest refraction spherical equivalent (MRSE) from -0.50 to -7.38 diopters (D) (mean sphere: -3.13+/-1.58 D) with up to -5.00 D of astigmatism (mean: -0.69+/-0.67 D). All eyes underwent treatment with the nonwavefront-guided aspheric algorithm of the SCHWIND AMARIS excimer laser. All eyes were targeted for emmetropia. Refractive outcomes and corneal higher order aberrations were analyzed pre- and postoperatively. Visual quality was assessed using photopic and mesopic contrast sensitivity. Six-month postoperative outcomes are reported. At 6 months postoperative, the MRSE for all eyes was -0.21+/-0.20 D, and 96% (343/358) of eyes had MRSE within +/-0.50 D. Uncorrected visual acuity was 20/20 or better in 98% (351/358) of eyes, and no eyes lost 2 or more lines of best spectacle-corrected visual acuity. The total corneal higher order aberrations root-mean-square increased by 0.09 microm, spherical aberration increased by 0.08 microm, and coma increased by 0.04 microm postoperatively. Photopic and mesopic contrast sensitivity did not change 6 months postoperatively. Treatment of myopia with astigmatism using the SCHWIND AMARIS excimer laser is safe, efficacious, predictable, and maintains visual quality.

Management of moderate and severe corneal astigmatism with AcrySof® toric intraocular lens implantation – Our experience

Science.gov (United States)

Farooqui, Javed Hussain; Koul, Archana; Dutta, Ranjan; Shroff, Noshir Minoo

2015-01-01

Purpose Visual performance following toric intraocular lens implantation for cataract with moderate and severe astigmatism. Setting Cataract services, Shroff Eye Centre, New Delhi, India. Design Case series. Method This prospective study included 64 eyes of 40 patients with more than 1.50 dioptre (D) of pre-existing corneal astigmatism undergoing phacoemulsification with implantation of the AcrySof® toric IntraOcular Lens (IOL). The unaided visual acuity (UCVA), best corrected visual acuity (BCVA), residual refractive sphere and refractive cylinders were evaluated. Toric IOL axis and alignment error was measured by slit lamp method and Adobe Photoshop (version 7) method. Patient satisfaction was evaluated using a satisfaction questionnaire at 3 months. Results The mean residual refractive astigmatism was 0.57 D at the final follow-up of 3 months. Mean alignment error was 3.44 degrees (SD = 2.60) by slit lamp method and 3.88 degrees (SD = 2.86) by Photoshop method. Forty-six (71.9%) eyes showed misalignment of 5 degrees or less, and 60 (93.8%) eyes showed misalignment of 10 degrees or less. The mean log MAR UCVA at 1st post-op day was 0.172 (SD = 0.02), on 7th post-op day was 0.138 (SD = 0.11), and on 30th post-op day was 0.081 (SD = 0.11). The mean log MAR BCVA at three months was −0.04 (SD = 0.76). Conclusion We believe that implantation of AcrySof® toric IOL is an effective, safe and predictable method to correct high amounts of corneal astigmatism during cataract surgery. PMID:26586976

Photorefractive keratectomy in the management of postradial keratotomy hyperopia and astigmatism

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Mohammad Ghoreishi

2017-01-01

Full Text Available Background: The aim of this study is to evaluate the results of photorefractive keratectomy (PRK in the management of postoperative hyperopia and astigmatism in patients with history of radial keratotomy (RK. Materials and Methods: This prospective nonrandomized noncomparative interventional case series enrolled consecutive eyes treated with PRK after RK. In cases, in which (1 wavefront (WF scan was undetectable during primary examinations; and/or, (2 WF data were not transferable to the excimer laser device, patients were treated with the tissue-saving (TS mode. Patients with detectable/transferable WF were assigned to WF-guided advanced personalized treatment (APT. Results: Thirty-two and 47 eyes were managed by APT and TS modes, respectively. Pooled analysis of both APT and TS groups showed improvement in uncorrected distant visual acuity and corrected distant visual acuity. The amount of sphere, cylinder, corneal cylinder, spherical equivalent, defocus equivalent, and total aberration showed improvement as well. Conclusion: PRK seems to bring favorable outcome and safety profile in the management of post-RK hyperopia and astigmatism. It is crucial for practitioners to warn their patients about the fact that they may still have progressive refractive instability regardless of their choice on the laser method of vision correction.

Surgically induced astigmatism after 3.0 mm temporal and nasal clear corneal incisions in bilateral cataract surgery

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Je Hwan Yoon

2013-01-01

Full Text Available Aims: To compare the corneal refractive changes induced after 3.0 mm temporal and nasal corneal incisions in bilateral cataract surgery. Materials and Methods: This prospective study comprised a consecutive case series of 60 eyes from 30 patients with bilateral phacoemulsification that were implanted with a 6.0 mm foldable intraocular lens through a 3.0 mm horizontal clear corneal incision (temporal in the right eyes, nasal in the left eyes. The outcome measures were surgically induced astigmatism (SIA and uncorrected visual acuity (UCVA 1 and 3 months, post-operatively. Results: At 1 month, the mean SIA was 0.81 diopter (D for the temporal incisions and 0.92 D for nasal incisions (P = 0.139. At 3 months, the mean SIA were 0.53 D for temporal incisions and 0.62 D for nasal incisions (P = 0.309. The UCVA was similar in the 2 incision groups before surgery, and at 1 and 3 months post-operatively. Conclusion: After bilateral cataract surgery using 3.0 mm temporal and nasal horizontal corneal incisions, the induced corneal astigmatic change was similar in both incision groups. Especially in Asian eyes, both temporal and nasal incisions (3.0 mm or less would be favorable for astigmatism-neutral cataract surgery.

Single-step transepithelial photorefractive keratectomy in myopia and astigmatism: 18-month follow-up.

Science.gov (United States)

Adib-Moghaddam, Soheil; Soleyman-Jahi, Saeed; Salmanian, Bahram; Omidvari, Amir-Houshang; Adili-Aghdam, Fatemeh; Noorizadeh, Farsad; Eslani, Medi

2016-11-01

To evaluate the long-term quantitative and qualitative optical outcomes of 1-step transepithelial photorefractive keratectomy (PRK) to correct myopia and astigmatism. Bina Eye Hospital, Tehran, Iran. Prospective interventional case series. Eyes with myopia with or without astigmatism were evaluated. One-step transepithelial PRK was performed with an aberration-free aspheric optimized profile and the Amaris 500 laser. Eighteen-month follow-up results for refraction, visual acuities, vector analysis, higher-order aberrations, contrast sensitivity, postoperative pain, and haze grade were assessed. The study enrolled 146 eyes (74 patients). At the end of follow-up, 93.84% of eyes had an uncorrected distance visual acuity of 20/20 or better and 97.94% of eyes were within ±0.5 diopter of the targeted spherical refraction. On vector analysis, the mean correction index value was close to 1 and the mean index of success and magnitude of error values were close to 0. The achieved correction vector was on an axis counterclockwise to the axis of the intended correction. Photopic and mesopic contrast sensitivities and ocular and corneal spherical, cylindrical, and corneal coma aberrations significantly improved (all P < .001). A slight amount of trefoil aberration was induced (P < .001, ocular aberration; P < .01, corneal aberration). No eye lost more than 1 line of corrected distance visual acuity. No eye had a haze grade of 2+ degrees or higher throughout the follow-up. Eighteen-month results indicate the efficacy and safety of transepithelial PRK to correct myopia and astigmatism. It improved refraction and quality of vision. None of the authors has a financial or proprietary interest in any material or method mentioned. Copyright © 2016 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Numerical Methods Are Feasible for Assessing Surgical Techniques: Application to Astigmatic Keratotomy

Energy Technology Data Exchange (ETDEWEB)

Ariza-Gracia, M.A.; Ortilles, A.; Cristobal, J.A.; Rodriguez, J.F.; Calvo, B.

2016-07-01

The present study proposes an experimental-numerical protocol whose novelty relies on using both the inflation and the indentation experiments simultaneously to obtain a set of material parameters which accounts for both deformation modes of the cornea: the physiological (biaxial tension) and the non-physiological (bending). The experimental protocol characterizes the corneal geometry and the mechanical response of the cornea when subjected to the experimental tests using an animal model (New Zealand rabbit's cornea). The numerical protocol reproduces the experimental tests by means of an inverse finite element methodology to obtain the set of material properties that minimizes both mechanical responses at the same time. To validate the methodology, an Astigmatic Keratotomy refractive surgery is performed on 4 New Zealand rabbit corneas. The pre and post-surgical topographies of the anterior corneal surface were measured using a MODI topographer (CSO, Italy) to control the total change in astigmatism. Afterwards, the surgery is numerically reproduced to predict the overall change of the cornea. Results showed an acceptable numerical prediction, close to the average experimental correction, validating the material parameters obtained with the proposed protocol. (Author)

Induced Higher-order aberrations after Laser In Situ Keratomileusis (LASIK) Performed with Wavefront-Guided IntraLase Femtosecond Laser in moderate to high Astigmatism.

Science.gov (United States)

Al-Zeraid, Ferial M; Osuagwu, Uchechukwu L

2016-03-22

Wavefront-guided Laser-assisted in situ keratomileusis (LASIK) is a widespread and effective surgical treatment for myopia and astigmatic correction but whether it induces higher-order aberrations remains controversial. The study was designed to evaluate the changes in higher-order aberrations after wavefront-guided ablation with IntraLase femtosecond laser in moderate to high astigmatism. Twenty-three eyes of 15 patients with moderate to high astigmatism (mean cylinder, -3.22 ± 0.59 dioptres) aged between 19 and 35 years (mean age, 25.6 ± 4.9 years) were included in this prospective study. Subjects with cylinder ≥ 1.5 and ≤2.75 D were classified as moderate astigmatism while high astigmatism was ≥3.00 D. All patients underwent a femtosecond laser-enabled (150-kHz IntraLase iFS; Abbott Medical Optics Inc) wavefront-guided ablation. Uncorrected (UDVA), corrected (CDVA) distance visual acuity in logMAR, keratometry, central corneal thickness (CCT) and higher-order aberrations (HOAs) over a 6 mm pupil, were assessed before and 6 months, postoperatively. The relationship between postoperative change in HOA and preoperative mean spherical equivalent refraction, mean astigmatism, and postoperative CCT were tested. At the last follow-up, the mean UDVA was increased (P < 0.0001) but CDVA remained unchanged (P = 0.48) and no eyes lost ≥2 lines of CDVA. Mean spherical equivalent refraction was reduced (P < 0.0001) and was within ±0.50 D range in 61% of eyes. The average corneal curvature was flatter by 4 D and CCT was reduced by 83 μm (P < 0.0001, for all), postoperatively. Coma aberrations remained unchanged (P = 0.07) while the change in trefoil (P = 0.047) postoperatively, was not clinically significant. The 4th order HOAs (spherical aberration and secondary astigmatism) and the HOA root mean square (RMS) increased from -0.18 ± 0.07 μm, 0.04 ± 0.03 μm and 0.47 ± 0.11 μm, preoperatively, to 0.33 ± 0

Implantation of a Multifocal Toric Intraocular Lens after Radial Keratotomy and Cross-Linking with Hyperopia and Astigmatism Residues: A Case Report

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Raffaele Nuzzi

2017-08-01

Full Text Available Radial keratotomy is a refractive surgical technique, widely used in the 80s and early 90s to correct myopia and astigmatism, but now overcome by more recent laser techniques. Important consequences, often in patients with more than 45 years of age, are progressive hyperopic shift and/or an increase in corneal astigmatism, whose main cause seems to be an increase in the curvature radius of the central portion of the cornea. This seems to be due to radial keratotomy incisions – with the consequent need for cross-linking – intraocular pressure, and corneal biomechanical parameters. The authors propose phacoemulsification with a customized multifocal toric intraocular lens implantation to correct the induced shift and hyperopic astigmatism. A decent postoperative visual acuity was observed with good patient satisfaction. A specific protocol must be applied to optimize the correct diagnosis, presurgical evaluation and postsurgical outcomes that are to be maintained over time, without regressions.

Anti-drift and auto-alignment mechanism for an astigmatic atomic force microscope system based on a digital versatile disk optical head.

Science.gov (United States)

Hwu, E-T; Illers, H; Wang, W-M; Hwang, I-S; Jusko, L; Danzebrink, H-U

2012-01-01

In this work, an anti-drift and auto-alignment mechanism is applied to an astigmatic detection system (ADS)-based atomic force microscope (AFM) for drift compensation and cantilever alignment. The optical path of the ADS adopts a commercial digital versatile disc (DVD) optical head using the astigmatic focus error signal. The ADS-based astigmatic AFM is lightweight, compact size, low priced, and easy to use. Furthermore, the optical head is capable of measuring sub-atomic displacements of high-frequency AFM probes with a sub-micron laser spot (~570 nm, FWHM) and a high-working bandwidth (80 MHz). Nevertheless, conventional DVD optical heads suffer from signal drift problems. In a previous setup, signal drifts of even thousands of nanometers had been measured. With the anti-drift and auto-alignment mechanism, the signal drift is compensated by actuating a voice coil motor of the DVD optical head. A nearly zero signal drift was achieved. Additional benefits of this mechanism are automatic cantilever alignment and simplified design.

CLINICAL STUDY TO EVALUATE THE VISUAL OUTCOME AND PATIENT COMFORT IN LASIK AND PHOTOREFRACTIVE KERATECTOMY IN LOW-TO-MODERATE MYOPIC ASTIGMATISM PATIENTS

OpenAIRE

Ashok Kumar P; Ananda Babu M; Radha Priyadharshini R; Jeevitha A

2017-01-01

BACKGROUND To evaluate visual outcomes following LASIK and Photorefractive Keratectomy (PRK) in low-to-moderate myopia and/or myopic astigmatism in age and refractive error matched eyes. MATERIALS AND METHODS Of a total 30 patients aged ≥21 years, 20 (40 eyes) underwent LASIK and 10 (20 eyes) underwent PRK for low-to-moderate myopia or myopic astigmatism. LASIK was performed with the Alcon wave light 500 and PRK with the alcohol application for epithelial removal. All abl...

Clinical Outcomes of SMILE With a Triple Centration Technique and Corneal Wavefront-Guided Transepithelial PRK in High Astigmatism.

Science.gov (United States)

Jun, Ikhyun; Kang, David Sung Yong; Reinstein, Dan Z; Arba-Mosquera, Samuel; Archer, Timothy J; Seo, Kyoung Yul; Kim, Tae-Im

2018-03-01

To comparatively investigate the clinical outcomes, vector parameters, and corneal aberrations of small incision lenticule extraction (SMILE) with a triple centration technique and corneal wavefront-guided transepithelial photorefractive keratectomy (PRK) for the correction of high astigmatism. This retrospective, comparative case series study included 89 eyes (89 patients) that received treatment for myopia with high astigmatism (≥ 2.50 diopters) using SMILE with a triple centration technique (SMILE group; 45 eyes) and corneal wavefront-guided transepithelial PRK (transepithelial PRK group; 44 eyes). Visual acuity measurement, manifest refraction, slit-lamp examination, autokeratometry, corneal topography, and evaluation of corneal wavefront aberration were performed preoperatively and at 1, 3, and 6 months after surgery. The safety, efficacy, vector parameters, and corneal aberrations at 6 months after surgery were compared between the two groups. At 6 months after surgery, the transepithelial PRK and SMILE groups exhibited comparable mean uncorrected distance visual acuities (-0.06 ± 0.07 and -0.05 ± 0.07 logMAR, respectively), safety, efficacy, and predictability of refractive and visual outcomes. There was a slight but statistically significant difference in the correction index between the transepithelial PRK and SMILE groups (0.96 ± 0.11 and 0.91 ± 0.10, respectively). Whereas the transepithelial PRK group exhibited increased corneal spherical aberration and significantly reduced corneal coma and trefoil, no changes in aberrometric values were noted in the SMILE group. Both SMILE with a triple centration technique and corneal wavefront-guided transepithelial PRK are effective and provide predictable outcomes for the correction of high myopic astigmatism, although slight undercorrection was observed in the SMILE group. The triple centration technique was helpful in astigmatism correction by SMILE. [J Refract Surg. 2018;34(3):156-163.]. Copyright 2018

Astigmatism treatment during phacoemulsification: a review of current surgical strategies and their rationale

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Giuliano de Oliveira Freitas

2013-12-01

Full Text Available Preexisting corneal astigmatism, present at the time of cataract surgery, is reviewed in detail throughout this article on its most important aspects such as occurrence rates, clinical relevance and current treatment options. Special emphasis is given to the latter aspect. Each method's rationale, advantage and limitation ishigh lightened. Comparisons between treatment options, whenever possible, are also provided.

Measuring the 3D motion of particles in microchannel acoustophoresis using astigmatism particle tracking velocimetry

DEFF Research Database (Denmark)

Augustsson, P.; Barnkob, Rune; Bruus, Henrik

2012-01-01

We introduce full three-dimensional tracking of particles in an acoustophoresis microchannel using Astigmatism Particle Tracking Velocimetry (APTV) [1]. For the first time the interaction between acoustic streaming and the primary acoustic radiation force in microchannel acoustophoresis are exami...... relative to the influence from the acoustic radiation force. The current study opens the route to optimized acoustophoretic system design and operation to enable manipulation of small biological components such as spores, bacteria and viruses.......We introduce full three-dimensional tracking of particles in an acoustophoresis microchannel using Astigmatism Particle Tracking Velocimetry (APTV) [1]. For the first time the interaction between acoustic streaming and the primary acoustic radiation force in microchannel acoustophoresis...... are examined in three dimensions. We have quantified the velocity of particles driven by the primary acoustic radiation force and acoustic streaming, respectively, using 0.5-μm and 5-μm particles. Increased ultrasound frequency and lowered viscosity of the medium reduced the influence of acoustic streaming...

Wavefront-guided laser-assisted subepithelial keratectomy in low myopia, myopic astigmatism and high myopia

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Seyed Javad Hashemian

2015-02-01

Full Text Available AIM: To compare the safety, efficacy, predictability, stability and complications of wavefront-guided laser-assisted subepithelial keratectomy(LASEKin low myopia, myopic astigmatism and high myopia correction.METHODS: A retrospective analysis of 416 eyes were assigned to 3 groups: 159 eyes with low myopia(LMand mean refractive spherical equivalent(MRSEof -3.68±1.33 dioptre(D; 161 eyes with myopic astigmatism(MAand MRSE of -5.99±2.24D and mean cylinder of 2.41±1.07D; and 96 eyes with high myopia(HMand MRSE of -7.41±0.80D. After an epithelial flap creation, a wavefront-based excimer laser ablation was performed. Safety, efficacy, predictability and stability were evaluated at day 10, 2, 6 and 12mo postoperatively.RESULTS:At 12mo, the MRSE was -0.36±0.31D in LM group, 0.15±0.41D in MA group and 0.58±0.68D in HM group. The uncorrected visual acuity(UCVAwas 20/20 in 90.60% of patients in LM group, 78.90% in MA group and 67% in HM group. Efficacy indices were 0.98, 1.04 and 0.92 in LM, MA and HM groups, respectively. Safety indices were 1.00, 1.07 and 1.05 in LM, MA and HM respectively. Five eyes(3.1%in the LM group gained 1 line. Forty-four eyes(27.3%in MA gained 1-3 lines and eighteen eyes(19.2%of HM group gained 1-2 lines of BSCVA. Only 2 eyes in LM group developed corneal haze. There were not statistically significant differences in efficacy and safety indices amongst three groups. CONCLUSION: Wavefront-guided LASEK is an effective and safe procedure for the treatment of LM, MA, and HM.although in myopic astigmatism the predictability, efficacy and safety indices had been better.

Application of the fractional Fourier transformation to digital holography recorded by an elliptical, astigmatic Gaussian beam

NARCIS (Netherlands)

Nicolas, F.; Coëtmellec, S.; Brunel, M.; Allano, D.; Lebrun, D.; Janssen, A.J.E.M.

2005-01-01

The authors have studied the diffraction pattern produced by a particle field illuminated by an elliptic and astigmatic Gaussian beam. They demonstrate that the bidimensional fractional Fourier transformation is a mathematically suitable tool to analyse the diffraction pattern generated not only by

INTRAOCULAR CORRECTION OF PRESBYOPIA BY MONOVISION IN PATIENTS WITH CATARACT AND CORNEAL ASTIGMATISM

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E. I. Belikova

2017-01-01

Full Text Available Purpose: To evaluate the results of intraocular correction of presbyopia by monovision in patients with cataract and primary corneal astigmatism and conduct a comparative analysis of these outcomes with the results of binocular multifocal IOLs implantation. Patients and methods. There were 21 patients with bilateral cataract surgery performed using toric monofocal intraocular lenses (monovision group in the study. The indications for the operation were: 1 primary corneal astigmatism ≥ 1.0D in patients with cataract, 2 inability to conduct excimer laser correction. Reduction of spectacle dependence by monovision was discussed during preoperative conversation. The age of patients range from 32 to 65 years. Target refraction: Emetronopia on the dominant eye (DG and myopia at 1.0–2.0 D in the non-dominant eye (NDG. Evaluation included measurement of uncorrected visual acuity, refraction, stereopsis, contrast sensitivity and patient satisfaction. The results were compared with the outcomes of binocular multifocal Iols implantation in 22 patients (44 eyes. Results. The spherical component decreased from 3.39±2.63D to 0.34±0.24D, cylinder decreased from 3.05±1.47D to 0.44±0,35D (P <0.01 in the monovision group three months after surgery . The deviation from target refraction was 0.30±0.35D. The mean difference between postoperative refraction on the two eyes was 1.92±0.57D. Postoperative corrected visual acuity significantly exceeded preoperative parameters. In 18 patients (88% the stereoscopic visual acuity did not exceed 60 seconds and corresponded to the age norm, in 3 patients (12% it was at the level of 80–100 arc seconds. In patients with multifocal IOLs, the stereovision values were identical (Ferrer-Blasco T. et al, 2008. Conclusion. The monovision is an effective method of reducing dependence on additional correction in patients with cataract and corneal astigmatism. Refractive outcomes, binocular visual acuity, predictability and

Analysis of the Ocular Refractive State in Fighting Bulls: Astigmatism Prevalence

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Juan M. Bueno

2017-01-01

Full Text Available The purpose of this study was to describe the ocular refractive state (ORS of fighting bulls. The study consisted of 90 ophthalmological healthy animals (85 in post-mortem and 5 in living conditions, resp.. The ORS of the eyes (2 per animal was determined using streak retinoscopy. In vivo animals were assessed at a fighting bull farm facility. Post-mortem measurements were carried out at a local arena. The ORS along the horizontal meridian ranged between −1.00 and +2.50 diopters (D, with a mean of +0.66±0.85 D in post-mortem animals. Values for in vivo conditions were similar (+0.75±0.46 D. Left and right eyes were highly correlated in both sets (p<0.001. A fairly good correlation was also observed when comparing living and post-mortem eyes in the same animals. Anisometropia ≥ 1.00 D was diagnosed in 3 animals. Astigmatism (≥+0.5 D was detected in 93% of the eyes. To our knowledge, the ORS of the fighting bull has been reported for the first time. Although values vary among individuals, all eyes presented a marked astigmatism. Whereas the horizontal meridian was slightly hyperopic, the vertical meridian was always closer to emmetropia. These results represent a starting point to understand the ocular optics of this kind of animals, which might benefit the selection of animals at the farm before being sent to the bullfighting arena.

Genome-wide meta-analysis of five asian cohorts identifies pdgfra as a susceptibility locus for corneal astigmatism

NARCIS (Netherlands)

Q. Fan (Qiao); X. Zhou (Xin); C.C. Khor; C.-Y. Cheng; L.-K. Goh; X. Sim (Xueling); W.-T. Tay; Y.-J. Li; T.-H. OngRick; C. Suo (Chen); B.K. Cornes (Belinda); M.K. Ikram (Kamran); K.S. Chia (Kee Seng); M. Seielstad (Mark); J. Liu (Jianjun); E.N. Vithana (Eranga); T.L. Young (Terri); E.S. Tai (Shyong); T.Y. Wong (Tien Yin); Y.Y. Teo (Yik Ying); S-M. Saw (Seang-Mei); T. Aung (Tin)

2011-01-01

textabstractCorneal astigmatism refers to refractive abnormalities and irregularities in the curvature of the cornea, and this interferes with light being accurately focused at a single point in the eye. This ametropic condition is highly prevalent, influences visual acuity, and is a highly

Topography-guided hyperopic and hyperopic astigmatism femtosecond laser-assisted LASIK: long-term experience with the 400 Hz eye-Q excimer platform

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Kanellopoulos AJ

2012-06-01

Full Text Available Anastasios John KanellopoulosDepartment of Ophthalmology, New York University Medical School, New York, NY, and LaserVision.gr Eye Institute, Athens, GreeceBackground: The purpose of this study was to evaluate the safety and efficacy of topography-guided ablation using the WaveLight 400 Hz excimer laser in laser-assisted in situ keratomileusis (LASIK for hyperopia and/or hyperopic astigmatism.Methods: We prospectively evaluated 208 consecutive LASIK cases for hyperopia with or without astigmatism using the topography-guided platform of the 400 Hz Eye-Q excimer system. The mean preoperative sphere value was +3.04 ± 1.75 (range 0.75–7.25 diopters (D and the mean cylinder value was –1.24 ± 1.41 (–4.75–0 D. Flaps were created either with Intralase FS60 (AMO, Irvine, CA or FS200 (Alcon, Fort Worth, TX femtosecond lasers. Parameters evaluated included age, preoperative and postoperative refractive error, uncorrected distance visual acuity, corrected distance visual acuity, flap diameter and thickness, topographic changes, higher order aberration changes, and low contrast sensitivity. These measurements were repeated postoperatively at regular intervals for at least 24 months.Results: Two hundred and two eyes were available for follow-up at 24 months. Uncorrected distance visual acuity improved from 5.5/10 to 9.2/10. At 24 (8–37 months, 75.5% of the eyes were in the ±0.50 D range and 94.4% were in the ±1.00 D range of the refractive goal. Postoperatively, the mean sphere value was –0.39 ± 0.3 and the cylinder value was –0.35 ± 0.25. Topographic evidence showed that ablation was made in the visual axis and not in the center of the cornea, thus correlating with the angle kappa. No significant complications were encountered in this small group of patients.Conclusion: Hyperopic LASIK utilizing the topography-guided platform of the 400 Hz Eye-Q Allegretto excimer and a femtosecond laser flap appears to be safe and effective for

Safety, efficacy, and predictability of laser in situ keratomileusis to correct myopia or myopic astigmatism with a 750 Hz scanning-spot laser system.

Science.gov (United States)

Tomita, Minoru; Watabe, Miyuki; Yukawa, Satoshi; Nakamura, Nobuo; Nakamura, Tadayuki; Magnago, Thomas

2014-02-01

To evaluate the clinical outcomes of laser in situ keratomileusis (LASIK) to correct myopia or myopic astigmatism using the Amaris 750S 750 Hz excimer laser. Private LASIK center, Tokyo, Japan. Case series. Patients with myopia or myopic astigmatism (spherical equivalent -0.50 to -11.63 diopters [D]), a corrected distance visual acuity (CDVA) of 20/20 or better, and an estimated residual bed thickness of 300 μm or more had LASIK using the aspheric aberration-free ablation profile of the 750 Hz scanning-spot laser and the Femto LDV Crystal Line femtosecond laser for flap creation. Study parameters included uncorrected distance visual acuity (UDVA), CDVA, manifest refraction, astigmatism, and higher-order aberrations (HOAs). The study included 1280 eyes (685 patients). At 3 months, 96.6% of eyes had a UDVA of 20/20 or better and 99.1% had 20/32 or better; 94.1% of eyes were within ± 0.50 D of the intended correction and 98.9% were within ± 1.00 D; 89.7% of eyes had no residual cylinder and 96.0% had a postoperative astigmatism of less than 0.50 D. All eyes had a postoperative CDVA of 20/20 or better. The HOAs increased postoperatively (PLaser in situ keratomileusis with the 750 Hz scanning-spot laser was safe, effective, and predictable. No specific clinical side effects that might be associated with a high repetition rate occurred. Mr. Magnago is an employee of Schwind eye-tech-solutions GmbH. No other author has a financial or proprietary interest in any material or method mentioned. Copyright © 2013 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Analysis of focusing error signals by differential astigmatic method under off-center tracking in the land-groove-type optical disk

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Shinoda, Masahisa; Nakatani, Hidehiko

2015-04-01

We theoretically calculate the behavior of the focusing error signal in the land-groove-type optical disk when the objective lens traverses on out of the radius of the optical disk. The differential astigmatic method is employed instead of the conventional astigmatic method for generating the focusing error signals. The signal behaviors are compared and analyzed in terms of the gain difference of the slope sensitivity of the focusing error signals from the land and the groove. In our calculation, the format of digital versatile disc-random access memory (DVD-RAM) is adopted as the land-groove-type optical disk model, and advantageous conditions for suppressing the gain difference are investigated. The calculation method and results described in this paper will be reflected in the next generation land-groove-type optical disks.

Computation of misalignment and primary mirror astigmatism figure error of two-mirror telescopes

Science.gov (United States)

Gu, Zhiyuan; Wang, Yang; Ju, Guohao; Yan, Changxiang

2018-01-01

Active optics usually uses the computation models based on numerical methods to correct misalignments and figure errors at present. These methods can hardly lead to any insight into the aberration field dependencies that arise in the presence of the misalignments. An analytical alignment model based on third-order nodal aberration theory is presented for this problem, which can be utilized to compute the primary mirror astigmatic figure error and misalignments for two-mirror telescopes. Alignment simulations are conducted for an R-C telescope based on this analytical alignment model. It is shown that in the absence of wavefront measurement errors, wavefront measurements at only two field points are enough, and the correction process can be completed with only one alignment action. In the presence of wavefront measurement errors, increasing the number of field points for wavefront measurements can enhance the robustness of the alignment model. Monte Carlo simulation shows that, when -2 mm ≤ linear misalignment ≤ 2 mm, -0.1 deg ≤ angular misalignment ≤ 0.1 deg, and -0.2 λ ≤ astigmatism figure error (expressed as fringe Zernike coefficients C5 / C6, λ = 632.8 nm) ≤0.2 λ, the misaligned systems can be corrected to be close to nominal state without wavefront testing error. In addition, the root mean square deviation of RMS wavefront error of all the misaligned samples after being corrected is linearly related to wavefront testing error.

Single-Step Transepithelial PRK vs Alcohol-Assisted PRK in Myopia and Compound Myopic Astigmatism Correction

OpenAIRE

Kaluzny, Bartlomiej J.; Cieslinska, Iwona; Mosquera, Samuel A.; Verma, Shwetabh

2016-01-01

Abstract Transepithelial photorefractive keratectomy (tPRK), where both the epithelium and stroma are removed in a single-step, is a relatively new procedure of laser refractive error correction. This study compares the 3-month results of myopia and compound myopic astigmatism correction by tPRK or conventional alcohol-assisted PRK (aaPRK). This prospective, nonrandomized, case?control study recruited 148 consecutive patients; 93 underwent tPRK (173 eyes) and 55 aaPRK (103 eyes). Refractive r...

Refractive lenticule extraction (ReLEx through a small incision (SMILE for correction of myopia and myopic astigmatism: current perspectives

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Ağca A

2016-10-01

Full Text Available Alper Ağca,1 Ahmet Demirok,2 Yusuf Yıldırım,1 Ali Demircan,1 Dilek Yaşa,1 Ceren Yeşilkaya,1 İrfan Perente,1 Muhittin Taşkapılı1 1Beyoğlu Eye Research and Training Hospital, 2Department of Ophthalmology, Istanbul Medeniyet University, Istanbul, Turkey Abstract: Small-incision lenticule extraction (SMILE is an alternative to laser-assisted in situ keratomileusis (LASIK and photorefractive keratectomy (PRK for the correction of myopia and myopic astigmatism. SMILE can be performed for the treatment of myopia ≤-12 D and astigmatism ≤5 D. The technology is currently only available in the VisuMax femtosecond laser platform. It offers several advantages over LASIK and PRK; however, hyperopia treatment, topography-guided treatment, and cyclotorsion control are not available in the current platform. The working principles, potential advantages, and disadvantages are discussed in this review. Keywords: SMILE, small-incision lenticule extraction, femtosecond laser, laser in situ keratomileusis, corneal biomechanics

Combined special capsular tension ring and toric IOL implantation for management of post-DALK high regular astigmatism with subluxated traumatic cataract

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Asim Kumar Kandar

2014-01-01

Full Text Available We report a case of 18-year-old male who has undergone phacoemulsification with implantation of toric IOL (AcrySof IQ SN6AT9 after fixation of lens capsule with Cionni′s capsular tension ring (CTR for subluxated traumatic cataract with high astigmatism after deep anterior lamellar keratoplasty (DALK. He underwent right eye DALK for advanced keratoconus four years earlier. He had history of trauma one year later with displaced clear crystalline lens into  anterior chamber and graft dehiscence, which was repaired successfully. The graft survived, but patient developed cataract with subluxated lens, for which phacoemulsification with implantation of toric IOL was done. Serial  topography showed regular corneal astigmatism of -5.50 diopter (K 1 42.75 D @130°, K 2 48.25 D @40°. At 10-month follow-up, the patient has BCVA 20/30 with + 0.75 DS/- 1.75 DC @ 110°. The capsular bag is quite stable with well-centered IOL. Combination of Cionni′s ring with toric IOL could be a good option to manage such complex cases.

Combined special capsular tension ring and toric IOL implantation for management of post-DALK high regular astigmatism with subluxated traumatic cataract.

Science.gov (United States)

Kandar, Asim Kumar

2014-07-01

We report a case of 18-year-old male who has undergone phacoemulsification with implantation of toric IOL (AcrySof IQ SN6AT9) after fixation of lens capsule with Cionni's capsular tension ring (CTR) for subluxated traumatic cataract with high astigmatism after deep anterior lamellar keratoplasty (DALK). He underwent right eye DALK for advanced keratoconus four years earlier. He had history of trauma one year later with displaced clear crystalline lens into  anterior chamber and graft dehiscence, which was repaired successfully. The graft survived, but patient developed cataract with subluxated lens, for which phacoemulsification with implantation of toric IOL was done. Serial  topography showed regular corneal astigmatism of -5.50 diopter (K 1 42.75 D @130°, K 2 48.25 D @40°). At 10-month follow-up, the patient has BCVA 20/30 with + 0.75 DS/- 1.75 DC @ 110°. The capsular bag is quite stable with well-centered IOL. Combination of Cionni's ring with toric IOL could be a good option to manage such complex cases.

Prevalência do astigmatismo e distribuição de seu eixo em pacientes de um serviço oftalmológico privado Prevalence of astigmatism and its axis in an ophthalmology private clinic

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Tatiana Rocha Rayes

2007-12-01

Full Text Available OBJETIVO: Verificar a prevalência do astigmatismo e a variação de seu eixo nas várias faixas etárias (2-99 anos em uma população de uma clínica oftalmológica privada na cidade de Florianópolis, Santa Catarina, Brasil. MÉTODOS: Foi realizado um estudo retrospectivo, descritivo, transversal com base na análise de prontuários. Foi considerado astigmatismo uma diferença entre o maior e menor meridiano da córnea de -0,50 dioptrias(D ou mais. Quanto ao eixo, consideramos: astigmatismo a favor da regra: entre 160º e 20º ; astigmatismo oblíquo: entre 21º e 69º e entre 111º e 159º ; astigmatismo contra a regra: entre 70º e 110º . Os dados apresentados e analisados se referem à refração efetivamente prescrita para o paciente. RESULTADOS: Foram encontrados 20.866 olhos astigmatas (47,6% - Intervalo de Confiança IC 95% - 47,1-48. O eixo do astigmatismo se apresentou a favor da regra em 9574 olhos (45,9% IC 95% 45,2-46,6, oblíquo em 3893 olhos (18,7% IC 95% 18,1-19,2, e contra a regra em 7399 olhos (35,5% IC 95% 34,8-36,1. Verificou-se que a distribuição do astigmatismo oblíquo permanece linear no avançar da idade, enquanto há uma inversão do eixo do cilindro, de a favor para contra a regra com o tempo. CONCLUSÃO: Ficou bem evidenciada neste trabalho a marcante mudança do eixo do astigmatismo com o avançar da idade. Não encontramos relação entre o grau das ametropias e o eixo do astigmatismo.PURPOSE: to determine the prevalence of astigmatism and the change of the axis according to the age in an ophthalmology private clinic population in the city of Florianópolis, Santa Catarina, Brazil. METHODS: A retrospective, descriptive, cross-sectional study was carried out based on the analyses of medical files. Astigmatism was classified as a cylindrical equivalent <-0,5 diopter (D. Astigmatism with the rule was defined as 160° to 20° , oblique astigmatism as 21° to 69° and 111° to 159° , and astigmatism against the

A comparison of Lea Symbol vs ETDRS letter distance visual acuity in a population of young children with a high prevalence of astigmatism.

Science.gov (United States)

Dobson, Velma; Clifford-Donaldson, Candice E; Miller, Joseph M; Garvey, Katherine A; Harvey, Erin M

2009-06-01

To compare visual acuity results obtained by use of the Lea Symbols chart with results obtained with Early Treatment Diabetic Retinopathy Study (ETDRS) charts in young children who are members of a population with a high prevalence of astigmatism. Subjects were 438 children ages 5 through 7 years who were enrolled in kindergarten or first grade on the Tohono O'odham Reservation: 241 (55%) had astigmatism >or=1.00 D in one or both eyes (range, 0.00-6.75 D). While wearing best correction, each child had right eye visual acuity tested with the 62 cm by 65 cm Lea Symbols chart at 3 m and with the 62 cm by 65 cm ETDRS chart at 4 m. Visual acuity was scored as the smallest optotype size at which the child correctly identified 3 of a maximum of 5 optotypes. ETDRS visual acuity also was scored based on the total number of letters that the child correctly identified. Correlation between Lea Symbols visual acuity and ETDRS visual acuity was 0.78 (p < 0.001). Mean Lea Symbols visual acuity was one-half line (0.04-0.06 logMAR) better than mean ETDRS visual acuity (p < 0.001). The difference between Lea Symbols and ETDRS visual acuity was not correlated with the mean of the Lea Symbols and ETDRS visual acuity scores, which ranged from -0.3 logMAR (20/10) to 0.74 logMAR (20/110). In this population of young children, in whom the primary source of reduced visual acuity is astigmatism-related amblyopia, the Lea Symbols chart produced visual acuity scores that were about 0.5 line better than visual acuity scores obtained with ETDRS charts.

Safety, Efficacy, Predictability and Stability Indices of Photorefractive Keratectomy for Correction of Myopic Astigmatism with Plano-Scan and Tissue-Saving Algorithms

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Mehrdad Mohammadpour

2013-10-01

Full Text Available Purpose: To assess the safety, efficacy and predictability of photorefractive keratectomy (PRK [Tissue-saving (TS versus Plano-scan (PS ablation algorithms] of Technolas 217z excimer laser for correction of myopic astigmatismMethods: In this retrospective study one hundred and seventy eyes of 85 patients (107 eyes (62.9% with PS and 63 eyes (37.1% with TS algorithm were included. TS algorithm was applied for those with central corneal thickness less than 500 µm or estimated residual stromal thickness less than 420 µm. Mitomycin C (MMC was applied for 120 eyes (70.6%; in case of an ablation depth more than 60 μm and/or astigmatic correction more than one diopter (D. Mean sphere, cylinder, spherical equivalent (SE refraction, uncorrected visual acuity (UCVA, best corrected visual acuity (BCVA were measured preoperatively, and 4 weeks,12 weeks and 24 weeks postoperatively.Results: One, three and six months postoperatively, 60%, 92.9%, 97.5% of eyes had UCVA of 20/20 or better, respectively. Mean preoperative and 1, 3, 6 months postoperative SE were -3.48±1.28 D (-1.00 to -8.75, -0.08±0.62D, -0.02±0.57 and -0.004± 0.29, respectively. And also, 87.6%, 94.1% and 100% were within ±1.0 D of emmetropia and 68.2, 75.3, 95% were within ±0.5 of emmetropia. The safety and efficacy indices were 0.99 and 0.99 at 12 weeks and 1.009 and 0.99 at 24 weeks, respectively. There was no clinically or statistically significant difference between the outcomes of PS or TS algorithms or between those with or without MMC in either group in terms of safety, efficacy, predictability or stability. Dividing the eyes with subjective SE≤4 D and SE≥4 D postoperatively, there was no significant difference between the predictability of the two groups. There was no intra- or postoperative complication.Conclusion: Outcomes of PRK for correction of myopic astigmatism showed great promise with both PS and TS algorithms.

Extended wavelet transformation to digital holographic reconstruction: application to the elliptical, astigmatic Gaussian beams.

Science.gov (United States)

Remacha, Clément; Coëtmellec, Sébastien; Brunel, Marc; Lebrun, Denis

2013-02-01

Wavelet analysis provides an efficient tool in numerous signal processing problems and has been implemented in optical processing techniques, such as in-line holography. This paper proposes an improvement of this tool for the case of an elliptical, astigmatic Gaussian (AEG) beam. We show that this mathematical operator allows reconstructing an image of a spherical particle without compression of the reconstructed image, which increases the accuracy of the 3D location of particles and of their size measurement. To validate the performance of this operator we have studied the diffraction pattern produced by a particle illuminated by an AEG beam. This study used mutual intensity propagation, and the particle is defined as a chirped Gaussian sum. The proposed technique was applied and the experimental results are presented.

Single-Step Transepithelial PRK vs Alcohol-Assisted PRK in Myopia and Compound Myopic Astigmatism Correction.

Science.gov (United States)

Kaluzny, Bartlomiej J; Cieslinska, Iwona; Mosquera, Samuel A; Verma, Shwetabh

2016-02-01

Transepithelial photorefractive keratectomy (tPRK), where both the epithelium and stroma are removed in a single-step, is a relatively new procedure of laser refractive error correction. This study compares the 3-month results of myopia and compound myopic astigmatism correction by tPRK or conventional alcohol-assisted PRK (aaPRK).This prospective, nonrandomized, case-control study recruited 148 consecutive patients; 93 underwent tPRK (173 eyes) and 55 aaPRK (103 eyes). Refractive results, predictability, safety, and efficacy were evaluated during the 3-month follow-up. The main outcome measures were uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and mean refractive spherical equivalent (MRSE).Mean preoperative MRSE was -4.30 ± 1.72 D and -4.33 ± 1.96 D, respectively (P = 0.87). The 3-month follow-up rate was 82.1% in the tPRK group (n = 145) and 86.4% in aaPRK group (n = 90), P = 0.81. Postoperative UDVA was 20/20 or better in 97% and 94% of eyes, respectively (P = 0.45). In the tPRK and aaPRK groups, respectively, 13% and 21% of eyes lost 1 line of CDVA, and 30% and 31% gained 1 or 2 lines (P = 0.48). Mean postoperative MRSE was -0.14 ± 0.26 D in the tPRK group and -0.12 ± 0.20 D in the aaPRK group (P = 0.9). The correlation between attempted versus achieved MRSE was equally high in both groups.Single-step transepithelial PRK and conventional PRK provide very similar results 3 months postoperatively. These procedures are predictable, effective, and safe for correction of myopia and compound myopic astigmatism.

Modelling lifetime cost consequences of toric compared with standard IOLs in cataract surgery of astigmatic patients in four European countries.

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Laurendeau, C; Lafuma, A; Berdeaux, G

2009-09-01

To compare the lifetime costs of freeing astigmatic patients from spectacles after bilateral cataract surgery implanting toric intraocular lenses (IOLs: i.e., Acrysof Toric) versus monofocal IOLs, in France, Italy, Germany and Spain. A Markov model followed patient cohorts from cataract surgery until death. Prevalence rates of patients not needing spectacles and the types of spectacles prescribed for those requiring them were obtained from clinical trials and national surveys. The economic perspective was societal. Mortality rates were incorporated into the model. Discount rates were applied. A sensitivity analysis was performed on non-discounted costs. Fewer patients with toric IOLs needed spectacles for distance vision than patients with monofocal IOLs. With monofocal IOLs more than 66% of patients needed complex spectacles compared to less than 25% implanted with toric IOLs. In France and Italy, toric IOLs reduced overall costs relative to otherwise high spectacle costs after cataract surgery. Savings were 897.0 euros (France), 822.5 euros (Germany), 895.8 euros (Italy) and 391.6 euros (Spain), without discounting. On applying a 3% discount rate the costs became 691.7 euros, 646.4 euros, 693.9 euros and 308.2 euros, respectively. Bilateral toric IOL implants in astigmatic patients decreased spectacle dependence for distance vision and the need for complex spectacles. The economic consequences for patients depended on the national spectacle costs usually incurred after cataract surgery.

Associations between anisometropia, amblyopia, and reduced stereoacuity in a school-aged population with a high prevalence of astigmatism.

Science.gov (United States)

Dobson, Velma; Miller, Joseph M; Clifford-Donaldson, Candice E; Harvey, Erin M

2008-10-01

To describe the relation between magnitude of anisometropia and interocular acuity difference (IAD), stereoacuity (SA), and the presence of amblyopia in school-aged members of a Native American tribe with a high prevalence of astigmatism. Refractive error (cycloplegic autorefraction confirmed by retinoscopy), best corrected monocular visual acuity (VA; Early Treatment Diabetic Retinopathy Study logMAR charts), and best corrected SA (Randot Preschool Stereoacuity Test) were measured in 4- to 13-year-old Tohono O'odham children (N = 972). Anisometropia was calculated in clinical notation (spherical equivalent and cylinder) and in two forms of vector notation that take into account interocular differences in both axis and cylinder magnitude. Astigmatism >or= 1.00 D was present in one or both eyes of 415 children (42.7%). Significant increases in IAD and presence of amblyopia (IAD >or= 2 logMAR lines) occurred, with >or=1 D of hyperopic anisometropia and >or=2 to 3 D of cylinder anisometropia. Significant decreases in SA occurred with >or=0.5 D of hyperopic, myopic, or cylinder anisometropia. Results for vector notation depended on the analysis used, but also showed disruption of SA at lower values of anisometropia than were associated with increases in IAD and presence of amblyopia. Best corrected IAD and presence of amblyopia are related to amount and type of refractive error difference (hyperopic, myopic, or cylindrical) between eyes. Disruption of best corrected random dot SA occurs with smaller interocular differences than those producing an increase in IAD, suggesting that the development of SA is particularly dependent on similarity of the refractive error between eyes.

Hartmann tests to measure the spherical and cylindrical curvatures and the axis orientation of astigmatic lenses or optical surfaces.

Science.gov (United States)

Hernández-Gómez, Geovanni; Malacara-Hernández, Zacarías; Malacara-Hernández, Daniel

2014-02-20

The measurement of astigmatic lenses, optical surfaces or wavefronts are a highly studied problem and many different instruments have been commercially fabricated to perform this task. Many of them use a Hartmann arrangement to obtain the result. In this paper, we analyze with detail the algorithms that can be used to make the necessary calculations and propose several alternatives with different advantages and disadvantages. Different mathematical algorithms that are involved in the calculation process have been given whereas any description of the instrument itself is not proposed, but only the different mathematical algorithms that are involved in the calculation process.

Astigmatism-free high-brightness 1060 nm edge-emitting lasers with narrow circular beam profile.

Science.gov (United States)

Miah, Md Jarez; Kalosha, Vladimir P; Bimberg, Dieter; Pohl, Johannes; Weyers, Markus

2016-12-26

1060 nm high-brightness vertical broad-area edge-emitting lasers providing anastigmatic high optical power into a narrow circular beam profile are demonstrated. Ridge-waveguide (RW) lasers yield record 2.2 W single-transverse mode power in the 1060-nm wavelength range under continuous-wave (cw) operation at room temperature with excellent beam quality factor M2 ≤ 2. Independent of operating current the astigmatism is only 2.5 µm. 3 mm long broad-area (BA) lasers produce a θvert as narrow as 9° full width at half maximum, which agrees well with our simulation results, being insensitive to drive current. 5 mm long BA lasers deliver highest ever reported cw 12 W multimode output power among lasers showing θvert <10° in the 1060-nm wavelength range. The emitted laser beams from both RW and BA lasers show a perfect circular shape with ≤10° divergence angle at record 2.1 W and 4.2 W cw-mode output power, respectively.

Relaxation in Thin Polymer Films Mapped across the Film Thickness by Astigmatic Single-Molecule Imaging

KAUST Repository

Oba, Tatsuya

2012-06-19

We have studied relaxation processes in thin supported films of poly(methyl acrylate) at the temperature corresponding to 13 K above the glass transition by monitoring the reorientation of single perylenediimide molecules doped into the films. The axial position of the dye molecules across the thickness of the film was determined with a resolution of 12 nm by analyzing astigmatic fluorescence images. The average relaxation times of the rotating molecules do not depend on the overall thickness of the film between 20 and 110 nm. The relaxation times also do not show any dependence on the axial position within the films for the film thickness between 70 and 110 nm. In addition to the rotating molecules we observed a fraction of spatially diffusing molecules and completely immobile molecules. These molecules indicate the presence of thin (<5 nm) high-mobility surface layer and low-mobility layer at the interface with the substrate. (Figure presented) © 2012 American Chemical Society.

LASIK and PRK in hyperopic astigmatic eyes: is early retreatment advisable?

Science.gov (United States)

Frings, Andreas; Richard, Gisbert; Steinberg, Johannes; Druchkiv, Vasyl; Linke, Stephan Johannes; Katz, Toam

2016-01-01

To analyze the refractive and keratometric stability in hyperopic astigmatic laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) during the first 6 months after surgery. This retrospective cross-sectional study included 97 hyperopic eyes; 55 were treated with LASIK and 42 with PRK. Excimer ablation for all eyes was performed using the ALLEGRETTO excimer laser platform using a mitomycin C for PRK and a mechanical microkeratome for LASIK. Keratometric and refractive data were analyzed during three consecutive follow-up intervals (6 weeks, 3 months, and 6 months). The corneal topography was obtained using Scheimpflug topography, and subjective refractions were acquired by expert optometrists according to a standardized protocol. After 3 months, mean keratometry and spherical equivalent were stable after LASIK, whereas PRK-treated eyes presented statistically significant (P1 D occurred. The optical zone diameter did not correlate with the development of regression. After corneal laser refractive surgery, keratometric changes are followed by refractive changes and they occur up to 6 months after LASIK and for at least 6 months after PRK, and therefore, caution should be applied when retreatment is planned during the 1st year after surgery because hyperopic refractive regression can lead to suboptimal visual outcome. Keratometric and refractive stability is earlier achieved after LASIK, and therefore, retreatment may be independent of late regression.

Comparison of corneal power, astigmatism, and wavefront aberration measurements obtained by a point-source color light-emitting diode-based topographer, a Placido-disk topographer, and a combined Placido and dual Scheimpflug device.

Science.gov (United States)

Ventura, Bruna V; Wang, Li; Ali, Shazia F; Koch, Douglas D; Weikert, Mitchell P

2015-08-01

To evaluate and compare the performance of a point-source color light-emitting diode (LED)-based topographer (color-LED) in measuring anterior corneal power and aberrations with that of a Placido-disk topographer and a combined Placido and dual Scheimpflug device. Cullen Eye Institute, Baylor College of Medicine, Houston, Texas USA. Retrospective observational case series. Normal eyes and post-refractive-surgery eyes were consecutively measured using color-LED, Placido, and dual-Scheimpflug devices. The main outcome measures were anterior corneal power, astigmatism, and higher-order aberrations (HOAs) (6.0 mm pupil), which were compared using the t test. There were no statistically significant differences in corneal power measurements in normal and post-refractive surgery eyes and in astigmatism magnitude in post-refractive surgery eyes between the color-LED device and Placido or dual Scheimpflug devices (all P > .05). In normal eyes, there were no statistically significant differences in 3rd-order coma and 4th-order spherical aberration between the color-LED and Placido devices and in HOA root mean square, 3rd-order coma, 3rd-order trefoil, 4th-order spherical aberration, and 4th-order secondary astigmatism between the color-LED and dual Scheimpflug devices (all P > .05). In post-refractive surgery eyes, the color-LED device agreed with the Placido and dual-Scheimpflug devices regarding 3rd-order coma and 4th-order spherical aberration (all P > .05). In normal and post-refractive surgery eyes, all 3 devices were comparable with respect to corneal power. The agreement in corneal aberrations varied. Drs. Wang, Koch, and Weikert are consultants to Ziemer Ophthalmic Systems AG. Dr. Koch is a consultant to Abbott Medical Optics, Inc., Alcon Surgical, Inc., and i-Optics Corp. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Advanced astigmatism-corrected tandem Wadsworth mounting for small-scale spectral broadband imaging spectrometer.

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Lei, Yu; Lin, Guan-yu

2013-01-01

Tandem gratings of double-dispersion mount make it possible to design an imaging spectrometer for the weak light observation with high spatial resolution, high spectral resolution, and high optical transmission efficiency. The traditional tandem Wadsworth mounting is originally designed to match the coaxial telescope and large-scale imaging spectrometer. When it is used to connect the off-axis telescope such as off-axis parabolic mirror, it presents lower imaging quality than to connect the coaxial telescope. It may also introduce interference among the detector and the optical elements as it is applied to the short focal length and small-scale spectrometer in a close volume by satellite. An advanced tandem Wadsworth mounting has been investigated to deal with the situation. The Wadsworth astigmatism-corrected mounting condition for which is expressed as the distance between the second concave grating and the imaging plane is calculated. Then the optimum arrangement for the first plane grating and the second concave grating, which make the anterior Wadsworth condition fulfilling each wavelength, is analyzed by the geometric and first order differential calculation. These two arrangements comprise the advanced Wadsworth mounting condition. The spectral resolution has also been calculated by these conditions. An example designed by the optimum theory proves that the advanced tandem Wadsworth mounting performs excellently in spectral broadband.

Comparison of surgically induced astigmatism in various incisions in manual small incision cataract surgery.

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Jauhari, Nidhi; Chopra, Deepak; Chaurasia, Rajan Kumar; Agarwal, Ashutosh

2014-01-01

To determine the surgically induced astigmatism (SIA) in Straight, Frown and Inverted V shape (Chevron) incisions in manual small incision cataract surgery (SICS). A prospective cross sectional study was done on a total of 75 patients aged 40y and above with senile cataract. The patients were randomly divided into three groups (25 each). Each group received a particular type of incision (Straight, Frown or Inverted V shape incisions). Manual SICS with intraocular lens (IOL) implantation was performed. The patients were compared 4wk post operatively for uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA) and SIA. All calculations were performed using the SIA calculator version 2.1, a free software program. The study was analyzed using SPSS version 15.0 statistical analysis software. The study found that 89.5% of patients in Straight incision group, 94.2% in Frown incision group and 95.7% in Inverted V group attained BCVA post-operatively in the range of 6/6 to 6/18. Mean SIA was minimum (-0.88±0.61D×90 degrees) with Inverted V incision which was statistically significant. Inverted V (Chevron) incision gives minimal SIA.

Effect of surgical skill on surgically-induced astigmatism in cataract surgery

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Numan Eraslan

2015-12-01

Full Text Available AIM:To evaluate the effect of surgical experience on surgically-induced astigmatism(SIAin patients with uncomplicated phacoemulsification surgery.METHODS:Fifty-three eyes of fifty patients, mean age 64.5±10.8y, were randomly divided into two groups(23 eyes and 30 eyes. First group was underwent surgery by cataract specialists and the second was by residents. At baseline all the patients were underwent a complete opthalmological examination including keratometry and autorefractometer measurements. Vector analysis programme including the Alpins' method was used for the calculation of SIA. All the measurements were repeated postoperative first day, first month and second month and changes were recorded. Shapiro Wilk and Mann-Whitney tests were applied for determining the statistical differences between the SIA with two groups.RESULTS:There were no significant differences in demographic data of the groups. Intergroup analysis showed, first group was more effective results in SIA postoperative first day(P=0.002, first month(P=0.004and the second month(P=0.001. For the first group, SIA were 0.79±0.41 diopter(Dat the first postoperative day, 0.54±0.41 D at the first postoperative month and 0.47±0.37 D at the second postoperative month. Second one was 1.27±0.66 D, 0.98±0.56 D and 0.94±0.54 D, respectively.CONCLUSION:According to the results, surgical experience was one of the factors that affects SIA. Residents would perform more phacoemilcification surgery to obtain more surgical experience.

Aspheric photorefractive keratectomy for myopia and myopic astigmatism with the SCHWIND AMARIS laser: 2 years postoperative outcomes

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Aslanides, Ioannis M.; Padroni, Sara; Arba-Mosquera, Samuel

2012-01-01

Purpose To evaluate mid-term refractive outcomes and higher order aberrations of aspheric PRK for low, moderate and high myopia and myopic astigmatism with the AMARIS excimer laser system (SCHWIND eye-tech-solutions GmbH, Kleinostheim, Germany). Methods This prospective longitudinal study evaluated 80 eyes of 40 subjects who underwent aspheric PRK. Manifest refractive spherical equivalent (MRSE) of up to −10.00 diopters (D) at the spectacle plane with cylinder up to 3.25 was treated. Refractive outcomes and corneal wavefront data (6 mm pupil to the 7th Zernike order) were evaluated out to 2 years postoperatively. Statistical significance was indicated by P  0.05, both cases). There was a statistical increase in postoperative coma (+0.12 μm) and spherical aberration (+0.14 μm) compared to preoperatively (P < 0.001, both cases). Conclusion Aspheric PRK provides excellent visual and refractive outcomes with induction in individual corneal aberrations but not overall corneal aberrations.

Changes in higher order aberrations after wavefront-guided PRK for correction of low to moderate myopia and myopic astigmatism: two-year follow-up.

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Wigledowska-Promienska, D; Zawojska, I

2007-01-01

To assess efficacy, safety, and changes in higher order aberrations after wavefront-guided photorefractive keratectomy (PRK) in comparison with conventional PRK for low to moderate myopia with myopic astigmatism using a WASCA Workstation with the MEL 70 G-Scan excimer laser. A total of 126 myopic or myopic-astigmatic eyes of 112 patients were included in this retrospective study. Patients were divided into two groups: Group 1, the study group; and Group 2, the control group. Group 1 consisted of 78 eyes treated with wavefront-guided PRK. Group 2 consisted of 48 eyes treated with spherocylindrical conventional PRK. Two years postoperatively, in Group 1, 5% of eyes achieved an uncorrected visual acuity (UCVA) of 0.05; 69% achieved a UCVA of 0.00; 18% of eyes experienced enhanced visual acuity of -0.18 and 8% of -0.30. In Group 2, 8% of eyes achieved a UCVA of 0.1; 25% achieved a UCVA of 0.05; and 67% achieved a UCVA of 0.00 according to logMAR calculation method. Total higher-order root-mean square increased by a factor 1.18 for Group 1 and 1.6 for Group 2. There was a significant increase of coma by a factor 1.74 in Group 2 and spherical aberration by a factor 2.09 in Group 1 and 3.56 in Group 2. The data support the safety and effectiveness of the wavefront-guided PRK using a WASCA Workstation for correction of low to moderate refractive errors. This method reduced the number of higher order aberrations induced by excimer laser surgery and improved uncorrected and spectacle-corrected visual acuity when compared to conventional PRK.

Night driving simulation in a randomized prospective comparison of Visian toric implantable collamer lens and conventional PRK for moderate to high myopic astigmatism.

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Schallhorn, Steven; Tanzer, David; Sanders, Donald R; Sanders, Monica; Brown, Mitch; Kaupp, Sandor E

2010-05-01

To compare changes in simulated night driving performance after Visian Toric Implantable Collamer Lens (TICL; STAAR Surgical) implantation and photorefractive keratectomy (PRK) for the correction of moderate to high myopic astigmatism. This prospective, randomized study consisted of 43 eyes implanted with the TICL (20 bilateral cases) and 45 eyes receiving conventional PRK (VISX Star S3 excimer laser) with mitomycin C (22 bilateral cases) for moderate to high myopia (-6.00 to -20.00 diopters[D] sphere) measured at the spectacle plane and 1.00 to 4.00 D of astigmatism. As a substudy, 27 eyes of 14 TICL patients and 41 eyes of 21 PRK patients underwent a simulated night driving test. The detection and identification distances of road signs and hazards with the Night Driving Simulator (Vision Sciences Research Corp) were measured with and without a glare source before and 6 months after each procedure. No significant difference was noted in the pre- to postoperative Night Driving Simulator in detection distances with and without the glare source between the TICL and PRK groups. The differences in identification distances without glare were significantly better for business and traffic road signs and pedestrian hazards in the TICL group relative to the PRK group whereas with glare, only the pedestrian hazards were significantly better. A clinically relevant change of Night Driving Simulator performance (>0.5 seconds change in ability to identify tasks postoperatively) was significantly better in the TICL group (with and without glare) for all identification tasks. The TICL performed better than conventional PRK in the pre- to postoperative Night Driving Simulator testing with and without a glare source present. Copyright 2010, SLACK Incorporated.

Laser in situ keratomileusis for residual hyperopic astigmatism after conductive keratoplasty.

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Kymionis, George D; Aslanides, Ioannis M; Khoury, Aghlab N; Markomanolakis, Marinos M; Naoumidi, Tatiana; Pallikaris, loannis G

2004-01-01

To report a case of laser in situ keratomileusis (LASIK) in a patient with previous conductive keratoplasty. A 48-year-old man underwent conductive keratoplasty for low hyperopic astigmatism (manifest refraction OD: +2.25 -0.50 x 77 degrees; OS: +2.50 -0.50 x 105 degrees). Three months postoperatively, UCVA was 20/25 and BSCVA was 20/20 in both eyes; manifest refraction OD: -0.25 -0.75 x 110 degrees; OS: +0.75 -0.75 x 50 degrees. Sixteen months after the operation, regression of refractive outcome was (manifest) OD: +1.75 -1.25 x 90 degrees; OS: +2.50 -0.50 x 85 degrees; UCVA was 20/40 in the right eye and 20/63 in the left eye and BSCVA was 20/20 in both eyes. LASIK was performed for hyperopic regression in the left eye using an automated microkeratome (Alcon SKBM, 130-microm plate; Aesculap-Meditec MEL 70 excimer laser). LASIK was uneventful and no intraoperative or postoperative complications related to the previous conductive keratoplasty procedure or LASIK were observed. Three months after LASIK and 19 months after the initial conductive keratoplasty, the patient's left eye was emmetropic; UCVA was 20/20(-2), BSCVA was 20/20 and manifest refraction was +0.25 -0.25 x 35 degrees. There was a uniform increase in topographical steepening. Visual acuity, refraction and topographic findings remained unchanged at 6 months. Even though our experience is limited, treatment of hyperopia with LASIK in an eye with refractive regression following previous conductive keratoplasty resulted in a predicted refractive outcome, with no complications, and improvement in visual acuity at 6 months follow-up.

Laser subepithelial keratomileusis for myopia of -6 to -10 diopters with astigmatism with the MEL60 laser.

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Bilgihan, Kamil; Hondur, Ahmet; Hasanreisoglu, Berati

2004-01-01

To evaluate the efficacy, predictability, and safety of laser subepithelial keratomileusis (LASEK) for treatment of high myopia with astigmatism. LASEK was performed in 61 eyes of 36 consecutive patients with myopic spherical equivalent refraction of -6.00 to -10.00 D using the Aesculap-Meditec MEL60 excimer laser. Data were collected prospectively with a follow-up of 6 to 17 months. Main outcome measures recorded were UCVA, BSCVA, residual refractive error, corneal haze, and complications. Ninety-six percent of eyes achieved 20/40 or better UCVA at 1 month. At 12 months, 64% of eyes achieved 20/20 and 92% achieved 20/40 or better UCVA. Two eyes lost 2 lines of BSCVA at 6 or 12 months. Accuracy of correction was +/- 0.50 D from emmetropia in 82% of eyes, and +/- 1.00 D in 90% at 12 months. No eye showed more than grade 1 haze. Grade 1 haze was observed in three eyes at 12 months. One patient had mild postoperative keratitis, which was successfully treated. LASEK with the Aesculap-Meditec MEL60 excimer laser appeared to be safe, effective, and highly predictable in treating high myopia.

Topography-guided treatment of irregular astigmatism with the wavelight excimer laser.

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Jankov, Mirko R; Panagopoulou, Sophia I; Tsiklis, Nikolaos S; Hajitanasis, Georgos C; Aslanides, loannis M; Pallikaris, loannis G

2006-04-01

To evaluate the feasibility, safety, and predictability of correcting high irregular astigmatism in symptomatic eyes with the use of topography-guided photoablation. In a prospective, non-comparative case series, 16 consecutive symptomatic eyes of 11 patients with small hyperopic and myopic excimer laser optical zones, decentered and irregular ablation after corneal graft, and corneal scars were operated. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest and cycloplegic refraction, and corneal topography, with asphericity and regularity, were analyzed. LASIK (n = 10) and photorefractive keratectomy (n = 6) were performed using the ALLEGRETTO WAVE excimer laser and T-CAT software (Topography-guided Customized Ablation Treatment; WaveLight Laser Technologie AG, Erlangen, Germany). In the LASIK group, UCVA improved from 0.81 +/- 0.68 IogMAR (20/130) (range: 0.2 to 2.0) to 0.29 +/- 0.21 logMAR (20/39) (range: 0.1 to 0.7) at 6 months. In the PRK group, mean UCVA improved from 0.89 +/- 0.87 IogMAR (20/157) (range: 0.1 to 2.0) to 0.42 +/- 0.35 logMAR (20/53) (range: 0.1 to 1.0) at 6 months. Best spectacle-corrected visual acuity did not change significantly in either group. One PRK patient lost one line of BSCVA. Refractive cylinder for the LASIK group improved from -2.53 +/- 1.71 diopters (D) (range: -0.75 to -5.75 D) to -1.28 +/- 0.99 D (range: 0 to -2.50 D) at 6 months. Refractive cylinder in the PRK group improved from -2.21 +/- 2.11 D (range: -0.25 to -5.50 D) to -1.10 +/- 0.42 D (range: -0.50 to -1.50 D). Index of surface irregularity showed a decrease from 60 +/- 12 (range: 46 to 89) to 50 +/- 9 (range: 32 to 63) at 6 months in the LASIK group whereas no significant change was noted in the PRK group. Subjective symptoms, such as glare, halos, ghost images, starbursts, and monocular diplopia, were not present postoperatively. Topography-guided LASIK and PRK resulted in a significant reduction of refractive cylinder and

CLINICAL STUDY TO EVALUATE THE VISUAL OUTCOME AND PATIENT COMFORT IN LASIK AND PHOTOREFRACTIVE KERATECTOMY IN LOW-TO-MODERATE MYOPIC ASTIGMATISM PATIENTS

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Ashok Kumar P

2017-04-01

Full Text Available BACKGROUND To evaluate visual outcomes following LASIK and Photorefractive Keratectomy (PRK in low-to-moderate myopia and/or myopic astigmatism in age and refractive error matched eyes. MATERIALS AND METHODS Of a total 30 patients aged ≥21 years, 20 (40 eyes underwent LASIK and 10 (20 eyes underwent PRK for low-to-moderate myopia or myopic astigmatism. LASIK was performed with the Alcon wave light 500 and PRK with the alcohol application for epithelial removal. All ablations were performed using the same excimer laser system. One surgeon operated all patients by using an excimer laser (Alcon wave light 500 system. Age and refractive error matched patients were divided in two groups. Preoperative and one year postoperative uncorrected visual acuity, best corrected visual acuity and manifest refractions were recorded to compare the outcomes of both the procedures. Outcome measures to assess the patient comfort levels in both groups include postoperative pain and quality of vision. Other outcome measures to assess the wound healing includes intraoperative complications, corneal haze and corneal reepithelialisation. RESULTS Sixty eyes of 30 patients were found matched regarding age and refractive error. In PRK group, among 10 patients, 5 (50% were males and 5 (50% were females, whereas in Lasik group, males were 12 (60% and 8 (40% were female patients. Mean preoperative MRSE was -4.06 ± 1.00 Dioptres (D for LASIK versus -4.50 ± 1.25 D for PRK. Complete flap healing was achieved by postoperative day 4 in 86.9% of LASIK eyes versus complete reepithelialisation in 92.4% of PRK eyes. Using Fisher exact test, a significantly higher percentage of LASIK eyes compared to PRK eyes achieved 20/15 or better at 1 month (35.8% vs. 17.8%, P=0.031, 3 months (69.3% vs. 49.3%, P=0.004, 6 months (79.1% vs. 59.9%, P0.50 D occurred in 12.4% of LASIK eyes within the 3- and 12-month interval versus 25.7% of PRK eyes (P=0.04. Patients in both groups were happy

Influência do astigmatismo corneano na acuidade visual final após implante de AcrySof® ReSTOR®: relato de caso Influence of corneal astigmatism in final visual acuity after implantation of AcrySofTM ReSTOR TM: case report

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Ricardo de Carvalho Rocha

2007-12-01

Full Text Available Atualmente tem-se desenvolvido novos tipos de lentes intra-oculares (LIO que objetivam eliminar a presbiopia e o seu uso vem se popularizando. Descreve-se o caso de um paciente com catarata bilateral e irregularidades corneanas e astigmatismo maior que 2 D à topografia, no qual implantou-se a LIO AcrySof® ReSTOR® no olho esquerdo associado à realização de incisões limbares relaxantes para tentar diminuir o astigmatismo corneano observado. A acuidade visual pós-operatória, tanto para perto quanto para longe, ficou abaixo das expectativas, sem melhora à refração e sem uma outra alteração que a justificasse, além das citadas. Após 45 dias, sem melhora da acuidade visual, efetuou-se o explante desta LIO, seguindo-se de implante de uma monofocal, sendo observada melhora da acuidade visual corrigida final. Assim, o presente caso clínico reforça a necessidade de uma correta seleção pré-operatória dos pacientes candidatos ao implante deste tipo de LIO multifocal, atentando inclusive para os dados topográficos.Currently, new types of intraocular lenses have been developed aiming to eliminate presbyopia and the use has become more popular. The authors report the case of a patient with bilateral cataract and corneal irregularities and astigmatism higher than 2D in the corneal topography, in which AcrySofTM ReSTOR TM intraocular lens was implanted in the left eye associated to relaxing limbal incisions trying to reduce corneal astigmatism. The near and distance postoperative visual acuity were worse than expected, with no improvement with refraction. Apparently, no other reason apart from irregular astigmatism/multifocal lens justified the low vision. After 45 days, with no visual acuity improvement, the intraocular lens was explanted and a monofocal one was implanted. The final corrected visual acuity improved. Thus, the present case emphasizes the need of a correct preoperative selection of patients to implant this type of

Surgically induced astigmatism after phacoemulsification with and without correction for posture-related ocular cyclotorsion: randomized controlled study.

LENUS (Irish Health Repository)

Dooley, Ian

2012-02-01

PURPOSE: To report the impact of posture-related ocular cyclotorsion on one surgeon\\'s surgically induced astigmatism (SIA) results and the variance in SIA. SETTING: Institute of Eye Surgery, Whitfield Clinic, Waterford, Ireland. METHODS: This prospective randomized controlled study included eyes that had phacoemulsification with intraocular lens implantation. Eyes were randomly assigned to have (intervention group) or not have (control group) correction for posture-related ocular cyclotorsion. In the intervention group, the clear corneal incision was placed precisely at the 120-degree meridian with instruments designed to correct posture-related ocular cyclotorsion. In the control group, the surgeon endeavored to place the incision at the 120-degree meridian, but without markings. RESULTS: The intervention group comprised 41 eyes and the control group, 61 eyes. The mean absolute SIA was 0.74 diopters (D) in the intervention group and 0.78 D in the control group; the difference between groups was not statistically significant (P>.5, unpaired 2-tailed Student t test). The variance in SIA was 0.29 D(2) and 0.31 D(2), respectively; the difference between groups was not statistically significant (P>.5, unpaired F test). CONCLUSIONS: Attempts to correct for posture-related ocular cyclotorsion did not influence SIA or its variance in a single-surgeon series. These results should be interpreted with full appreciation of the limitations of currently available techniques to correct for posture-related ocular cyclotorsion in the clinical setting.

Academic and Workplace-related Visual Stresses Induce Detectable Deterioration Of Performance, Measured By Basketball Trajectories and Astigmatism Impacting Athletes Or Students In Military Pilot Training.

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Mc Leod, Roger D.

2004-03-01

Separate military establishments across the globe can confirm that a high percentage of their prospective pilots-in-training are no longer visually fit to continue the flight training portion of their programs once their academic coursework is completed. I maintain that the visual stress induced by those intensive protocols can damage the visual feedback mechanism of any healthy and dynamic system beyond its usual and ordinary ability to self-correct minor visual loss of acuity. This deficiency seems to be detectable among collegiate and university athletes by direct observation of the height of the trajectory arc of a basketball's flight. As a particular athlete becomes increasingly stressed by academic constraints requiring long periods of concentrated reading under highly static angular convergence of the eyes, along with unfavorable illumination and viewing conditions, eyesight does deteriorate. I maintain that induced astigmatism is a primary culprit because of the evidence of that basketball's trajectory! See the next papers!

Analysis of behavior of focusing error signals generated by astigmatic method when a focused spot moves beyond the radius of a land-groove-type optical disk

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Shinoda, Masahisa; Nakatani, Hidehiko; Nakai, Kenya; Ohmaki, Masayuki

2015-09-01

We theoretically calculate behaviors of focusing error signals generated by an astigmatic method in a land-groove-type optical disk. The focusing error signal from the land does not coincide with that from the groove. This behavior is enhanced when a focused spot of an optical pickup moves beyond the radius of the optical disk. A gain difference between the slope sensitivities of focusing error signals from the land and the groove is an important factor with respect to stable focusing servo control. In our calculation, the format of digital versatile disc-random access memory (DVD-RAM) is adopted as the land-groove-type optical disk model, and the dependences of the gain difference on various factors are investigated. The gain difference strongly depends on the optical intensity distribution of the laser beam in the optical pickup. The calculation method and results in this paper will be reflected in newly developed land-groove-type optical disks.

Study on the distribution of the dominant eye in people with myopia and astigmatism and the relationship between dominant eye and the two

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Wen-Li Duan

2015-11-01

Full Text Available AIM:To study the distribution of the dominant eye in people with myopia and astigmatism and the relationship between dominant eye and the two. METHODS:Three hundred and eighty patients who went our hospital for optometry consecutively were enrolled, using hole-in-card method to detect the dominant eye. The records of age, gender, vision acuity and other related information were analyzed by SPSS 11.0 software. RESULTS: 1Most of the dominant eyes were right eyes which accounted for 66.84%, and the ametropia degree on right eyes was relatively higher; 2Dominant eyes had no significant association with gender, age and uncorrected vision acuity(P>0.05; 3There was no significant correlation between the dominant eyes and ametropia degree(P>0.05. But in the group which the difference of cylinder degree between two eyes were ≥1D, only 20% of the dominant eyes had higher ametropia degree, which was different from the other two groups. CONCLUSION:High cylinder of anisometropia may affect the choice of the dominant eye. High sphere of anisometropia may be the result of the choice of dominant eye.

The use of WaveLight® Contoura to create a uniform cornea: the LYRA Protocol. Part 3: the results of 50 treated eyes.

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Motwani, Manoj

2017-01-01

To demonstrate how using the Wavelight Contoura measured astigmatism and axis eliminates corneal astigmatism and creates uniformly shaped corneas. A retrospective analysis was conducted of the first 50 eyes to have bilateral full WaveLight ® Contoura LASIK correction of measured astigmatism and axis (vs conventional manifest refraction), using the Layer Yolked Reduction of Astigmatism Protocol in all cases. All patients had astigmatism corrected, and had at least 1 week of follow-up. Accuracy to desired refractive goal was assessed by postoperative refraction, aberration reduction via calculation of polynomials, and postoperative visions were analyzed as a secondary goal. The average difference of astigmatic power from manifest to measured was 0.5462D (with a range of 0-1.69D), and the average difference of axis was 14.94° (with a range of 0°-89°). Forty-seven of 50 eyes had a goal of plano, 3 had a monovision goal. Astigmatism was fully eliminated from all but 2 eyes, and 1 eye had regression with astigmatism. Of the eyes with plano as the goal, 80.85% were 20/15 or better, and 100% were 20/20 or better. Polynomial analysis postoperatively showed that at 6.5 mm, the average C3 was reduced by 86.5% and the average C5 by 85.14%. Using WaveLight ® Contoura measured astigmatism and axis removes higher order aberrations and allows for the creation of a more uniform cornea with accurate removal of astigmatism, and reduction of aberration polynomials. WaveLight ® Contoura successfully links the refractive correction layer and aberration repair layer using the Layer Yolked Reduction of Astigmatism Protocol to demonstrate how aberration removal can affect refractive correction.

The use of Wavelight® Contoura to create a uniform cornea: the LYRA protocol. Part 3: the results of 50 treated eyes

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Motwani M

2017-05-01

Full Text Available Manoj Motwani Motwani LASIK Institute, San Diego, CA, USA Purpose: To demonstrate how using the Wavelight Contoura measured astigmatism and axis eliminates corneal astigmatism and creates uniformly shaped corneas. Patients and methods: A retrospective analysis was conducted of the first 50 eyes to have bilateral full WaveLight® Contoura LASIK correction of measured astigmatism and axis (vs conventional manifest refraction, using the Layer Yolked Reduction of Astigmatism Protocol in all cases. All patients had astigmatism corrected, and had at least 1 week of follow-up. Accuracy to desired refractive goal was assessed by postoperative refraction, aberration reduction via calculation of polynomials, and postoperative visions were analyzed as a secondary goal. Results: The average difference of astigmatic power from manifest to measured was 0.5462D (with a range of 0–1.69D, and the average difference of axis was 14.94° (with a range of 0°–89°. Forty-seven of 50 eyes had a goal of plano, 3 had a monovision goal. Astigmatism was fully eliminated from all but 2 eyes, and 1 eye had regression with astigmatism. Of the eyes with plano as the goal, 80.85% were 20/15 or better, and 100% were 20/20 or better. Polynomial analysis postoperatively showed that at 6.5 mm, the average C3 was reduced by 86.5% and the average C5 by 85.14%. Conclusions: Using WaveLight® Contoura measured astigmatism and axis removes higher order aberrations and allows for the creation of a more uniform cornea with accurate removal of astigmatism, and reduction of aberration polynomials. WaveLight® Contoura successfully links the refractive correction layer and aberration repair layer using the Layer Yolked Reduction of Astigmatism Protocol to demonstrate how aberration removal can affect refractive correction. Keywords: WaveLight Contoura, topographic guided ablation, LASIK, PRK, uniform cornea, Contoura with LYRA Protocol, measured astigmatism

Clinical analysis of outpatients with ametropia in Hebeisheng Eye Hospital

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Xiao Chen

2017-11-01

Full Text Available AIM: To perform a clinical analysis of 1 500 cases of outpatients with ametropia in Hebeisheng Eye Hospital, to provide a theoretical basis for diagnosis, treatment, and prevention of patients with ametropia.METHODS: Totally 1 500 cases(2 840 eyesof outpatient with ametropia were chosen as the research objects in Hebeisheng Eye Hospital from June 2013 to July 2014. All cases were treated with TOPCON RM-8800 computer optometry instrument for objective optometry, and used TOPCON phoropter for subjective optometry. The combination of the two instruments was taken to determine the diopter later. Diopter and axial distribution of the myopic astigmatism and hyperopic astigmatism were observed, age of astigmatic patient, distribution of astigmatism axis were observed as well. Meanwhile, a total of 150 cases were chosen randomly to measure their corneal curvature, anterior chamber depth, axial length and other static refractive index. All indexes were compared with those of the normal people subsequently, such as amplitude of accommodation, negative relative accommodation, positive relative accommodation, sensitivity of accommodation and other dynamic refractive index. RESULTS: Ametropia types of all patients were mainly simple myopia, simple myopia astigmatism, compound myopic astigmatism, simple hypermetropia, simple hyperopia astigmatism, compound hyperopic astigmatism and mixed astigmatism, the proportion were 38.99%, 3.27%, 23.94%, 4.68%, 1.34%, 13.52%, 15.25% respectively. There were 773 eyes with myopia astigmatism. The proportion of people with a myopia astigmatism diopter of above -0.25 to -0.50, -0.75 to -1.00, -1.25 to -1.50, above -1.75 were 31.05%, 38.55%, 16.56%, 13.84%. There were 421 eyes with hyperopia astigmatism, the proportion of people with hyperopia astigmatism diopter of 0.25-0.50, 0.75-1.00, 1.25- 1.50, >1.75 were 26.60%, 24.94%, 16.63%, 31.83%. Static refractive index of 150 patients(300 eyesshowed that corneal curvature was(41

The use of Wavelight® Contoura to create a uniform cornea: the LYRA protocol. Part 3: the results of 50 treated eyes

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Motwani M

2017-01-01

Manoj Motwani Motwani LASIK Institute, San Diego, CA, USA Purpose: To demonstrate how using the Wavelight Contoura measured astigmatism and axis eliminates corneal astigmatism and creates uniformly shaped corneas. Patients and methods: A retrospective analysis was conducted of the first 50 eyes to have bilateral full WaveLight® Contoura LASIK correction of measured astigmatism and axis (vs conventional manifest refraction), using the Layer Yolked Reduction of Astigmatism Protocol in...

Ceratectomia fotorrefrativa (PRK com mitomicina C a 0,02% para correção de grau acentuado de astigmatismo hipermetrópico composto secundário a cirurgia de ceratotomia radial (RK Photorefractive keratectomy (PRK with mitomicyn C 0,02% for the management of high degree of hyperopic astigmatism following radial keratectomy

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Adamo Lui Netto

2009-06-01

Full Text Available Descrever o efeito da cirurgia fotorrefrativa (PRK associada ao uso de mitomicina C a 0,02% para correção de grau acentuado de astigmatismo hipermetrópico composto apresentado após cirurgia de ceratotomia radial (RK realizada há 12 anos.To describe PRK with mitomicyn C effects for the management of high-degree hyperopic astigmatism following Radial Keratectomy performed 12 years ago.

Using corneal topography design personalized cataract surgery programs

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Jin-Ou Huang

2014-08-01

Full Text Available AIM:To investigate how to design personalized cataract surgery programs to achieve surgical correction of preoperative corneal astigmatism with surgical astigmatism under the guidance of corneal topography, improve postoperative visual quality and reduce the cost of treatment. METHODS: Totally 202 cases(226 eyescataract patients were divided into randomized treatment group and individualized treatment group. According to the method and location of the incision, randomized treatment group were divided into 8 groups. Surgical astigmatism after different incision were calculated with the use of preoperative and postoperative corneal astigmatism through vector analysis method. Individualized treatment groups were designed personably for surgical method with reference of every surgically induced astigmatism, the surgical method chooses the type of surgical incision based on close link between preoperative corneal astigmatism and surgically induced astigmatism, and the incision was located in the steep meridian. The postoperative corneal astigmatism of individualized treatment group was observed. RESULTS: Postoperative corneal astigmatism of individualized treatment group were lower than that of 3.0mm clear corneal tunnel incision in the randomized treatment group, there were statistically significance difference, while with 3.0mm sclera tunnel incision group there were no statistically significance difference. After 55.8% of patients with the use of individualized surgical plan could undergo the operation of extracapsular cataract extraction with relatively low cost and rigid intraocular lens implantation, the per capita cost of treatment could be reduced. CONCLUSION: Personalized cataract surgery programs are designed to achieve surgical correction of preoperative corneal astigmatism under the use of corneal topography, improve postoperative visual quality and reduce the cost of treatment.

Quality factor of aberrated gaussian laser beams

CSIR Research Space (South Africa)

Mafusire, C

2010-09-01

Full Text Available 15 20 25 30 35 M 4 © CSIR 2010 www.csir.co.za Conclusion • Laser beam quality depends on - y-Astigmatism - y-Coma - x-Coma - y-Triangular astigmatism - x-Triangular astigmatism - Spherical aberration...

[Comparative clinical study of wavefront-guided laser in situ keratomileusis with versus without iris recognition for myopia or myopic astigmatism].

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Wang, Wei-qun; Zhang, Jin-song; Zhao, Xiao-jin

2011-10-01

To explore the postoperative visual acuity results of wavefront-guided LASIK with iris recognition for myopia or myopic astigmatism and the changes of higher-order aberrations and contrast sensitivity function (CSF). Series of prospective case studies, 158 eyes (85 cases) of myopia or myopic astigmatism were divided into two groups: one group underwent wavefront-guided LASIK with iris recognition (iris recognition group); another group underwent wavefront-guided LASIK treatment without iris recognition through the limbus maring point (non-iris recognition group). To comparative analyze the postoperative visual acuity, residual refraction, the RMS of higher-order aberrations and CSF of two groups. There was no statistical significance difference between two groups of the average uncorrected visual acuity (t = 0.039, 0.058, 0.898; P = 0.844, 0.810, 0.343), best corrected visual acuity (t = 0.320, 0.440, 1.515; P = 0.572, 0.507, 0.218), and residual refraction [spherical equivalent (t = 0.027, 0.215, 0.238; P = 0.869, 0.643, 0.626), spherical (t = 0.145, 0.117, 0.038; P = 0.704, 0.732, 0.845) and cylinder (t = 1.676, 1.936, 0.334; P = 0.195, 0.164, 0.563)] at postoperative 10 days, 1 month and 3 month. The security index of iris recognition group at postoperative 3 month was 1.06 and non-iris recognition group was 1.03; the efficacy index of iris recognition group is 1.01 and non-iris recognition group was 1.00. Postoperative 3 month iris recognition group 93.83% eyes and non-iris recognition group of 90.91% eyes spherical equivalent within ± 0.50 D (χ(2) = 0.479, P = 0.489), iris recognition group of 98.77% eyes and non-iris recognition group of 97.40% eyes spherical equivalent within ± 1.00 D (Fisher test, P = 0.613). There was no significance difference between the two groups of security, efficacy and predictability. Non-iris recognition group postoperative 1 month and postoperative 3 months 3-order order aberrations root mean square value (RMS) higher than the

Lente de contato de material híbrido em pacientes com ceratocone e astigmatismo miópico composto Hybrid material contact lens in keratoconus and myopic astigmatism patients

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Fernando Leal

2007-03-01

óculos, exceto para a freqüência B (3 cpg, maior nos usuários de óculos. As aberrações de alta ordem analisadas apresentaram diminuição estatisticamente significante, quando comparados os pacientes sem e com uso de lentes de contato, com exceção da aberração esférica e do coma. CONCLUSÃO: A lente de contato de material híbrido, quando utilizada por portadores de ceratocone e astigmatismo miópico composto, propiciaram desempenho visual e conforto satisfatórios, em níveis que não diferiram, das lentes de contato rígidas-gás-permeáveis nos dois grupos de pacientes.PURPOSE: To evaluate comfort and visual performance in relation to two different used contact lens types: hybrid material (HM and rigid-gas-permeable (RGP, in patients with regular myopic astigmatism and with keratoconus. METHODS: A randomized, double masked, prospective study of 22 patients with the diagnosis of myopic astigmatism (8 with myopic astigmatism and 14 with keratoconus was conducted. Fifteen patients were female and 7 were male, and mean age was: 32.13 ± 8.12 years. In one of the eyes a rigid-gas-permeable contact lens was adapted (DK 30, and in the other a hybrid material contact lens was adapted (DK 23. All patients were submitted to the following tests: measurement of comfort level by means of the analogical visual scale, tear break-up time, best corrected visual acuity with the Bailey-Lovie scale adapted for 4 meters, functional acuity contrast test (FACT and wavefront analysis. RESULTS: In relation to comfort, there was no association with the evaluated contact lens type (p=0.350. There was a variation in comfort level during the first 7 days. The visual acuity increased between the 7th and the 15th day of adaptation. Visual acuity stabilized right after this period. The visual acuity did not show differences in relation to the studied lens type. It was verified that there was no difference in the tear break-up time (p=0.989 in relation to the studied lenses type and

Prospective study of toric IOL outcomes based on the Lenstar LS 900® dual zone automated keratometer

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Gundersen Kjell

2012-07-01

Full Text Available Abstract Background To establish clinical expectations when using the Lenstar LS 900® dual-zone automated keratometer for surgery planning of toric intraocular lenses. Methods Fifty eyes were measured with the Lenstar LS 900® dual-zone automated keratometer . Surgical planning was performed with the data from this device and the known surgically induced astigmatism of the surgeon. Post-operative refractions and visual acuity were measured at 1 month and 3 months. Results Clinical outcomes from 43 uncomplicated surgeries showed an average post-operative refractive astigmatism of 0.44D ±0.25D. Over 70% of eyes had 0.50D or less of refractive astigmatism and no eye had more than 1.0D of refractive astigmatism. Uncorrected visual acuity was 20/32 or better in all eyes at 3 months, with 70% of eyes 20/20 or better. A significantly higher number of eyes had 0.75D or more of post-operative refractive astigmatism when the standard deviation of the pre-operative calculated corneal astigmatism angle, reported by the keratometer, was > 5 degrees. Conclusions In this single-site study investigating the use of the keratometry from the Lenstar LS 900® for toric IOL surgical planning, clinical outcomes appear equivalent to those reported in the literature for manual keratometry and somewhat better than has been reported for some previous automated instruments. A high standard deviation in the pre-operative calculated astigmatism angle, as reported by the keratometer, appears to increase the likelihood of higher post-operative refractive astigmatism.

Surgically induced astigmatism after phacoemulsification by temporal clear corneal and superior clear corneal approach: a comparison

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Nikose AS

2018-01-01

Full Text Available Archana Sunil Nikose, Dhrubojyoti Saha, Pradnya Mukesh Laddha, Mayuri Patil Department of Ophthalmology, N.K.P. Salve Institute and LMH, Nagpur, Maharashtra, India Introduction: Cataract surgery has undergone various advances since it was evolved from ancient couching to the modern phacoemulsification cataract surgery. Surgically induced astigmatism (SIA remains one of the most common complications. The introduction of sutureless clear corneal incision has gained increasing popularity worldwide because it offers several advantages over the traditional sutured limbal incision and scleral tunnel. A clear corneal incision has the benefit of being bloodless and having an easy approach, but SIA is still a concern.Purpose: In this study, we evaluated the SIA in clear corneal incisions with temporal approach and superior approach phacoemulsification. Comparisons between the two incisions were done using keratometric readings of preoperative and postoperative refractive status.Methodology: It was a hospital-based prospective interventional comparative randomized control trial of 261 patients conducted in a rural-based tertiary care center from September 2012 to August 2014. The visual acuity and detailed anterior segment and posterior segment examinations were done and the cataract was graded according to Lens Opacification Classification System II. Patients were divided for phacoemulsification into two groups, group A and group B, who underwent temporal and superior clear corneal approach, respectively. The patients were followed up on day 1, 7, 30, and 90 postoperatively. The parameters recorded were uncorrected visual acuity, best-corrected visual acuity, slit lamp examination, and keratometry. The mean difference of SIA between 30th and 90th day was statistically evaluated using paired t-test, and all the analyses were performed using SPSS 18.0 (SPSS Inc. software.Results: The mean postoperative SIA in group A was 0.998 D on the 30th day, which

Analysis of refractive state in 708 children with ametropic amblyopia

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Ju-Fen Huang

2016-01-01

Full Text Available AIM: To analyze the refractive state and explore the epidemiologic feature of children with ametropic amblyopia.METHODS: This study retrospectively analyzed 708 children(1 416 eyeswith amblyopia from January 2012 to December 2013 in Special Department of Strabismus and Amblyopic and Department of Pediatric Ophthalmology in our hospital, who were diagnosed as ametropic amblyopia and accepted centrally comprehensive training. The refractive state were given epidemiologic analyze.RESULTS: In the 708 cases(1 416 eyes, there were 190 eyes with hyperopia(13.42%,612 eyes with hyperopia astigmatism(43.22%,18 eyes with myopia(1.27%,134 eyes with myopia astigmatism(9.46%,462 eyes with mixed astigmatism(32.63%. The distributions of refractive state in children at different age were different, and the difference was statistically significant(PCONCLUSION: Hyperopia ametropia and mixed astigmatism are the main types of refractive errors in amblyopia children. The level of amblyopia is related to refractive state and astigmatism axial.

The evolution of refractive status in Chinese infants during the first year of life and its affected factors

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Shu-Juan Yu

2017-08-01

Full Text Available AIM: To study the evolution of the refractive status and examine the affected factors in infants during the first year of life in a large sample size in China. METHODS: A total of 1258 babies (2516 eyes aged 32wk gestational age to 1y participated in the study, including 766 premature and 492 full-term infants. First, each baby received an orthoptic examination, slit-lamp checking and fundus imaging. Patients with diseases which might affect refractive status were excluded from the cohort. The cycloplegia retinoscopy was performed. Their neonatal histories were reviewed. Each measurement contained the refractive status and calculation of the spherical equivalent (SE. RESULTS: Refractive state showed an average hyperopia of +0.94±1.63 D at early ages, followed by a trend toward more hyperopia. The refractive state reached the top (+2.43±1.46 D at the age of one to two months. Then gliding till one year old when the refractive state reached +0.59±1.41 D. The prevalence of astigmatism was 42.17% in the study, being 2.82% myopic astigmatism and 39.35% hyperopic astigmatism. The 94.1% of hyperopic astigmatism was with-the-rule astigmatism and 71.83% of myopic astigmatism was with-the-rule astigmatism. Refractive state between boys and girls was different. The mean SE of boys was +1.97±1.57 D, while that of girls was +1.79±1.46 D, and the difference was significant. CONCLUSION: Before one year old, the change of refractive status is associated with checking age and sex. At the age of one to two months, the degree of hyperopia reaches the top. Boys have more hyperopic degree than girls, and with-the-rule astigmatism is predominant. Excluding premature infants with advanced retinopathy of prematurity, premature and full-term children have same refraction status.

Up-to-date analysis of school myopia, 6

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Kamiya, Sadayoshi; Saishin, Motosugu; Uosato, Hiroshi; Asai, Teruo; Nomura, Ken; Saito, Michiko; Okada, Shigemi; Aono, Shizue.

1985-01-01

In a previous report we determined that, ultrasonically, axial length does not show any increase after 6 years of age, although lens anterior-posterior thickness increases throughout life. To confirm these results we determined axial length and lens thickness using a G.E. CT Scan at Gifu City Hospital on a total of 63 cases (126 eyes) including males and females from 6 to 77 years old. From the equatorial section of the eyeball, depth of anterior chamber, axial length, eyeball width and lens thickness and width were measured; lens volume was then calculated mathematically based on these data. The results obtained were as follows: Results obtained via two different methods corresponded well; we therefore conclude that the axial length of the eye does not increase with age, although the anterior-posterior thickness of the lens does, while the lens equatorial axis increases slightly with age, causing the lens to become rounder and its volume to increase. On the other hand, to observe the percentage frequency distribution of the direction of astigmatism, to the 6775 astigmatic eyes excludins cases of astigmatic defect reported in a previous paper we added 2157 astigmatic eyes from 20 to 85 years old, of out patients of Kamiya eye clinic. We were able to clarify the fact that astigmatism with-the-rule increases from 9 -- 10 years to 20 years of age, decreasing thereafter, astigmatism against-the-rule decreasing, in contrast, during the same age range, increasing after 20 years of age. At 40 years the percentages cross over, while oblique astigmatism does not show any change with age. Based on these findings we conclude that changes in the direction of astigmatic axis depend upon the chronological development of the lens as a function of age. (author)

Contact Lens Visual Rehabilitation in Keratoconus and Corneal Keratoplasty

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Yelda Ozkurt

2012-01-01

Full Text Available Keratoconus is the most common corneal distrophy. It’s a noninflammatory progressive thinning process that leads to conical ectasia of the cornea, causing high myopia and astigmatism. Many treatment choices include spectacle correction and contact lens wear, collagen cross linking, intracorneal ring segments implantation and finally keratoplasty. Contact lenses are commonly used to reduce astigmatism and increase vision. There are various types of lenses are available. We reviewed soft contact lenses, rigid gas permeable contact lenses, piggyback contact lenses, hybrid contact lenses and scleral-semiscleral contact lenses in keratoconus management. The surgical option is keratoplasty, but even after sutur removal, high astigmatism may stil exists. Therefore, contact lens is an adequate treatment option to correct astigmatism after keratoplasty.

Posição viciosa de cabeça por astigmatismo mal corrigido: relato de caso Abnormal head position caused by incorrect prescription for astigmatism: case report

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Flávia Augusta Attié de Castro

2005-10-01

Full Text Available A posição viciosa de cabeça é uma condição compensatória que visa proporcionar aos pacientes melhor rendimento visual. Pode ser causada por problemas oftalmológicos, como distúrbios oculomotores (nistagmos, estrabismos e altos astigmatismos. No entanto, compromete a estética e, a longo prazo, pode causar transtornos ortopédicos (coluna cervical e assimetrias faciais. Relatamos o caso de uma garota, JL, 8 anos, com cabeça inclinada para esquerda havia vários anos. Fazia uso de óculos prescritos em outro serviço para correção de astigmatismo misto: OD= +2,00 DE Ç -5,50 DC a 180º e OE= +2,25 DE Ç -5,75 DC a 180º. No exame oftálmico, a paciente apresentava cabeça inclinada para a esquerda e acuidade visual com correção de 0,5 no OD e 0,7 OE. Os testes de cobertura simples e alternado não evidenciaram desvio ocular. Rotações oculares, biomicroscopia e fundoscopia também não mostraram alterações. Na refratometria sob cicloplegia e teste de lentes foram encontrados: OD= +3,50 DE Ç -6,00 DC a 10º e OE= +3,50 DE Ç -6,00 DC a 170º, com acuidade visual igual a 1,0 nos olhos direito e esquerdo. Foram prescritas as lentes encontradas no exame e a paciente retornou com a correção nova sem a inclinação de cabeça. Erros refracionais mal corrigidos também podem gerar torcicolo e, muitas vezes, passam despercebidos. Refratometria sob cicloplegia e teste de lentes são fundamentais para um diagnóstico preciso.Abnormal head position is a compensatory condition which improves patients' vision. It can be caused by ophthalmological problems such as oculomotor imbalances (strabismus, nystagmus and high astigmatisms. However, it results in esthetic impairment, orthopedic trouble and facial asymmetries. We describe a case of a girl, JL, 8 years, with abnormal head position tilted to the left since the last glasses were prescribed. The correction used by the patient was: right eye = +2.00 sph à -5.5 cyl 180° and left eye = +2

Preliminary observation of refractive cataract surgery assisted by femtosecond laser

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Xiao-Li Wang

2015-12-01

Full Text Available AIM:To compare the differences of visual acuity and corneal astigmatism postoperatively between conventional refractive cataract surgery and that assisted by femtosecond laser.METHODS:Sixty patients(60 eyeswith age-related cataract and cornea astigmatism were divided into femtosecond group and conventional group randomly or voluntarily. The flat shaft, steep shaft and diopter of corneal astigmatism in patients in femtosecond group were inputted into the online vector calculators to get the location and width of the incision. Then femtosecond laser was used to make corneal releasing incision, the main and auxiliary incision. Phacoemulsification and aspheric multifocal intraocular lens implantation were undergone. Patients in conventional group received full-thickness relaxing incision by cornea paracentesis knife at the steepest meridian axis during phacoemulsification. Then aspheric multifocal intraocular lenses were implanted. Uncorrected distance visual acuity(UCDVA, uncorrected near visual acuity(UCNVAand cornea astigmatism were observed at 1d,1wk and 1mo postoperative. RESULTS:UCVA of patients in both groups was improved after the surgeries. UCDVA and UCNVA of femtosecond group were higher than those of conventional group, while the cornea astigmatism of femtosecond group was lower than that of conventional group.CONCLUSION:Refractile cataract surgery assisted by femtosecond laser canoffer better visual quality than conventional refractive cataract surgery because of lower cornea astigmatism and better visual acuity.

Comparison of the effects of cylindrical correction with and without iris recognition technology in wavefront laser-assisted in situ keratomileusis.

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Wang, Tsung-Jen; Lin, Yu-Huang; Chang, David C-K; Chou, Hsiu-Chu; Wang, I-Jong

2012-04-01

  To analyse the magnitude of cylindrical corrections over which cyclotorsion compensation with iris recognition (IR) technology is beneficial during wavefront laser-assisted in situ keratomileusis.   A retrospectively comparative case series.   Fifty-four eyes that underwent wavefront laser-assisted in situ keratomileusis without IR (non-IR group) and 53 eyes that underwent wavefront laser-assisted in situ keratomileusis with IR (IR group) were recruited.   Subgroup analysis based on baseline astigmatism were: a low degree of astigmatism (≥1.00 D to <2.00 D), a moderate degree of astigmatism (≥2.00 D to <3.00 D) and a high degree of astigmatism (≥3.00 D).   Vector and non-vector analyses were used for comparison.   The mean cylinder was -1.89 ± 0.76 D in the non-IR group and -2.00 ± 0.77 D in the IR group. Postoperatively, 38 eyes (74.50%) in the IR group and 31 eyes (57.50%) in the non-IR group were within ± 0.50 D of the target induced astigmatism vector (P = 0.063). The difference vector was 0.49 ± 0.28 in the IR group and 0.63 ± 0.40 in the non-IR group (P = 0.031). In the analysis of subgroups, the magnitude of error was significantly lower in the moderate IR subgroup than that of the moderate non-IR subgroup (P = 0.034). Furthermore, the moderate IR subgroup had a lower mean difference vector (P = 0.0078) and a greater surgically induced astigmatism (P = 0.036) than those of the moderate non-IR group.   Wavefront laser-assisted in situ keratomileusis for the treatment of astigmatism using IR technology was effective and accurate for the treatment of myopic astigmatism. © 2011 The Authors. Clinical and Experimental Ophthalmology © 2011 Royal Australian and New Zealand College of Ophthalmologists.

Small-incision lenticule extraction (SMILE)

DEFF Research Database (Denmark)

Hansen, Rasmus Søgaard; Lyhne, Niels; Grauslund, Jakob

2016-01-01

surgery was 0.07 ± 0.03 (logMAR). However, 12 eyes (1.6 %) lost 2 or more lines of CDVA from before surgery to 3 months postoperatively. Simultaneous treatment of up to 3.00 D of astigmatism was not associated with less predictable refractive outcomes. CONCLUSIONS: In the short term, SMILE seemed......PURPOSE: To study the outcomes of small-incision lenticule extraction (SMILE) for treatment of myopia and myopic astigmatism. METHODS: Retrospective study of patients treated for myopia or myopic astigmatism with SMILE, using a VisuMax(®) femtosecond laser (Carl Zeiss Meditec, Jena, Germany...

Observation of lens aberrations for high resolution electron microscopy II: Simple expressions for optimal estimates

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Saxton, W. Owen, E-mail: wos1@cam.ac.uk

2015-04-15

This paper lists simple closed-form expressions estimating aberration coefficients (defocus, astigmatism, three-fold astigmatism, coma / misalignment, spherical aberration) on the basis of image shift or diffractogram shape measurements as a function of injected beam tilt. Simple estimators are given for a large number of injected tilt configurations, optimal in the sense of least-squares fitting of all the measurements, and so better than most reported previously. Standard errors are given for most, allowing different approaches to be compared. Special attention is given to the measurement of the spherical aberration, for which several simple procedures are given, and the effect of foreknowledge of this on other aberration estimates is noted. Details and optimal expressions are also given for a new and simple method of analysis, requiring measurements of the diffractogram mirror axis direction only, which are simpler to make than the focus and astigmatism measurements otherwise required. - Highlights: • Optimal estimators for CTEM lens aberrations are more accurate and/or use fewer observations. • Estimators have been found for defocus, astigmatism, three-fold astigmatism, coma and spherical aberration. • Estimators have been found relying on diffractogram shape, image shift and diffractogram orientation only, for a variety of beam tilts. • The standard error for each estimator has been found.

Refractive Error in a Sample of Black High School Children in South Africa.

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Wajuihian, Samuel Otabor; Hansraj, Rekha

2017-12-01

This study focused on a cohort that has not been studied and who currently have limited access to eye care services. The findings, while improving the understanding of the distribution of refractive errors, also enabled identification of children requiring intervention and provided a guide for future resource allocation. The aim of conducting the study was to determine the prevalence and distribution of refractive error and its association with gender, age, and school grade level. Using a multistage random cluster sampling, 1586 children, 632 males (40%) and 954 females (60%), were selected. Their ages ranged between 13 and 18 years with a mean of 15.81 ± 1.56 years. The visual functions evaluated included visual acuity using the logarithm of minimum angle of resolution chart and refractive error measured using the autorefractor and then refined subjectively. Axis astigmatism was presented in the vector method where positive values of J0 indicated with-the-rule astigmatism, negative values indicated against-the-rule astigmatism, whereas J45 represented oblique astigmatism. Overall, patients were myopic with a mean spherical power for right eye of -0.02 ± 0.47; mean astigmatic cylinder power was -0.09 ± 0.27 with mainly with-the-rule astigmatism (J0 = 0.01 ± 0.11). The prevalence estimates were as follows: myopia (at least -0.50) 7% (95% confidence interval [CI], 6 to 9%), hyperopia (at least 0.5) 5% (95% CI, 4 to 6%), astigmatism (at least -0.75 cylinder) 3% (95% CI, 2 to 4%), and anisometropia 3% (95% CI, 2 to 4%). There was no significant association between refractive error and any of the categories (gender, age, and grade levels). The prevalence of refractive error in the sample of high school children was relatively low. Myopia was the most prevalent, and findings on its association with age suggest that the prevalence of myopia may be stabilizing at late teenage years.

Refraction and Ocular Biometry of Preschool Children in Shanghai, China.

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Zhang, Luoli; He, Xiangui; Qu, Xiaomei; You, Xiaofang; Wang, Bingjie; Shi, Huijing; Tan, Hui; Zou, Haidong; Zhu, Jianfeng

2018-01-01

To investigate the refraction and ocular biometry characteristics and to examine the prevalence of refractive errors in preschool children aged 3 to 6 years in Shanghai, China. A school-based cross-sectional study was conducted in Jiading and Xuhui District, Shanghai, in 2013. We randomly selected 7 kindergartens in Jiading District and 10 kindergartens in Xuhui District, with a probability proportionate to size. The children underwent comprehensive eye examinations, including cycloplegic refraction and biometric measurements. Myopia, hyperopia, astigmatism were defined as spherical equivalent (SE) ≤ -0.50 D, SE ≥ +2.00 D, and cylindrical diopters ≤ -1.00 D. The mean SE for 3- to 6-year-old children was +1.20 D (standard deviation [SD] 1.05), and the mean axial length (AL) was 22.29 mm (SD 0.73). The overall prevalence of myopia and astigmatism was 3.7% and 18.3%, respectively. No difference in prevalence of astigmatism was found across age groups. There was a statistically significant association between lower cylindrical diopters and higher spherical diopters (Spearman's correlation: -0.21, P < 0.001). Chinese children aged 3 to 6 years in the Shanghai area were mostly mildly hyperopic, with a low prevalence of myopia. Refractive astigmatism for children may be relatively stable throughout the preschool stage. Astigmatism was significantly associated with refractive error.

Facts about Astigmatism

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... a cornea that is curved more like a football, with some areas that are steeper or more ... Media Policies and Other Important Links NEI Employee Emergency Information NEI Intranet (Employees Only) *PDF files require ...

Simulation of the impact of refractive surgery ablative laser pulses with a flying-spot laser beam on intrasurgery corneal temperature.

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Shraiki, Mario; Arba-Mosquera, Samuel

2011-06-01

To evaluate ablation algorithms and temperature changes in laser refractive surgery. The model (virtual laser system [VLS]) simulates different physical effects of an entire surgical process, simulating the shot-by-shot ablation process based on a modeled beam profile. The model is comprehensive and directly considers applied correction; corneal geometry, including astigmatism; laser beam characteristics; and ablative spot properties. Pulse lists collected from actual treatments were used to simulate the temperature increase during the ablation process. Ablation efficiency reduction in the periphery resulted in a lower peripheral temperature increase. Steep corneas had lesser temperature increases than flat ones. The maximum rise in temperature depends on the spatial density of the ablation pulses. For the same number of ablative pulses, myopic corrections showed the highest temperature increase, followed by myopic astigmatism, mixed astigmatism, phototherapeutic keratectomy (PTK), hyperopic astigmatism, and hyperopic treatments. The proposed model can be used, at relatively low cost, for calibration, verification, and validation of the laser systems used for ablation processes and would directly improve the quality of the results.

[Refractive precision and objective quality of vision after toric lens implantation in cataract surgery].

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Debois, A; Nochez, Y; Bezo, C; Bellicaud, D; Pisella, P-J

2012-10-01

To study efficacy and predictability of toric IOL implantation for correction of preoperative corneal astigmatism by analysing spherocylindrical refractive precision and objective quality of vision. Prospective study of 13 eyes undergoing micro-incisional cataract surgery through a 1.8mm corneal incision with toric IOL implantation (Lentis L313T(®), Oculentis) to treat over one D of preoperative corneal astigmatism. Preoperative evaluation included keratometry, subjective refraction, and total and corneal aberrometry (KR-1(®), Topcon). Six months postoperatively, measurements included slit lamp photography, documenting IOL rotation, tilt or decentration, uncorrected visual acuity, best-corrected visual acuity and objective quality of vision measurement (OQAS(®) Visiometrics, Spain). Postoperatively, mean uncorrected distance visual acuity was 8.33/10 ± 1.91 (0.09 ± 0.11 LogMar). Mean postoperative refractive sphere was 0.13 ± 0.73 diopters. Mean refractive astigmatism was -0.66 ± 0.56 diopters with corneal astigmatism of 2.17 ± 0.68 diopters. Mean IOL rotation was 4.4° ± 3.6° (range 0° to 10°). Mean rotation of this IOL at 6 months was less than 5°, demonstrating stability of the optic within the capsular bag. Objective quality of vision measurements were consistent with subjective uncorrected visual acuity. Implantation of the L313T(®) IOL is safe and effective for correction of corneal astigmatism in 1.8mm micro-incisional cataract surgery. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

Design of high power solid-state pulsed laser resonators

International Nuclear Information System (INIS)

Narro, R.; Ponce, L.; Arronte, M.

2009-01-01

Methods and configurations for the design of high power solid-state pulsed laser resonators, operating in free running, are presented. For fundamental mode high power resonators, a method is proposed for the design of a resonator with joined stability zones. In the case of multimode resonators, two configurations are introduced for maximizing the laser overall efficiency due to the compensation of the astigmatism induced by the excitation. The first configuration consists in a triangular ring resonator. The results for this configuration are discussed theoretically, showing that it is possible to compensate the astigmatism of the thermal lens virtually in a 100%; however this is only possible for a specific pumping power. The second configuration proposes a dual-active medium resonator, rotated 90 degree one from the other around the optical axis, where each active medium acts as an astigmatic lens of the same dioptric power. The reliability of this configuration is corroborated experimentally using a Nd:YAG dual-active medium resonator. It is found that in the pumping power range where the astigmatism compensation is possible, the overall efficiency is constant, even when increasing the excitation power with the consequent increase of the thermal lens dioptric power. (Author)

The correlation between variation of visual acuity and the anterior chamber depth in the early period after phacoemulsification

Directory of Open Access Journals (Sweden)

Kai-jian CHEN

2011-04-01

Full Text Available Objective To investigate the correlation between the visual acuity variation and the anterior chamber depth in the early period after phacoemulsification.Methods Thirty-six eyes of 32 patients with age-related cataract underwent 3.2mm clear corneal incision phacoemulsification and intraocular lens(IOL implantation.The visual acuity was examined and horizontal curvature(K1,vertical curvature(K2,corneal astigmatism,and anterior chamber depth were measured with IOL-master preoperatively and also on 1,3,7 and 15 postoperative days.The changes in parameters were compared,and the correlations among visual acuity,corneal astigmatism and anterior chamber depth were analyzed.Results Before operation and 1d,3d,7d and 15d after operation,the corneal astigmatism was-0.87±0.40D,-1.92±1.38D,-1.69±1.13D,-1.45±0.79D and-1.36±0.74D;the anterior chamber depth was 3.08±0.35mm,4.04±0.38mm,4.28±0.29mm,4.22±0.17mm and 4.22±0.16mm;the visual acuity was 0.18±0.10,0.44±0.14,0.59±0.12,0.61±0.11 and 0.62±0.14.Significant difference was found between pre-operative and postoperative visual acuity,corneal astigmatism and anterior chamber depth,and it was also found in corneal astigmatism between 1d and 15d post operation(P < 0.05,as well as in anterior chamber depth and visual acuity between 1d and 3d post operation(P < 0.05.A positive correlation was found between visual acuity and corneal astigmatism on 1d(r=0.42,P < 0.05,3d(r=0.35,P < 0.05 and 7d(r=0.35,P < 0.05 post operation;and a negative correlation was found between visual acuity and anterior chamber depth on 3d(r=-0.29,P < 0.05,7d(r=-0.43,P < 0.01 and 15d(r=-0.37,P < 0.05 post operation.Conclusion Both the corneal astigmatism and the anterior chamber depth are correlated with the visual acuity variation in the early period after phacoemulsification.

Small incision corneal refractive surgery using the small incision lenticule extraction (SMILE) procedure for the correction of myopia and myopic astigmatism: results of a 6 month prospective study.

Science.gov (United States)

Sekundo, Walter; Kunert, Kathleen S; Blum, Marcus

2011-03-01

This 6 month prospective multi-centre study evaluated the feasibility of performing myopic femtosecond lenticule extraction (FLEx) through a small incision using the small incision lenticule extraction (SMILE) procedure. Prospective, non-randomised clinical trial. PARTICIPANTS; Ninety-one eyes of 48 patients with myopia with and without astigmatism completed the final 6 month follow-up. The patients' mean age was 35.3 years. Their preoperative mean spherical equivalent (SE) was −4.75±1.56 D. A refractive lenticule of intrastromal corneal tissue was cut utilising a prototype of the Carl Zeiss Meditec AG VisuMax femtosecond laser system. Simultaneously two opposite small ‘pocket’ incisions were created by the laser system. Thereafter, the lenticule was manually dissected with a spatula and removed through one of incisions using modified McPherson forceps. Uncorrected visual acuity (UCVA) and best spectacle corrected visual acuity (BSCVA) after 6 months, objective and manifest refraction as well as slit-lamp examination, side effects and a questionnaire. Six months postoperatively the mean SE was −0.01 D±0.49 D. Most treated eyes (95.6%) were within ±1.0 D, and 80.2% were within ±0.5 D of intended correction. Of the eyes treated, 83.5% had an UCVA of 1.0 (20/20) or better, 53% remained unchanged, 32.3% gained one line, 3.3% gained two lines of BSCVA, 8.8% lost one line and 1.1% lost ≥2 lines of BSCVA. When answering a standardised questionnaire, 93.3% of patients were satisfied with the results obtained and would undergo the procedure again. SMILE is a promising new flapless minimally invasive refractive procedure to correct myopia.

Comparison between children dilated computer and retinoscopy

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Li-Li Qi

2015-06-01

Full Text Available AIM: To investigate the dilation effect of computer optometry and retinoscopy optometry before and after mydriasis in children and to understand whether the application of computer refractor in children.METHODS: Therelated data of 500 children cases(1 000 eyeswith ametropia in our hospital were analyzed. The children firstly received computer optometry, and then use the 10g/L atropine sulfate eye gel drops, respectively. After 3d, they were performed computer optometry and retinoscopy, and compared the effect of two refraction.RESULTS: Spherical reading of computer optometry group was 2.70±2.75DS, cylinder degree was 1.54±1.10DC, were lower than those of retinoscopy group(PPPP>0.05. Before mydriasis, astigmatism was 1.54±1.10D, astigmatic axis was(14.38±11.11°. After mydriasis, astigmatism was 1.45±1.21D and astigmatic axis was(12.78±10.31°, significantly higher than those of retinoscopy(PCONCLUSION: Children optometry concerns the visual development of children. Computer optometry and retinoscopy are the pros and cons. As for computer optometry can not replace retinoscopy optometry, it can be used as an auxiliary tool for fast optometry.

Use of ultrasonic dissection in the early surgical management of periorbital haemangiomas.

Science.gov (United States)

Claude, O; Picard, A; O'Sullivan, N; Baccache, S; Momtchilova, M; Enjolras, O; Vazquez, M P; Diner, P A

2008-12-01

To evaluate the efficacy and safety of the early surgical excision of periorbital haemangiomas with an ultrasonic scalpel in infants at risk of visual impairment. A retrospective analysis of 67 infants diagnosed to be at risk of amblyopia from periorbital haemangiomas, treated consecutively with the Dissectron between 1994 and 2005. Ophthalmic outcome parameters included the pre- and postoperative measurement of visual axis occlusion, strabismus, astigmatism, and degree of amblyopia. Visual performance showed an overall improvement of 30% following treatment. Seventy-six patients were found to have abnormal ophthalmic examinations preoperatively, compared to 46 following surgery. After surgery, visual axis occlusion decreased from 73 to 6%; amblyopia decreased from 67 to 22%, strabismus decreased from 26 to 18% and astigmatism (>onedioptre) decreased from 66 to 31%. Mean astigmatism values decreased from 3.5 to 1.9 dioptres. No new cases of astigmatism, strabismus or amblyopia were diagnosed postoperatively. Three minor complications resolved with conservative treatment. All patients were satisfied with the outcome of their surgery. Early surgical excision of periorbital haemangiomas using the Dissectron in infants with an established risk of visual impairment is a safe and effective alternative to pharmacological therapy. The use of the Dissectron is associated with reduced operative times and a shorter hospital stay.

Photorefractive keratectomy (PRK) at 193 nm using an erodible mask: new developments and clinical progress

Science.gov (United States)

Gordon, Michael; Seiler, Theo; Carey, Joseph P.; Friedman, Marc D.; Johnsson, N. M. F.; King, Michael C.; Muller, David F.

1993-06-01

This paper reports on our progress using an erodible mask to perform photorefractive keratectomy (PRK) for the correction of myopic astigmatism. We describe modifications to the mask, the mask eye cup and the surgical microscope aimed at simplifying the procedure and improving the ergonomics of the hardware. We report the clinical results of the post-op exam for 20 patients who have undergone PRK for myopic astigmatism under a Phase IIA study. The results compare favorably with an earlier Phase IIA study for performing PRK with a computer-controlled iris. Most important, the clinical data show the absence of any significant corneal haze and no significant decrease in spectacle corrected visual acuity. Although more long term follow-up is needed, the preliminary results support the safety and effectiveness of using an erodible mask to perform PRK for myopic astigmatism.

Refractive status of primary school children in Mopani district, Limpopo Province, South Africa

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R.G. Mabaso

2006-12-01

Full Text Available This article reports part of the findings of a study carried out to determine the causes, prevalence,  and  distribution  of  ocular  dis-orders  among  rural  primary  school  children in  Mopani  district  of  Limpopo  Province, South Africa. Three hundred and eighty eight children  aged  8  to  15  years  were  randomly selected from five randomly selected schools. Non-cycloplegic retinoscopy and auto-refrac-tion were performed on each child. The preva-lence of hyperopia, myopia, and astigmatism was  73.1%,  2.5%  and  31.3%  respective-ly.  Hyperopia  (Nearest  spherical  equivalent power (FNSE ranged from +0.75 to +3.50 D for the right and left eyes with means of +1.05 ±  0.35  D  and  +1.08  ±  0.34  D  respectively. Myopia (FNSE ranged from –0.50 to –1.75 D for the right eye and –0.50 to –2.25 D for the left eye with means of –0.75 ± 0.55 D and –0.93 ± 0.55 D respectively. Regression model for myopia, shows that age had an odds ratio of  1.94  (1.15  to  3.26,  indicating  a  signifi-cant increased risk of myopia with increasing age.  Correcting  cylinders  for  the  right  eyes ranged from –0.25 to –4.50 D (mean = −0.67 ± 0.47 D and for the left eyes from –0.25 to –2.50 D (mean = −0.60 ± 0.30 D. With-the-rule  (WTR  astigmatism  (66.5%  was  more common, followed by against-the-rule (ATR astigmatism (28.1% and oblique (OBL astig-matism  (5.4%.  With-the-rule  astigmatism was  more  common  in  females  than  males; ATR astigmatism and OBL astigmatism were common in males. Regular vision screening programmes,  appropriate  referral  and  vision correction  in  primary  schools  in  Mopani district  are  recommended  in  order  to  elimi-nate  refractive  errors  among  the  children.

Risk Factors for Retreatment Following Myopic LASIK with Femtosecond Laser and Custom Ablation for the Treatment of Myopia.

Science.gov (United States)

Kruh, Jonathan N; Garrett, Kenneth A; Huntington, Brian; Robinson, Steve; Melki, Samir A

2017-01-01

To identify risks factors for retreatment post-laser in situ keratomeliusis (LASIK). A retrospective chart review from December 2008 to September 2012 identified 1,402 patients (2,581 eyes) that underwent LASIK treatment for myopia with the Intralase™ FS, STAR S4 IR™ Excimer Laser, and WaveScan WaveFront™ technology. In this group, 83 patients were retreated. All charts were reviewed for preoperative age, gender, initial manifest refraction spherical equivalent (MRSE), total astigmatism, and iris registration. Increased incidence rates of retreatment post-LASIK were preoperative age >40 years (p -3.0 D (p = 0.02), and astigmatism >1D (p = 0.001). Iris registration capture did not significantly reduce the retreatment rate (p = 0.12). Risk factors for retreatment included preoperative age >40 years, initial MRSE > -3.0 D, and astigmatism >1D. There was no difference in retreatment rate for patients based on gender or iris registration capture.

Prospects for electron beam aberration correction using sculpted phase masks

Energy Technology Data Exchange (ETDEWEB)

Shiloh, Roy, E-mail: royshilo@post.tau.ac.il; Remez, Roei; Arie, Ady

2016-04-15

Technological advances in fabrication methods allowed the microscopy community to take incremental steps towards perfecting the electron microscope, and magnetic lens design in particular. Still, state of the art aberration-corrected microscopes are yet 20–30 times shy of the theoretical electron diffraction limit. Moreover, these microscopes consume significant physical space and are very expensive. Here, we show how a thin, sculpted membrane is used as a phase-mask to induce specific aberrations into an electron beam probe in a standard high resolution TEM. In particular, we experimentally demonstrate beam splitting, two-fold astigmatism, three-fold astigmatism, and spherical aberration. - Highlights: • Thin membranes can be used as aberration correctors in electron columns. • We demonstrate tilt, twofold-, threefold-astigmatism, and spherical aberrations. • Experimental and physical-optics simulation results are in good agreement. • Advantages in cost, size, nonmagnetism, and nearly-arbitrary correction.

Prevalence of correctable visual impairment in primary school children in Qassim Province, Saudi Arabia.

Science.gov (United States)

Aldebasi, Yousef H

2014-01-01

The worldwide prevalence of refractive errors (RE), which is a common cause of treatable visual impairment among children, varies widely. We assessed the prevalence of correctable visual impairment (uncorrected RE) in primary school children in Qassim, Saudi Arabia. A cross-sectional study was conducted in 21 primary schools. A total of 5176 children (mean age 9.5±1.8 years), 2573 boys (49.7%) and 2603 girls (50.3%), underwent a comprehensive eye examination. The examinations consisted of visual acuity, autorefraction, cover test, ocular motility, pupillary evaluation, anterior segment examination, cycloplegic auto-refraction and dilated fundus examination with direct ophthalmoscopy. The children were divided into groups based on their age and gender. The overall prevalence of RE in the better eye was 18.6% (n=963), and the prevalence of uncorrected RE 16.3% (n=846), with only 2.3% (n=127) of children wearing spectacles during examination. The prevalence of uncorrected myopia (5.8%) and myopic astigmatism (5.4%) was higher compared to that of hyperopic astigmatism (2.7%), mixed astigmatism (1.7%) and hyperopia (0.7%). The anisometropia prevalence was 3.6%. Risks for astigmatism, myopia and anisometropia were positively associated with age. In addition, myopia and anisometropia risks were also associated with female gender, while risk of astigmatism was correlated with male gender. Few children with vision reducing RE wore spectacles; an additional 16.3% of children could benefit from spectacle prescription. The prevalence of uncorrected RE in children is relatively high and represents an important public health problem in school-aged children in Qassim province. Performance of routine periodical vision screening throughout childhood may reverse this situation. Copyright © 2013 Spanish General Council of Optometry. Published by Elsevier Espana. All rights reserved.

[Laser thermokeratoplasty in the treatment of hyperopia in children].

Science.gov (United States)

Kulikova, I L; Pashtaev, N P; Suslikov, S V

2006-01-01

The effectiveness, safety, and stability of multimodality treatment for hyperopia, hyperopic and mixed astigmatism complicated by amblyopia and anisometropia were studied in 117 patients (117 eyes) aged 9 to 16 years, by using the new laser units "Lik-100" and "Glasser" at 1.54 microm. The patients were divided into 3 groups: 1) 43 patients (43 eyes) with hyperopia, spheric anisometropia and amblyopia; 2) 38 patients (38 eyes) with hyperopia, simple and complicated hyperopic astigmatism, astigmatic anisometropia, and amblyopia; 3) 36 patients (36 eyes) with hyperopia, simple and complicated hyperopic astigmatism, mixed anisometropia, and amblyopia. All the groups underwent multimodality treatment involving laser thermokeratoplasty and drug therapy for amblyopia. In children and adolescents, the refraction effect was 2.99 and 3.61 (mean 3.37 +/- 0.60) diopters, respectively. Astigmatism diminished by 2.01 diopters (63%) in children and by 2.62 diopters (79%) in adolescents (mean 2/35 diopters). The predictability of a refraction effect in the range of +/- 0.5 diopters averaged 77% in all the groups. Anisometropia diminished by an average of 2.88 +/- 0.8 diopters, which was 85% of the baseline data (the upper range of residual refraction was not more than 1.5 diopters. In all the groups, uncorrectable visual acuity increased by an average of 0.36 diopters (0.43 and 0.4 diopters in children and adolescents, respectively); correctable visual acuity increased by an average of 0.22 diopters (0.36 and 0.31 diopters in children and adolescents, respectively). Loss of correctable visual acuity lines did not greater than 2.7% (5 eyes). That of endothelial cells was not more than 6-8%. The angle of squint strabismus could be decreased or corrected in 79% after treatment. Binocular vision restored in 57%.

Customized photorefractive keratectomy to correct high ametropia after penetrating keratoplasty: A pilot study

OpenAIRE

De Rosa, Giuseppe; Boccia, Rosa; Santamaria, Carmine; Fabbozzi, Lorenzo; De Rosa, Luigi; Lanza, Michele

2014-01-01

Purpose: To evaluate preliminarily the safety and efficacy of customized photorefractive keratectomy (PRK) to correct ametropia and irregular astigmatism after penetrating keratoplasty (PK). Methods: This pilot study included five eyes of five patients with a mean spherical equivalent of −5.1 ± 1.46 D (range from −2.75 to −6.50 D). In all cases, ametropia and irregular astigmatism was corrected with topography-guided customized PRK. Ocular examinations with topographic analysis were perfor...

Primary Pterygium in a 7-Year-Old Boy: A Report of a Rare Case and Dilemma of its Management

OpenAIRE

Noor, Raja Azmi Mohd

2003-01-01

Primary pterygium in children is uncommon but is associated with severe visual problems. Astigmatism is the main visual problem caused by pterygium. Significant amounts of astigmatism occur long before a pterygium encroaches the visual axis. Early surgical intervention is safe and effective. It is associated with significant visual improvement in outcome. This is a case report on seven-year-old Malay boy who presented with a growth over nasal aspect of the right eye of 1 year duration. His ri...

Demonstrating optical aberrations in the laboratory

CSIR Research Space (South Africa)

Naidoo, Darryl

2009-07-01

Full Text Available THE TANGENTIAL AND SAGITTAL FOCI DO NOT COINCIDE AND THE SYSTEM APPEARS TO HAVE 2 POINTS OF FOCUS SAGITTAL PLANE TANGENTIAL PLANE TANGENTIAL IMAGE OPTICAL AXIS OBJECT POINT SAGITTAL IMAGE ASTIGMATISM © CSIR 2008 www....csir.co.za ASTIGMATISM ARISES WHEN THE TANGENTIAL AND SAGITTAL FOCI DO NOT COINCIDE AND THE SYSTEM APPEARS TO HAVE 2 POINTS OF FOCUS SAGITTAL PLANE TANGENTIAL PLANE TANGENTIAL IMAGE OPTICAL AXIS OBJECT POINT SAGITTAL IMAGE FOCAL PLANE COMA IMAGE A B θ COMA...

Vision though afocal instruments: generalized magnification and eye-instrument interaction

Science.gov (United States)

Harris, William F.; Evans, Tanya

2018-04-01

In Gaussian optics all observers experience the same magnification, the instrument's angular magnification, when viewing distant objects though a telescope or other afocal instruments. However, analysis in linear optics shows that this is not necessarily so in the presence of astigmatism. Because astigmatism may distort and rotate images it is appropriate to work with generalized angular magnification represented by a 2 × 2 matrix. An expression is derived for the generalized magnification for an arbitrary eye looking through an arbitrary afocal instrument. With afocal instruments containing astigmatic refracting elements not all eyes experience the same generalized magnification; there is interaction between eye and instrument. Eye-instrument interaction may change as the instrument is rotated about its longitudinal axis, there being no interaction in particular orientations. A simple numerical example is given. For sake of completeness, expressions for generalized magnification are also presented in the case of instruments that are not afocal and objects that are not distant.

Quantitative pump-induced wavefront distortions in laser-diode- and flash-lamp-pumped Nd:YLF laser rods

International Nuclear Information System (INIS)

Skeldon, M.D.; Saager, R.B.; Seka, W.

1999-01-01

Detailed interferometric measurements of the induced thermal distortions due to laser-diode and xenon flashlamp pumping of Nd:YLF are presented. The thermal distortions are quantified in terms of the primary aberrations of defocus, astigmatism, coma, and spherical. Defocus and astigmatism are shown to dominate the thermal aberrations. The measured defocus and astigmatism are converted to the conventional thermal-focal lengths in two perpendicular directions with respect to the Nd:YLF crystalline c axis for each of the two polarization states σ and π. A comparison of the thermal-focal lengths measured with the xenon flashlamp- and laser-diode-pumped rods is given when the rods are pumped to the same small-signal gain. The authors calculate effective dioptric-power coefficients from the data for comparison to those reported in the literature for krypton-flashlamp pumping. A thermal-time constant of 1.5 s is measured for the laser-diode-pumped Nd:YLF laser rod

Comparison of Keratometry Obtained by a Swept Source OCT-Based Biometer with a Standard Optical Biometer and Scheimpflug Imaging.

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Asena, Leyla; Akman, Ahmet; Güngör, Sirel Gür; Dursun Altınörs, Dilek

2018-04-09

To assess agreement of a swept source-optical coherence tomography (SS-OCT) based Biometer with a standard IOLMaster device and Scheimpflug Imaging (SI) to acquire keratometric measurements in cataract patients. In this prospective comparative study, 101 eyes of 101 cataract surgery candidates, aged 24-81 years, were sequentially examined using three devices. Keratometry values at the flat (K1) and steep (K2) axis, mean corneal power (Km) and magnitude of corneal astigmatism as well as J0 and J45 vectoral components of astigmatism obtained with the SS-OCT based biometer (IOLMaster 700) were compared with those obtained with the IOLMaster 500 and SI. The agreement between measurements was evaluated by the Bland-Altman method, intraclass correlation coefficients (ICCs) and repeated-measures analysis of variance. Mean K1 values from the three devices were similar (p = 0.09). Mean K2 and Km values of IOLMaster 700 were higher than SI and lower than IOLMaster 500 (p = 0.04 for K2 and p = 0.02 for Km). There was a strong correlation between K1, K2, Km and magnitude of astigmatism obtained with all devices (r ≥ 0.80 and p devices was excellent for keratometric measurements. Mean K2, Km and astigmatism measurements from IOLMaster 700 were lower than IOLMaster 500 and higher than SI. However, the differences were quite small and are not expected to affect the final IOL power.

Three-year results of small incision lenticule extraction and wavefront-guided femtosecond laser-assisted laser in situ keratomileusis for correction of high myopia and myopic astigmatism.

Science.gov (United States)

Xia, Li-Kun; Ma, Jing; Liu, He-Nan; Shi, Ce; Huang, Qing

2018-01-01

To compare and calculate the 3-year refractive results, higher-order aberrations (HOAs), contrast sensitivity (CS) and dry eye parameters after small incision lenticule extraction (SMILE) and wavefront-guided femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) for correction of high myopia and myopic astigmatism. In this prospective, non-randomized comparative study, 78 eyes with spherical equivalent (SE) of -8.11±1.09 diopters (D) received a SMILE surgery, and 65 eyes with SE of -8.05±1.12 D received a wavefront-guided FS-LASIK surgery with the VisuMax femtosecond laser (Carl Zeiss Meditec, Jena, Germany) for flap cutting. Visual acuity, manifest refraction, CS, HOAs, ocular surface disease index (OSDI) and tear break-up time (TBUT) were evaluated during a 3-year follow-up. The difference of uncorrected distance visual acuity (UDVA) postoperatively was achieved at 1mo and at 3mo, whereas the difference of the mean UDVA between two groups at 3y were not statistically significant ( t =-1.59, P =0.13). The postoperative change of SE was 0.89 D in the FS-LASIK group ( t =5.76, P =0.00), and 0.14 D in the SMILE group ( t =0.54, P =0.59) from 1mo to 3y after surgery. At 3-year postoperatively, both HOAs and spherical aberrations in the SMILE group were obviously less than those in the FS-LASIK group ( P =0.00), but the coma root mean square (RMS) was higher in the SMILE group (0.59±0.26) than in the FS-LASIK group (0.29±0.14, P =0.00). The mesopic CS values between two groups were not statistically significant at 3y postoperatively. Compared with the FS-LASIK group, lower OSDI scores and longer TBUT values were found in the SMILE group at 1mo and 3mo postoperatively. With regard to safety, no eye lost any line of CDVA in both groups at 3y after surgery. Both SMILE and wavefront-guided FS-LASIK procedures provide good visual outcomes. Both procedures are effective and safe, but SMILE surgery achieve more stable long-term refractive outcome and better

Toric Intraocular Lens Outcomes in Patients With Glaucoma.

Science.gov (United States)

Brown, Reay H; Zhong, Le; Bozeman, Caroline W; Lynch, Mary G

2015-06-01

To report the outcomes of toric intraocular lens implantation in patients with glaucoma and corneal astigmatism. One hundred twenty-six eyes of 87 patients with glaucoma and corneal astigmatism that underwent cataract surgery with an AcrySof toric intraocular lens (Alcon Laboratories, Inc., Fort Worth, TX) implant were selected for this single-center, retrospective case series. Corrected distance visual acuity, intraocular pressure, and refractive astigmatism were measured in each eye preoperatively and postoperatively. Uncorrected distance visual acuity and toric alignment were measured postoperatively. The uncorrected distance visual acuity was 0.04 ± 0.08 logMAR (20/22 Snellen) for all eyes. Ninety-eight percent of all eyes achieved an uncorrected distance visual acuity of 20/40 or better, with 76% achieving 20/25 or better and 47% achieving 20/20. The corrected distance visual acuity for all eyes was 0.01 ± 0.03 logMAR (20/20.5 Snellen) postoperatively. The refractive cylinder improved from 1.47 ± 1.10 diopters preoperatively to 0.31 ± 0.37 diopters postoperatively. The residual refractive cylinder was 1.00 diopter or less in 97% of eyes, 0.75 diopters or less in 90% of eyes, and 0.50 diopters or less in 83% of eyes. Mean misalignment was 4.4° ± 5.1°. Intraocular pressure decreased by a mean of 2.3 ± 3.3 mm Hg following the surgery. Toric intraocular lenses can reliably reduce astigmatism and improve uncorrected vision in eyes with cataract and glaucoma. Copyright 2015, SLACK Incorporated.

Facoemulsificação por córnea clara no meridiano mais curvo Phacoemulsification using clear cornea incision in steepest meridian

Directory of Open Access Journals (Sweden)

Fernando Pistarini Gonçalves

2007-03-01

Full Text Available OBJETIVOS: Avaliar o efeito da facoemulsificação com incisão em córnea clara no meridiano mais curvo sobre a magnitude do astigmatismo ceratométrico pré-operatório. Mapear a magnitude do astigmatismo cirurgicamente induzido por incisões nas posições nasal (N, temporal (T, temporal superior (TS e temporal inferior (TI. MÉTODOS: Foi realizado estudo ceratométrico prospectivo em 48 olhos de 48 pacientes, submetidos a facoemulsificação com incisão do meridiano mais curvo. As medidas ceratométricas foram realizadas no pré-operatório e um mês após a realização da cirurgia. O astigmatismo cirurgicamente induzido foi determinado pelo método das coordenadas retangulares em 10 passos, modificado. RESULTADOS: Foram operados 21 olhos direitos e 27 olhos esquerdos e, de acordo com a posição das incisões em córnea clara, foram divididos em: 16 olhos N, 4 olhos T, 22 olhos TS, 6 olhos TI. A média da ametropia cilíndrica pré-operatória foi de 1,06D ± 0,65 e a pós-operatória de 0,89D ± 0,80. Houve diminuição estatisticamente significativa no astigmatismo corneal preexistente (p=0,016. A média total de astigmatismo cirurgicamente induzido foi de 0,94D ± 0,56. Em relação aos grupos o astigmatismo cirurgicamente induzido foi de 1,06D ± 0,66 em N, 0,87D ± 0,20 em T, 0,95D ± 0,55 em TS e 0,61D ± 0,25 em TI. Não houve diferença estatística com relação ao astigmatismo cirurgicamente induzido nos grupos N, T, TS e TI (p=0,426. CONCLUSÃO: A técnica se mostrou efetiva na redução do astigmatismo ceratométrico pré-operatório. A média do astigmatismo cirurgicamente induzido foi de 1,06D ± 0,66 em N, 0,95D ± 0,55 em TS, 0,61D ± 0,25 em T e 0,87D ± 0,20 em TI.PURPOSE: To evaluate the effect of phacoemulsification through clear cornea incision in the steepest meridian (ISM, on the magnitude of preoperative keratometric astigmatism. To map the magnitude of surgically induced astigmatism (SIA by clear cornea incision

Phacoemulsification and intraocular lens implantation in patients with oculocutaneous albinism.

Science.gov (United States)

Dávila, Pedro J; Ulloa-Padilla, Jan P; Izquierdo, Natalio J

2017-01-01

To evaluate the benefits of phacoemulsification and intraocular lens implantation in patients with oculocutaneous albinism (OCA). The charts of 195 patients with OCA who visited a local eye clinic were reviewed. All of these patients had genetic linkage analysis to establish OCA type. Frequencies and Paired t-test analysis were determined. Of the 195 patients, nine (4.6%) underwent clear cornea phacoemulsification with intraocular lens implantation. Seven of the nine patients with OCA had the Hermansky-Pudlak (HPS) type 1; two had OCA type 1. Pre-operative BCVA of all eyes ranged from 1.0 to 2.3 logMAR with a mean of 1.42 logMAR and a standard deviation of 0.41 logMAR. Post-operative BCVA of all eyes ranged from 1.0 to 1.30 logMAR with a mean of 1.04 logMAR and a standard deviation of 0.10 logMAR. BCVA improved after phacoemulsification surgery and intraocular lens implantation (p = 0.002). Pre-operative astigmatism of all eyes ranged from +0.50 to +5.75 with a mean of +2.25 and a standard deviation of +2.40. Post-operative astigmatism of all eyes ranged from +0.50 to +2.00 with a mean of +1.23 and a standard deviation of +0.42. Astigmatism improved after phacoemulsification surgery and intraocular lens implantation (p = 0.05). Nine patients with OCA who underwent phacoemulsification and intraocular lens implant experienced improved visual acuity and reduced astigmatism post-operatively. These results suggest cataract surgery may improve vision and refractive errors, and thus quality of life, in patients with albinism.

Visual outcomes after implantation of a novel refractive toric multifocal intraocular lens

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Talita Shimoda

2014-04-01

Full Text Available Purpose: To assess the postoperative outcomes of a novel toric multifocal in traocular lens (IOL in patients with cataract and corneal astigmatism. Methods: This prospective nonrandomized study included patients with cataract, corneal astigmatism, and a motivation for spectacle independence. In all patients, a Rayner M-flex® T toric IOL was implanted in the capsular bag. Three months after surgery, the distance, intermediate, and near visual acuities; spherical equivalent; residual refractive astigmatism; defocus curve; and contrast sensitivity were evaluated. A patient satisfaction and visual phenomena questionnaire was administered to all patients. Results: Thirty-four eyes of 18 patients were included in this study. Three months after surgery, the mean corrected distance visual acuity (logMAR was 0.00 ± 0.08 at 6 m, 0.20 ± 0.09 at 70 cm, and 0.08 ± 0.11 at 40 cm. Uncorrected distance vision acuity was 20/40 or better in 100% eyes. The preoperative mean refractive cylinder (RC was -2.19 (SD: ± 0.53. After a 3-month follow-up, the average RC was -0.44 D (SD: ± 0.27; p<0.001. Contrast sensitivity levels were high. At the last follow-up, 87.5% patients were spectacle-independent for near, intermediate, and distance vision, and approximately 44% patients reported halos and glare. Conclusion: Toric multifocal IOL implantation in patients with cataract and corneal astigmatism using the Rayner M-flex® T toric IOL was a simple, safe, and accurate option. This technology provides surgeons with a feasible option for meeting patient expectations of an enhanced lifestyle resulting from decreased spectacle dependence.

Risk Factors Associated with Childhood Strabismus: The Multi-Ethnic Pediatric Eye Disease and Baltimore Pediatric Eye Disease Studies

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Cotter, Susan; Varma, Rohit; Tarczy-Hornoch, Kristina; McKean-Cowdin, Roberta; Lin, Jesse; Wen, Ge; Wei, Jolyn; Borchert, Mark; Azen, Stan; Torres, Mina; Tielsch, James M.; Friedman, David S.; Repka, Michael X.; Ibironke, Joanne Katz Josephine; Giordano, Lydia

2011-01-01

Objective To investigate risk factors associated with esotropia or exotropia in infants and young children. Design Population-based cross-sectional prevalence study. Participants Population-based samples of 9970 children ages 6 to 72 months from California and Maryland. Methods Participants were preschool African-American, Hispanic, and non-Hispanic white children participating in the Multiethnic Pediatric Eye Disease Study and the Baltimore Eye Disease Study. Data were obtained by parental interview and ocular examination. Odd ratios and 95% confidence intervals were calculated to evaluate the association of demographic, behavioral, and clinical risk factors with esotropia and exotropia. Main Outcome Measures Odds ratios (ORs) for various risk factors associated with esotropia or exotropia diagnosis based on cover testing. Results In multivariate logistic regression analysis, esotropia was independently associated with prematurity, maternal smoking during pregnancy, older preschool age (48–72 months), anisometropia, and hyperopia. There was a severity-dependent association of hyperopia with the prevalence of esotropia, with ORs increasing from 6.4 for 2.00 Diopters (D) to strabismus, female sex, astigmatism (OR 2.5 for 1.50 to <2.50 D, and 5.9 for ≥ 2.5 D of astigmatism), and aniso-astigmatism in the J0 component (OR ≥ 2 for J0 aniso-astigmatism ≥ 0.25 D). Conclusions Prematurity and maternal smoking during pregnancy are associated with a higher risk of having esotropia and exotropia. Refractive error is associated in a severity-dependent manner to the prevalence of esotropia and exotropia. Because refractive error is correctable, these risk associations should be considered when developing guidelines for the screening and management of refractive error in infants and young children children. PMID:21856012

Topography-modified refraction (TMR): adjustment of treated cylinder amount and axis to the topography versus standard clinical refraction in myopic topography-guided LASIK.

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Kanellopoulos, Anastasios John

2016-01-01

To evaluate the safety, efficacy, and contralateral eye comparison of topography-guided myopic LASIK with two different refraction treatment strategies. Private clinical ophthalmology practice. A total of 100 eyes (50 patients) in consecutive cases of myopic topography-guided LASIK procedures with the same refractive platform (FS200 femtosecond and EX500 excimer lasers) were randomized for treatment as follows: one eye with the standard clinical refraction (group A) and the contralateral eye with the topographic astigmatic power and axis (topography-modified treatment refraction; group B). All cases were evaluated pre- and post-operatively for the following parameters: refractive error, best corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA), topography (Placido-disk based) and tomography (Scheimpflug-image based), wavefront analysis, pupillometry, and contrast sensitivity. Follow-up visits were conducted for at least 12 months. Mean refractive error was -5.5 D of myopia and -1.75 D of astigmatism. In group A versus group B, respectively, the average UDVA improved from 20/200 to 20/20 versus 20/16; post-operative CDVA was 20/20 and 20/13.5; 1 line of vision gained was 27.8% and 55.6%; and 2 lines of vision gained was 5.6% and 11.1%. In group A, 27.8% of eyes had over -0.50 diopters of residual refractive astigmatism, in comparison to 11.7% in group B ( P Topography-modified refraction (TMR): topographic adjustment of the amount and axis of astigmatism treated, when different from the clinical refraction, may offer superior outcomes in topography-guided myopic LASIK. These findings may change the current clinical paradigm of the optimal subjective refraction utilized in laser vision correction.

A comparison between Goldmann applanation tonometry and dynamic contour tonometry after photorefractive keratectomy.

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Sadigh, Afshin Lotfi; Fouladi, Rohollah F; Hashemi, Hassan; Beheshtnejad, Amir Houshang

2013-02-01

The intraocular pressure (IOP) could be measured by both Goldmann applanation tonometry (GAT) and dynamic contour tonometry (DCT). Although these two methods have been discussed widely after laser-assisted sub-epithelial keratectomy (LASIK), there is little data in the cases undergoing photorefractive keratectomy (PRK). We aimed to compare the changes of IOP measurements obtained by GAT and DCT after PRK for myopia/myopic astigmatism. This prospective study enrolled 77 candidates (154 eyes) for PRK to correct myopia or myopic astigmatism and 30 matched patients (30 eyes) with myopia or myopic astigmatism who served as controls. Changes of the IOP measurements (ΔIOP) obtained by GAT and DCT before and at 6 months after PRK in the operated eyes, and at baseline and 6 months later in the controls, were documented. Changes of the central corneal thickness (ΔCCT) were determined in the same fashion. The mean IOP readings obtained by DCT were comparable before and at 6 months after procedure (18.34 ± 3.03 mmHg and 17.87 ± 2.61 mmHg respectively, p = 0.41); whereas the mean IOP reading obtained by GAT decreased significantly 6 months postoperatively (17.92 ± 3.63 mmHg and 16.25 ± 2.66 mmHg, p vs 0.07 ± 0.44 mmHg, p = 0.02). The mean DCT-obtained ΔIOP was just marginally insignificant between the operated and nonoperated eyes (-0.63 ± 0.59 vs 0.02 ± 0.38 mmHg respectively; p = 0.09). The authors recommend DCT after PRK in the cases with myopia or myopic astigmatism.

Variation of contrast sensitivity after femtosecond laser in situ keratomileusis in changes environments

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Jing Zhou

2015-01-01

Full Text Available AIM: To evaluate the difference of contrast sensitivity(CSin photopic and scotopic environments in eyes with myopia and myopic astigmatism operated with femtosecond laser in situ keratomileusis(femto-LASIKand laser in situ keratomileusis(LASIK.METHODS: In a prospective study 160 myopia and myopic astigmatism patients' eyes were involved, which accepted femto-LASIK or LASIK in our hospital from January 2010 to February 2012. The myopia degree was -1.50～-10.00D, the astigmatism degree ≤-6.0D. Eighty eyes were treated with femto-LASIK in group A, and 80 eyes were treated with LASIK in group B, All patients in the treatment group completed the final 6mo of follow-up. The uncorrected visual acuity(UCVAand the best spectacle-corrected visual acuity(BSCVA, objective and manifest refractions, results of slit-lamp examination, the side effects, intraocular pressure, corneal topography, CS in photopic and scotopic environments were noted.RESULTS: All of operations on 160 cases were successful without severe complication after 6 mo follow-up. CS of femto-LASIK group(group Aat each spatial frequency environment were higher than that of LASIK group(group B. In group A, after 1mo the photopic CS, after 3mo of scotopic CS recovered to the preoperative level, 6mo after surgery improved than before the operation. In group B, after 3mo photopic CS to the preoperative level, scotopic CS at 6mo after operation was still not recovered to the preoperative level.CONCLUSION:Femto-LASIK for correction of myopia and myopic astigmatism, in improving the postoperative contrast sensitivity under shade environment has more advantages than LASIK.

Fourier analysis algorithm for the posterior corneal keratometric data: clinical usefulness in keratoconus.

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Sideroudi, Haris; Labiris, Georgios; Georgantzoglou, Kimon; Ntonti, Panagiota; Siganos, Charalambos; Kozobolis, Vassilios

2017-07-01

To develop an algorithm for the Fourier analysis of posterior corneal videokeratographic data and to evaluate the derived parameters in the diagnosis of Subclinical Keratoconus (SKC) and Keratoconus (KC). This was a cross-sectional, observational study that took place in the Eye Institute of Thrace, Democritus University, Greece. Eighty eyes formed the KC group, 55 eyes formed the SKC group while 50 normal eyes populated the control group. A self-developed algorithm in visual basic for Microsoft Excel performed a Fourier series harmonic analysis for the posterior corneal sagittal curvature data. The algorithm decomposed the obtained curvatures into a spherical component, regular astigmatism, asymmetry and higher order irregularities for averaged central 4 mm and for each individual ring separately (1, 2, 3 and 4 mm). The obtained values were evaluated for their diagnostic capacity using receiver operating curves (ROC). Logistic regression was attempted for the identification of a combined diagnostic model. Significant differences were detected in regular astigmatism, asymmetry and higher order irregularities among groups. For the SKC group, the parameters with high diagnostic ability (AUC > 90%) were the higher order irregularities, the asymmetry and the regular astigmatism, mainly in the corneal periphery. Higher predictive accuracy was identified using diagnostic models that combined the asymmetry, regular astigmatism and higher order irregularities in averaged 3and 4 mm area (AUC: 98.4%, Sensitivity: 91.7% and Specificity:100%). Fourier decomposition of posterior Keratometric data provides parameters with high accuracy in differentiating SKC from normal corneas and should be included in the prompt diagnosis of KC. © 2017 The Authors Ophthalmic & Physiological Optics © 2017 The College of Optometrists.

Six-month clinical outcomes after hyperopic correction with the SCHWIND AMARIS Total-Tech laser

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Arbelaez, María Clara; Vidal, Camila; Arba Mosquera, Samuel

2011-01-01

Purpose To evaluate postoperative clinical outcomes, and corneal High Order Aberrations, among eyes with hyperopia up to +5 D of spherical equivalent, that have undergone LASIK treatments using the SCHWIND AMARIS laser system. Methods At six-month follow-up, 100 eyes with preoperative hyperopia or hyperopic astigmatism up to +5 D of spherical equivalent were retrospectively analysed. Standard examinations, pre- and postoperative wavefront analysis with a corneal-wavefront-analyzer (OPTIKON Scout) were performed. Aberration-Free aspheric treatments were planned with Custom Ablation Manager software and ablations performed using the SCHWIND AMARIS flying-spot excimer laser system (both SCHWIND eye-tech-solutions). LASIK flaps were created using a LDV femtosecond laser (Ziemer Group) in all cases. Clinical outcomes were evaluated in terms of predictability, refractive outcome, safety, and wavefront aberration. Results At six month, 90 % of eyes achieved ≥ 20/25 UCVA and 44 % achieved ≥ 20/16 UCVA. Seventy-four percent of eyes were within ± 0.25D of spherical equivalent and 89 % within ± 0.50D, with 94 % within 0.50D of astigmatism. Mean spherical equivalent was −0.12 ± 0.51D and 0.50 ± 0.51D for the astigmatism. Fifty-two percent of eyes improved BSCVA vs. only 19 % losing lines of BSCVA. Predictability slope for refraction was 1.03 and intercept +0.01 D. On average, negative corneal spherical aberrations were significantly increased by the treatments, no other aberration terms changed from pre- to postoperative values. Conclusions LASIK for hyperopia and hyperopic astigmatism with SCHWIND AMARIS yields very satisfactory visual outcomes. Preoperative refractions were postoperatively reduced to subclinical values with no clinically relevant induction of corneal HOA.

Optical and Biometric Characteristics of Anisomyopia in Human Adults

Science.gov (United States)

Tian, Yibin; Tarrant, Janice; Wildsoet, Christine F.

2011-01-01

Purpose To investigate the role of higher order optical aberrations and thus retinal image degradation in the development of myopia, through the characterization of anisomyopia in human adults in terms of their optical and biometric characteristics. Methods The following data were collected from both eyes of fifteen young adult anisometropic myopes and sixteen isometropic myopes: subjective and objective refractive errors, corneal power and shape, monochromatic optical aberrations, anterior chamber depth, lens thickness, vitreous chamber depth, and best corrected visual acuity. Monochromatic aberrations were analyzed in terms of their higher order components, and further analyzed in terms of 31 optical quality metrics. Interocular differences for the two groups (anisomyopes vs. isomyopes) were compared and the relationship between measured ocular parameters and refractive errors also analyzed across all eyes. Results As expected, anisomyopes and isomyopes differed significantly in terms of interocular differences in vitreous chamber depth, axial length and refractive error. However, interocular differences in other optical properties showed no significant intergroup differences. Overall, higher myopia was associated with deeper anterior and vitreous chambers, higher astigmatism, more prolate corneas, and more positive spherical aberration. Other measured optical and biometric parameters were not significantly correlated with spherical refractive error, although some optical quality metrics and corneal astigmatism were significantly correlated with refractive astigmatism. Conclusions An optical cause for anisomyopia related to increased higher order aberrations is not supported by our data. Corneal shape changes and increased astigmatism in more myopic eyes may be a by-product of the increased anterior chamber growth in these eyes; likewise, the increased positive spherical aberration in more myopic eyes may be a product of myopic eye growth. PMID:21797915

Prevalence of refractive errors in the European adult population: the Gutenberg Health Study (GHS).

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Wolfram, Christian; Höhn, René; Kottler, Ulrike; Wild, Philipp; Blettner, Maria; Bühren, Jens; Pfeiffer, Norbert; Mirshahi, Alireza

2014-07-01

To study the distribution of refractive errors among adults of European descent. Population-based eye study in Germany with 15010 participants aged 35-74 years. The study participants underwent a detailed ophthalmic examination according to a standardised protocol. Refractive error was determined by an automatic refraction device (Humphrey HARK 599) without cycloplegia. Definitions for the analysis were myopia +0.5 D, astigmatism >0.5 cylinder D and anisometropia >1.0 D difference in the spherical equivalent between the eyes. Exclusion criterion was previous cataract or refractive surgery. 13959 subjects were eligible. Refractive errors ranged from -21.5 to +13.88 D. Myopia was present in 35.1% of this study sample, hyperopia in 31.8%, astigmatism in 32.3% and anisometropia in 13.5%. The prevalence of myopia decreased, while the prevalence of hyperopia, astigmatism and anisometropia increased with age. 3.5% of the study sample had no refractive correction for their ametropia. Refractive errors affect the majority of the population. The Gutenberg Health Study sample contains more myopes than other study cohorts in adult populations. Our findings do not support the hypothesis of a generally lower prevalence of myopia among adults in Europe as compared with East Asia.

[Comparison of refraction with or without cycloplegia using Retinomax® or Plusoptix® devices].

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Bui Quoc, E; Guilmin Crepon, S; Tinguely, S; Lavallee, G; Busquet, G; Angot, M; Vera, L

2017-03-01

To evaluate the refraction in children measured with Plusoptix ® without cycloplegia vs. Retinomax ® apparatus with cycloplegia. Measure of refraction with Plusoptix ® in children>1year old referred for systematic vision screening, then measurement after cycloplegia with cyclopentolate by the Retinomax ® device. Thirty-three children were included, i.e. 66eyes. Mean age was 40.7months (minimum 12; maximum 114). The Spearman correlation coefficient for the spherical equivalent was 0.52 (Plusoptix ® vs. Retinomax ® comparison; P<0.0001=moderate correlation). The Spearman correlation coefficient was 0.73 for astigmatism (Plusoptix ® vs. Retinomax ® comparison; P<0.0001=strong correlation). The Plusoptix ® sensitivity for measurement of refraction was 57%, 43% and 43% respectively for spherical equivalent, sphere and astigmatism. The correlation of astigmatism values is strong, whereas the correlation of sphere values is moderate. Plusoptix ® seems to be unable to measure the exact refraction, because there is too large a dispersion of refraction measurements with Plusoptix ® , compared to the exact refraction measured with the Retinomax ® . Moreover, the sensitivity of Plusoptix ® is low. Cycloplegic refraction remains indispensable in children. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Three-year results of small incision lenticule extraction and wavefront-guided femtosecond laser-assisted laser in situ keratomileusis for correction of high myopia and myopic astigmatism

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Li-Kun Xia

2018-03-01

Full Text Available AIM: To compare and calculate the 3-year refractive results, higher-order aberrations (HOAs, contrast sensitivity (CS and dry eye parameters after small incision lenticule extraction (SMILE and wavefront-guided femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK for correction of high myopia and myopic astigmatism. METHODS: In this prospective, non-randomized comparative study, 78 eyes with spherical equivalent (SE of -8.11±1.09 diopters (D received a SMILE surgery, and 65 eyes with SE of -8.05±1.12 D received a wavefront-guided FS-LASIK surgery with the VisuMax femtosecond laser (Carl Zeiss Meditec, Jena, Germany for flap cutting. Visual acuity, manifest refraction, CS, HOAs, ocular surface disease index (OSDI and tear break-up time (TBUT were evaluated during a 3-year follow-up. RESULTS: The difference of uncorrected distance visual acuity (UDVA postoperatively was achieved at 1mo and at 3mo, whereas the difference of the mean UDVA between two groups at 3y were not statistically significant (t=-1.59, P=0.13. The postoperative change of SE was 0.89 D in the FS-LASIK group (t=5.76, P=0.00, and 0.14 D in the SMILE group (t=0.54, P=0.59 from 1mo to 3y after surgery. At 3-year postoperatively, both HOAs and spherical aberrations in the SMILE group were obviously less than those in the FS-LASIK group (P=0.00, but the coma root mean square (RMS was higher in the SMILE group (0.59±0.26 than in the FS-LASIK group (0.29±0.14, P=0.00. The mesopic CS values between two groups were not statistically significant at 3y postoperatively. Compared with the FS-LASIK group, lower OSDI scores and longer TBUT values were found in the SMILE group at 1mo and 3mo postoperatively. With regard to safety, no eye lost any line of CDVA in both groups at 3y after surgery. CONCLUSION: Both SMILE and wavefront-guided FS-LASIK procedures provide good visual outcomes. Both procedures are effective and safe, but SMILE surgery achieve more stable long

Refractive errors, visual impairment, and the use of low-vision devices in albinism in Malawi.

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Schulze Schwering, M; Kumar, N; Bohrmann, D; Msukwa, G; Kalua, K; Kayange, P; Spitzer, M S

2015-04-01

This study focuses on the refractive implications of albinism in Malawi, which is mostly associated with the burden of visual impairment. The main goal was to describe the refractive errors and to analyze whether patients with albinism in Malawi, Sub-Saharan Africa, benefit from refraction. Age, sex, refractive data, uncorrected and best-corrected visual acuity (UCVA, BCVA), colour vision, contrast sensitivity, and the prescription of sunglasses and low vision devices were collected for a group of 120 albino individuals with oculocutaneous albinism (OCA). Refractive errors were evaluated objectively and subjectively by retinoscopy, and followed by cycloplegic refraction to reconfirm the results. Best-corrected visual acuity (BCVA) was also assessed binocularly. One hundred and twenty albino subjects were examined, ranging in age from 4 to 25 years (median 12 years), 71 (59 %) boys and 49 (41 %) girls. All exhibited horizontal pendular nystagmus. Mean visual acuity improved from 0.98 (0.33) logMAR to 0.77 (0.15) logMAR after refraction (p < 0.001). The best improvement of VA was achieved in patients with mild to moderate myopia. Patients with albinism who were hyperopic more than +1.5 D hardly improved from refraction. With the rule (WTR) astigmatism was more present (37.5 %) than against the rule (ATR) astigmatism (3.8 %). Patients with astigmatism less than 1.5 D improved in 15/32 of cases (47 %) by 2 lines or more. Patients with astigmatism equal to or more than 1.5 D in any axis improved in 26/54 of cases (48 %) by 2 lines or more. Refraction improves visual acuity of children with oculocutaneous albinism in a Sub-Saharan African population in Malawi. The mean improvement was 2 logMAR units.

Bilateral implantation of +3.0 D multifocal toric intraocular lenses: results of a US Food and Drug Administration clinical trial.

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Lehmann, Robert; Modi, Satish; Fisher, Bret; Michna, Magda; Snyder, Michael

2017-01-01

The purpose of this study was to evaluate the clinical outcomes of apodized diffractive +3.0 D multifocal toric intraocular lens (IOL) implantations in subjects with preoperative corneal astigmatism. This was a prospective cohort study conducted at 21 US sites. The study population consisted of 574 subjects, aged ≥21 years, with preoperative astigmatism 0.75-2.82 D, and potential postoperative visual acuity (VA) ≥0.2 logMAR, undergoing bilateral cataract removal by phacoemulsification. The intervention was bilateral implantation of aspheric apodized diffractive +3.0 D multifocal toric or spherical multifocal nontoric IOLs. The main outcome measures were monocular uncorrected near and distance VA and safety at 12 months. A total of 373/386 and 182/188 subjects implanted with multifocal toric and nontoric IOLs, respectively, completed 12-month follow-up after the second implantation. Toric IOLs were nonin-ferior in monocular uncorrected distance (4 m) and near (40 cm) VA but had >1 line better binocular uncorrected intermediate VA (50, 60, and 70 cm) than nontoric IOLs. Toric IOLs reduced cylinder to within 0.50 D and 1.0 D of target in 278 (74.5%) and 351 (94.1%) subjects, respectively. Mean ± standard deviation (SD) differences between intended and achieved axis orientation in the first and second implanted eyes were 5.0°±6.1° and 4.7°±4.0°, respectively. Mean ± SD 12-month IOL rotations in the first and second implanted eyes were 2.7°±5.8° and 2.2°±2.7°, respectively. No subject receiving toric IOLs required secondary surgical intervention due to optical lens properties. Multifocal toric IOLs were noninferior to multifocal nontoric IOLs in uncorrected distance and near VAs in subjects with preexisting corneal astigmatism and effectively corrected astigmatism of 0.75-2.82 D.

New Refractive Surgery Procedures and Their Implications for Aviation Safety

National Research Council Canada - National Science Library

Nakagawara, Van B; Wood, Kathryn J; Montgomery, Ron W

2006-01-01

...., myopia, hyperopia, astigmatism) with corrective surgery. Prior Federal Aviation Administration research studies have shown that the number of civil airmen with refractive surgery continues to increase...

Primary pterygium in a 7-year-old boy: a report of a rare case and dilemma of its management.

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Noor, Raja Azmi Mohd

2003-07-01

Primary pterygium in children is uncommon but is associated with severe visual problems. Astigmatism is the main visual problem caused by pterygium. Significant amounts of astigmatism occur long before a pterygium encroaches the visual axis. Early surgical intervention is safe and effective. It is associated with significant visual improvement in outcome. This is a case report on seven-year-old Malay boy who presented with a growth over nasal aspect of the right eye of 1 year duration. His right eye visual acuity is affected up to 6/12. The dilemma pased to early surgical interview is the high rate of recurrancean the young age group. This problem is highlighted in this case report.

Visual function after implantation of single-piece toric hydrophilic acrylic intraocular lenses with hydrophobic surface six months after cataract surgery

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Alja Črnej

2012-06-01

Conclusion: Patients with medium to high corneal astigmatism and implanted single-piece toric hydrophilic acrylic IOLs with hydrophobic surface have very good visual function six months postoperatively.

[A design of refractometer based on blur circle].

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Zhang, Yikui; Huang, Shenghai; Ye, Huifang; Zou, Ruitao; Tong, Gengmin; Zhuo, Ran

2011-03-01

Design a convenient and stable eye refractometer based on the theory of blur circle. Analyze the retinal blur circle in both Emsly reduced eye model and Liou & Brennan 1997 eye model by ZEMAX. Design the coefficients including PD (pupil diameter) and NO' (length between node point and fovea) with the purpose of improving the accuracy. At last, compare the clinical optometry data from this refractor with the data obtained from optometry hospital in Wenzhou. The blur circle diameters are nearly the same in both reduced eye model and the Liou & Brennan 1997 eye model. With the PD = 4 mm and NO' = 20 mm, the refractor shows a fine accuracy in optometry. The paired t test shows that the myopia group and the astigmatism axial direction group have no statistical difference between the data from the blur circle refractor and the hospital (P > 0.05), while the astigmatism degree group has the result of P = 0.41 which may be caused by the poor cooperation of pediatric patients. 80% of the astigmatism degree data differ from the data from the hospital in less than 0.75D. The blur circle refractor, with the features of convenience and fine accuracy, is promised to be a new style of refractometer in the future.

Spectacles in Children‑ Do's and Don'ts

African Journals Online (AJOL)

Conclusions: Children have visual needs that differ from adults, and therefore, the prescription of glasses has to ... treatment of myopia, hypermetropia, astigmatism, and anisometropia. ... accommodative esotropia, strabismic amblyopia, and.

Six-month clinical outcomes after hyperopic correction with the SCHWIND AMARIS Total-Tech laser

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María Clara Arbelaez

2010-10-01

Conclusions: LASIK for hyperopia and hyperopic astigmatism with SCHWIND AMARIS yields very satisfactory visual outcomes. Preoperative refractions were postoperatively reduced to subclinical values with no clinically relevant induction of corneal HOA.

Refractive errors in Cameroonians diagnosed with complete oculocutaneous albinism

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Eballé AO

2013-07-01

Full Text Available André Omgbwa Eballé1,3, Côme Ebana Mvogo2, Christelle Noche4, Marie Evodie Akono Zoua2, Andin Viola Dohvoma21Faculty of Medicine and Pharmaceutical Sciences, University of Douala, Douala, Cameroon, 2Faculty of Medicine and Biomedical Sciences, University of Yaoundé I, Yaoundé, Cameroon; 3Yaoundé Gynaeco-obstetric and Paediatric Hospital. Yaoundé, Cameroon; 4Faculty of Medicine, Université des Montagnes. Bangangté, CameroonBackground: Albinism causes significant eye morbidity and amblyopia in children. The aim of this study was to determine the refractive state in patients with complete oculocutaneous albinism who were treated at the Gynaeco-Obstetric and Paediatric Hospital, Yaoundé, Cameroon and evaluate its effect on vision.Methods: We carried out this retrospective study at the ophthalmology unit of our hospital. All oculocutaneous albino patients who were treated between March 1, 2003 and December 31, 2011 were included.Results: Thirty-five patients (70 eyes diagnosed with complete oculocutaneous albinism were enrolled. Myopic astigmatism was the most common refractive error (40%. Compared with myopic patients, those with myopic astigmatism and hypermetropic astigmatism were four and ten times less likely, respectively, to demonstrate significant improvement in distance visual acuity following optical correction.Conclusion: Managing refractive errors is an important way to reduce eye morbidity-associated low vision in oculocutaneous albino patients.Keywords: albinism, visual acuity, refraction, Cameroon

Visual and Refractive Outcomes after Cataract Surgery with Implantation of a New Toric Intraocular Lens

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Cinzia Mazzini

2013-06-01

Full Text Available Purpose: The aim of this study was to evaluate and report the visual, refractive and aberrometric outcomes of cataract surgery with implantation of the new aspheric Tecnis ZCT toric intraocular lens (IOL in eyes with low to moderate corneal astigmatism. Methods: We conducted a prospective study of 19 consecutive eyes of 17 patients (mean age: 78 years with a visually significant cataract and moderate corneal astigmatism [higher than 1 diopter (D] undergoing cataract surgery with implantation of the aspheric Tecnis ZCT toric IOL (Abbott Medical Optics. Visual, refractive and aberrometric changes were evaluated during a 6-month follow-up. Ocular aberrations as well as IOL rotation were evaluated by means of the OPD-Station II (Nidek. Results: The six-month postoperative spherical equivalent and power vector components of the refractive cylinder were within ±0.50 D in all eyes (100%. Postoperative logMAR uncorrected and corrected distance visual acuities (UDVA/CDVA were 0.1 (about 20/25 or better in almost all eyes (94.74%. The mean logMAR CDVA improved significantly from 0.41 ± 0.23 to 0.02 ± 0.05 (p Conclusion: Cataract surgery with implantation of the aspheric Tecnis ZCT IOL is a predictable and effective procedure for visual rehabilitation in eyes with cataract and low to moderate corneal astigmatism, providing an excellent postoperative ocular optical quality.

Ocular biometric measurements in cataract surgery candidates in Portugal.

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Ferreira, Tiago B; Hoffer, Kenneth J; Ribeiro, Filomena; Ribeiro, Paulo; O'Neill, João G

2017-01-01

Describe the ocular biometric parameters and their associations in a population of cataract surgery candidates. A cross-sectional study of 13,012 eyes of 6,506 patients was performed. Biometric parameters of the eyes were measured by optical low-coherence reflectometry. The axial length (AL), mean keratometry (K) and astigmatism, anterior chamber depth (ACD) (epithelium to lens), lens thickness (LT), and Corneal Diameter (CD) were evaluated. The mean age was 69 ± 10 years (44-99 years). Mean AL, Km, and ACD were 23.87 ± 1.55 mm (19.8-31.92 mm), 43.91 ± 1.71 D (40.61-51.14 D), and 3.25 ± 0.44 mm (2.04-5.28 mm), respectively. The mean LT was 4.32 ± 0.49 mm (2.73-5.77 mm) and the mean CD was 12.02 ± 0.46 mm (10.50-14.15 mm). The mean corneal astigmatism was 1.08 ± 0.84 D (0.00-7.58 D) and 43.5% of eyes had astigmatism ≥ 1.00 D. Male patients had longer AL and ACDs (p biometric values for the Portuguese population. The greatest predictor of ocular biometrics was gender. There was no significant correlation between age and AL, ACD, or Km. These results may be relevant in the evaluation of refractive error and in the calculation of intraocular lens power.

A comparison of cycloplegic autorefraction and retinoscopy in Indian children.

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Guha, Sujata; Shah, Sanil; Shah, Khyati; Hurakadli, Preeti; Majee, Debalina; Gandhi, Shyamali

2017-01-01

Correction of significant refractive errors in childhood helps in preventing amblyopia and strabismus. India has a huge demand for eye-care services related to uncorrected refractive errors with limited manpower resources. This can be overcome by autorefractors, which are free of operator bias, do not need skilled eye-care professionals and can be operated with ease. Hence, the purpose of this study, the first in the Indian population, was to determine the accuracy of autorefraction compared to traditional retinoscopy under cycloplegia. A cross-sectional study of all children meeting our inclusion criteria was conducted from July till October 2011 in a tertiary eye care centre. Children underwent cycloplegic (cyclopentolate plus tropicamide) refraction with an auto-refractometer (Topcon KR-8900) and traditional retinoscopy and the results were compared. Patients were divided into three groups: Group 1: Myopia and myopic astigmatism, Group 2: Hyperopia and hyperopic astigmatism and Group 3: Mixed astigmatism. Clinically significant difference was defined as either of more than 0.50 D difference in sphere, more than 0.5 D difference in cylinder or more than 20 degrees difference in axis. The left eyes of 294 children (148 male) were included in the study. Mean age was 8.22 ± 3.47 years. Clinically significant differences were noted in 13.22 per cent of eyes in Group 1, 15.09 per cent of eyes in Group 2 and 20.90 per cent of eyes in Group 3. Clinically significant differences were more common in children aged less than six years (25 per cent) compared to older children (9.19 per cent). Comparing the sphere, cylinder, spherical equivalent and length of power vector values gained by autorefraction and retinoscopy, no statistically significant differences were found in any group. Autorefraction with Topcon KR-8900 can be used reliably in Indian children older than six years, if conducted under cycloplegia. In mixed astigmatism and children less than six years, it should

Prevalence and risk factors for myopia and other refractive errors in an adult population in southern India.

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Joseph, Sanil; Krishnan, Tiruvengada; Ravindran, Ravilla D; Maraini, Giovanni; Camparini, Monica; Chakravarthy, Usha; Ravilla, Thulasiraj D; Hutchings, Andrew; Fletcher, Astrid E

2018-05-01

To investigate prevalence and risk factors for myopia, hyperopia and astigmatism in southern India. Randomly sampled villages were enumerated to identify people aged ≥40 years. Participants were interviewed for socioeconomic and lifestyle factors and attended a hospital-based ophthalmic examination including visual acuity measurement and objective and subjective measurement of refractive status. Myopia was defined as spherical equivalent (SE) worse than -0.75 dioptres (D), hyperopia as SE ≥+1D and astigmatism as cylinder <-0.5. The age-standardised prevalences of myopia, hyperopia and astigmatism were 35.6% (95% CI: 34.7-36.6), 17.0% (95% CI: 16.3-17.8) and 32.6 (29.3-36.1), respectively. Of those with myopia (n = 1490), 70% had advanced cataract. Of these, 79% had presenting visual acuity (VA) less than 6/18 and after best correction, 44% of these improved to 6/12 or better and 27% remained with VA less than 6/18. In multivariable analyses (excluding patients with advanced cataract), increasing nuclear opacity score, current tobacco use, and increasing height were associated with higher odds of myopia. Higher levels of education were associated with increased odds of myopia in younger people and decreased odds in older people. Increasing time outdoors was associated with myopia only in older people. Increasing age and female gender were associated with hyperopia, and nuclear opacity score, increasing time outdoors, rural residence and current tobacco use with lower odds of hyperopia. After controlling for myopia, factors associated with higher odds of astigmatism were age, rural residence, and increasing nuclear opacity score and increasing education with lower odds. In contrast to high-income settings and in agreement with studies from low-income settings, we found a rise in myopia with increasing age reflecting the high prevalence of advanced cataract. © 2018 The Authors. Ophthalmic and Physiological Optics published by John Wiley & Sons Ltd on behalf of

Erros de refração como causas de baixa visual em crianças da rede de escolas públicas da regional de Botucatu - SP Refractive errors as causes of visual impairment in children from public schools of the Botucatu region - SP

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Claudia Akemi Shiratori de Oliveira

2009-04-01

Full Text Available OBJETIVO: Estudar a ocorrência dos erros refracionais em escolares de nosso meio. MÉTODOS: Estudo transversal avaliando crianças da pré-escola e do ensino básico, quanto ao sexo, tipo de erro refracional, acuidade visual e tratamento realizado. RESULTADOS: Quatro mil seiscentos e vinte e três crianças foram submetidas a exame de acuidade visual, das quais 8,1% apresentaram necessidade de exame oftalmológico completo. Houve 63,2% de portadores de astigmatismo hipermetrópico, 15,7% de astigmatismo miópico, 12,5% de astigmatismo misto, 4,9% de hipermetropia e 3,7% de miopia. Foi indicada a prescrição de lentes corretoras para 48,7% da amostra estudada. A frequência de erros refracionais na população foi de 3,9%. CONCLUSÃO: O astigmatismo hipermetrópico foi o erro de refracional mais frequente, havendo necessidade de tratamento em cerca de 50% das crianças triadas com frequência de 3,9% de erro refracional passível de correção na população de estudo.PURPOSE: To evaluate the refractive errors as cause of visual impairment in school children from the Botucatu region. METHODS: A sectional study was conducted evaluating preschool and elementary school students, according to gender, refractive error, visual acuity and treatment. RESULTS: Four thousand six hundred and twenty-three (4,623 children were submitted to visual acuity evaluation and 8.1% of them were submitted to complete ocular examination. There were 63.2% hyperopic astigmatism, 15.7% myopic astigmatism, 12.5% astigmatism, 4.9% hyperopia and 3.7% myopia. Corrective lenses were prescribed for 48.7% of the evaluated children. CONCLUSION: The most frequent refractive error was hyperopic astigmatism and 50% of the children received treatment. The frequency of refractive errors was 3.9% of the studied population.

Functional and refractive results after one month of AcrySof toric intraocular lens implantation

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Francisco Alba-Bueno

2011-04-01

Conclusions: The implantation of SN60T toric IOL in patients with CA higher than 0.75 D is a safe, predictable and effective way of reducing refractive astigmatism in patients undergoing cataract surgery.

Small Incision Cataract Surgery (SICS with Clear Corneal Incision and SICS with Scleral Incision – A Comparative Study

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Md Shafiqul Alam

2014-01-01

Full Text Available Background: Age related cataract is the leading cause of blindness and visual impairment throughout the world. With the advent of microsurgical facilities simple cataract extraction surgery has been replaced by small incision cataract surgery (SICS with posterior chamber intra ocular lens implant, which can be done either with clear corneal incision or scleral incision. Objective: To compare the post operative visual outcome in these two procedures of cataract surgery. Materials and method: This comparative study was carried out in the department of Ophthalmology, Delta Medical College & Hospital, Dhaka, Bangladesh, during the period of January 2010 to December 2012. Total 60 subjects indicated for age related cataract surgery irrespective of sex with the age range of 40-80 years with predefined inclusion and exclusion criteria were enrolled in the study. Subjects were randomly and equally distributed in 2 groups; Group A for SICS with clear corneal incision and group B for SICS with scleral incision. Post operative visual out come was evaluated by determining visual acuity and astigmatism in different occasions and was compared between groups. Statistical analysis was done by SPSS for windows version12. Results: The highest age incidence (43.3% was found between 61 to 70 years of age group. Among study subjects 40 were male and 20 were female. Preoperative visual acuity and astigmatism were evenly distributed between groups. Regarding postoperative unaided visual outcome, 6/12 or better visual acuity was found in 19.98% cases in group A and 39.6% cases in group B at 1st week. At 6th week 6/6 vision was found in 36.3% in Group A and 56.1% in Group B and 46.2% in group A and 66% in group B without and with correction respectively. With refractive correction, 6/6 vision was attained in 60% subjects of group A and 86.67% of group B at 8th week. Post operative visual acuity was statistically significant in all occasions. Postoperative astigmatism of

Optical design of Kirkpatrick-Baez microscope for ICF

International Nuclear Information System (INIS)

Mu Baozhong; Yi Shengzhen; Huang Shengling; Wang Zhanshan

2008-01-01

A new flux-resolution optical design method of Kirkpatrick-Baez microscope (KB microscope) is proposed. In X-ray imaging diagnostics of inertial confinement fusion(ICF), spatial resolution and flux are always the key parameters. While the traditional optical design of KB microscope is to correct on-axis spherical aberration and astigmatic aberration, flux-resolution method is based on lateral aberration of full field and astigmatic aberration. Thus the spatial resolution related to field dimension and light flux can be estimated. By the expressions of spatial resolution and actual limits in ICF, rules of how to set original structure and optical design flow are summarized. An instance is presented and it shows that the design has met the original targets and overcome the shortcomings of image characterization in compressed core by traditional spherical aberration correction. (authors)

Láser in situ keratomileusis en la corrección de miopía y astigmatismo residual posqueratotomía radial en casos seleccionados Laser in situ keratomileusis to correct myopia and residual astigmatism after radial keratotomy in selected cases

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Eneida Pérez Candelaria

2010-01-01

descriptive study was performed in 55 eyes from 31 patients with residual myopia and/or astigmatism after radial keratotomy, who were re-operated on using Laser in situ keratomileusis at Refractive Surgery Service of "Ramón Pando Ferrer" Cuban Institute of Ophthalmology from January to June 2007. Strict inclusion and exclusion criteria were applied to select the patients, on the basis of following variables: residual refractive errors in average spheral equivalent, visual acuity without correction and best visual acuity with correction before and after LASIK as well as the transoperative and postoperative complications. The average follow-up period were 12 ± 3 months. RESULTS: The spheral equivalent after LASIK was substantially reduced in the first day of the postoperative phase and kept stable in the last appointment with the specialist. The visual acuity without correction after LASIK was 1,0 (20/20 in 22 eyes (40% and > 0,5 (20/40 in 44 eyes (80 %. In eleven eyes (20%, the best corrected visual acuity improved by one line in the Snellen´s chart. The transoperative complication was found in one eye with central corneal flap perforation whereas the reported postoperative complications were detritus and hematic remains in the interphase in 2 eyes, fine foldings of the flap in one eye and epithelization of the interphase out of the visual axis also in one eye. CONCLUSIONS: The Laser in situ keratomileusis can be used successfully to correct myopia and astigmatism after radial keratotomy in duly selected cases.

Standard ophthalmic exam

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... the eye ( glaucoma ) using a method called tonometry Color blindness is tested using cards with colored dots that ... Astigmatism (abnormally curved cornea) Blocked tear duct Cataracts Color blindness Corneal abrasion (or dystrophy) Corneal ulcers and infections ...

Functional outcomes and patient satisfaction after laser in situ keratomileusis for correction of myopia.

NARCIS (Netherlands)

Tahzib, N.G.; Bootsma, S.J.; Eggink, F.A.G.J.; Nabar, V.A.; Nuijts, R.M.

2005-01-01

PURPOSE: To determine subjective patient satisfaction and self-perceived quality of vision after laser in situ keratomileusis (LASIK) to correct myopia and myopic astigmatism. SETTING: Department of Ophthalmology, Academic Hospital Maastricht, Maastricht, The Netherlands. METHODS: A validated

Productivity associated with visual status of computer users.

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Daum, Kent M; Clore, Katherine A; Simms, Suzanne S; Vesely, Jon W; Wilczek, Dawn D; Spittle, Brian M; Good, Greg W

2004-01-01

The aim of this project is to examine the potential connection between the astigmatic refractive corrections of subjects using computers and their productivity and comfort. We hypothesize that improving the visual status of subjects using computers results in greater productivity, as well as improved visual comfort. Inclusion criteria required subjects 19 to 30 years of age with complete vision examinations before being enrolled. Using a double-masked, placebo-controlled, randomized design, subjects completed three experimental tasks calculated to assess the effects of refractive error on productivity (time to completion and the number of errors) at a computer. The tasks resembled those commonly undertaken by computer users and involved visual search tasks of: (1) counties and populations; (2) nonsense word search; and (3) a modified text-editing task. Estimates of productivity for time to completion varied from a minimum of 2.5% upwards to 28.7% with 2 D cylinder miscorrection. Assuming a conservative estimate of an overall 2.5% increase in productivity with appropriate astigmatic refractive correction, our data suggest a favorable cost-benefit ratio of at least 2.3 for the visual correction of an employee (total cost 268 dollars) with a salary of 25,000 dollars per year. We conclude that astigmatic refractive error affected both productivity and visual comfort under the conditions of this experiment. These data also suggest a favorable cost-benefit ratio for employers who provide computer-specific eyewear to their employees.

Simultaneous versus sequential penetrating keratoplasty and cataract surgery.

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Hayashi, Ken; Hayashi, Hideyuki

2006-10-01

To compare the surgical outcomes of simultaneous penetrating keratoplasty and cataract surgery with those of sequential surgery. Thirty-nine eyes of 39 patients scheduled for simultaneous keratoplasty and cataract surgery and 23 eyes of 23 patients scheduled for sequential keratoplasty and secondary phacoemulsification surgery were recruited. Refractive error, regular and irregular corneal astigmatism determined by Fourier analysis, and endothelial cell loss were studied at 1 week and 3, 6, and 12 months after combined surgery in the simultaneous surgery group or after subsequent phacoemulsification surgery in the sequential surgery group. At 3 and more months after surgery, mean refractive error was significantly greater in the simultaneous surgery group than in the sequential surgery group, although no difference was seen at 1 week. The refractive error at 12 months was within 2 D of that targeted in 15 eyes (39%) in the simultaneous surgery group and within 2 D in 16 eyes (70%) in the sequential surgery group; the incidence was significantly greater in the sequential group (P = 0.0344). The regular and irregular astigmatism was not significantly different between the groups at 3 and more months after surgery. No significant difference was also found in the percentage of endothelial cell loss between the groups. Although corneal astigmatism and endothelial cell loss were not different, refractive error from target refraction was greater after simultaneous keratoplasty and cataract surgery than after sequential surgery, indicating a better outcome after sequential surgery than after simultaneous surgery.

Ptosis - infants and children

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Blepharoptosis - children; Congenital ptosis; Eyelid drooping - children; Eyelid drooping - amblyopia; Eyelid drooping - astigmatism ... Ptosis in infants and children is often due to a problem with the muscle that raises the eyelid. A nerve problem in the eyelid can ...

Influence of eye micromotions on spatially resolved refractometry

Science.gov (United States)

Chyzh, Igor H.; Sokurenko, Vyacheslav M.; Osipova, Irina Y.

2001-01-01

The influence eye micromotions on the accuracy of estimation of Zernike coefficients form eye transverse aberration measurements was investigated. By computer modeling, the following found eye aberrations have been examined: defocusing, primary astigmatism, spherical aberration of the 3rd and the 5th orders, as well as their combinations. It was determined that the standard deviation of estimated Zernike coefficients is proportional to the standard deviation of angular eye movements. Eye micromotions cause the estimation errors of Zernike coefficients of present aberrations and produce the appearance of Zernike coefficients of aberrations, absent in the eye. When solely defocusing is present, the biggest errors, cased by eye micromotions, are obtained for aberrations like coma and astigmatism. In comparison with other aberrations, spherical aberration of the 3rd and the 5th orders evokes the greatest increase of the standard deviation of other Zernike coefficients.

Customized photorefractive keratectomy to correct high ametropia after penetrating keratoplasty: A pilot study

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Giuseppe De Rosa

2015-07-01

Conclusion: Our pilot study suggests that customized PRK can be a safe and effective method for treating ametropia and irregular astigmatisms after PK. Future studies with larger samples and longer follow-ups should be performed to confirm these results.

Incisões relaxantes limbares durante a cirurgia de catarata: resultados após seguimento de um ano Limbal relaxing incisions during cataract surgery: one-year follow-up

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João Carlos Arraes

2006-06-01

ções pós-operatórias significativas.PURPOSE: To evaluate astigmatism variation between preoperative, 1st and 12th postoperative month of patients who underwent cataract surgery with limbal relaxing incisions (LRI aiming to reduce the preoperative astigmatism. METHODS: Sixteen patients who underwent cataract surgery by the phacoemulsification technique with a 5.5 mm escleral incision, at the Altino Ventura Foudation, between April and July of 2002. The limbal relaxing incisions were performed according to Gills' modified nomogram (1D - 1 LRI of 6 mm; 1-2D - 2 LRI of 6 mm; 2-3D - 2 LRI of 8 mm. They were done in the most curved meridians, determined by preoperative corneal topography. RESULTS: Significant reduction in preoperative astigmatism was observed in the 1st postoperative month in 2 limbal relaxing incisions of the 6 mm group (57% topographic astigmatism and 87% refractional and in 2 limbal relaxing incisions of the 8 mm group (50% topographic astigmatism and 65% refractional, maintaining the reduction with no significant alteration until the 12th postoperative month. The 1 limbal relaxing incision of the 6 mm group did not yield significant astigmatism reduction, but there was no significant alteration until de 12th postoperative month. There were also no complications such as postoperative discomfort, glare, aniseiconia, diplopia, incision infection and corneal thinning or ectasia. CONCLUSION: Two limbal relaxing incisions of 8 and 6 mm aiming to correct preoperative astigmatism of 2 to 3D and 1 to 2D, respectively, were safe and effective with a stable effect in the first postoperative follow-up year. The 1 limbal relaxing incision of 6 mm aiming to reduce 1 diopter of preoperative astigmatism was not effective, but it did not induce any significant postoperative complications.

Dark refraction shift with allowance for astigmatism

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W.D.H. Gillan

2005-12-01

Full Text Available Purpose: To show that the dark refraction shift (dark focus is a more complicated phenomenon than implied when presented as spherical. Methods: Fifty autorefractor measurements of refractive state of the right eye were obtained in light  and  dark  conditions.  Multivariate  methods were used to analyze the data and stereo-pair scat-ter plots, polar meridional profiles and other means of presenting results are used to show important characteristics of the dark refraction shift. Results: The complexity of the dark refrac-tion shift is indicated by stereo-pair scatter plots showing the amount of stigmatic and antistigmatic variation that occurs in light and dark conditions. The mean dark refraction shift is presented in a complete manner including all three components of refractive state. The greater variance and covari-ance under dark conditions is clearly shown by the term-by-term dark-light variance-covariance ratio and polar profiles  of variance and covariance.Conclusions: The  dark  refraction  shift  is  a more complicated phenomenon than implied by representations as purely spherical in nature.

Computerized calculation scheme for toric intraocular lenses.

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Langenbucher, Achim; Seitz, Berthold

2004-06-01

While a number of intraocular lens (IOL) power prediction formulae are well established for determination of spherical lenses, no common strategy has been published for the computation of toric IOLs. The purpose of this study is to describe a paraxial computing scheme for tracing an axial pencil of rays through the 'optical system eye' containing astigmatic refractive surfaces with their axes at random. The capabilities of this computing scheme are demonstrated with clinical examples. Based on a schematic model eye with spherocylindric surfaces, we use two alternative notations for description of vergences or prescriptions: (1) standard notation (refraction in both cardinal meridians and axis), and (2) component notation (spherical equivalent and cylindric component in 0 degrees and 45 degrees. Refractive surfaces are added to the vergence in component notation, whereas the transformation of the vergence through media is performed in the standard notation for both cardinal meridians. For calculation of the toric lens implant, a pencil of rays is traced through the spectacle and the cornea to the estimated lens position as well as backwards from the retina to the estimated lens position. For calculation of residual spectacle refraction, a pencil of rays is traced backwards from the retina through the toric lens implant and the cornea to the spectacle plane. In example 1 we calculate a 'thin toric lens' for compensation of a corneal astigmatism to achieve a spherical target refraction. In example 2 we compute a 'thick toric lens', which has to compensate for an oblique corneal astigmatism and rotate the spectacle cylinder to the against the rule position to enhance near vision. In example 3 we estimate the residual refraction at the corneal plane after implantation of a thick toric lens, when the cylinder of the lens implant is compensating the corneal cylinder in part and the axis of implantation is not fully aligned with the axis of the corneal astigmatism. This

OCULAR DISORDERS IN CHILDREN WITH DEVELOPMENTAL DELAY

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Meera Suresh Joshi

2017-08-01

Full Text Available BACKGROUND In India, an estimated 1.5-2.5% children below 2 years of age are developmentally delayed. A higher incidence of ocular disability is seen in these children, refractive errors and strabismus being most common. These can add to the overall burden of health as most of them have developmental comorbidities. The aim of the study is to study the ocular disorders in children with developmental delay. MATERIALS AND METHODS We studied 112 children between the 2-12 years of age diagnosed to have developmental delay. All the subjects underwent a detailed ophthalmic evaluation including visual acuity testing using Snellen’s charts (3m and 6m and Log MAR charts (recorded as per Snellen’s vision testing to maintain uniformity, cycloplegic refraction, torchlight and slit-lamp evaluation and dilated fundus examination. The data was tabulated and represented using bar diagrams, Pie charts and graphs. The results were expressed as percentages. Design-Cross-sectional, observational study. RESULTS 66 boys and 46 girls (total 112 were evaluated. The mean age of the study population was 7.8 years ± 2.4 SD. The aetiology of developmental delay was cerebral palsy (64%, Down syndrome (22%, autism (7%, intellectual disability (4.5% and 1 case each of congenital hypothyroidism and ataxia telangiectasia. The prevalence of ocular disorders was found to be 84.8%, which was slightly higher in girls (87% as compared to boys (83%. Refractive error (79.5% was the commonest ocular disorder followed by strabismus (46.4%. Astigmatism (44.6% was the commonest refractive error, which was divided into myopic astigmatism (19.6%, hyperopic astigmatism (13.8% and mixed astigmatism (11.2%. Simple hyperopia was seen in 21.9% subjects and simple myopia in 12.1%. Exotropia (52% was commoner than esotropia (48%. Other ocular abnormalities included optic atrophy, nystagmus, epicanthal folds, cataract, mongoloid slant, ptosis, telecanthus, conjunctival telangiectasia and

Method of increasing power within an optical cavity with long path lengths

Energy Technology Data Exchange (ETDEWEB)

Leen, John Brian; Bramall, Nathan E.

2018-03-13

A cavity-enhanced absorption spectroscopy instrument has an optical cavity with two or more cavity mirrors, one mirror of which having a hole or other aperture for injecting a light beam, and the same or another mirror of which being partially transmissive to allow exit of light to a detector. A spherical-spherical configuration with at least one astigmatic mirror or a spherical-cylindrical configuration where the spherical mirror could also be astigmatic prevents a reentrant condition wherein the injected beam would prematurely exit the cavity through the aperture. This combination substantially increases the number of passes of the injected beam through a sample volume for sensitive detection of chemical species even in less than ideal conditions including low power laser or LED sources, poor mirror reflectivity or detector noise at the wavelengths of interest, or cavity alignment issues such as vibration or temperature and pressure changes.

Coma-free alignment of high resolution electron microscopes with the aid of optical diffractograms

International Nuclear Information System (INIS)

Zemlin, F.; Weiss, K.; Schiske, P.; Kunath, W.; Herrmann, K.-H.

1978-01-01

Alignment by means of current commutating and defocusing of the objective does not yield the desired rotational symmetry of the imaging pencils. This was found while aligning a transmission electron microscope with a single field condenser objective. A series of optical diffractograms of micrographs taken under the same tilted illumination yet under various azimuths have been arranged in a tableau, wherein strong asymmetry is exhibited. Quantitative evaluation yields the most important asymmetric aberration to be the axial coma, which becomes critical when a resolution better than 5 A 0 is obtained. The tableau also allows an assessment of the three-fold astigmatism. A procedure has been developed which aligns the microscope onto the coma-free and dispersion-free pencil axis and does not rely on current communication. The procedure demands equal appearance of astigmatic carbon film images produced under the same tilt yet diametrical azimuth. (Auth.)

Effect of iris registration on outcomes of LASIK for myopia with the VISX CustomVue platform

DEFF Research Database (Denmark)

Moshirfar, Majid; Chen, Michael C; Espandar, Ladan

2009-01-01

PURPOSE: To compare visual outcomes after LASIK using the VISX STAR S4 CustomVue, with and without Iris Registration technology. METHODS: In this retrospective study, LASIK was performed on 239 myopic eyes, with or without astigmatism, of 142 patients. Iris registration LASIK was performed on 121...... eyes and non-iris registration LASIK was performed on 118 eyes. Primary outcome measures were uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and manifest refraction. RESULTS: At 6 months, the mean values for UCVA (logMAR) were 0.00 +/- 0.09 in the iris registration...... magnitude of error of surgically induced astigmatism was -0.09 in the iris registration group and -0.04 in the non-iris registration group (P = .25). CONCLUSIONS: Wavefront-guided LASIK with the VISX STAR S4 CustomVue laser system, independent of iris registration status, is effective, safe, and predictable...

Refractive status and optical components of premature babies with or without retinopathy of prematurity at 3-4 years old.

Science.gov (United States)

Ouyang, Li-Juan; Yin, Zheng-Qin; Ke, Ning; Chen, Xin-Ke; Liu, Qin; Fang, Jing; Chen, Lin; Chen, Xiu-Rong; Shi, Hui; Tang, Ling; Pi, Lian-Hong

2015-01-01

To investigate the refractive status and optical components of premature babies with or without retinopathy of prematurity (ROP) at 3-4 years old, and to explore the influence of prematurity and ROP on the refractive status and optical components. Premature babies receiving fundus examination were recruited into ROP group and non-ROP group, with age-matched full-term babies as controls. The incidence of myopia was the highest in ROP (3/59, 5.08%). The incidence of astigmatism was significantly different between ROP (37.29%, 22/59) and controls (17.86%, 15/84). The corneal refractive power in ROP and non-ROP was more potent compared with controls (PPremature babies with or without ROP are susceptible to myopia and astigmatism. ROP, prematurity and low birth-weight synergistically influence the development of refractive status and optical components, of which the prematurity and low birth-weight are more important.

Analysis of excimer laser radiant exposure effect toward corneal ablation volume at LASIK procedure

Science.gov (United States)

Adiati, Rima Fitria; Rini Rizki, Artha Bona; Kusumawardhani, Apriani; Setijono, Heru; Rahmadiansah, Andi

2016-11-01

LASIK (Laser Asissted In Situ Interlamelar Keratomilieusis) is a technique for correcting refractive disorders of the eye such as myopia and astigmatism using an excimer laser. This procedure use photoablation technique to decompose corneal tissues. Although preferred due to its efficiency, permanency, and accuracy, the inappropriate amount radiant exposure often cause side effects like under-over correction, irregular astigmatism and problems on surrounding tissues. In this study, the radiant exposure effect toward corneal ablation volume has been modelled through several processes. Data collecting results is laser data specifications with 193 nm wavelength, beam diameter of 0.065 - 0.65 cm, and fluence of 160 mJ/cm2. For the medical data, the myopia-astigmatism value, cornea size, corneal ablation thickness, and flap data are taken. The first modelling step is determining the laser diameter between 0.065 - 0.65 cm with 0.45 cm increment. The energy, power, and intensity of laser determined from laser beam area. Number of pulse and total energy is calculated before the radiant exposure of laser is obtained. Next is to determine the parameters influence the ablation volume. Regression method used to create the equation, and then the spot size is substituted to the model. The validation used is statistic correlation method to both experimental data and theory. By the model created, it is expected that any potential complications can be prevented during LASIK procedures. The recommendations can give the users clearer picture to determine the appropriate amount of radiant exposure with the corneal ablation volume necessary.

One-year follow-up of femtosecond laser-assisted penetrating keratoplasty

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Tan JCH

2013-02-01

Full Text Available Johnson Choon-Hwai Tan, Wee-Jin HengNational Healthcare Group Eye Institute, Tan Tock Seng Hospital, SingaporeBackground: The purpose of this report is to describe the initial outcomes of femtosecond laser-assisted penetrating keratoplasty.Methods: This retrospective surgical case series consisted of 10 eyes from 10 patients undergoing penetrating keratoplasty at a tertiary center. Femtosecond laser was used to perform a zig-square incision on the donor cornea with matched dimensions on the recipient cornea. Outcomes measured included: unaided visual acuity and best spectacle-corrected visual acuity preoperatively and at one, 3, 6, and 12 months postoperatively; manifest refractive and topographic astigmatism at 3, 6, and 12 months postoperatively; and endothelial cell density loss, calculated at the end of the one-year follow-up period.Results: At one-year follow-up, there was an improvement in unaided visual acuity from a mean preoperative logMAR of 1.67 to 0.44, and best spectacle-corrected visual acuity from a mean preoperative logMAR of 1.33 to 0.13. By postoperative month 3, mean manifest refractive and topographic astigmatism was 2.31 ± 1.41 D and 2.59 ± 1.57 D, respectively. The mean reduction in endothelial cell density was 20.7% after one year of follow-up.Conclusion: Femtosecond laser-assisted penetrating keratoplasty provided a good visual outcome and early visual rehabilitation due to precise graft-host alignment and reduced astigmatism in the early postoperative months.Keywords: penetrating keratoplasty, femtosecond laser-assisted keratoplasty

Comparison of biometric predictability and final refraction expected in phacoemulsification surgery with and without trabeculectomy

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Fernanda Guedes Oliveira

Full Text Available Abstract Objective: The main purpose of this article is to compare the predictability of biometric results and final refractive outcomes expected in patients undergoing cataract surgery through phacoemulsification with and without associated trabeculectomy. Methods: Cataract patients who have undergone phacoemulsification surgery alone (control group or associated with trabeculectomy (study group screened. All surgeries were performed following standard protocol. For enrollment, biometrics calculated by IOL Master (Carl Zeiss Meditec, Inc. biometry, refraction and intraocular pressure (IOP before and after surgery were required. Data was compared between groups in addition to the correlation between variation of IOP and final refraction. Results: Thirty eyes per group were enrolled. Only prior IOP (p <0.001, IOP post-surgery (p = 0.01 and the difference in IOP (p <0.001 were statistically significant. Axial length, IOL diopter used, expected spherical refraction by biometrics and astigmatism pre- and post-surgery were similar in both groups (p=0.1; 0.4; 0.4; 0.5 and 0.3, respectively. Spherical predictability by biometrics within 0.25 diopters was noted in both the control group (range 0.06 ± 0.45 and study group (range 0.25 ± 0.97, p = 0.3. There was no statistical significance between groups for the difference between final cylinder and corneal astigmatism (p = 0.9, and the difference between axis of refractive and corneal astigmatism (p = 0.7. Conclusion: The biometric predictability in phacoemulsification surgery and the expected final refraction are significant, andare not modified by trabeculectomy in the combined surgeries.

CTER-rapid estimation of CTF parameters with error assessment.

Science.gov (United States)

Penczek, Pawel A; Fang, Jia; Li, Xueming; Cheng, Yifan; Loerke, Justus; Spahn, Christian M T

2014-05-01

In structural electron microscopy, the accurate estimation of the Contrast Transfer Function (CTF) parameters, particularly defocus and astigmatism, is of utmost importance for both initial evaluation of micrograph quality and for subsequent structure determination. Due to increases in the rate of data collection on modern microscopes equipped with new generation cameras, it is also important that the CTF estimation can be done rapidly and with minimal user intervention. Finally, in order to minimize the necessity for manual screening of the micrographs by a user it is necessary to provide an assessment of the errors of fitted parameters values. In this work we introduce CTER, a CTF parameters estimation method distinguished by its computational efficiency. The efficiency of the method makes it suitable for high-throughput EM data collection, and enables the use of a statistical resampling technique, bootstrap, that yields standard deviations of estimated defocus and astigmatism amplitude and angle, thus facilitating the automation of the process of screening out inferior micrograph data. Furthermore, CTER also outputs the spatial frequency limit imposed by reciprocal space aliasing of the discrete form of the CTF and the finite window size. We demonstrate the efficiency and accuracy of CTER using a data set collected on a 300kV Tecnai Polara (FEI) using the K2 Summit DED camera in super-resolution counting mode. Using CTER we obtained a structure of the 80S ribosome whose large subunit had a resolution of 4.03Å without, and 3.85Å with, inclusion of astigmatism parameters. Copyright © 2014 Elsevier B.V. All rights reserved.

Production and Characterization of Femtosecond-Laser-Induced Air Plasma

Science.gov (United States)

2008-03-01

thereby eliminating the acoustic reflections. As advertised , the plasma spark was now visible to the goggled eye with the room lights on, marking a...focusing mirrors instead of achromatic lenses. This change would eliminate chromatic aberrations, although curved mirrors do introduce astigmatism into the

A wavefront analyzer for terahertz time-domain spectrometers

DEFF Research Database (Denmark)

Abraham, E.; Brossard, M.; Fauche, P.

2017-01-01

the terahertz wavefront and calculate its Zernike coefficients. In particular, we especially show that the focus spot of the spectrometer suffers from optical aberrations such as remaining defocus, first and second order astigmatisms, as well as spherical aberration. This opens a route to wavefront correction...

An Evaluation of the Softperm Contact Lens in the Simulated Aircraft Environment

Science.gov (United States)

1991-01-01

information for future use. SPHERICAL LENSES FOR: Cosmetic Refractive Ametropia (not aphakic) may include astigmatism not in excess of 4.00 diopters which...SoftPerm- Contact Lenses are indicated for daily wear for the cor- rection of Cosmetic Refractive Ametropia (not aphakic) by persons with non

Orientation identification of the power spectrum

NARCIS (Netherlands)

Rudnaya, M.; Mattheij, R.M.M.; Maubach, J.M.L.

2010-01-01

The image Fourier transform is widely used for defocus and astigmatism correction in electron microscopy. The shape of a power spectrum (the square of a modulus of image Fourier transform) is directly related to the three microscope’s controls, namely defocus and two-fold (two-parameter)

Long-term results of photorefractive keratectomy for myopia and myopic astigmatism Resultados a longo prazo de ceratectomia fotorefrativa para miopia e astigmatismo miópico

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Ester Sakae Yamazaki

2007-12-01

Full Text Available PURPOSE: To assess the long-term refractive outcomes of photorefractive keratectomy in myopia and myopic astigmatism. METHODS: A retrospective study of 120 photorefractive keratectomy operated eyes with at least four-year follow-up (maximum of 96 months, mean follow-up 55 months. We divided patients into group 1 (G1 spherical equivalent (SE up to -4.00 diopters (D and group 2 (G2 SE >-4.00 D. The Summit Apex Plus® excimer laser was used for ablation. All eyes were analyzed in terms of uncorrected and best spectacle corrected visual acuity (UCVA/BSCVA and cycloplegic refraction. Data were analyzed using the Refractive Surgery Consultant Elite database software. RESULTS: G1 with 85 eyes (49 patients presented mean SE -2.42 D and G2 with 35 eyes (22 patients and mean SE of -4.45 D. Ninety-four percent of eyes in G1 and 82.9% of G2 were within ±1.00 D of emmetropia at 4 years. The UCVA was 20/30 or better in 82.0% of G1 eyes and 77.0% of G2 in the last postoperative follow-up. No patient lost more than one line in G2 compared to 13.0% in G1. Eyes that gained one or more lines after 4-year follow-up were 11.9% G1 and 2.9% in G2, respectively. A statistically significant positive correlation was found between achieved versus attempted refractive correction in both groups (r=0.925, pOBJETIVO: Relatar os resultados a longo prazo da cirurgia de ceratectomia fotorefrativa em miopia e astigmatismo miópico. MÉTODOS: Estudo retrospectivo de120 olhos operados de ceratectomia fotorefrativa com um mínimo intervalo de 4 anos de seguimento pós-operatório (máximo de 96 meses e seguimento médio de 55 meses. Dividimos em grupo 1 (G1 com equivalente esférico (SE até -4.00 dioptrias (D e grupo 2(G2 SE > -4.00 D. O excimer laser Summit Apex Plus® foi usado na ablação. Foram obtidas acuidade visual não corrigida (UCVA e melhor acuidade visual corrigida (BSCVA e refração sob cicloplegia. Os dados foram analisados utilizando o programa Refractive Surgery

Generalized magnification in visual optics. Part 2: Magnification as affine transformation

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W. F. Harris

2010-12-01

Full Text Available In astigmatic systems magnification may be different in different directions.  It may also be accompanied by rotation or reflection.  These changes from object to image are examples of generalized magnification.  They are represented by  2 2×  matrices.  Because they are linear transformations they can be called linear magnifications.  Linear magnifications account for a change in appearance without regard to position.  Mathematical structure suggests a natural further generalization to a magnification that is complete in the sense that it accountsfor change in appearance and position.  It is represented by a  3 3×  matrix with a dummy third row. The transformation is called affine in linear algebra which suggests that these generalized magnifica-tions be called affine magnifications.  The purpose of the paper is to define affine magnification in the context of astigmatic optics.  Several examples are presented and illustrated graphically. (S Afr Optom 2010 69(4 166-172

Rotation of lathe-cut hydrogel lenses on the eye.

Science.gov (United States)

Harris, M G; Harris, K L; Ruddell, D

1976-01-01

The rotation lathe-cut HydroCurveTM gel contact lens was measured on six eyes to evaluate the parameters that influence lens rotation and to determine if this lens could be used to correct astigmatism. Of the 72 observations made, 73.6% showed some lens rotation, and 33.4% of the sample rotated more than 5 degrees per 10 blinks. Of the observations in which rotation was noted, 88.7% were encyclorotation. These results are similar to those found for spin-cast hydrogel lenses. None of the lens parameters evaluated seemed to be related to lens rotation, whereas the eye parameters studied were. Lenses were more likely to rotate on eyes with smaller corneal diameters, smaller palpebral apertures, and corneal curvatures steeper than 4 3.00 DK (X2, N =72, p less than 0.05). Our findings indicate that some method of lens stabilization will be needed before lathe-cut hydrogel lenses can be used to effectively correct astigmatism.

Topography-guided custom ablation treatment for treatment of keratoconus

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Rohit Shetty

2013-01-01

Full Text Available Keratoconus is a progressive ectatic disorder of the cornea which often presents with fluctuating refraction and high irregular astigmatism. Correcting the vision of these patients is often a challenge because glasses are unable to correct the irregular astigmatism and regular contact lenses may not fit them very well. Topography-guided custom ablation treatment (T-CAT is a procedure of limited ablation of the cornea using excimer laser with the aim of regularizing the cornea, improving the quality of vision and possibly contact lens fit. The aim of the procedure is not to give a complete refractive correction. It has been tried with a lot of success by various groups of refractive surgeons around the world but a meticulous and methodical planning of the procedure is essential to ensure optimum results. In this paper, we attempt to elucidate the planning for a T-CAT procedure for various types of cones and asphericities.

Corneal perforation after conductive keratoplasty with previous refractive surgery.

Science.gov (United States)

Kymionis, George D; Titze, Patrik; Markomanolakis, Marinos M; Aslanides, Ioannis M; Pallikaris, Ioannis G

2003-12-01

A 56-year-old woman had conductive keratoplasty (CK) for residual hyperopia and astigmatism. Three years before the procedure, the patient had arcuate keratotomy, followed by laser in situ keratomileusis 2 years later for high astigmatism correction in both eyes. During CK, a corneal perforation occurred in the right eye; during the postoperative examination, an iris perforation and anterior subcapsule opacification were seen beneath the perforation site. The perforation was managed with a bandage contact lens and an antibiotic-steroid ointment; it had a negative Seidel sign by the third day. The surgery in the left eye was uneventful. Three months after the procedure, the uncorrected visual acuity was 20/32 and the best corrected visual acuity 20/20 in both eyes with a significant improvement in corneal topography. Care must be taken to prevent CK-treated spots from coinciding with areas in the corneal stroma that might have been altered by previous refractive procedures.

A portable non-contact displacement sensor and its application of lens centration error measurement

Science.gov (United States)

Yu, Zong-Ru; Peng, Wei-Jei; Wang, Jung-Hsing; Chen, Po-Jui; Chen, Hua-Lin; Lin, Yi-Hao; Chen, Chun-Cheng; Hsu, Wei-Yao; Chen, Fong-Zhi

2018-02-01

We present a portable non-contact displacement sensor (NCDS) based on astigmatic method for micron displacement measurement. The NCDS are composed of a collimated laser, a polarized beam splitter, a 1/4 wave plate, an aspheric objective lens, an astigmatic lens and a four-quadrant photodiode. A visible laser source is adopted for easier alignment and usage. The dimension of the sensor is limited to 115 mm x 36 mm x 56 mm, and a control box is used for dealing with signal and power control between the sensor and computer. The NCDS performs micron-accuracy with +/-30 μm working range and the working distance is constrained in few millimeters. We also demonstrate the application of the NCDS for lens centration error measurement, which is similar to the total indicator runout (TIR) or edge thickness difference (ETD) of a lens measurement using contact dial indicator. This application has advantage for measuring lens made in soft materials that would be starched by using contact dial indicator.

Donor cross-linking for keratoplasty: a laboratory evaluation.

Science.gov (United States)

Mukherjee, Achyut; Hayes, Sally; Aslanides, Ioannis; Lanchares, Elena; Meek, Keith M

2015-12-01

This laboratory-based investigation compares the topographic outcomes of conventional penetrating keratoplasty with that of a novel procedure in which donor corneas are cross-linked prior to keratoplasty. Penetrating keratoplasty procedures with continuous running sutures were carried out in a porcine whole globe model. Sixty eyes were randomly paired as 'donor' and 'host' tissue before being assigned to one of two groups. In the cross-linked group, donor corneas underwent riboflavin/UVA cross-linking prior to being trephined and sutured to untreated hosts. In the conventional keratoplasty group, both host and donor corneas remained untreated prior to keratoplasty. Topographic and corneal wavefront measurements were performed following surgery, and technical aspects of the procedure evaluated. Mean keratometric astigmatism was significantly lower in the cross-linked donor group at 3.67D (SD 1.8 D), vs. 8.43 D (SD 2.4 D) in the conventional keratoplasty group (p < 0.005). Mean wavefront astigmatism was also significantly reduced in the cross-linked donor group 4.71 D (SD 2.1) vs. 8.29D (SD 3.6) in the conventional keratoplasty group (p < 0.005). Mean RMS higher order aberration was significantly lower in the cross-linked donor group at 1.79 um (SD 0.98), vs. 3.05 um (SD 1.9) in the conventional keratoplasty group (P = 0.02). Qualitative analysis revealed less tissue distortion at the graft-host junction in the cross-linked group. Cross-linking of donor corneas prior to keratoplasty reduces intraoperative induced astigmatism and aberrations in an animal model. Further studies are indicated to evaluate the implications of this potential modification of keratoplasty surgery.

Image-guided system versus manual marking for toric intraocular lens alignment in cataract surgery.

Science.gov (United States)

Webers, Valentijn S C; Bauer, Noel J C; Visser, Nienke; Berendschot, Tos T J M; van den Biggelaar, Frank J H M; Nuijts, Rudy M M A

2017-06-01

To compare the accuracy of toric intraocular lens (IOL) alignment using the Verion Image-Guided System versus a conventional manual ink-marking procedure. University Eye Clinic Maastricht, Maastricht, the Netherlands. Prospective randomized clinical trial. Eyes with regular corneal astigmatism of at least 1.25 diopters (D) that required cataract surgery and toric IOL implantation (Acrysof SN6AT3-T9) were randomly assigned to the image-guided group or the manual-marking group. The primary outcome was the alignment of the toric IOL based on preoperative images and images taken immediately after surgery. Secondary outcome measures were residual astigmatism, uncorrected distance visual acuity (UDVA), and complications. The study enrolled 36 eyes (24 patients). The mean toric IOL misalignment was significantly less in the image-guided group than in the manual group 1 hour (1.3 degrees ± 1.6 [SD] versus 2.8 ± 1.8 degrees; P = .02) and 3 months (1.7 ± 1.5 degrees versus 3.1 ± 2.1 degrees; P image-guided group and manual group, respectively (P > .05). The mean UDVA was 0.03 ± 0.10 logarithm of minimum angle of resolution (logMAR) and 0.04 ± 0.09 logMAR, respectively (both P > .05). No intraoperative complications occurred during any surgery. The IOL misalignment was significantly less with digital marking than with manual marking; this did not result in a better UDVA or lower residual refractive astigmatism. Copyright © 2017 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

A simple but precise method for quantitative measurement of the quality of the laser focus in a scanning optical microscope.

Science.gov (United States)

Trägårdh, J; Macrae, K; Travis, C; Amor, R; Norris, G; Wilson, S H; Oppo, G-L; McConnell, G

2015-07-01

We report a method for characterizing the focussing laser beam exiting the objective in a laser scanning microscope. This method provides the size of the optical focus, the divergence of the beam, the ellipticity and the astigmatism. We use a microscopic-scale knife edge in the form of a simple transmission electron microscopy grid attached to a glass microscope slide, and a light-collecting optical fibre and photodiode underneath the specimen. By scanning the laser spot from a reflective to a transmitting part of the grid, a beam profile in the form of an error function can be obtained and by repeating this with the knife edge at different axial positions relative to the beam waist, the divergence and astigmatism of the postobjective laser beam can be obtained. The measured divergence can be used to quantify how much of the full numerical aperture of the lens is used in practice. We present data of the beam radius, beam divergence, ellipticity and astigmatism obtained with low (0.15, 0.7) and high (1.3) numerical aperture lenses and lasers commonly used in confocal and multiphoton laser scanning microscopy. Our knife-edge method has several advantages over alternative knife-edge methods used in microscopy including that the knife edge is easy to prepare, that the beam can be characterized also directly under a cover slip, as necessary to reduce spherical aberrations for objectives designed to be used with a cover slip, and it is suitable for use with commercial laser scanning microscopes where access to the laser beam can be limited. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

Visual acuity measures do not reliably detect childhood refractive error--an epidemiological study.

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Lisa O'Donoghue

Full Text Available PURPOSE: To investigate the utility of uncorrected visual acuity measures in screening for refractive error in white school children aged 6-7-years and 12-13-years. METHODS: The Northern Ireland Childhood Errors of Refraction (NICER study used a stratified random cluster design to recruit children from schools in Northern Ireland. Detailed eye examinations included assessment of logMAR visual acuity and cycloplegic autorefraction. Spherical equivalent refractive data from the right eye were used to classify significant refractive error as myopia of at least 1DS, hyperopia as greater than +3.50DS and astigmatism as greater than 1.50DC, whether it occurred in isolation or in association with myopia or hyperopia. RESULTS: Results are presented from 661 white 12-13-year-old and 392 white 6-7-year-old school-children. Using a cut-off of uncorrected visual acuity poorer than 0.20 logMAR to detect significant refractive error gave a sensitivity of 50% and specificity of 92% in 6-7-year-olds and 73% and 93% respectively in 12-13-year-olds. In 12-13-year-old children a cut-off of poorer than 0.20 logMAR had a sensitivity of 92% and a specificity of 91% in detecting myopia and a sensitivity of 41% and a specificity of 84% in detecting hyperopia. CONCLUSIONS: Vision screening using logMAR acuity can reliably detect myopia, but not hyperopia or astigmatism in school-age children. Providers of vision screening programs should be cognisant that where detection of uncorrected hyperopic and/or astigmatic refractive error is an aspiration, current UK protocols will not effectively deliver.

Visual impairment and amblyopia in Malaysian pre-school children - The SEGPAEDS study.

Science.gov (United States)

Chew, F L M; Thavaratnam, L K; Shukor, I N C; Ramasamy, S; Rahmat, J; Reidpath, D D; Allotey, P; Alagaratnam, J

2018-02-01

Little is known regarding the extent of visual impairment amongst pre-school children in Malaysia. To determine the prevalence of visual impairment and amblyopia in Malaysian preschool children. A cross-sectional, population-based study was conducted on children aged four to six years from 51 participating kindergartens in the district of Segamat, Johor, Malaysia from 20 March 2016 to 6 April 2016. All subjects had initial eye screening consisting of LogMar visual acuity, orthoptics examination and Spot vision screener assessment. Subjects who failed the initial eye screening were invited for a formal eye assessment consisting of cycloplegic refraction and a comprehensive ocular examination. Definitions of visual impairment and amblyopia were based on the Multi-Ethnic Pediatric Eye Disease Study criteria. A total of 1287 children were recruited. Mean subject age was 5.03 (SD:0.77) and males represented 52.3% of subjects. Subjects by ethnicity were Malay (54.8%), Chinese (27.7%), Indian (15.6%) and Orang Asli (1.9%). Formal eye assessment was required for 221 subjects and 88.8% required ophthalmic intervention. Refractive error, representing 95.4% of diagnosed ocular disorders, comprised of astigmatism (84%), myopia (9%) and hypermetropia (6.9%). With-the-rule astigmatism was present in 93.4% of the subjects with astigmatism. Visual impairment was present in 12.5% of our subjects, with 61% having bilateral visual impairment. Of the subjects with visual impairment, 59.1% had moderate visual impairment. The prevalence of amblyopia was 7.53%, and 66% of the amblyopic subjects had bilateral amblyopia. Our study highlights an urgent need for initiation of preschool vision screening in Malaysia.

Refractive error magnitude and variability: Relation to age.

Science.gov (United States)

Irving, Elizabeth L; Machan, Carolyn M; Lam, Sharon; Hrynchak, Patricia K; Lillakas, Linda

2018-03-19

To investigate mean ocular refraction (MOR) and astigmatism, over the human age range and compare severity of refractive error to earlier studies from clinical populations having large age ranges. For this descriptive study patient age, refractive error and history of surgery affecting refraction were abstracted from the Waterloo Eye Study database (WatES). Average MOR, standard deviation of MOR and astigmatism were assessed in relation to age. Refractive distributions for developmental age groups were determined. MOR standard deviation relative to average MOR was evaluated. Data from earlier clinically based studies with similar age ranges were compared to WatES. Right eye refractive errors were available for 5933 patients with no history of surgery affecting refraction. Average MOR varied with age. Children <1 yr of age were the most hyperopic (+1.79D) and the highest magnitude of myopia was found at 27yrs (-2.86D). MOR distributions were leptokurtic, and negatively skewed. The mode varied with age group. MOR variability increased with increasing myopia. Average astigmatism increased gradually to age 60 after which it increased at a faster rate. By 85+ years it was 1.25D. J 0 power vector became increasingly negative with age. J 45 power vector values remained close to zero but variability increased at approximately 70 years. In relation to comparable earlier studies, WatES data were most myopic. Mean ocular refraction and refractive error distribution vary with age. The highest magnitude of myopia is found in young adults. Similar to prevalence, the severity of myopia also appears to have increased since 1931. Copyright © 2018 Spanish General Council of Optometry. Published by Elsevier España, S.L.U. All rights reserved.

Photorefractive keratectomy after cataract surgery in uncommon cases: long-term results

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Anna Maria Roszkowska

2018-04-01

Full Text Available AIM: To evaluate the efficacy and safety of the excimer laser correction of the residual refractive errors after cataract extraction with intraocular lens (IOL implantation in uncommon cases. METHODS: Totally 24 patients with high residual refractive error after cataract surgery with IOL implantation were examined. Twenty-two patients had a history of phacoemulsification and IOL implantation, and two had extra-capsular cataract extraction with IOL implantation. Detailed examination of preoperative medical records was done to explain the origin of the post-cataract refractive errors. All patients underwent photorefractire keratectomy (PRK enhancement. The mean outcome measures were refraction, uncorretted visual acuity (UCVA, best corrected visual acuity (BCVA and corneal transparency and follow up ranged from 1 to 8y. RESULTS: The principal causes of residual ametropia was inexact IOL calculation in abnormal eyes with high myopia and congenital lens abnormalities, followed by corneal astigmatism both suture induced and preexisting. After cataract surgery and before the laser enhancement the mean spherical equivalent (SE was -0.56±3 D ranging from -4.62 to +2.25 D in high myopic patients, instead it was -1±1.73 D ranging from -3.25 to +3.75 D in the astigmatic eyes, with a mean cylinder of -3.75±0 ranging from -3 to +5.50 D. After laser refractive surgery the mean SE was 0.1±0.73, ranging from -0.50 to +1.50 in the myopic group, and it was -0.50±0.57 ranging from -1.25 to +0.50 in astigmatic patients, with a mean cylinder of -0.25±0.75. In myopic patients the mean UCVA and BCVA were 0.038±0.072 logMAR and 0.018±0.04 respectively, both ranging from 0.10 to 0.0. In astigmatic patients, the mean UCVA and BCVA were 0.213±0.132 and 0.00±0.0 respectively, UCVA ranging from 0.50 to 0.22 and BCVA was 0.00. All patients presented normal corneal transparency. No ocular hypertension was detected and no corneal haze was observed. All registered

The Auckland Cataract Study: 2 year postoperative assessment of aspects of clinical, visual, corneal topographic and satisfaction outcomes

Science.gov (United States)

Thompson, A M; Sachdev, N; Wong, T; Riley, A F; Grupcheva, C N; McGhee, C N

2004-01-01

Aim: To assess clinical, visual, computerised corneal topographic, and subjective satisfaction with visual acuity, in a cohort of subjects 2 years after phacoemulsification surgery in a public hospital in New Zealand. Methods: Prospective study of a representative sample of 97 subjects (20%) randomly selected from 480 subjects in the original Auckland Cataract Study (ACS) cohort. The clinical assessment protocol was identical to the ACS and included an extensive questionnaire to enable direct comparisons to be made between the two groups. Results: The study population was predominantly female (66%) with a mean age of 76.3 (SD 9.9) years. New systemic and ocular disease affected 18.4% and 10.3% of subjects respectively, and 10.3% required referral to either a general practitioner (2.1%) or ophthalmologist (8.2%). Mean best spectacle corrected visual acuity (BSCVA) was 0.2 (0.2) logMAR units (6/9 Snellen equivalent), with mean spherical equivalent −0.37 (1.01) dioptres (D) and astigmatism −1.07 (0.70) D 2 years postoperatively, compared to mean BSCVA 0.1 (0.2) logMAR units (6/7.5 Snellen equivalent), spherical equivalent −0.59 (1.07) D, and astigmatism −1.14 (0.77) D 4 weeks after surgery. 94.9% of subjects retained a BSCVA of 6/12 or better, irrespective of pre-existing ocular disease. The overall posterior capsule opacification (PCO) rate was 20.4% and this was visually insignificant in all but 3.1% of eyes that had already undergone Nd:YAG posterior capsulotomy. Orbscan II elevation technology demonstrated corneal stability 2 years after uncomplicated phacoemulsification. Although corneal astigmatism was eliminated in approximately half of the subjects 1 month postoperatively, astigmatism showed a tendency to regress towards the preoperative level with local corneal thickening at the site of incision 2 years after cataract surgery. Of fellow eyes, 61.2% had undergone cataract surgery. Overall, 75.3% of subjects were moderately to very satisfied with their

Pramana – Journal of Physics | Indian Academy of Sciences

Indian Academy of Sciences (India)

... for third-order aberration in the reconstructed wave front of point objects are established by Meier. But Smith, Neil Mohon, Sweatt independently reported that their results differ from that of Meier. We found that coefficients for spherical aberration, astigmatism, tally with Meier's while coefficients for distortion and coma differ.

Retreatments after multifocal intraocular lens implantation: an analysis

Directory of Open Access Journals (Sweden)

Gundersen KG

2016-03-01

Full Text Available Kjell Gunnar Gundersen,1 Sarah Makari,2 Steffen Ostenstad,1 Rick Potvin2 1Ifocus Eye Clinic, Haugesund, Norway; 2Science in Vision, Akron, NY, USA Purpose: To determine the incidence and etiology of required retreatment after multifocal intraocular lens (IOL implantation and to evaluate the methods and clinical outcomes of retreatment.Patients and methods: A retrospective chart review of 416 eyes of 209 patients from one site that underwent uncomplicated cataract surgery with multifocal IOL implantation. Biometry, the IOL, and refractive data were recorded after the original implantation, with the same data recorded after retreatment. Comments related to vision were obtained both before and after retreatment for retreated patients.Results: The multifocal retreatment rate was 10.8% (45/416 eyes. The eyes that required retreatment had significantly higher residual refractive astigmatism compared with those who did not require retreatment (1.21±0.51 D vs 0.51±0.39 D, P<0.01. The retreatment rate for the two most commonly implanted primary IOLs, blended bifocal (10.5%, 16/152 and bilateral trifocal (6.9%, 14/202 IOLs, was not statistically significantly different (P=0.12. In those requiring retreatment, refractive-related complaints were most common. Retreatment with refractive corneal surgery, in 11% of the eyes, and piggyback IOLs, in 89% of the eyes, was similarly successful, improving patient complaints 78% of the time.Conclusion: Complaints related to ametropia were the main reasons for retreatment. Residual astigmatism appears to be an important determinant of retreatment rate after multifocal IOL implantation. Retreatment can improve symptoms for a high percentage of patients; a piggyback IOL is a viable retreatment option. Keywords: piggyback IOL, Sulcoflex, toric, STAAR, symptoms, astigmatism

Autorefraction versus subjective refraction in a radially asymmetric multifocal intraocular lens.

Science.gov (United States)

van der Linden, Jan Willem; Vrijman, Violette; Al-Saady, Rana; El-Saady, Rana; van der Meulen, Ivanka J; Mourits, Maarten P; Lapid-Gortzak, Ruth

2014-12-01

To evaluate whether the automated refraction (AR) correlates with subjective manifest (MR) refraction in eyes implanted with radially asymmetric multifocal intraocular lens (IOLs). This retrospective study evaluated 52 eyes (52 patients) implanted with a radially asymmetric multifocal IOL (LS-312 MF30, Oculentis, Germany). At 3 months postoperatively, the AR and MR values were compared to determine the correlation between the sphere (S), the spherical equivalent (SE) and the astigmatic components J0 and J45. The difference of mean spherical measurement was +0.98D ± 0.62, with the AR measuring more myopic. The difference of the mean spherical equivalent was +1.11D ± 0.57, again with AR being more myopic. Both these differences were statistically significant (p < 0.001). The astigmatic components showed less differences, with the mean difference of the J0 being -0.09D ± 0.43, and the J45 of +0.04D ± 0.47, which were both not statistically significant (p = 0.123 and p = 0.531, respectively). Correlation analysis of the refractive parameters showed r(2) = 0.067, r(2) = 0.078, r(2) = 0.018 and r(2) = 0.015, respectively, all of which point to a low correlation between the AR and the MR. Autorefraction shows poor correlation to manifest subjective refraction with these radially asymmetric multifocal IOLs. The autorefraction systematically underestimates the spherical and spherical equivalent power, while the correlation between the astigmatic components was also low. Autorefraction seems not a valid starting point for manifest subjective refraction with these types of lenses, unless a corrective factor of about +1 dioptre is used. © 2014 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Single-segment and double-segment INTACS for post-LASIK ectasia.

Directory of Open Access Journals (Sweden)

Hassan Hashemi

2014-09-01

Full Text Available The objective of the present study was to compare single segment and double segment INTACS rings in the treatment of post-LASIK ectasia. In this interventional study, 26 eyes with post-LASIK ectasia were assessed. Ectasia was defined as progressive myopia regardless of astigmatism, along with topographic evidence of inferior steepening of the cornea after LASIK. We excluded those with a history of intraocular surgery, certain eye conditions, and immune disorders, as well as monocular, pregnant and lactating patients. A total of 11 eyes had double ring and 15 eyes had single ring implantation. Visual and refractive outcomes were compared with preoperative values based on the number of implanted INTACS rings. Pre and postoperative spherical equivalent were -3.92 and -2.29 diopter (P=0.007. The spherical equivalent decreased by 1 ± 3.2 diopter in the single-segment group and 2.56 ± 1.58 diopter in the double-segment group (P=0.165. Mean preoperative astigmatism was 2.38 ± 1.93 diopter which decreased to 2.14 ± 1.1 diopter after surgery (P=0.508; 0.87 ± 1.98 diopter decrease in the single-segment group and 0.67 ± 1.2 diopter increase in the double-segment group (P=0.025. Nineteen patients (75% gained one or two lines, and only three, who were all in the double-segment group, lost one or two lines of best corrected visual acuity. The spherical equivalent and vision significantly decreased in all patients. In these post-LASIK ectasia patients, the spherical equivalent was corrected better with two segments compared to single segment implantation; nonetheless, the level of astigmatism in the single-segment group was significantly better than that in the double-segment group.

Outcomes of LASIK and PRK in previous penetrating corneal transplant recipients.

Science.gov (United States)

Kovoor, Timmy A; Mohamed, Engy; Cavanagh, H Dwight; Bowman, R Wayne

2009-09-01

To evaluate the safety and efficacy of excimer laser refractive surgery in correcting refractive error in eyes that have undergone previous penetrating keratoplasty (PK). Twenty-three keratorefractive procedures on 16 eyes from 16 consecutive subjects were evaluated between 2002 and 2008. Each patient presented a previous history of a PK with subsequent postoperative myopia and astigmatism. Keratometric value, manifest refraction, best-corrected visual acuity, uncorrected visual acuity, and complications were determined. There were a total of 14 photorefractive keratectomy (PRK) procedures performed on 11 eyes and 9 laser in situ keratomileusis (LASIK) procedures performed on 5 eyes. In the PRK group, the preoperative post-PK manifest refractive spherical equivalent and cylindrical error were -6.22 +/- 6.23 diopter and 5.23 +/- 2.26 D, respectively. The PRK postoperative manifest refractive spherical equivalent and cylindrical error were -3.61 +/- 4.23 D (P=0.25) and 3.21 +/- 1.78 D (P=0.02), respectively. In the LASIK group, the preoperative post-PK manifest refractive spherical equivalent and cylindrical error were -3.05 +/- 3.29 D and 4.11 +/- 2.38 D, respectively. The LASIK postoperative manifest refractive spherical equivalent and cylindrical error were -1.51 +/- 2.02 D (P=0.24) and 2.08 +/- 1.26 D (P=0.03), respectively. There was a 2-line or greater improvement of uncorrected visual acuity in 8 of the 14 PRK treatments and 5 of the 9 LASIK treatments. There were two episodes of acute graft rejection. One of the episodes resolved with topical and oral corticosteroids, and the other episode required a repeat corneal transplantation. PRK and LASIK are effective tools in reducing surgically induced astigmatism after penetrating corneal transplantation in most patients in this case series. The reduction of astigmatism may allow improved contact lens or spectacle fitting to achieve best-corrected binocular visual acuity.

Refractive error study in young subjects: results from a rural area in Paraguay

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Isabel Signes-Soler

2017-03-01

Full Text Available AIM: To evaluate the distribution of refractive error in young subjects in a rural area of Paraguay in the context of an international cooperation campaign for the prevention of blindness. METHODS: A sample of 1466 young subjects (ranging from 3 to 22 years old, with a mean age of 11.21±3.63 years old, were examined to assess their distance visual acuity (VA and refractive error. The first screening examination performed by trained volunteers, included visual acuity testing, autokeratometry and non-cycloplegic autorefraction. Inclusion criteria for a second complete cycloplegic eye examination by an optometrist were VA <20/25 (0.10 logMAR or 0.8 decimal and/or corneal astigmatism ≥1.50 D. RESULTS: An uncorrected distance VA of 0 logMAR (1.0 decimal was found in 89.2% of children. VA <20/25 and/or corneal astigmatism ≥1.50 D was found in 3.9% of children (n=57, with a prevalence of hyperopia of 5.2% (0.2% of the total in this specific group. Furthermore, myopia (spherical equivalent ≤-0.5 D was found in 37.7% of the refracted children (0.5% of the total. The prevalence of refractive astigmatism (cylinder ≤-1.50 D was 15.8% (0.6% of the total. Visual impairment (VI (0.05≤VA≤0.3 was found in 12/114 (0.4% of the refracted eyes. Main causes for VI were refractive error (58%, retinal problems (17%, 2/12, albinism (17%, 2/12 and unknown (8%, 1/12. CONCLUSION: A low prevalence of refractive error has been found in this rural area of Paraguay, with higher prevalence of myopia than of hyperopia.

Refractive errors among children, adolescents and adults attending eye clinics in Mexico

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Francisco Gomez-Salazar

2017-05-01

Full Text Available AIM: To assess the proportion of refractive errors in the Mexican population that visited primary care optometry clinics in fourteen states of Mexico. METHODS: Refractive data from 676 856 patients aged 6 to 90y were collected from optometry clinics in fourteen states of Mexico between 2014 and 2015. The refractive errors were classified by the spherical equivalent (SE, as follows: sphere+½ cylinder. Myopia (SE>-0.50 D, hyperopia (SE>+0.50 D, emmetropia (-0.50≤SE≤+0.50, and astigmatism alone (cylinder≥-0.25 D. A negative cylinder was selected as a notation. RESULTS: The proportion (95% confidence interval among all of the subjects was hyperopia 21.0% (20.9-21.0, emmetropia 40.7% (40.5-40.8, myopia 24.8% (24.7-24.9 and astigmatism alone 13.5% (13.4-13.5. Myopia was the most common refractive error and frequency seemed to increase among the young population (10 to 29 years old, however, hyperopia increased among the aging population (40 to 79 years old, and astigmatism alone showed a decreasing trend with age (6 to 90y; from 19.7% to 10.8%. There was a relationship between age and all refractive errors (approximately 60%, aged 50 and older. The proportion of any clinically important refractive error was higher in males (61.2% than in females (58.3%; P<0.0001. From fourteen states that collected information, the proportion of refractive error showed variability in different geographical areas of Mexico. CONCLUSION: Myopia is the most common refractive error in the population studied. This study provides the first data on refractive error in Mexico. Further programs and studies must be developed to address the refractive errors needs of the Mexican population.

CTER—Rapid estimation of CTF parameters with error assessment

Energy Technology Data Exchange (ETDEWEB)

Penczek, Pawel A., E-mail: Pawel.A.Penczek@uth.tmc.edu [Department of Biochemistry and Molecular Biology, The University of Texas Medical School, 6431 Fannin MSB 6.220, Houston, TX 77054 (United States); Fang, Jia [Department of Biochemistry and Molecular Biology, The University of Texas Medical School, 6431 Fannin MSB 6.220, Houston, TX 77054 (United States); Li, Xueming; Cheng, Yifan [The Keck Advanced Microscopy Laboratory, Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94158 (United States); Loerke, Justus; Spahn, Christian M.T. [Institut für Medizinische Physik und Biophysik, Charité – Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin (Germany)

2014-05-01

In structural electron microscopy, the accurate estimation of the Contrast Transfer Function (CTF) parameters, particularly defocus and astigmatism, is of utmost importance for both initial evaluation of micrograph quality and for subsequent structure determination. Due to increases in the rate of data collection on modern microscopes equipped with new generation cameras, it is also important that the CTF estimation can be done rapidly and with minimal user intervention. Finally, in order to minimize the necessity for manual screening of the micrographs by a user it is necessary to provide an assessment of the errors of fitted parameters values. In this work we introduce CTER, a CTF parameters estimation method distinguished by its computational efficiency. The efficiency of the method makes it suitable for high-throughput EM data collection, and enables the use of a statistical resampling technique, bootstrap, that yields standard deviations of estimated defocus and astigmatism amplitude and angle, thus facilitating the automation of the process of screening out inferior micrograph data. Furthermore, CTER also outputs the spatial frequency limit imposed by reciprocal space aliasing of the discrete form of the CTF and the finite window size. We demonstrate the efficiency and accuracy of CTER using a data set collected on a 300 kV Tecnai Polara (FEI) using the K2 Summit DED camera in super-resolution counting mode. Using CTER we obtained a structure of the 80S ribosome whose large subunit had a resolution of 4.03 Å without, and 3.85 Å with, inclusion of astigmatism parameters. - Highlights: • We describe methodology for estimation of CTF parameters with error assessment. • Error estimates provide means for automated elimination of inferior micrographs. • High computational efficiency allows real-time monitoring of EM data quality. • Accurate CTF estimation yields structure of the 80S human ribosome at 3.85 Å.

Prevalence of common visual problems among primary school ...

African Journals Online (AJOL)

Hypermetropia predominated (7.8%), followed by myopia (3.6%) and astigmatism (3.5%). Ninety percent of the children with vision less than 6/6 in any eye could have their vision improved by refractive complications and disability. A total of 62.4% of these children with visual disability could have their functional vision in ...

[Regularities of the refractive genesis of school myopia and criteria for its prediction].

Science.gov (United States)

Onufriĭchuk, O N; Rozenblium, Iu Z

2007-01-01

The paper provides the data of a 2-year monitoring of ocular refraction in 327 consecutive 10-14-year-old schoolchildren (654 eyes) unrandomized under natural conditions and cycloplegia. The authors studied whether there was an association of refraction and its changes with absolute and relative accommodation, habitual accommodation tonicity, the length of the anteroposterior optic axis, and the presence of pseudomyopathy and astigmatism. Over 2 years, myopia occurred in 15.4% of the eyes, its degree increased from -0.88 (-1.37/-0.50) to -1.25 (-2.31/-0.62) diopters. Criteria for myopia prediction were identified. These included a relative accommodation reserve of less than 2.5 diopters, an anteroposterior optic axis length of more than 24.33 mm, a habitual accommodation tonicity of less than + 0.41 diopters, the presence of pseudomyopia (77.8% of cases), reversed astigmatism and underlying emmetropia. A mathematical model was constructed for prediction of myopia, the proportion of its correct prediction being 90.4%, which makes it possible to recommend for clinical application.

Keratometric alterations following the 25-gauge transconjunctival sutureless pars plana vitrectomy versus the conventional pars plana vitrectomy.

Science.gov (United States)

Citirik, Mehmet; Batman, Cosar; Bicer, Tolga; Zilelioglu, Orhan

2009-09-01

To assess the alterations in keratometric astigmatism following the 25-gauge transconjunctival sutureless pars plana vitrectomy versus the conventional pars plana vitrectomy. Sixteen consecutive patients were enrolled into the study. Conventional vitrectomy was applied to eight of the cases and 25-gauge transconjunctival sutureless vitrectomy was performed in eight patients. Keratometry was performed before and after the surgery. In the 25-gauge transconjunctival sutureless pars plana vitrectomy group, statistically significant changes were not observed in the corneal curvature in any post-operative follow-up measurement (p > 0.05); whereas in the conventional pars plana vitrectomy group, statistically significant changes were observed in the first postoperative day (p = 0.01) and first postoperative month (p = 0.03). We noted that these changes returned to baseline in three months (p = 0.26). Both 25-gauge transconjunctival sutureless and conventional pars plana vitrectomy are effective surgical modalities for selected diseases of the posterior segment. Surgical procedures are critical for the visual rehabilitation of the patients. The post-operative corneal astigmatism of the vitrectomised eyes can be accurately determined at least two months post-operatively.

Analysis of corneal topography in patients with pure microphthalmia in Eastern China.

Science.gov (United States)

Hu, Pei-Hong; Gao, Gui-Ping; Yu, Yao; Pei, Chong-Gang; Zhou, Qiong; Huang, Xin; Zhang, Ying; Shao, Yi

2015-12-01

To determine the typical corneal changes in pure microphthalmia using a corneal topography system and identify characteristics that may assist in early diagnosis. Patients with pure microphthalmia and healthy control subjects underwent corneal topography analysis (Orbscan IIZ® Corneal Topography System; Bausch and Lomb, Bridgewater, NJ, USA) to determine degree of corneal astigmatism (mean A), simulation of corneal astigmatism (sim A), mean keratometry (mean K), simulated keratometry (sim K), irregularities in the 3 - and 5-mm zone, and mean thickness of nine distinct corneal regions. Patients with pure microphthalmia (n = 12) had significantly higher mean K, sim K, mean A, sim A, 3.0 mm irregularity and 5.0 mm irregularity, and exhibited significantly more false keratoconus than controls (n = 12). There was a significant between-group difference in the morphology of the anterior corneal surface and the central curvature of the cornea. Changes in corneal morphology observed in this study could be useful in borderline situations to confirm the diagnosis of pure microphthalmia. © The Author(s) 2015.

The Gaussian beam mode analysis of classical phase aberrations in diffraction-limited optical systems

International Nuclear Information System (INIS)

Trappe, Neil; Murphy, J Anthony; Withington, Stafford

2003-01-01

Gaussian beam mode analysis (GBMA) offers a more intuitive physical insight into how light beams evolve as they propagate than the conventional Fresnel diffraction integral approach. In this paper we illustrate that GBMA is a computationally efficient, alternative technique for tracing the evolution of a diffracting coherent beam. In previous papers we demonstrated the straightforward application of GBMA to the computation of the classical diffraction patterns associated with a range of standard apertures. In this paper we show how the GBMA technique can be expanded to investigate the effects of aberrations in the presence of diffraction by introducing the appropriate phase error term into the propagating quasi-optical beam. We compare our technique to the standard diffraction integral calculation for coma, astigmatism and spherical aberration, taking - for comparison - examples from the classic text 'Principles of Optics' by Born and Wolf. We show the advantages of GBMA for allowing the defocusing of an aberrated image to be evaluated quickly, which is particularly important and useful for probing the consequences of astigmatism and spherical aberration

Four spot laser anemometer and optical access techniques for turbine applications

Science.gov (United States)

Wernet, Mark P.

A time-of-flight anemometer (TOFA) system, utilizing a spatial lead-lag filter for bipolar pulse generation was constructed and tested. This system, called a Four Spot Laser Anemometer, was specifically designed for use in high speed, turbulent flows in the presence of walls or surfaces. The TOFA system uses elliptical spots to increase the flow acceptance angle to be comparable with that of a fringe type anemometer. The tightly focused spots used in the Four Spot yield excellent flare light rejection capabilities. Good results were obtained to 75 microns normal to a surface, with a f/2.5 collecting lens. This system is being evaluated for use in a warm turbine facility. Results from both a particle lag velocity experiment and boundary layer profiles will be discussed. In addition, an analysis of the use of curved windows in a turbine casing will be presented. Curved windows, matching the inner radius of the turbine casing, preserve the flow conditions, but introduce astigmatic aberrations. A correction optic was designed that virtually eliminates these astigmatic aberrations throughout the intrablade survey region for normal incidence.

Four spot laser anemometer and optical access techniques for turbine applications

International Nuclear Information System (INIS)

Wernet, M.P.

1987-01-01

A time-of-flight anemometer (TOFA) system, utilizing a spatial lead-lag filter for bipolar pulse generation was constructed and tested. This system, called a Four Spot Laser Anemometer, was specifically designed for use in high speed, turbulent flows in the presence of walls or surfaces. The TOFA system uses elliptical spots to increase the flow acceptance angle to be comparable with that of a fringe type anemometer. The tightly focused spots used in the Four Spot yield excellent flare light rejection capabilities. Good results were obtained to 75 microns normal to a surface, with a f/2.5 collecting lens. This system is being evaluated for use in a warm turbine facility. Results from both a particle lag velocity experiment and boundary layer profiles will be discussed. In addition, an analysis of the use of curved windows in a turbine casing will be presented. Curved windows, matching the inner radius of the turbine casing, preserve the flow conditions, but introduce astigmatic aberrations. A correction optic was designed that virtually eliminates these astigmatic aberrations throughout the intrablade survey region for normal incidence

The Gaussian beam mode analysis of classical phase aberrations in diffraction-limited optical systems

Science.gov (United States)

Trappe, Neil; Murphy, J. Anthony; Withington, Stafford

2003-07-01

Gaussian beam mode analysis (GBMA) offers a more intuitive physical insight into how light beams evolve as they propagate than the conventional Fresnel diffraction integral approach. In this paper we illustrate that GBMA is a computationally efficient, alternative technique for tracing the evolution of a diffracting coherent beam. In previous papers we demonstrated the straightforward application of GBMA to the computation of the classical diffraction patterns associated with a range of standard apertures. In this paper we show how the GBMA technique can be expanded to investigate the effects of aberrations in the presence of diffraction by introducing the appropriate phase error term into the propagating quasi-optical beam. We compare our technique to the standard diffraction integral calculation for coma, astigmatism and spherical aberration, taking—for comparison—examples from the classic text 'Principles of Optics' by Born and Wolf. We show the advantages of GBMA for allowing the defocusing of an aberrated image to be evaluated quickly, which is particularly important and useful for probing the consequences of astigmatism and spherical aberration.

The Effects of Pilot Age, Lighting, and Head-Down Time on Visual Accommodation

Science.gov (United States)

1979-02-06

technique for determining the extent of ametropia (nearsighted- ness, farsightedness, astigmatism) and as an aid in the fitting (8.1)of eyeglasses. Knoll... Ametropia with a Gas LASER", "Amerinan 1onu~nl nf Onpw’rp"r-_ Vol. 43, No. 7: 415-418, 1966. 4. Oliver, G. M. "Sparkling Spots and Random Diffractions

Varied Human Tolerance to the Combined Conditions of Low Contrast and Diminished Luminance: A Quasi-Meta Analysis

Science.gov (United States)

2017-08-30

conditions (e.g., dry eyes , mild cataractous conditions, Stevens-Johnson Syndrome ) using CS alone as the performance index. More commonly, it has been...subjects tested under conditions of spherical blur, astigmatic blur, low luminance, and one eye vs. two eyes ...conditions). The vast majority of past mesopic visual performance studies were predominantly isolated to evaluations of various eye disease

Op art and visual perception.

Science.gov (United States)

Wade, N J

1978-01-01

An attempt is made to list the visual phenomena exploited in op art. These include moire frinlude moiré fringes, afterimages, Hermann grid effects, Gestalt grouping principles, blurring and movement due to astigmatic fluctuations in accommodation, scintillation and streaming possibly due to eye movements, and visual persistence. The historical origins of these phenomena are also noted.

Mudanças na refração após cirurgia de correção de esotropia Refractive changes following surgery for correction of esotropia

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Marcelo F. Gaal Vadas

2001-08-01

Full Text Available Objetivo: Estudar o comportamento da refração e da curvatura corneana em pacientes com esotropia essencial submetidos à cirurgia monocular para correção do estrabismo. Métodos: Estudo prospectivo em que 42 olhos de 21 pacientes com esotropia essencial de ângulo moderado, sem quaisquer outros estrabismos associados, foram selecionados e submetidos ao exame oftalmológico completo e à cirurgia monocular. O olho contralateral serviu como grupo controle. Foram feitas avaliações de pré-operatório, pós-operatório de 1 mês e pós-operatório de 6 meses. O astigmatismo pré-operatório foi confrontado com os astigmatismos pós-operatórios por análise vetorial e cálculo do valor polar. Resultados: Obtivemos, nos olhos operados, redução significante (pPurpose: To evaluate changes in refraction and corneal curvature following surgery for correction of acquired esotropia. Methods: 42 eyes of 21 patients with acquired moderate angle esotropia without any other form of strabismus were prospectively enrolled and submitted to a complete ophthalmological examination followed by recess/resect procedure in a single eye. Data from the fellow eye were selected as control. Ophthalmological assessment was carried out preoperatively, 1 month after surgery and 6 months after surgery, where astigmatism was compared using vector analysis and the polar value concept. Results: The eyes submitted to surgery revealed a significant (p<0.05 decrease in spherical equivalent, from 3.28 ± 1.98 diopters to 3.05 ± 1.95 diopters. Refraction data disclosed a significant increase in the 90° component of net astigmatism, from 0.458 ± 0.594 diopters to 1.002 ± 0.718 diopters, which was also observed in keratometric readings:1.083 ± 0.560 diopters to 1.690 ± 0.591 diopters. Surgically induced astigmatism, assessed using refraction data was 0.63 ± 0.27 diopters at an average axis of 92.30 ± 14.91 degrees, and 0.71 ± 0.27 diopters at an average axis of 94.45 �

Comparison of corneal power obtained from VERION image-guided surgery system and four other devices

Directory of Open Access Journals (Sweden)

Lin HY

2017-07-01

Full Text Available Hung-Yuan Lin,1,* Hsin-Yang Chen,1,2,* Han Bor Fam,3 Ya-Jung Chuang,1 Ronald Yeoh,4 Pi-Jung Lin5 1Universal Eye Center, Zhongli Branch, Zhongli County, TaoYuan City, Taiwan, Republic of China; 2Ophthalmology Department, Ningbo First Hospital, Ningbo, Zhejiang Province, People’s Republic of China; 3Ophthalmology Department, Tan Tock Seng Hospital, Jalan Tan Tock Seng, 4Ophthalmology Department, Eye and Retina Surgeons, Camden Medical Centre, Singapore; 5Universal Eye Center, Xinnan Branch, Taipei City, Taiwan, Republic of China *These authors contributed equally to this work Purpose: To assess the corneal keratometric values obtained using the VERION image-guided surgery system and other devices.Methods: This study evaluated the right eyes of 115 cataract patients before intraocular lens (IOL implantation through consecutive tests using 5 devices: VERION Reference Unit , Placido-based corneal topography (OPD-Scan III, monochromatic light-emitting diodes (LenStar LS900 and AL-Scan, and rotary prism technology (auto kerato-refractometer KR-8800. Analyzed parameters were corneal steep and flat keratometric values (Ks and Kf and corneal astigmatism and axis. These parameters were evaluated using the one-sample two-tailed t-test and the 95% limits of agreement (95% LOAs between the devices.Results: The mean corneal cylinder value measurements were -0.97±0.63 D, -0.88± 0.60 D, -0.90±0.69 D, -0.90±0.67 D, and -0.83±0.60 D with VERION, LenStar, AL-Scan (2.4 mm, OPD III, and KR-8800, respectively. Only KR-8800 showed a significant difference from VERION in the corneal cylinder value (P<0.05. The mean differences in the Kf and Ks of VERION compared to those of OPD III were 0.18±0.45 D and 0.17±0.38 D (P<0.05, respectively. The 95% LOAs of Bland–Altman analysis for the corneal astigmatism axis of the VERION with LenStar, AL-Scan (2.4 mm, OPD III, and KR-8800 were -26.25° to 58.71°, -20.61° to 47.44°, -25.03° to 58.98°, and -27.85�

Accuracy of modal wavefront estimation from eye transverse aberration measurements

Science.gov (United States)

Chyzh, Igor H.; Sokurenko, Vyacheslav M.

2001-01-01

The influence of random errors in measurement of eye transverse aberrations on the accuracy of reconstructing wave aberration as well as ametropia and astigmatism parameters is investigated. The dependence of mentioned errors on a ratio between the number of measurement points and the number of polynomial coefficients is found for different pupil location of measurement points. Recommendations are proposed for setting these ratios.

An Astigmatic Detection System for Polymeric Cantilever-based Sensors

DEFF Research Database (Denmark)

Hwu, En-Te; Liao, Hsien-Shun; Bosco, Filippo

2012-01-01

fluctuation measurements on cantilever beams with a subnanometer resolution. Furthermore, an external excitation can intensify the resonance amplitude, enhancing the signal- to-noise ratio. The full width at half maximum (FWHM) of the laser spot is 568 nm, which facilitates read-out on potentially...

Cancellation of RF Coupler-Induced Emittance Due to Astigmatism

Energy Technology Data Exchange (ETDEWEB)

Dowell, David H.; /SLAC

2016-12-11

It is well-known that the electron beam quality required for applications such as FEL’s and ultra-fast electron diffraction can be degraded by the asymmetric fields introduced by the RF couplers of superconducting linacs. This effect is especially troublesome in the injector where the low energy beam from the gun is captured into the first high gradient accelerator section. Unfortunately modifying the established cavity design is expensive and time consuming, especially considering that only one or two sections are needed for an injector. Instead, it is important to analyze the coupler fields to understand their characteristics and help find less costly solutions for their cancellation and mitigation. This paper finds the RF coupler-induced emittance for short bunches is mostly due to the transverse spatial sloping or tilt of the field, rather than the field’s time-dependence. It is shown that the distorting effects of the coupler can be canceled with a static (DC) quadrupole lens rotated about the z-axis.

Geometric phases in astigmatic optical modes of arbitrary order

International Nuclear Information System (INIS)

Habraken, Steven J. M.; Nienhuis, Gerard

2010-01-01

The transverse spatial structure of a paraxial beam of light is fully characterized by a set of parameters that vary only slowly under free propagation. They specify bosonic ladder operators that connect modes of different orders, in analogy to the ladder operators connecting harmonic-oscillator wave functions. The parameter spaces underlying sets of higher-order modes are isomorphic to the parameter space of the ladder operators. We study the geometry of this space and the geometric phase that arises from it. This phase constitutes the ultimate generalization of the Gouy phase in paraxial wave optics. It reduces to the ordinary Gouy phase and the geometric phase of nonastigmatic optical modes with orbital angular momentum in limiting cases. We briefly discuss the well-known analogy between geometric phases and the Aharonov-Bohm effect, which provides some complementary insights into the geometric nature and origin of the generalized Gouy phase shift. Our method also applies to the quantum-mechanical description of wave packets. It allows for obtaining complete sets of normalized solutions of the Schroedinger equation. Cyclic transformations of such wave packets give rise to a phase shift, which has a geometric interpretation in terms of the other degrees of freedom involved.

Visual deficits in Nepalese patients with oculocutaneous albinism.

Science.gov (United States)

Khanal, Safal; Pokharel, Amrit; Kandel, Himal

2016-01-01

Albinism poses a significant threat to visual functions and causes remarkable ocular morbidity often resulting in visual disabilities. The study aimed at describing the visual status in patients with diagnosed cases of complete oculocutaneous albinism (OCA) attending to a tertiary eye hospital in Nepal. This was a cross-sectional descriptive hospital-based study of all diagnosed oculocutaneous albinotic cases (16 males and 9 females; mean age of 16 years) who visited the Department of Ophthalmology at the Institute of Medicine, for ocular consultation between September 1, 2011 and December 1, 2013. Twenty-five cases (50 eyes) with OCA were enrolled in the study. All the participants had maximally reduced visual acuity (mean: 1.24±0.50logMAR). Myopic astigmatism was the most common refractive error (n=17; 34%). 58% of all participants had with-the-rule astigmatism. Considering the spherical equivalent power, most of the eyes (n=30; 60%) had myopia, with overall mean SE refractive error of -1.59±5.39D. Visual acuity improved significantly with refractive correction in place (paired sample t-test, palbinism. Copyright © 2014 Spanish General Council of Optometry. Published by Elsevier Espana. All rights reserved.

Prevalence of amblyopia and refractive errors among primary school children

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Zhale Rajavi

2015-01-01

Results: Amblyopia was present in 2.3% (95% CI: 1.8% to 2.9% of participants with no difference between the genders. Amblyopic subjects were significantly younger than non-amblyopic children (P=0.004. Overall, 15.9% of hyperopic and 5.9% of myopic cases had amblyopia. The prevalence of hyperopia ≥+2.00D, myopia ≤-0.50D, astigmatism ≥0.75D, and anisometropia (≥1.00D was 3.5%, 4.9%, 22.6%, and 3.9%, respectively. With increasing age, the prevalence of myopia increased (P<0.001, that of hyperopia decreased (P=0.007, but astigmatism showed no change. Strabismus was found in 2.3% of cases. Strabismus (OR=17.9 and refractive errors, especially anisometropia (OR=12.87 and hyperopia (OR=11.87, were important amblyogenic risk factors. Conclusion: The high prevalence of amblyopia in our subjects in comparison to developed countries reveals the necessity of timely and sensitive screening methods. Due to the high prevalence of amblyopia among children with refractive errors, particularly high hyperopia and anisometropia, provision of glasses should be specifically attended by parents and supported by the Ministry of Health and insurance organizations.

Adjustable bipod flexures for mounting mirrors in a space telescope.

Science.gov (United States)

Kihm, Hagyong; Yang, Ho-Soon; Moon, Il Kweon; Yeon, Jeong-Heum; Lee, Seung-Hoon; Lee, Yun-Woo

2012-11-10

A new mirror mounting technique applicable to the primary mirror in a space telescope is presented. This mounting technique replaces conventional bipod flexures with flexures having mechanical shims so that adjustments can be made to counter the effects of gravitational distortion of the mirror surface while being tested in the horizontal position. Astigmatic aberration due to the gravitational changes is effectively reduced by adjusting the shim thickness, and the relation between the astigmatism and the shim thickness is investigated. We tested the mirror interferometrically at the center of curvature using a null lens. Then we repeated the test after rotating the mirror about its optical axis by 180° in the horizontal setup, and searched for the minimum system error. With the proposed flexure mount, the gravitational stress at the adhesive coupling between the mirror and the mount is reduced by half that of a conventional bipod flexure for better mechanical safety under launch loads. Analytical results using finite element methods are compared with experimental results from the optical interferometer. Vibration tests verified the mechanical safety and optical stability, and qualified their use in space applications.

Validity of automated refraction after segmented refractive multifocal intraocular lens implantation.

Science.gov (United States)

Albarrán-Diego, César; Muñoz, Gonzalo; Rohrweck, Stephanie; García-Lázaro, Santiago; Albero, José Ricardo

2017-01-01

To evaluate the clinical utility of automated refraction (AR) and keratometry (KR) compared with subjective or manifest refraction (MR) after cataract or refractive lens exchange surgery with implantation of Lentis Mplus X (Oculentis GmbH) refractive multifocal intraocular lens (IOL). Eighty-six eyes implanted with the Lentis Mplus X multifocal IOL were included. MR was performed in all patients followed by three consecutive AR measurements using the Topcon KR-8000 autorefractor. Assessment of repeatability of consecutive AR before and after dilation with phenylephrine 10%, and comparison of the AR and KR with MR using vector analysis were performed at 3mo follow-up. Analysis showed excellent repeatability of the AR measurements. Linear regression of AR versus MR showed good correlation for sphere and spherical equivalent, whereas the correlation for astigmatism was low. The mean difference AR-MR was -1.28±0.29 diopters (D) for sphere. Astigmatism showed better correlation between KR and MR. We suggest AR sphere plus 1.25 D and the KR cylinder as the starting point for MR in eyes with a Lentis Mplus X multifocal IOL. If AR measurements are equal to MR, decentration of the IOL should be suspected.

Manual small incision extracapsular cataract surgery in Australia.

Science.gov (United States)

van Zyl, Lourens; Kahawita, Shyalle; Goggin, Michael

2014-11-01

Examination of the results and describing the technique of manual small incision extracapsular cataract extraction on patients with advanced cataracts in urban Australia. A descriptive case series. Thirty-eight patients at three public hospitals, one tertiary and two secondary ophthalmic units in urban Australia. Forty eyes with dense mature cataracts with hand movement vision or worse underwent a planned manual small incision extracapsular cataract extraction instead of traditional phaco-emulsification. Postoperative visual aquity, surgically induced astigmatism and complications. Seventy-eight per cent of patients had an uncorrected visual acuity of 6/12 or better on the first postoperative day. Eighty-three per cent of patients had a distance corrected visual acuity of 6/9 or better 3 months postoperatively. One case was complicated by a posterior capsule rupture. No cases of endophthalmitis were reported. The summated vector mean of the surgically induced astigmatism was 0.089D at 93°. Manual small incision extracapsular cataract extraction is an efficacious cataract surgery technique with good visual outcome and is a safe alternative to phaco-emulsification in suitable cases in a first-world setting. © 2014 Royal Australian and New Zealand College of Ophthalmologists.

Four spot laser anemometer and optical access techniques for turbine applications

Science.gov (United States)

Wernet, Mark P.

1987-01-01

A time-of-flight anemometer (TOFA) system utilizing a spatial lead-lag filter for bipolar pulse generation has been constructed and tested. This system, called a four-spot laser anemometer, was specifically designed for use in high-speed, turbulent flows in the presence of walls or surfaces. The TOFA system uses elliptical spots to increase the flow acceptance angle to be comparable with that of a fringe-type anemometer. The tightly focused spots used in the four spot yield excellent flare light rejection capabilities. Good results have been obtained to 75 microns normal to a surface, with an f/2.5 collection lens. This system is being evaluated for use in a warm turbine facility. Results from both a particle-lag velocity experiment and boundary layer profiles will be discussed. In addition, an analysis of the use of curved windows in a turbine casing will be presented. Curved windows, matching the inner radius of the turbine casing, preserve the flow conditions, but introduce astigmatic aberrations. A correction optic was designed that virtually eliminates these astigmatic aberrations throughout the intrablade survey region for normal incidence.

Complications of femtosecond laser corneal small incision lenticule extraction

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Qing-Hong Lin

2017-07-01

Full Text Available AIM:To investigate the safety and complications of femtosecond laser corneal small incision lenticule extraction(SMILEprocedure and discuss the prevention and treatment.METHODS: We retrospectively studied the complications of 403 patients(799 eyeswith myopia and myopic astigmatism treated by SMILE.RESULTS: All the patients underwent the operation successfully. Only 1 case(1 eyesuffered from dark spot and changed to femtosecond laser-assisted LASIK(FS-LASIK, 5 cases(5 eyes, 0.6%suffered from the suction loss, 11 cases(17 eyes, 2.1%developed opaque bubble layer. All patients gained perfect uncorrected visual acuity(UCVA(20/20. The best corrected visual acuity(BCVAdid not decrease after operations. The incidence of haze and diffuse lamellar keratitis was low(0.3% and 0.4%, respectivelyand no other complications were observed. There was 9 eyes in 6 patients(1.1%found regression of refraction at 6mo after surgery, while the UCVA of rest patients reached 1.0 at 3mo after surgery.CONCLUSION: The SMILE procedure has high safety for myopia and myopic astigmatism. Effective prevention and management of the complications is the key to achieve the satisfactory visual acuity.

Compensation of aberrations of deflected electron probe by means of dynamical focusing with stigmator

International Nuclear Information System (INIS)

Baba, Norio; Ebe, Toyoe; Ikehata, Koichi; Ito, Yasuhiro; Terada, Hiroshi

1979-01-01

Electron beam passing through a deflecting field is in general, subjected to aberrations such as distortion, astigmatism and coma in accordance with the deflecting angle. Accordingly the aberration defect of deflected beam is the most serious limiting factor in the performances of micromachining, microminiaturization and high resolution scanning electron microscopes. From many investigators' results, it is obvious that three important compensation methods to aberrations exist in principle, i.e., double deflection system, dynamical focusing, and the dynamical correction using a stigmator. In this paper, based on the aberration formula derived from the eikonal or the path method, the practical data of the aberration constants of deflected electron beam for the sequential deflection system with parallel plates are calculated, and using its result, the distorted spot patterns of an electron probe deflected in two-dimensional directions for various defocusings are graphically displayed by the aid of a computer. Further, by means of the dynamical focusing with a stigmator, the conditions to completely compensate the second order astigmatic aberration are derived, and spot patterns and the electron density distributions within the spots in the case when the compensating conditions are satisfied are also graphically displayed. (Wakatsuki, Y.)

Epidemiology of ametropia of U.S. Army recruits.

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McAlister, W H; Wingert, T A

1995-02-01

All people attempting to enlist in the U.S. Army must undergo a physical examination that requires a rudimentary vision screening. Those who pass the physical, upon reporting to basic training, are again evaluated and any treatment necessary to allow the recruits to function during their initial indoctrination is provided. Those who fail to see 20/20 O.D. and O.S. with their current spectacles fail the screening and are evaluated by an optometrist. If their condition is not disqualifying, appropriate correction is prescribed. We reviewed the records of all the recruits in a 1-month period who either required spectacles to see 20/20 or failed the screening at the 43rd AG BN (reception). Epidemiological evaluation revealed most to be either simple myopes or myopic astigmats. Hyperopia and hyperopic astigmatism accounted for the next most common diagnosis. Other conditions included anisometropia, antimetropia, amblyopia, keratoconus, and nystagmus. Examinations of these recruits were very limited, with dilated fundus evaluations being performed only when there was a high probability of a disqualifying condition. Therefore, it is unknown what retinal disease or degeneration may be present other than what would be visible with direct ophthalmoscopy.

Long-term outcomes of limbal relaxing incisions during cataract surgery: aberrometric analysis

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Monaco G

2015-08-01

Full Text Available Gaspare Monaco, Antonio ScialdoneDepartment of Ophthalmology, Ospedale Fatebenefratelli e Oftalmico, Milan, ItalyPurpose: To compare the final changes in corneal wavefront aberration by limbal relaxing incisions (LRIs after cataract surgery.Methods: This prospective cumulative interventional nonrandomized case study included cataract and astigmatic patients undergoing LRIs and phaco with intraocular lens implantation. LRIs were planned using Donnenfeld nomogram. The root mean square of corneal wave aberration for total Z(n,i(1≤n≤8, astigmatism Z(2,±1, coma Z(3–5–7,±1, trefoil Z(3–5–7,±2, spherical Z(4–6–8,0, and higher-order aberration (HOA Z(3≤n≤8 was examined before and 3 years after surgery (optical path difference-Scan II [OPD-Scan II]. Uncorrected distance visual acuity and best-corrected distance visual acuity (CDVA for distance, keratometric cylinder, and variations in average corneal power were also analyzed.Results: Sixty-four eyes of 48 patients were included in the study. Age ranged from 42 to 92 years (70.6±8.4 years. After LRIs, uncorrected distance visual acuity and best-corrected distance visual acuity improved statistically (P<0.01. The keratometric cylinder value decreased by 40.1%, but analysis of KP90 and KP135 polar values did not show any decrease that could be statistically confirmed (P=0.22 and P=0.24. No significant changes were detected in root mean square of total (P=0.61 and HOAs (P=0.13 aberrations. LRIs did not induce alteration in central corneal power confirming a 1:1 coupling ratio.Conclusion: LRIs determined a nonsignificant alteration of corneal HOA. Therefore, LRIs can be still considered a qualitatively viable mean in those cases where toric intraocular lenses are contraindicated or not available. Yet, the authors raise the question of nonpersonalized nomograms, as in the present study, LRIs did not reach the preset target cylinder. Keywords: astigmatism, ocular wavefront, intraocular

[Clinical findings in members of a Czech family with retinitis pigmentosa caused by the c.2426_2427delAG mutation in RPGR].

Science.gov (United States)

Kousal, B; Skalická, P; Diblík, P; Kuthan, P; Langrová, H; Lišková, P

2013-03-01

To describe the phenotype of members of the first Czech retinitis pigmentosa family with an identified molecular genetic cause (c.2426_2427delAG in RPGR), followed for more than 13 years. Medical records were reviewed and a detailed ophthalmic examination including spectral-domain optical coherence tomography and full-field and multifocal electroretinography (ERG) was performed in two affected males, three female carriers and one unaffected female. A 22-year-old male who denied suffering from nyctalopia had a best corrected visual acuity (BCVA) of 0.63 in both eyes. Moderate myopia and myopic astigmatism were present bilaterally. Color vision and contrast sensitivity were normal. There was an eccentric constriction of the visual fields that spared the central 20 degrees in both eyes. Fundus examination revealed bilateral pigmentary changes in the mid-periphery. Full-field ERG documented a 10% rod and 20% cone response. The phenotype of his cousin, also aged 22 years, was more severe. He complained of nyctalopia since 12 years of age. His BCVA was 0.3 in the right eye and 0.5 in the left eye. Myopia and astigmatism were present bilaterally. Contrast sensitivity and color vision were severely impaired. Full field ERG was extinct, but some activity on multifocal ERG was still detectable. The constriction of the visual fields reached 5 degrees in both eyes. Fundus examination showed the typical retinitis pigmentosa appearance. All carriers denied that they suffered from nyctalopia, but two of them had decreased BCVA in at least one eye. None exhibited typical bone spicules or a tapetal-like reflex. Significant refractive errors were present in all eyes of the carriers. The finding of moderate or high myopia and astigmatism in males with retinitis pigmentosa as well as refractive errors in female relatives indicates possible X-linked inheritance, which may be especially important in pedigrees where the transmission pattern can not be clearly established. Our study

The status of refractive errors in elementary school children in South Jeolla Province, South Korea

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Jang JU

2015-07-01

Full Text Available Jung Un Jang,1 Inn-Jee Park2 1Department of Optometry, Eulji University, Seongnam, 2Department of Optometry, Kaya University, Gimhae, South Korea Purpose: To assess the prevalence of refractive errors among elementary school children in South Jeolla Province of South Korea. Methods: The subjects were aged 8–13 years; a total of 1,079 elementary school children from Mokpo, South Jeolla Province, were included. In all participants, uncorrected visual acuity and objective and subjective refractions were determined using auto Ref-Keratometer and phoropter. A spherical equivalent of -0.50 diopter (D or worse was defined as myopia, +0.50 D or more was defined as hyperopia, and a cylinder refraction greater than 0.75 D was defined as astigmatism. Results: Out of 1,079 elementary school children, the prevalence of uncorrected, best-corrected, and corrected visual acuity with own spectacles of 20/40 or worse in the better eye was 26.1%, 0.4%, and 20.2%, respectively. The uncorrected visual acuity was 20/200 or worse in the better eye in 5.7% of school children, and 5.2% of them already wore corrective spectacles. The prevalence of myopia, hyperopia, and astigmatism was 46.5% (95% confidence interval [CI]: 43.56–49.5, 6.2% (95% CI: 4.92–7.81, and 9.4% (95% CI: 7.76–11.25, respectively. Conclusion: The present study reveals a considerably higher prevalence of refractive error among elementary school children in South Jeolla Province of South Korea, exceeding 50% of subjects. The prevalence of myopia in the school children in Korea is similar to many other countries including People’s Republic of China, Malaysia, and Hong Kong. This may indicate that genetics and educational influences, such as studying and learning, may play a role in the progression of myopia in Korean elementary school children. Keywords: refractive error, elementary school children, visual acuity, myopia, astigmatism

The parameters of the porcine eyeball.

Science.gov (United States)

Sanchez, Irene; Martin, Raul; Ussa, Fernando; Fernandez-Bueno, Ivan

2011-04-01

The eye of the domestic pig (Sus scrofa domestica) is an ex vivo animal model often used in vision sciences research (retina studies, glaucoma, cataracts, etc.). However, only a few papers have compiled pig eye anatomical descriptions. The purpose of this paper is to describe pig and human eye anatomical parameters to help investigators in their choice of animal model depending on their study objective. A wide search of current medical literature was performed (English language) using PubMed. Anteroposterior axial length and corneal radius, astigmatism, vertical and horizontal diameter, and pachymetry (slit-scan and ultrasound) were measured in five enucleated pig eyes of animals 6 to 8 months old. Horizontal corneal diameter was 14.31 ± 0.25 mm (CI 95% 14.03 mm-14.59 mm), vertical diameter was 12.00 ± 0 mm, anteroposterior length was 23.9 ± 0.08 mm (CI 95% 23.01 mm-29.99 mm), central corneal ultrasound pachymetry was 877.6 ± 13.58 μm (CI 95% 865.70 μm-889.50 μm) and slit-scan pachymetry was 906.2 ± 15.30 μm (CI 95% 892.78 μm-919.61 μm). Automatic keratometry (main meridians) was 41.19 ± 1.76D and 38.83 ± 2.89D (CI 95% 40.53D-41.81D and 37.76D-39.89D respectively) with an astigmatism of 2.36 ± 1.70D (CI 95% 1.72D-3.00D), and manual keratometry was 41.05 ± 0.54D and 39.30 ± 1.15D (CI 95% 40.57D-41.52D and 38.29D-40.31D respectively) with an astigmatism of 1.75 ± 1.31D (CI 95% 0.60D-2.90D). This paper describes the anatomy of the pig eyeball for easy use and interpretation by researchers who are considering their choice of animal model in vision sciences research.

Calculation of beam paths in optical systems containing inhomogeneous isotropic media with cylindrical distribution of the refractive index

International Nuclear Information System (INIS)

Grammatin, A.P.; Degen, A.B.; Katranova, N.A.

1995-01-01

A system of differential equations convenient for numerical computer integrating is proposed to calculate beam paths, elementary astigmatic beams, and the optical path in isotropic media with cylindrical distribution of the refractive index. A method for selecting the step of this integration is proposed. This technique is implemented in the program package for computers of the VAX series meant for the computer-aided design of optical systems. 4 refs

Compact adaptive optic-optical coherence tomography system

Science.gov (United States)

Olivier, Scot S [Livermore, CA; Chen, Diana C [Fremont, CA; Jones, Steven M [Danville, CA; McNary, Sean M [Stockton, CA

2011-05-17

Badal Optometer and rotating cylinders are inserted in the AO-OCT to correct large spectacle aberrations such as myopia, hyperopic and astigmatism for ease of clinical use and reduction. Spherical mirrors in the sets of the telescope are rotated orthogonally to reduce aberrations and beam displacement caused by the scanners. This produces greatly reduced AO registration errors and improved AO performance to enable high order aberration correction in a patient eyes.

Method and system for automatically correcting aberrations of a beam of charged particles

International Nuclear Information System (INIS)

1975-01-01

The location of a beam of charged particles within a deflection field is determined by its orthogonal deflection voltages. With the location of the beam in the field, correction currents are supplied to a focus coil and to each of a pair of stigmator coils to correct for change of focal length and astigmatism due to the beam being deflected away from the center of its deflection field

Heme Oxygenase-2 as a novel target to treat inflammation and chronic neuropathic pain associated with corneal injury and surgery

OpenAIRE

Marrazzo, Giuseppina

2012-01-01

Corneal refractive surgery aims at correcting alteration of the shape of the cornea correlated with myopia, hyperopia and astigmatism. More than 12 million patients have undergone refractive surgery since it was approved (see http://www. laser-eye-surgery statistics.com/). Laser-assisted in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) are the most used techniques to perform experimental corneal surgery. Several studies demonstrated that after epithelial removal (first...

Optical Quality, Threshold Target Identification, and Military Target Task Performance After Advanced Keratorefractive Surgery

Science.gov (United States)

2012-05-01

Expiration Date 27 October 2011 2 cornea is approved by the Food and Drug Administration (FDA) and the procedure is not considered...and Drug Administration , the Department of Walter Reed National Military Medical Center, Bethesda IRBNet# 20481 IRB Approval Date: 29 November 2011...farsightedness or astigmatism, the clear front surface of your eye, the “ cornea ”, does not have the proper focusing power. To correct this deficiency you must

Automatic diagnostic system for measuring ocular refractive errors

Science.gov (United States)

Ventura, Liliane; Chiaradia, Caio; de Sousa, Sidney J. F.; de Castro, Jarbas C.

1996-05-01

Ocular refractive errors (myopia, hyperopia and astigmatism) are automatic and objectively determined by projecting a light target onto the retina using an infra-red (850 nm) diode laser. The light vergence which emerges from the eye (light scattered from the retina) is evaluated in order to determine the corresponding ametropia. The system basically consists of projecting a target (ring) onto the retina and analyzing the scattered light with a CCD camera. The light scattered by the eye is divided into six portions (3 meridians) by using a mask and a set of six prisms. The distance between the two images provided by each of the meridians, leads to the refractive error of the referred meridian. Hence, it is possible to determine the refractive error at three different meridians, which gives the exact solution for the eye's refractive error (spherical and cylindrical components and the axis of the astigmatism). The computational basis used for the image analysis is a heuristic search, which provides satisfactory calculation times for our purposes. The peculiar shape of the target, a ring, provides a wider range of measurement and also saves parts of the retina from unnecessary laser irradiation. Measurements were done in artificial and in vivo eyes (using cicloplegics) and the results were in good agreement with the retinoscopic measurements.

Can the Bruckner test be used as a rapid screening test to detect significant refractive errors in children?

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Kothari Mihir

2007-01-01

Full Text Available Purpose: To assess the suitability of Brückner test as a screening test to detect significant refractive errors in children. Materials and Methods: A pediatric ophthalmologist prospectively observed the size and location of pupillary crescent on Brückner test as hyperopic, myopic or astigmatic. This was compared with the cycloplegic refraction. Detailed ophthalmic examination was done for all. Sensitivity, specificity, positive predictive value and negative predictive value of Brückner test were determined for the defined cutoff levels of ametropia. Results: Ninety-six subjects were examined. Mean age was 8.6 years (range 1 to 16 years. Brückner test could be completed for all; the time taken to complete this test was 10 seconds per subject. The ophthalmologist identified 131 eyes as ametropic, 61 as emmetropic. The Brückner test had sensitivity 91%, specificity 72.8%, positive predictive value 85.5% and negative predictive value 83.6%. Of 10 false negatives four had compound hypermetropic astigmatism and three had myopia. Conclusions: Brückner test can be used to rapidly screen the children for significant refractive errors. The potential benefits from such use may be maximized if programs use the test with lower crescent measurement cutoffs, a crescent measurement ruler and a distance fixation target.

Retinal dysfunction and refractive errors: an electrophysiological study of children

Science.gov (United States)

Flitcroft, D I; Adams, G G W; Robson, A G; Holder, G E

2005-01-01

Aims: To evaluate the relation between refractive error and electrophysiological retinal abnormalities in children referred for investigation of reduced vision. Methods: The study group comprised 123 consecutive patients referred over a 14 month period from the paediatric service of Moorfields Eye Hospital for electrophysiological investigation of reduced vision. Subjects were divided into five refractive categories according to their spectacle correction: high myopia (⩽−6D), low myopia (>−6D and ⩽−0.75D), emmetropia (>−0.75 and 1.5D) and ERG abnormalities (18/35 with high astigmatism v 20/88 without, χ2 test, p = 0.002). There was no significant variation in frequency of abnormalities between low myopes, emmetropes, and low hyperopes. The rate of abnormalities was very similar in both high myopes (8/15) and high hyperopes (5/10). Conclusions: High ametropia and astigmatism in children being investigated for poor vision are associated with a higher rate of retinal electrophysiological abnormalities. An increased rate of refractive errors in the presence of retinal pathology is consistent with the hypothesis that the retina is involved in the process of emmetropisation. Electrophysiological testing should be considered in cases of high ametropia in childhood to rule out associated retinal pathology. PMID:15774929

Efficacy on chopping with lens loop-pad in the small incision extracapsular cataract surgery with intraocular lens implantation

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Xiao-Ning Peng

2014-04-01

Full Text Available AIM: To study the clinical effects of chopping with lens loop-pad in the small incision extracapsular cataract surgery with intraocular lens implantation.METHODS:A total of 75 cases(80 eyes, in which loop-pad and chop knife were performed to chop nucleus before implanting intraocular lens. Visual acuity, postoperative astigmatism degree, intraoperative and postoperative complications were observed. The post-operative follow-up periods ranged from 3 to 12mo.RESULTS: The visual acuity was 0.3-0.5 in 37 eyes and 0.6 or better in 21 eyes at 1d, while was respectively in 43 eyes and in 26 eyes at 1mo. Compared with preoperative astigmatism(0.85±0.29D, there were significant difference at postoperative 1wk(1.75±0.55D(PP>0.05. Intraoperative posterior capsule rupture occurred in 4 eyes, which implantation was successful in 1 eye and 3 eyes was managed viaciliary sulcus. Two eyes had dermatoglyphic pattern edema in corneal endothelium which recovered after about 3d. Two eyes had local patchy opacities which recovered in 2wk. Two eyes had transient high intraocular pressure.CONCLUSION: The surgery is efficient, low cost, easy process and less complications, it is worth to be popularized.

Validity of automated refraction after segmented refractive multifocal intraocular lens implantation

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César Albarrán-Diego

2017-11-01

Full Text Available AIM: To evaluate the clinical utility of automated refraction (AR and keratometry (KR compared with subjective or manifest refraction (MR after cataract or refractive lens exchange surgery with implantation of Lentis Mplus X (Oculentis GmbH refractive multifocal intraocular lens (IOL. METHODS: Eighty-six eyes implanted with the Lentis Mplus X multifocal IOL were included. MR was performed in all patients followed by three consecutive AR measurements using the Topcon KR-8000 autorefractor. Assessment of repeatability of consecutive AR before and after dilation with phenylephrine 10%, and comparison of the AR and KR with MR using vector analysis were performed at 3mo follow-up. RESULTS: Analysis showed excellent repeatability of the AR measurements. Linear regression of AR versus MR showed good correlation for sphere and spherical equivalent, whereas the correlation for astigmatism was low. The mean difference AR-MR was -1.28±0.29 diopters (D for sphere. Astigmatism showed better correlation between KR and MR. CONCLUSION: We suggest AR sphere plus 1.25 D and the KR cylinder as the starting point for MR in eyes with a Lentis Mplus X multifocal IOL. If AR measurements are equal to MR, decentration of the IOL should be suspected.

Image transfer with spatial coherence for aberration corrected transmission electron microscopes

International Nuclear Information System (INIS)

Hosokawa, Fumio; Sawada, Hidetaka; Shinkawa, Takao; Sannomiya, Takumi

2016-01-01

The formula of spatial coherence involving an aberration up to six-fold astigmatism is derived for aberration-corrected transmission electron microscopy. Transfer functions for linear imaging are calculated using the newly derived formula with several residual aberrations. Depending on the symmetry and origin of an aberration, the calculated transfer function shows characteristic symmetries. The aberrations that originate from the field’s components, having uniformity along the z direction, namely, the n-fold astigmatism, show rotational symmetric damping of the coherence. The aberrations that originate from the field’s derivatives with respect to z, such as coma, star, and three lobe, show non-rotational symmetric damping. It is confirmed that the odd-symmetric wave aberrations have influences on the attenuation of an image via spatial coherence. Examples of image simulations of haemoglobin and Si [211] are shown by using the spatial coherence for an aberration-corrected electron microscope. - Highlights: • The formula of partial coherence for aberration corrected TEM is derived. • Transfer functions are calculated with several residual aberrations. • The calculated transfer function shows the characteristic damping. • The odd-symmetric wave aberrations can cause the attenuation of image via coherence. • The examples of aberration corrected TEM image simulations are shown.

Clinical observation of transepithelial photorefractive keratectomy for myopia

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Xiao-Ning Yang

2013-10-01

Full Text Available AIM: To assess the effectiveness and safety of transepithelial photorefractive keratectomy(TransPRKusing the AMARIS laser platform. METHODS: Eighty myopic cases(156 eyeswith or without astigmatism were treated by TransPRK. In all eyes, treatments were planned with Custom Ablation Manager Software and ablations performed with the SCHWIND AMARIS system. Clinical outcomes of visual acuity, manifest refraction, intraocular pressure, and corneal topography were observed and analyzed. The follow-up period was one year.RESULTS: All patients completed the 1-year follow-up. After one-year follow-up, 47 cases(92 eyes, 58.8%achieved an uncorrected distance visual acuity(UDVA≥1.0. Twenty cases(40 eyes, 25%was 0.8 and 13 cases(24 eyes, 16.3%was 0.6. Sixty-three cases(121 eyes, 78.8%were close to or above best corrected visual acuity(BCVA. Seventeen cases(34 eyes, 21.2%were slightly lower than BCVA 1 row or two. Nine cases(18 eyes, 11.3%got dry eye postoperatively. 16 cases(32 eyes, 20%complain of glare and poor night vision. CONCLUSION: The results show that TransPRK for myopia with or without astigmatism is safe and effective. The postoperative visual outcomes are stable.

Image transfer with spatial coherence for aberration corrected transmission electron microscopes

Energy Technology Data Exchange (ETDEWEB)

Hosokawa, Fumio, E-mail: hosokawa@bio-net.co.jp [BioNet Ltd., 2-3-28 Nishikityo, Tachikwa, Tokyo (Japan); Tokyo Institute of Technology, 4259 Nagatsuta, Midoriku, Yokohama 226-8503 (Japan); Sawada, Hidetaka [JEOL (UK) Ltd., JEOL House, Silver Court, Watchmead, Welwyn Garden City, Herts AL7 1LT (United Kingdom); Shinkawa, Takao [BioNet Ltd., 2-3-28 Nishikityo, Tachikwa, Tokyo (Japan); Sannomiya, Takumi [Tokyo Institute of Technology, 4259 Nagatsuta, Midoriku, Yokohama 226-8503 (Japan)

2016-08-15

The formula of spatial coherence involving an aberration up to six-fold astigmatism is derived for aberration-corrected transmission electron microscopy. Transfer functions for linear imaging are calculated using the newly derived formula with several residual aberrations. Depending on the symmetry and origin of an aberration, the calculated transfer function shows characteristic symmetries. The aberrations that originate from the field’s components, having uniformity along the z direction, namely, the n-fold astigmatism, show rotational symmetric damping of the coherence. The aberrations that originate from the field’s derivatives with respect to z, such as coma, star, and three lobe, show non-rotational symmetric damping. It is confirmed that the odd-symmetric wave aberrations have influences on the attenuation of an image via spatial coherence. Examples of image simulations of haemoglobin and Si [211] are shown by using the spatial coherence for an aberration-corrected electron microscope. - Highlights: • The formula of partial coherence for aberration corrected TEM is derived. • Transfer functions are calculated with several residual aberrations. • The calculated transfer function shows the characteristic damping. • The odd-symmetric wave aberrations can cause the attenuation of image via coherence. • The examples of aberration corrected TEM image simulations are shown.

Clinical observation of four-fixable intraocular lens suspensory

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Yu-Ming Teng

2015-06-01

Full Text Available AIM: To discuss the four-fixable intraocular lens(IOLsuspensory in the absence of capsular intraocular lens implantation, suspensory ligament rupture caused by congenital dislocation of the lens, traumatic cataract and posterior capsular rupture without capsular support, which need to line hanging IOL for intraoperative clinical observation.METHODS: The 31 cases(32 eyeswho were accepted the four-fixable IOL suspensory from May 2012 to May 2014 in our hospital were retrospectively analyzed. The postoperative visual acuity, corneal astigmatism, intraoperative and postoperative complications were comprehensively analyzed.RESULTS: Patients were followed up 6mo～1a, corrected visual acuity >0.5(12 eyes, 38%, 0.1～0.5(18 eyes, 56%, and CONCLUSION: It is designed to support non-capsular IOL implantation and design, and the concept of changing the past presence of suspended dislocated IOL implantation surgery, positional deviation and, sutures and other complications split the incidence is greatly reduced. It is consistent with the physiological characteristics of the human eye, and it is the IOL surgical sling best stability, intraoperative and postoperative complications, the best visual acuity and corneal astigmatism minimal surgical approachat least, and the four-point suspension suture fixation of IOL is designed to obtain a practical transformation of Chinese patent.

Macroeconomic landscape of refractive surgery in the United States.

Science.gov (United States)

Corcoran, Kevin J

2015-07-01

This review examines the economic history of refractive surgery and the decline of laser-assisted in-situ keratomileusis (LASIK) in the USA, and the emergence of refractive cataract surgery as an area of growth. Since it peaked in 2007 at 1.4 million procedures per year, LASIK has declined 50% in the USA, whereas refractive cataract surgery, including presbyopia-correcting intraocular lenses (IOLs), astigmatism-correcting IOLs, and femtosecond laser-assisted cataract surgery, has grown to 350 000 procedures per year, beginning in 2003. Patients are price-sensitive and responsive to publicity (good or bad) about refractive surgery and refractive cataract surgery. LASIK's decline has been partially offset by the emergence of refractive cataract surgery. About 11% of all cataract surgery in the USA involves presbyopia-correcting IOLs, astigmatism-correcting IOLs, or a femtosecond laser. From the surgeon's perspective, there are high barriers to entry into the marketplace for refractive surgery and refractive cataract surgery due to the high capital cost of excimer and femtosecond lasers, the high skill level required to deliver spectacular results to demanding patients who pay out of pocket, and the necessity to perform a high volume of surgeries to satisfy both of these requirements. Probably, less than 7% of US cataract surgeons can readily meet all of these requirements.

Repeatability and Comparison of Keratometry Values Measured with Potec PRK-6000 Autorefractometer, IOLMaster, and Pentacam

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Adem Türk

2014-05-01

Full Text Available Objectives: To research the repeatability and intercompatibility of keratometry values measured with Potec PRK-6000 autorefractometer, IOL Master, and Pentacam. Materials and Methods: In this prospective study, consecutive measurements were performed in two different sessions with the mentioned three devices on 110 eyes of 55 subjects who had no additional ocular pathology except for refraction error. The consistency of flat and steep keratometry, average keratometry, and corneal astigmatism values obtained in both sessions was compared by using intraclass correlation coefficient (ICC. The measurement differences between the devices were statistically compared as well. Results: The mean age of the study subjects was 23.05±3.01 (18-30 years. ICC values of average keratometry measurements obtained in the sessions were 0.996 for Potec PRK-6000 autorefractometer, 0.997 for IOL Master, and 0.999 for Pentacam. There was high compatibility between the three devices in terms of average keratometry values in Bland-Altman analysis. However, there were statistically significant differences between the devices in terms of parameters other than corneal astigmatism. Conclusion: The repeatability of the three devices was found considerably high in keratometry measurements. However, it is not appropriate for these devices to be substituted for each other in keratometry measurements. (Turk J Ophthalmol 2014; 44: 179-83

Microscopy system of atomic force based on a digital optical reading unit and a buzzer-scanner; Sistema de microscopia de fuerza atomica basada en una unidad de lectura optica digital y un escaner-zumbador

Energy Technology Data Exchange (ETDEWEB)

Dabirian, R.; Loza M, D. [Universidad de las Fuerzas Armadas-ESPE, Departamento de Ciencias de la Energia y Mecanica, Sangolqui (Ecuador); Wang, W. M.; Hwu, E. T., E-mail: whoand@gmail.com [Academia Sinica, Institute of Physics, Taipei, 11529 Taiwan (China)

2015-07-01

An astigmatic detection system (Ads) based on a compact disk/digital-versatile-disk (Cd-DVD) astigmatic optical pickup unit is presented. It can achieve a resolution better than 0.3 nm in detection of the vertical displacement and is able to detect the two-dimensional angular tilt of the object surface. Furthermore, a novel scanner design actuated by piezoelectric disk buzzers is presented. The scanner is composed of a quad-rod actuation structure and several piezoelectric disks. It can be driven directly with low-voltage and low-current sources, such as analogue outputs of a data acquisition card and enables a sufficient scanning range of up to μm. In addition, an economic, high-performance streamlined atomic force microscopy (AFM) was constructed, using the buzzer-scanner to move the sample relative to the probe, and using a Cd/DVD optical pickup unit to detect the mechanical resonance of a micro fabricated cantilever. The performance of the AFM is evaluated. The high sensitivity and high bandwidth of the detection system makes the equipment suitable for characterizing nano scale elements. An AFM using our detection system for detecting the deflection of micro fabricated cantilevers can resolve individual atomic steps on graphite surfaces. (Author)

Microscopy system of atomic force based on a digital optical reading unit and a buzzer-scanner

International Nuclear Information System (INIS)

Dabirian, R.; Loza M, D.; Wang, W. M.; Hwu, E. T.

2015-01-01

An astigmatic detection system (Ads) based on a compact disk/digital-versatile-disk (Cd-DVD) astigmatic optical pickup unit is presented. It can achieve a resolution better than 0.3 nm in detection of the vertical displacement and is able to detect the two-dimensional angular tilt of the object surface. Furthermore, a novel scanner design actuated by piezoelectric disk buzzers is presented. The scanner is composed of a quad-rod actuation structure and several piezoelectric disks. It can be driven directly with low-voltage and low-current sources, such as analogue outputs of a data acquisition card and enables a sufficient scanning range of up to μm. In addition, an economic, high-performance streamlined atomic force microscopy (AFM) was constructed, using the buzzer-scanner to move the sample relative to the probe, and using a Cd/DVD optical pickup unit to detect the mechanical resonance of a micro fabricated cantilever. The performance of the AFM is evaluated. The high sensitivity and high bandwidth of the detection system makes the equipment suitable for characterizing nano scale elements. An AFM using our detection system for detecting the deflection of micro fabricated cantilevers can resolve individual atomic steps on graphite surfaces. (Author)

Advanced Optics for the Remote Steering ITER ECRH Upper Launcher

International Nuclear Information System (INIS)

Bruschi, A; Cirant, S; Moro, A; Platania, P; Sozzi, C

2005-01-01

The optics of the ECRH Upper Launcher in ITER based on the Remote Steering concept needs special attention, since any focussing element in front of the waveguide has combined effects on the range of steering angles achievable and the beam width in the plasma region. The effects are studied in detail for a setup composed by 8 beams per port (three ports), for a spherical and a hyperbolic mirror surface. Gaussian beam analysis is compared to beam pattern calculations with the optical physics code GRASP, in order to verify the validity of gaussian optics approximation. The standard description with simply astigmatic beams, not adequate in more complex systems as the proposed two-mirror set-up, requires approximations, which are compared with the generalized astigmatic beam description. The ohmic losses at the end mirrors and the related localized heating due to the very large power density cause deformations that depends on the design of the cooling circuit. The distortion of the beam shape has been evaluated in a realistic case of mirror cooling with a small-channel system. The quantification of the effect depends on the precise evaluation ohmic losses and their enhancement in the long term due to the surface deterioration

Scleral Fixation of Posteriorly Dislocated Intraocular Lenses by 23-Gauge Vitrectomy without Anterior Segment Approach

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Jeroni Nadal

2015-01-01

Full Text Available Background. To evaluate visual outcomes, corneal changes, intraocular lens (IOL stability, and complications after repositioning posteriorly dislocated IOLs and sulcus fixation with polyester sutures. Design. Prospective consecutive case series. Setting. Institut Universitari Barraquer. Participants. 25 eyes of 25 patients with posteriorly dislocated IOL. Methods. The patients underwent 23-gauge vitrectomy via the sulcus to rescue dislocated IOLs and fix them to the scleral wall with a previously looped nonabsorbable polyester suture. Main Outcome Measures. Best corrected visual acuity (BCVA LogMAR, corneal astigmatism, endothelial cell count, IOL stability, and postoperative complications. Results. Mean follow-up time was 18.8 ± 10.9 months. Mean surgery time was 33 ± 2 minutes. Mean BCVA improved from 0.30 ± 0.48 before surgery to 0.18 ± 0.60 (p=0.015 at 1 month, which persisted to 12 months (0.18 ± 0.60. Neither corneal astigmatism nor endothelial cell count showed alterations 1 year after surgery. Complications included IOL subluxation in 1 eye (4%, vitreous hemorrhage in 2 eyes (8%, transient hypotony in 2 eyes (8%, and cystic macular edema in 1 eye (4%. No patients presented retinal detachment. Conclusion. This surgical technique proved successful in the management of dislocated IOL. Functional results were good and the complications were easily resolved.

Scleral Fixation of Posteriorly Dislocated Intraocular Lenses by 23-Gauge Vitrectomy without Anterior Segment Approach.

Science.gov (United States)

Nadal, Jeroni; Kudsieh, Bachar; Casaroli-Marano, Ricardo P

2015-01-01

Background. To evaluate visual outcomes, corneal changes, intraocular lens (IOL) stability, and complications after repositioning posteriorly dislocated IOLs and sulcus fixation with polyester sutures. Design. Prospective consecutive case series. Setting. Institut Universitari Barraquer. Participants. 25 eyes of 25 patients with posteriorly dislocated IOL. Methods. The patients underwent 23-gauge vitrectomy via the sulcus to rescue dislocated IOLs and fix them to the scleral wall with a previously looped nonabsorbable polyester suture. Main Outcome Measures. Best corrected visual acuity (BCVA) LogMAR, corneal astigmatism, endothelial cell count, IOL stability, and postoperative complications. Results. Mean follow-up time was 18.8 ± 10.9 months. Mean surgery time was 33 ± 2 minutes. Mean BCVA improved from 0.30 ± 0.48 before surgery to 0.18 ± 0.60 (p = 0.015) at 1 month, which persisted to 12 months (0.18 ± 0.60). Neither corneal astigmatism nor endothelial cell count showed alterations 1 year after surgery. Complications included IOL subluxation in 1 eye (4%), vitreous hemorrhage in 2 eyes (8%), transient hypotony in 2 eyes (8%), and cystic macular edema in 1 eye (4%). No patients presented retinal detachment. Conclusion. This surgical technique proved successful in the management of dislocated IOL. Functional results were good and the complications were easily resolved.

DEVICE FOR MEASURING OF THERMAL LENS PARAMETERS IN LASER ACTIVE ELEMENTS WITH A PROBE BEAM METHOD

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A. N. Zakharova

2015-01-01

Full Text Available We have developed a device for measuring of parameters of thermal lens (TL in laser active elements under longitudinal diode pumping. The measurements are based on the probe beam method. This device allows one to determine sign and optical power of the lens in the principal meridional planes, its sensitivity factor with respect to the absorbed pump power and astigmatism degree, fractional heat loading which make it possible to estimate integral impact of the photoelastic effect to the formation of TL in the laser element. The measurements are performed in a linearly polarized light at the wavelength of 532 nm. Pumping of the laser element is performed at 960 nm that makes it possible to study laser materials doped with Yb3+ and (Er3+, Yb3+ ions. The precision of measurements: for sensitivity factor of TL – 0,1 m-1/W, for astigmatism degree – 0,2 m-1/W, for fractional heat loading – 5 %, for the impact of the photoelastic effect – 0,5 × 10-6 K-1. This device is used for characterization of thermal lens in the laser active element from an yttrium vanadate crystal, Er3+,Yb3+:YVO .

Zernike phase spatial filter for measuring the aberrations

OpenAIRE

Svetlana N. Khonina; Victor V. Kotlyar; Dmitriy V. Kirsh

2015-01-01

To measure directly the wavefront aberration coefficients, we propose to use the multi8order diffractive element fitted with the set of Zernike polynomials. Polynomials of lowest degree describe defocusing (ametropy) and astigmatism. Coefficients of highest degree correspond to the spherical aberration of oblique rays that occurs as a consequence of misalignment of the crystalline lens and foveola, as well as deflection at the periphery of the crystalline lens. Mul^order elements allow severa...

Weakly oval electron lense

International Nuclear Information System (INIS)

Daumenov, T.D.; Alizarovskaya, I.M.; Khizirova, M.A.

2001-01-01

The method of the weakly oval electrical field getting generated by the axially-symmetrical field is shown. Such system may be designed with help of the cylindric form coaxial electrodes with the built-in quadrupole duplet. The singularity of the indicated weakly oval lense consists of that it provides the conducting both mechanical and electronic adjustment. Such lense can be useful for elimination of the near-axis astigmatism in the electron-optical system

[Tapeto-retinal degeneration combined with incomplete general albinism (author's transl)].

Science.gov (United States)

Ivandić, T

1975-05-01

Report on a family, which presented the rare autosomal dominant transmitted, incomplete general albinism associated with autosomal recessive inherited, diffuse tapeto-retinal degeneration "sine pigmento". hypopigmentation of skin, eyebrows and hair, blue iris and fundus albinoticus with hypoplasia of the macula. In 3 cases additionally appeared: waxy pallor of optic disc, vascular narrowing, reflexless hypoplastic macula, pigmentless periphery, acquired blue-yellow blindness, concentric limitation of the visual field, reduced darkadaptation, abolished electroretinogram and myopic astigmatism.

Thomas Young's contributions to geometrical optics.

Science.gov (United States)

Atchison, David A; Charman, W Neil

2011-07-01

In addition to his work on physical optics, Thomas Young (1773-1829) made several contributions to geometrical optics, most of which received little recognition in his time or since. We describe and assess some of these contributions: Young's construction (the basis for much of his geometric work), paraxial refraction equations, oblique astigmatism and field curvature, and gradient-index optics. © 2011 The Authors. Clinical and Experimental Optometry © 2011 Optometrists Association Australia.

Analysis of Corneal Astigmatism with NIDEK Axial Length Scan in ...

African Journals Online (AJOL)

2018-04-04

Apr 4, 2018 ... AL‑scan optical biometric device in healthy cataract patients. Patients and Methods. In this retrospective study, patient datasets were acquired between March 1, 2014 and April 15, 2016, at the. Department of Ophthalmology, Afyon Kocatepe University. The Bursa Yüksek Ihtisas Hospital's Ethics Committee.

Comparação entre os resultados pós-operatórios de pacientes submetidos ao procedimento tríplice e transplante de córnea combinado a fixação secundária de lente intra-ocular Comparison between the postoperative results of triple procedure and combined penetrating keratoplasty/ transsclerally sutured posterior chamber lens implantation

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Daniela Maggioni Pereira Leão

2006-08-01

Full Text Available OBJETIVO: Comparar os resultados pós-operatórios de 2 grupos de pacientes submetidos a transplante de córnea com técnicas e tempo cirúrgico diferentes, em relação à abordagem do cristalino e/ou lente intra-ocular. MÉTODOS: Neste estudo retrospectivo foram analisados 37 olhos de pacientes divididos em 2 grupos: extração de catarata, implante de lentes intra-oculares (LIO e transplante de córnea no mesmo tempo cirúrgico - grupo 1 (G1 e extração de catarata sem implante de lentes intra-oculares no primeiro tempo cirúrgico e fixação secundária de lentes intra-oculares associada a transplante de córnea no segundo tempo cirúrgico - grupo 2 (G2. As variáveis estudadas foram: acuidade visual, pressão intra-ocular (PIO, astigmatismo refracional, astigmatismo ceratométrico e complicações pós-operatórias. RESULTADOS: Foi observado melhora da acuidade visual nos 2 grupos (G1 pPURPOSE: To compare the outcomes of two surgical techniques of penetrating keratoplasty with different surgical time, regarding the crystalline and the intraocular lens. METHODS: This retrospective study included 37 patients' eyes divided into 2 groups: extracapsular cataract extraction, posterior chamber intraocular lens implantation and penetrating keratoplasty (Group 1, G1 and transscleral fixation of posterior chamber lens and penetrating keratoplasty (Group 2, G2. The following parameters were recorded: visual acuity, intraocular pressure, refractive astigmatism, complication and keratometric astigmatism. RESULTS: Visual acuity improved in the two groups (G1 p<0.001 and G2 p=0.008. In G2 a significant change for the worse of intraocular pressure outcome was observed when compared with the other group (p=0.014. Regarding refractive and keratometric astigmatism no significant differences between the groups were found. The follow-up was 11 months. CONCLUSION: The most important negative prognostic factor affecting visual acuity was the postkeratoplasty

Compact optical processor for Hough and frequency domain features

Science.gov (United States)

Ott, Peter

1996-11-01

Shape recognition is necessary in a broad band of applications such as traffic sign or work piece recognition. It requires not only neighborhood processing of the input image pixels but global interconnection of them. The Hough transform (HT) performs such a global operation and it is well suited in the preprocessing stage of a shape recognition system. Translation invariant features can be easily calculated form the Hough domain. We have implemented on the computer a neural network shape recognition system which contains a HT, a feature extraction, and a classification layer. The advantage of this approach is that the total system can be optimized with well-known learning techniques and that it can explore the parallelism of the algorithms. However, the HT is a time consuming operation. Parallel, optical processing is therefore advantageous. Several systems have been proposed, based on space multiplexing with arrays of holograms and CGH's or time multiplexing with acousto-optic processors or by image rotation with incoherent and coherent astigmatic optical processors. We took up the last mentioned approach because 2D array detectors are read out line by line, so a 2D detector can achieve the same speed and is easier to implement. Coherent processing can allow the implementation of tilers in the frequency domain. Features based on wedge/ring, Gabor, or wavelet filters have been proven to show good discrimination capabilities for texture and shape recognition. The astigmatic lens system which is derived form the mathematical formulation of the HT is long and contains a non-standard, astigmatic element. By methods of lens transformation s for coherent applications we map the original design to a shorter lens with a smaller number of well separated standard elements and with the same coherent system response. The final lens design still contains the frequency plane for filtering and ray-tracing shows diffraction limited performance. Image rotation can be done

Two kinds of manual chopping methods applied in small incision extracapsular cataract extraction

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Xia Jiang

2016-02-01

Full Text Available AIM:To research clinical effect of two manual chopping methods for small incision extracapsular cataract extraction. METHODS: We observed 143 cases(184 eyeswith grade Ⅳ or higher taken the small incision cataract extraction and intraocular lens implantation. Patients were given randomly knifed chopping with closed hook(92 eyesor double knifed chopping(92 eyes. The intra-operative posterior capsule rupture was observed and compared. At 1d, 1wk and 1mo postoperatively, visual acuity, corneal edema and corneal astigmatism were observed and analyzed. RESULTS:There were 10 eyes in patients accepting knifed chopping with closed hook with intra-operative posterior capsule rupture and 1 eye in patients accepting double knifed chopping. The difference between the two groups was statistically significant. The visual acuity of patients accepting knifed chopping with closed hook(92 eyesat 1d postoperatively was 0.380±0.105, and that of patients accepting double knifed chopping(92 eyeswas 0.420±0.095; the difference between the two groups was statistically significant. The visual acuity of patients accepting knifed chopping with closed hook(84 eyesat 1wk postoperatively was 0.480±0.123, and that of patients accepting double knifed chopping(86 eyeswas 0.520±0.085; the difference between the two groups was statistically significant. The visual acuity of patients accepting knifed chopping with closed hook(60 eyesat 1mo postoperatively was 0.610±0.083, and that of patients accepting double knifed chopping(52 eyeswas 0.643±0.072; the difference between the two groups was not statistically significant. The differences on corneal edema and corneal astigmatism between the two methods at 1d, 1wk and 1mo postoperatively were not statistically significant. CONCLUSION:The application of knifed chopping with closed hook and double knifed chopping in small incision extracapsular cataract extraction and intraocular lens implantation can effectively treat with

Control of multiple filamentation in air

Science.gov (United States)

Fibich, Gadi; Eisenmann, Shmuel; Ilan, Boaz; Zigler, Arie

2004-08-01

In this Letter we provide what is believed to be the first experimental evidence of suppression of the number of filaments for high-intensity laser pulses propagating in air by beam astigmatism. We also show that the number, pattern, and spatial stability of the filaments can be controlled by varying the angle that a focusing lens makes with the axial direction of propagation. This new methodology can be useful for applications involving atmospheric propagation, such as remote sensing.

New techniques in lamellar keratoplasty.

Science.gov (United States)

Alio, Jorge L; Shah, Sunil; Barraquer, Carmen; Bilgihan, Kamil; Anwar, Mohammed; Melles, Gerrit R J

2002-08-01

In the past years, several lamellar keratoplasty surgical techniques have been developed, modified or improved in the past years, including microkeratome assisted anterior and posterior lamellar keratoplasty, anterior lamellar keratoplasty using air-dissection or visco-dissection, sutureless posterior lamellar keratoplasty, LASIK for postkeratoplasty astigmatism, and excimer laser assisted keratophakia for keratoconus or to manage complications after LASIK. These procedures may continue to gain interest as alternative procedures for a penetrating keratoplasty in the treatment of various corneal disorders.

Vitreous loss-causes, associations, and outcomes: Eight-year analysis in Melaka Hospital

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Thanigasalam Thevi

2018-01-01

CONCLUSION: Vitreous loss occurred in almost all types of cataract surgeries, especially by junior surgeons, among those aged <40 years and significantly caused poor visual outcome compared to other complications. Pseudoexfoliation had higher occurrence of vitreous loss. Vitreous loss patients had impaired/poor visual outcome due to preexisting comorbidity and astigmatism. Patients at risk and junior surgeons should be closely monitored to improve outcomes. Further studies need to be done to see why and when the vitreous loss occurred.

Research on Calculation of the IOL Tilt and Decentration Based on Surface Fitting

OpenAIRE

Li, Lin; Wang, Ke; Yan, Yan; Song, Xudong; Liu, Zhicheng

2013-01-01

The tilt and decentration of intraocular lens (IOL) result in defocussing, astigmatism, and wavefront aberration after operation. The objective is to give a method to estimate the tilt and decentration of IOL more accurately. Based on AS-OCT images of twelve eyes from eight cases with subluxation lens after operation, we fitted spherical equation to the data obtained from the images of the anterior and posterior surfaces of the IOL. By the established relationship between IOL tilt (decentrati...

Phakic intraocular lenses for the treatment of refractive errors: an evidence-based analysis.

Science.gov (United States)

2009-01-01

The objective of this analysis is to review the effectiveness, safety, and cost-effectiveness of phakic intraocular lenses (pIOLs) for the treatment of myopia, hyperopia, and astigmatism. CONDITION AND TARGET POPULATION REFRACTIVE ERRORS: Refractive errors occur when the eye cannot focus light properly. In myopia (near- or short-sightedness), distant objects appear blurry because the axis of the eye is too long or the cornea is too steep, so light becomes focused in front of the retina. Hyperopia (far sightedness) occurs when light is focused behind the retina causing nearby objects to appear blurry. In astigmatism, blurred or distorted vision occurs when light is focused at two points rather than one due to an irregularly shaped cornea or lens. Refractive errors are common worldwide, but high refractive errors are less common. In the United States, the prevalence of high myopia (≤ -5 D) in people aged 20 to 39, 40 to 59, and 60 years and older is 7.4% (95% confidence interval [CI], 6.5% - 8.3%), 7.8% (95% CI, 6.4% - 8.6%), and 3.1% (95% CI, 2.2% - 3.9%), respectively. The prevalence of high hyperopia (≥ 3 D) is 1.0% (95% CI, .6% - 1.4%), 2.4% (95% CI, 1.7% - 3.0%), and 10.0% (95% CI, 9.1% - 10.9%) for the same age groupings. Finally, the prevalence of astigmatism (≥ 1 D cylinder) is 23.1% (95% CI, 21.6% - 24.5%), 27.6% (95% CI, 25.8% - 29.3%) and 50.1% (48.2% - 52.0%). LOW VISION: According to the Ontario Schedule of Benefits, low visual acuity is defined by a best spectacle corrected visual acuity (BSCVA) of 20/50 (6/15) or less in the better eye and not amenable to further medical and/or surgical treatment. Similarly, the Ontario Assistive Devices Program defines low vision as BSCVA in the better eye in the range of 20/70 or less that cannot be corrected medically, surgically, or with ordinary eyeglasses or contact lenses. Estimates of the prevalence of low vision vary. Using the criteria of BSCVA ranging from 20/70 to 20/160, one study estimated that 35

Refractive errors in children and adolescents in Bucaramanga (Colombia).

Science.gov (United States)

Galvis, Virgilio; Tello, Alejandro; Otero, Johanna; Serrano, Andrés A; Gómez, Luz María; Castellanos, Yuly

2017-01-01

The aim of this study was to establish the frequency of refractive errors in children and adolescents aged between 8 and 17 years old, living in the metropolitan area of Bucaramanga (Colombia). This study was a secondary analysis of two descriptive cross-sectional studies that applied sociodemographic surveys and assessed visual acuity and refraction. Ametropias were classified as myopic errors, hyperopic errors, and mixed astigmatism. Eyes were considered emmetropic if none of these classifications were made. The data were collated using free software and analyzed with STATA/IC 11.2. One thousand two hundred twenty-eight individuals were included in this study. Girls showed a higher rate of ametropia than boys. Hyperopic refractive errors were present in 23.1% of the subjects, and myopic errors in 11.2%. Only 0.2% of the eyes had high myopia (≤-6.00 D). Mixed astigmatism and anisometropia were uncommon, and myopia frequency increased with age. There were statistically significant steeper keratometric readings in myopic compared to hyperopic eyes. The frequency of refractive errors that we found of 36.7% is moderate compared to the global data. The rates and parameters statistically differed by sex and age groups. Our findings are useful for establishing refractive error rate benchmarks in low-middle-income countries and as a baseline for following their variation by sociodemographic factors.

Refractive errors in children and adolescents in Bucaramanga (Colombia

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Virgilio Galvis

Full Text Available ABSTRACT Purpose: The aim of this study was to establish the frequency of refractive errors in children and adolescents aged between 8 and 17 years old, living in the metropolitan area of Bucaramanga (Colombia. Methods: This study was a secondary analysis of two descriptive cross-sectional studies that applied sociodemographic surveys and assessed visual acuity and refraction. Ametropias were classified as myopic errors, hyperopic errors, and mixed astigmatism. Eyes were considered emmetropic if none of these classifications were made. The data were collated using free software and analyzed with STATA/IC 11.2. Results: One thousand two hundred twenty-eight individuals were included in this study. Girls showed a higher rate of ametropia than boys. Hyperopic refractive errors were present in 23.1% of the subjects, and myopic errors in 11.2%. Only 0.2% of the eyes had high myopia (≤-6.00 D. Mixed astigmatism and anisometropia were uncommon, and myopia frequency increased with age. There were statistically significant steeper keratometric readings in myopic compared to hyperopic eyes. Conclusions: The frequency of refractive errors that we found of 36.7% is moderate compared to the global data. The rates and parameters statistically differed by sex and age groups. Our findings are useful for establishing refractive error rate benchmarks in low-middle-income countries and as a baseline for following their variation by sociodemographic factors.

Microincision versus small-incision coaxial cataract surgery using different power modes for hard nuclear cataract.

Science.gov (United States)

Kim, Eun Chul; Byun, Yong Soo; Kim, Man Soo

2011-10-01

To compare the efficacy of microincision and small-incision coaxial phacoemulsification in treating hard cataracts using different ultrasound power modes. Department of Ophthalmology, Seoul St. Mary's Hospital, College of Medicine, Catholic University of Korea, Seoul, Korea. Randomized clinical trial. Eyes with hard cataract were randomized to have an initial incision of 1.80 mm, 2.20 mm, or 2.75 mm. The eyes in each group were equally randomized to treatment with burst, pulse, or continuous mode. Ultrasound time (UST), mean cumulative dissipated energy (CDE), corrected distance visual acuity (CDVA), surgically induced corneal astigmatism, incisional and central corneal thickness (CCT), and endothelial cell counts were evaluated. The study enrolled 180 eyes, 60 in each group. Two months postoperatively, there were no statistically significant differences in UST, CDE, CDVA, CCT, or percentage endothelial cell loss between the 3 incision groups. The 2.75 mm incision induced more astigmatism at 2 months and less incisional corneal edema at 1 week than the 1.80 mm or 2.20 mm incision (Phard cataract. The intraoperative energy use and ocular damage was less with the pulse and burst modes than with the continuous mode. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2011 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

[Descemet's stripping automated endothelial keratoplasty (DEAEK). Systematic review of clinical-effectiveness and safety].

Science.gov (United States)

Paz-Valiñas, L; de la Fuente-Cid, R; de Rojas-Silva, M V; López-Rodríguez, I; López-García, M

2015-04-01

To conduct a systematic review of the efficacy/effectiveness, safety and cost of Descemet's stripping automated endothelial keratoplasty (DSAEK) technique in patients with corneal endothelial failure. Comprehensive literature search conducted in the main biomedical databases from January-May 2012. Following a critical perusal of the total of 485 abstracts retrieved, 16 case series and one economic evaluation study were included. Corrected distance visual acuity and uncorrected distance visual acuity improved after treatment with DSAEK, attaining values of 0.6 to 0.8 and 0.5 respectively. The degree of post-DSAEK astigmatism was not significant with respect to baseline values. The main complications were graft dislocation-detachment (1.5-23%), primary failure (0-12%) and endothelial rejection (0.8-8.5%). In Fuchs' dystrophy and bullous keratopathy, data on the effectiveness of DSAEK indicate post-intervention improvement in uncorrected and corrected distance visual acuity. Astigmatism arising after DSAEK was not significant. The most significant post-DSAEK complications are linked to the viability of the graft, with the most frequent complications being dislocation-detachment and, to a lesser extent, endothelial rejection. The studies that assess DSAEK are case series, and for the most part retrospective. The quality of this type of studies is both low and limited. Copyright © 2012 Sociedad Española de Oftalmología. Published by Elsevier España, S.L.U. All rights reserved.

A handheld open-field infant keratometer (an american ophthalmological society thesis).

Science.gov (United States)

Miller, Joseph M

2010-12-01

To design and evaluate a new infant keratometer that incorporates an unobstructed view of the infant with both eyes (open-field design). The design of the open-field infant keratometer is presented, and details of its construction are given. The design incorporates a single-ring keratoscope for measurement of corneal astigmatism over a 4-mm region of the cornea and includes a rectangular grid target concentric within the ring to allow for the study of higher-order aberrations of the eye. In order to calibrate the lens and imaging system, a novel telecentric test object was constructed and used. The system was bench calibrated against steel ball bearings of known dimensions and evaluated for accuracy while being used in handheld mode in a group of 16 adult cooperative subjects. It was then evaluated for testability in a group of 10 infants and toddlers. Results indicate that while the device achieved the goal of creating an open-field instrument containing a single-ring keratoscope with a concentric grid array for the study of higher-order aberrations, additional work is required to establish better control of the vertex distance. The handheld open-field infant keratometer demonstrates testability suitable for the study of infant corneal astigmatism. Use of collimated light sources in future iterations of the design must be incorporated in order to achieve the accuracy required for clinical investigation.

Eye micromotions influence on an error of Zernike coefficients reconstruction in the one-ray refractometry of an eye

Science.gov (United States)

Osipova, Irina Y.; Chyzh, Igor H.

2001-06-01

The influence of eye jumps on the accuracy of estimation of Zernike coefficients from eye transverse aberration measurements was investigated. By computer modeling the ametropy and astigmatism have been examined. The standard deviation of the wave aberration function was calculated. It was determined that the standard deviation of the wave aberration function achieves the minimum value if the number of scanning points is equal to the number of eye jumps in scanning period. The recommendations for duration of measurement were worked out.

The impact of pediatric vision disorders in adulthood.

Science.gov (United States)

Davidson, Stefanie; Quinn, Graham E

2011-02-01

In addition to refractive errors such as myopia and astigmatism, ocular disorders that occur in infants, toddlers, and children may present lifelong problems for the child. Conditions such as strabismus, amblyopia, and retinopathy of prematurity may require adaptations in adulthood. In addition, vision disorders that occur in childhood may manifest as problems well into adulthood. When visual impairment is present, there may be further effects on overall health, self-perception, educational attainment, job choices, and a number of other social factors.

Do evidence-based guidelines change clinical practice patterns?

DEFF Research Database (Denmark)

Kessel, Line; Erngaard, Ditte; Flesner, Per

2017-01-01

In 2013, the Danish Health and Medicines Authorities published a National Clinical Guideline on the treatment of age-related cataracts. The guideline provided evidence-based recommendations on the indication for cataract surgery, cataract surgery in patients with age-related macular degeneration......, on the use of toric intraocular lenses (IOLs) to correct preoperative corneal astigmatism, the use of intracameral and topical antibiotics to prevent endophthalmitis, choice of anti-inflammatory medication to control postoperative inflammation and prevent cystoid macular oedema, the use of immediate...

Quantum electronics for atomic physics and telecommunication

CERN Document Server

Nagourney, Warren G

2014-01-01

Nagourney provides a course in quantum electronics for researchers in atomic physics and other related areas (including telecommunications). The book covers the usual topics, such as Gaussian beams, optical cavities, lasers, non-linear optics, modulation techniques and fibre optics, but also includes a number of areas not usually found in a textbook on quantum electronics, such as the enhancement of non-linear processes in a build-up cavity or periodically poled waveguide, impedance matching into a cavity and astigmatism in ring cavities.

Fator de correção para indivíduos com capacidade acomodativa baseado no uso do refrator automático Correction factor for individuals with accommodative capacity based on automated refractor

Directory of Open Access Journals (Sweden)

Rodrigo Ueno Takahagi

2009-12-01

values with and without cycloplegy effect according to age. RESULTS: The correlation between the astigmatism diopter values with and without cicloplegy ranged from 81.52% to 92.27%. Analyzing the spherical diopter values, the correlation was lower (53.57% to 87.78%. The astigmatism axis also revealed low correlation values (28.86% to 58.80%. The multiple regression model according to age demonstrated multiple determination coefficient with high values for myopia (86.38% and astigmatism (79.79%. The lowest multiple determination coefficient was observed for astigmatism axis (17.70%. CONCLUSION: It was possible to demonstrate a high correlation in refractive errors with and without cycloplegy effect on the cylindrical ametropies. Mathematical formules, for cylindrical and spherical ametropies, were presented as a correction factor for refraction of the patients not submitted to cycloplegy.

Toric Intraocular Lenses in the Correction of Astigmatism During Cataract Surgery

DEFF Research Database (Denmark)

Kessel, Line; Andresen, Jens; Tendal, Britta

2016-01-01

TOPIC: We performed a systematic review and meta-analysis to evaluate the benefit and harms associated with implantation of toric intraocular lenses (IOLs) during cataract surgery. Outcomes were postoperative uncorrected distance visual acuity (UCDVA) and distance spectacle independence. Harms were...

Quantum Electronics for Atomic Physics

CERN Document Server

Nagourney, Warren

2010-01-01

Quantum Electronics for Atomic Physics provides a course in quantum electronics for researchers in atomic physics. The book covers the usual topics, such as Gaussian beams, cavities, lasers, nonlinear optics and modulation techniques, but also includes a number of areas not usually found in a textbook on quantum electronics. It includes such practical matters as the enhancement of nonlinear processes in a build-up cavity, impedance matching into a cavity, laser frequencystabilization (including servomechanism theory), astigmatism in ring cavities, and atomic/molecular spectroscopic techniques

Detection of benzene and toluene gases using a midinfrared continuous-wave external cavity quantum cascade laser at atmospheric pressure.

Science.gov (United States)

Sydoryk, Ihor; Lim, Alan; Jäger, Wolfgang; Tulip, John; Parsons, Matthew T

2010-02-20

We demonstrate the application of a commercially available widely tunable continuous-wave external cavity quantum cascade laser as a spectroscopic source for the simultaneous detection of multiple gases. We measured broad absorption features of benzene and toluene between 1012 and 1063 cm(-1) (9.88 and 9.41 microm) at atmospheric pressure using an astigmatic Herriott multipass cell. Our results show experimental detection limits of 0.26 and 0.41 ppm for benzene and toluene, respectively, with a 100 m path length for these two gases.

Modification of an achromatic mass spectrometer to include transverse focusing

Energy Technology Data Exchange (ETDEWEB)

Baril, M; Noel, M

1987-08-15

Modification has been made to a magnetic mass spectrometer, comprising a magnetic prism and a parallel plane mirror, to increase its transmission and to obtain a stigmatic image. This has been done by adding two quadrupole lenses, one between the magnetic prism and the mirror to add some focusing in the transverse direction, the other after the mirror to correct the astigmatism created by the first quadrupole lens. In this paper, we derive all the parameters of the quadrupole lenses needed to ensure this objective.

Photorefractive keratectomy in refractive accommodative esotropia.

Science.gov (United States)

Bilgihan, K; Akata, F; Or, M; Hasanreisoğlu, B

1997-01-01

Photorefractive keratectomy (PRK) was performed on a 19-year-old man with hyperopic astigmatism and refractive accommodative esotropia. The patient was orthophoric while wearing spectacles, but had an esotropia of 30 prism dioptres at near and distance vision without spectacles. The best corrected visual acuity of the right eye was 20/50 and of the left eye was 20/20. The excessive accommodative convergence of the patient was eliminated by correcting the hyperopic refractive error by performing PRK, and the patient became orthophoric after the treatment.

Generalized beam quality factor of aberrated truncated Gaussian laser beams

CSIR Research Space (South Africa)

Mafusire, C

2011-07-01

Full Text Available with a quadratic refractive index profile, a change in the beam quality factor can be used to infer the pre- sence of aberrations and thereby study the media of interest. For these reasons, among others, research into the beam qual- ity factor... very much like a normal lens (without the rotational symmetry associated with defocus) since the beam quality factor is calculated in the principal axes. With y-astigmatism, the lenslike behavior does not take place in the principal axes where...

Sensitive visual test for concave diffraction gratings.

Science.gov (United States)

Bruner, E. C., Jr.

1972-01-01

A simple visual test for the evaluation of concave diffraction gratings is described. It is twice as sensitive as the Foucault knife edge test, from which it is derived, and has the advantage that the images are straight and free of astigmatism. It is particularly useful for grating with high ruling frequency where the above image faults limit the utility of the Foucault test. The test can be interpreted quantitatively and can detect zonal grating space errors of as little as 0.1 A.

Transferences of Purkinje systems

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W. F. Harris

2011-12-01

Full Text Available The transferences of heterocentric astigmatic Purkinje systems are special: submatrices B and C, that is, the disjugacy and the divergence of the system, are symmetric and submatrix D (the divarication is the transpose of submatrix A (the dilation.  It is the primary purpose of this paper to provide a proof.  The paper also derives other relationships among the fundamental properties and compact expressions for the transference and optical axis locator of a Purkinje system. (S Afr Optom 2011 70(2 57-60

Cataract and keratoconus: minimizing complications in intraocular lens calculations.

Science.gov (United States)

Bozorg, Sara; Pineda, Roberto

2014-01-01

Patients with both cataract and keratoconus present unique challenges for the surgeon. Accurate keratometry (K) and axial length (AL) readings may be impossible, and uncertainty is introduced when estimating the corneal power for intraocular lens (IOL) selection. Different options on how to choose an IOL and how to manage irregular astigmatism of a keratoconic patient with cataract have been proposed and are reviewed. The stage of keratoconus and the history of the patient are both critical in determining the strategy used in treatment of cataracts.

Refractive errors in premature infants with retinopathy of prematurity after anti-vascular endothelial growth factor (anti-VEGF therapy

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Vujanović Milena S.

2017-01-01

Full Text Available Background/Aim. Retinopathy of prematurity (ROP is a vasoproliferative retinopathy which affects the blood vessels of the retina during its development. The aim of this study was to evaluate the incidence and the degree of refractive errors in premature infants with severe ROP treated with antivascular endothelial growth factor (anti-VEGF (bevacizumab. Methods. This prospective study included 21 patients (42 eyes nine months old who received intravitreal injection of anti-VEGF therapy. The control group consisted of 45 patients (90 eyes who were subjected to laser treatment. In cycloplegia each patient underwent retinoscopy, keratorefractometry, and A-scan ultrasonography. Results. Myopia was present in 47.62% of the eyes in the study group and in 33.33% of the eyes in the control group, but there were no statistically significant differences between these groups. Seven (16.67% eyes in the study group and 17 (18.89% eyes in the control group were discovered to have high myopia (SE– spherical equivalents < -3.0 D – dioptre. Clinically significant hypermetropia was higher in the study group (47.62% than in the control group (34.44%, but with no statistically significant difference. In addition, high hypermetropia was significantly greater in the control group (15.56% than in the study group (11.90% (p < 0.001. Astigmatism was more common in the control group than in the study group (81.11% vs 71.43%, respectively, especially high astigmatism (56% vs 43%, respectively. Also the more common form of astigmatism was with the rule (WTR both in the study and the control group (42.86% vs 55.56%, respectively. Anisometropia was significantly greater in the control group (24.44% than in the study group (9.52% (p < 0.05. The children from the study group had significantly greater lens thickness, and a shorter anterior chamber depth than children from the control group (p < 0.01. There was no significant difference in the axial length of the eye between

Effects of Silicone Hydrogel Contact Lens Application on Corneal High-order Aberration and Visual Guality in Patients with Corneal Opacities

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Sevda Aydın Kurna

2012-03-01

Full Text Available Pur po se: Evaluation of the corneal high-order aberrations and visual quality changes after application of silicone hydrogel contact lenses in patients with corneal opacities due to various etiologies. Ma te ri al and Met hod: Fifteen eyes of 13 patients with corneal opacities were included in the study. During the ophthalmologic examination before and after contact lens application, visual acuity was measured with Snellen acuity chart and contrast sensitivity - with Bailey-Lowie Charts in letters. Aberrations were measured with corneal aberrometer (NIDEK Magellan Mapper under a naturally dilated pupil. Spherical aberration, coma, trefoil, irregular astigmatism and total high-order root mean square (RMS values were recorded. Measurements were repeated with balafilcon A lenses (PureVision 2 HD, B&L on all patients. Re sults: Patient age varied between 23 and 50 years. Two eyes had subepithelial infiltrates due to adenoviral keratitis, 1 had nebulae due to previous infections or trauma, and 2 had Salzmann’s nodular degeneration. We observed a mean increase of 1 line in visual acuity and 5 letters in contrast sensitivity with contact lenses versus glasses in the patients. Mean RMS values of spherical aberration, irregular astigmatism and total high-order aberrations decreased significantly with contact lenses. Dis cus si on: Silicone hydrogel soft contact lenses may improve visual quality by decreasing the corneal aberrations in patients with corneal opacities. (Turk J Ophthalmol 2012; 42: 97-102

Analysis of refractive status and related factors of pupils in Hetian Road primary school in Zhabei community, Shanghai, 2011

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Wei Zhu

2013-06-01

Full Text Available AIM: To evaluate the refractive status of pupils of Hetian Road primary school in Zhabei community of Shanghai and analyze the relationships between visual acuity and relative factors. METHODS: All the in-school students of Hetian Road primary school in Zhabei community of Shanghai were involved in the study. Four hundred and sixty pupils out of 465 pupils were investigated(The rate was 98.9%. There were 445 pupils with fully data collection. Uncorrected visual acuity(UCVA, age, height(H, weight(W, body mass index(BMI, diopter of spherical(S, diopter of cylinder(C, spherical equivalent(SE, axial length(ALand corneal curvature(Kwere examined. The refractive status was described and the influence of relative factors was analyzed. UCVA measurement uses the standard logarithmic visual acuity chart, recording by decimal number, then transform into LogMar vision for statistical analysis. RESULTS: In total, the average age was 9.49±1.47 year, SE was -0.85±1.82D and UCVA was +0.09±0.28. The prevalence of myopia and astigmatism was 40.9% and 58.9%, respectively. With getting older, the prevalence of myopia increased with the average myopic SE developing significantly(P=0.000. UCVA and AL increased in the same time, SE decreased gradually(PPCONCLUSION: The prevalence of myopia and astigmatism was high in Hetian Road primary school in Zhabei community of Shanghai. Visual acuity is closely related to AL and growth factors.

Which soft contact lens power is better for piggyback fitting in keratoconus?

Science.gov (United States)

Romero-Jiménez, Miguel; Santodomingo-Rubido, Jacinto; Flores-Rodríguez, Patricia; González-Méijome, Jose Manuel

2013-02-01

To evaluate the impact of differente soft contact lens power in the anterior corneal curvature and regularity in subjects with keratoconus. Nineteen subjects (30 eyes) with keratoconus were included in the study. Six corneal topographies were taken with Pentacam Eye System over the naked eye and successively with soft lens (Senofilcon A) powers of -3.00, -1.50, 0.00, +1.50 and +3.00 D. Corneal measurements of mean central keratometry (MCK), maximum tangential curvature (TK), maximum front elevation (MFE) and eccentricity (Ecc) at 6 and 8 mm diameters as well as anterior corneal surface high order aberrations (i.e. total RMS, spherical- and coma-like and secondary astigmatism) were evaluated. Negative- and plano-powered soft lenses flattened (ppowered lenses did not induce any significant changes (p>0.05 in all cases) in MCK in comparison to the naked eye. The TK power decreased with negative lenses (psoft lens power in comparison to the naked eye (p>0.05 in all cases). Corneal eccentricity increased at 8 mm diameter for all lens powers (p0.05). Statistically differences were found in coma-like and secondary astigmatism (both ppowered soft contact lenses provide a flatter anterior surface in comparison to positive-powered lenses in subjects with keratoconus and thus they might be more suitable for piggyback contact lens fitting. Copyright © 2012 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

Visual outcome and refractive status in first 3 years of age in preterm infants suffered from laser-treated Type 1 retinopathy of prematurity (ROP): a 6-year retrospective review in a tertiary centre in Hong Kong.

Science.gov (United States)

Lok, Julie Y C; Yip, Wilson W K; Luk, Abbie S W; Chin, Joyce K Y; Lau, Henry H W; Young, Alvin L

2018-02-01

To report the visual outcome and refractive status in first 3 years of age in preterm infants suffered from laser-treated Type 1 retinopathy of prematurity (ROP): a 6-year review in Hong Kong DESIGN: Retrospective case series METHODOLOGY: Clinical records of all infants suffered from Type 1 ROP who had undergone laser therapy between 2007 and 2012 were retrospectively reviewed. Basic demographic data, serial changes of refractive error, visual acuity, severity of ROP and laser were analyzed. Correlation with myopia and astigmatism progression, body weight, height, growth and gestational age were also analyzed. Among 494 babies screened, 14 Chinese babies (26 eyes) recruited with 1:1 male-to-female ratio in this study. All eyes showed gradual progression of myopia in first 3 years of age but no significant change of astigmatism. Further correlation analysis showed no correlation with laser energy consumed, birth weight (p = 0.14), head circumference growth (p = 0.57) and body weight growth (p = 0.71). However, severity of myopia was related to the post-conceptual age when receiving laser therapy (p < 0.005), gestation age (p = 0.02) and possibly body height growth with age (p = 0.05). Myopia in early life is one of the most common ocular sequelae in Type 1 ROP survivors. Early detection of refractive error is important for prompt correction and visual rehabilitation to prevent amblyopia.

Aperture referral in dioptric systems with stigmatic elements

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W. F. Harris

2012-12-01

Full Text Available A previous paper develops the general theory of aperture referral in linear optics and shows how several ostensibly distinct concepts, including the blur patch on the retina, the effective corneal patch, the projective field and the field of view, are now unified as particular applications of the general theory.  The theory allows for astigmatism and heterocentricity.  Symplecticity and the generality of the approach, however, make it difficult to gain insight and mean that the material is not accessible to readers unfamiliar with matrices and linear algebra. The purpose of this paper is to examine whatis, perhaps, the most important special case, that in which astigmatism is ignored.  Symplecticity and, hence, the mathematics become greatly simplified. The mathematics reduces largely to elementary vector algebra and, in some places, simple scalar algebra and yet retains the mathematical form of the general approach.  As a result the paper allows insight into and provides a stepping stone to the general theory.  Under referral an aperture under-goes simple scalar magnification and transverse translation.  The paper pays particular attention to referral to transverse planes in the neighbourhood of a focal point where the magnification may be positive, zero or negative.  Circular apertures are treated as special cases of elliptical apertures and the meaning of referred apertures of negative radius is explained briefly. (S Afr Optom 2012 71(1 3-11

Patient satisfaction and acceptance of spherical equivalent spectacles correction wear in rural India.

Science.gov (United States)

Reddy, B Sandeep; Das, Taraprasad; Mirdha, Ghansyam S; Reddy, Nagavardhan

2017-08-01

The aim of this study was to explore the possibilities of acceptance of a ready-to-dispense spherical equivalent (SE) of spherocylindrical (SC) correction spectacles in rural India. Snellen visual acuity with SE power of refracted SC lenses was prospectively collected from all individuals visiting vision centers in Phase 1 (vision correction accuracy) of the study conducted in two South Indian districts. The satisfaction level was recorded by asking one standard question. The SE spectacles were dispensed in vision centers of one district in Phase 2 (SE acceptance) with a suggestion to return, if unsatisfied, for free exchange of spectacles within a month of dispensing. In Phase 1, 929 of 3529 patients were refracted and it was found that 320 patients and one eye of one patient (641 eyes) had astigmatism. The average age was 41 (±16; range: 7-84) years. There was no reduction of visual acuity in SE of 0.25 Dcyl (100% satisfaction) and progressive decrease in satisfaction to 43%, 26%, and 19% with SE correction of 0.50, 0.75, and 1.00 Dcyl, respectively. In Phase 2, 988 of 6168 patients needed refraction and 240 had astigmatism. A total of 103 patients (206 eyes) accepted SE equivalent spectacles. No client returned for the free exchange of spectacles. Dispensing SE power up to 1 Dcyl in ready - made spectacles could be considered in remote rural populations in resource-poor economic conditions.

Ocular Manifestations of Noonan Syndrome: A Prospective Clinical and Genetic Study of 25 Patients.

Science.gov (United States)

van Trier, Dorothée C; Vos, Anna M C; Draaijer, Renske W; van der Burgt, Ineke; Draaisma, Jos M Th; Cruysberg, Johannes R M

2016-10-01

To determine the full spectrum of ocular manifestations in patients with Noonan syndrome (NS). Prospective cross-sectional clinical and genetic study in a tertiary referral center. Twenty-five patients with NS (mean age, 14 years; range, 8 months-25 years) clinically diagnosed by validated criteria. All patients were examined by the same team following a detailed study protocol. Genetic analyses were performed in 23 patients. Ocular abnormalities of vision and refraction, external ocular features, ocular position and motility, anterior segment, posterior segment, and intraocular pressure. Ocular features of vision and refraction were amblyopia (32%), myopia (40%), and astigmatism (52%). External ocular features were epicanthic folds (84%), hypertelorism (68%), ptosis (56%), high upper eyelid crease (64%), lower eyelid retraction (60%), abnormal upward slanting palpebral fissures (36%), downward slanting palpebral fissures (32%), and lagophthalmos (28%). Orthoptic abnormalities included strabismus (40%), abnormal stereopsis (44%), and limited ocular motility (40%). Anterior segment abnormalities included prominent corneal nerves (72%) and posterior embryotoxon (32%). Additional ocular features were found, including nonglaucomatous optic disc excavation (20%), relatively low (Noonan syndrome is a clinical diagnosis with multiple genetic bases associated with an extensive variety of congenital ocular abnormalities. Ocular features of NS are characterized by 1 or more developmental anomalies of the eyelids (involving the position, opening, and closure) associated with various other ocular abnormalities in childhood, including amblyopia, myopia, astigmatism, strabismus, limited ocular motility, prominent corneal nerves, and posterior embryotoxon. Copyright © 2016 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

Anisometropia and ptosis in patients with monocular elevation deficiency

International Nuclear Information System (INIS)

Zafar, S.N.; Islam, F.; Khan, A.M.

2016-01-01

Objective: To determine the effect of ptosis on the refractive error in eyes having monocular elevation deficiency Place and Duration of Study: Al-Shifa Trust Eye Hospital, Rawalpindi, from January 2011 to January 2014. Methodology: Visual acuity, refraction, orthoptic assessment and ptosis evaluation of all patients having monocular elevation deficiency (MED) were recorded. Shapiro-Wilk test was used for tests of normality. Median and interquartile range (IQR) was calculated for the data. Non-parametric variables were compared, using the Wilcoxon signed ranks test. P-values of <0.05 were considered significant. Results: A total of of 41 MED patients were assessed during the study period. Best corrected visual acuity (BCVA) and refractive error was compared between the eyes having MED and the unaffected eyes of the same patient. The refractive status of patients having ptosis with MED were also compared with those having MED without ptosis. Astigmatic correction and vision had significant difference between both the eyes of the patients. Vision was significantly different between the two eyes of patients in both the groups having either presence or absence of ptosis (p=0.04 and p < 0.001, respectively). Conclusion: Significant difference in vision and anisoastigmatism was noted between the two eyes of patients with MED in this study. The presence or absence of ptosis affected the vision but did not have a significant effect on the spherical equivalent (SE) and astigmatic correction between both the eyes. (author)

Refractive and ocular biometric profile of children with a history of laser treatment for retinopathy of prematurity

Science.gov (United States)

Kaur, Savleen; Sukhija, Jaspreet; Katoch, Deeksha; Sharma, Mansi; Samanta, Ramanuj; Dogra, Mangat R

2017-01-01

Purpose: Indian children belong to a diverse socioeconomic strata with retinopathy of prematurity (ROP) developing in mature, higher birth weight babies as well. The purpose of our study is to analyze the long-term status of refractive errors and its relationship with ocular biometry in children with ROP who were laser treated at a tertiary center in North India. Methods: Cross sectional study. Children (biometric status. Results: Thirty-six children presenting to us at the mean age of 7.37 ± 3.07 years (6–15 years) were included. Mean spherical equivalent (SE) was −4.05 D ± 5.10. 75% were myopic, with high astigmatism in 31%. Higher lens thickness (P = 0.03) and higher SE (P = 0.002) at 1 year postnatal age were predictors of larger SE. 79.4% achieved a favorable functional outcome (visual acuity ≥20/40). 5.88% achieved unsatisfactory outcome (<20/200) despite having a favorable structural outcome. Conclusion: There are a substantial number of children who develop myopia and high astigmatism while undergoing laser treatment for ROP. We found myopia in our cohort to be lenticular and greater axial length contributing to the development of high myopia. An initial large refractive error predicts the future development of myopia in these children. Nearly 6% of patients with good structural outcome have unexplained subnormal vision. Our threshold for prescribing glasses in these children should be low. PMID:28905827

Exact optics - III. Schwarzschild's spectrograph camera revised

Science.gov (United States)

Willstrop, R. V.

2004-03-01

Karl Schwarzschild identified a system of two mirrors, each defined by conic sections, free of third-order spherical aberration, coma and astigmatism, and with a flat focal surface. He considered it impractical, because the field was too restricted. This system was rediscovered as a quadratic approximation to one of Lynden-Bell's `exact optics' designs which have wider fields. Thus the `exact optics' version has a moderate but useful field, with excellent definition, suitable for a spectrograph camera. The mirrors are strongly aspheric in both the Schwarzschild design and the exact optics version.

[Visual development and amblyopia prophylaxis in pediatric glaucoma].

Science.gov (United States)

Steffen, H

2011-07-01

In children with congenital glaucoma the functional long-term result is often disappointing even if the intraocular pressure is well controlled. The reason for this discrepancy is attributed to amblyogenic factors responsible for interfering with normal visual development. These amblyogenic factors are corneal edema, irregular astigmatism and non-corrected ametropia as monocular causes. Binocular causes are anisometropia-induced suppression and strabismus. Full ametropic correction and a very early prophylaxis and treatment of amblyopia with a close follow-up are mandatory to reduce amblyogenic visual impairment in children with congenital glaucoma.

Design of an imaging microscope for soft X-ray applications

Science.gov (United States)

Hoover, Richard B.; Shealy, David L.; Gabardi, David R.; Walker, Arthur B. C., Jr.; Lindblom, Joakim F.

1988-01-01

An imaging soft X-ray microscope with a spatial resolution of 0.1 micron and normal incidence multilayer optics is discussed. The microscope has a Schwarzschild configuration, which consists of two concentric spherical mirrors with radii of curvature which minimize third-order spherical aberration, coma, and astigmatism. The performance of the Stanford/MSFC Cassegrain X-ray telescope and its relevance to the present microscope are addressed. A ray tracing analysis of the optical system indicates that diffraction-limited performance can be expected for an object height of 0.2 mm.

Design of the Advanced Virgo non-degenerate recycling cavities

International Nuclear Information System (INIS)

Granata, M; Barsuglia, M; Flaminio, R; Freise, A; Hild, S; Marque, J

2010-01-01

Advanced Virgo is the project to upgrade the interferometric gravitational wave detector Virgo, and it foresees the implementation of power and signal non-degenerate recycling cavities. Such cavities suppress the build-up of high order modes of the resonating sidebands, with some advantage for the commissioning of the detector and the build-up of the gravitational signal. Here we present the baseline design of the Advanced Virgo non-degenerate recycling cavities, giving some preliminary results of simulations about the tolerances of this design to astigmatism, mirror figure errors and thermal lensing.

Fibrinous anterior uveitis following laser in situ keratomileusis

Directory of Open Access Journals (Sweden)

Parmar Pragya

2009-01-01

Full Text Available A 29-year-old woman who underwent laser in situ keratomileusis (LASIK for myopic astigmatism in both eyes presented with severe pain, photophobia and decreased visual acuity in the left eye eight days after surgery. Examination revealed severe anterior uveitis with fibrinous exudates in the anterior chamber, flap edema and epithelial bullae. Laboratory investigations for uveitis were negative and the patient required systemic and intensive topical steroids with cycloplegics to control the inflammation. This case demonstrates that severe anterior uveitis may develop after LASIK and needs prompt and vigorous management for resolution.

A case of decentered IOL managed with optic buttonholing.

Science.gov (United States)

Gupta, Shikha; Khokhar, Sudarshan; Agarwal, Tushar

2014-12-01

We describe an unusual case which presented with late lateral IOL decentration secondary to bag subluxation in the presence of a posterior capsular defect. Instead of approaching the case with the usual IOL exchange with iris-fixated or anterior chamber IOL or by fixating it to the sclera, a relatively non-invasive sutureless method of IOL re-centration was performed by buttonholing the optic into the posterior capsular defect. It enabled a perfect IOL centration with minimal incidence of astigmatism, inflammation, macular edema, secondary glaucoma, or corneal decompensation.

Incidência das ametropias no Hospital Universitário em Campo Grande (MS entre 1996 e 1998 Incidence of ametropias in the University Hospital of Campo Grande (MS between 1996 and 1998

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Eduardo Velasco de Barros

2000-06-01

Medical Files (SAME was carried out, applying a research protocol to 2,361 charts of patients presenting some type of ametropia who were attended at the NHU between 1996 and 1998, with information on sex, age and type of ametropia (myopia, hyperopia, astigmatism or presbyopia. The data were analyzed and discussed. Results: There was prevalence of females (60% in all cases of ametropia, the greatest number of attended people being patients with presbyopia (987 cases, followed by hyperopia (701, myopia (434 and astigmatism (239. Myopia was present mostly in the age range of 20 to 29 years, hyperopia between 0 and 9 years and astigmatism between 10 and 39 years, while the highest incidence of presbyopia was in the age range over 40 years. Conclusion: The number of female patients is higher than that of males, even considering each ametropia separately. Some hypotheses are proposed. Myopia is more frequent at ages between 10 and 39 years. Hyperopia occurs more frequently in children and newborns, tending to decrease with age because of eyeball increase. Astigmatism was characterized as a defect occurring in adolescents and young adults. Presbyopia was the commonest refraction error and its incidence occurred in the age range over 40 years, similarly to data found in the literature.

Topography-guided photorefractive keratectomy for irregular astigmatism after small incision lenticule extraction.

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Ivarsen, Anders; Hjortdal, Jesper Ø

2014-06-01

To report the outcome of topography-guided photorefractive keratectomy (PRK) after complicated small incision lenticule extraction (SMILE). Retrospective case series of 5 eyes with irregular topography and ghost images after complicated SMILE. All eyes received transepithelial topography-guided PRK. Two eyes were treated with 0.02% mitomycin C. Patients were examined after a minimum of 3 months with evaluation of uncorrected (UDVA) and corrected (CDVA) distance visual acuity, Pentacam tomography (Oculus Optikgeräte, Wetzlar, Germany), and whole-eye aberrometry. In 3 eyes, subjective symptoms were diminished and UDVA, CDVA, topography, and corneal wavefront aberrations were improved. The remaining 2 eyes developed significant haze with worsened topography and wavefront aberrations. One eye experienced a two-line reduction in CDVA. Eyes with haze development had not been treated with mitomycin C. Transepithelial topography-guided PRK may reduce visual symptoms after complicated SMILE if postoperative haze can be controlled. To reduce the risk of haze development, application of mitomycin C may be considered. Copyright 2014, SLACK Incorporated.

Measuring higher order optical aberrations of the human eye: techniques and applications

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L. Alberto V. Carvalho

2002-11-01

Full Text Available In the present paper we discuss the development of "wave-front", an instrument for determining the lower and higher optical aberrations of the human eye. We also discuss the advantages that such instrumentation and techniques might bring to the ophthalmology professional of the 21st century. By shining a small light spot on the retina of subjects and observing the light that is reflected back from within the eye, we are able to quantitatively determine the amount of lower order aberrations (astigmatism, myopia, hyperopia and higher order aberrations (coma, spherical aberration, etc.. We have measured artificial eyes with calibrated ametropia ranging from +5 to -5 D, with and without 2 D astigmatism with axis at 45º and 90º. We used a device known as the Hartmann-Shack (HS sensor, originally developed for measuring the optical aberrations of optical instruments and general refracting surfaces in astronomical telescopes. The HS sensor sends information to a computer software for decomposition of wave-front aberrations into a set of Zernike polynomials. These polynomials have special mathematical properties and are more suitable in this case than the traditional Seidel polynomials. We have demonstrated that this technique is more precise than conventional autorefraction, with a root mean square error (RMSE of less than 0.1 µm for a 4-mm diameter pupil. In terms of dioptric power this represents an RMSE error of less than 0.04 D and 5º for the axis. This precision is sufficient for customized corneal ablations, among other applications.

Refractive error in school children in Agona Swedru, Ghana

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G. O. Ovenseri-Ogbomo

2010-12-01

Full Text Available Uncorrected refractive errors remains a public health problem among different population groups. Among schoolchildren, uncorrected refractive errors have a considerable impact on learning andacademic achievement especially in underserved and under-resourced communities. A school based cross-sectional study was carriedout to estimate the prevalence and distribution of refractive error among schoolchildren in the Agona Swedru municipality of Central Region of Ghana. 637 schoolchildren aged 11-18 years old were randomly selected for the study. Non-cycloplegic refraction was performed on each child who failed the reading test. Hyperopia was defined as spherical power of ≥ + 0.75 D, myopia as ≤ – 0.50 D and astigmatism as a cylindrical power of ≤ – 0.50 D. Of the children examined, only 13.3% had previously had an eye examination.Visual impairment (VA of 6/12 or worse in the better eye was present in 4.5% of the children examined. Of those who failed the reading test, 85.9% had refractive error. The prevalence of hyperopia, myopia and astigmatism was 5.0%, 1.7% and 6.6% respectively. The study concludes that uncorrected refractive error is a common cause of visual impairment among schoolchildren in the municipality. A low uptake of eye care is also noted in the study. The study therefore recommends that the education authority in collaboration with the District Health Directorate institute appropriate measures to ensure compulsory eye examination for schoolchildren in the Agona Swedru district. (S Afr Optom 2010 69(2 86-92

Peripheral refraction in normal infant rhesus monkeys

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Hung, Li-Fang; Ramamirtham, Ramkumar; Huang, Juan; Qiao-Grider, Ying; Smith, Earl L.

2008-01-01

Purpose To characterize peripheral refractions in infant monkeys. Methods Cross-sectional data for horizontal refractions were obtained from 58 normal rhesus monkeys at 3 weeks of age. Longitudinal data were obtained for both the vertical and horizontal meridians from 17 monkeys. Refractive errors were measured by retinoscopy along the pupillary axis and at eccentricities of 15, 30, and 45 degrees. Axial dimensions and corneal power were measured by ultrasonography and keratometry, respectively. Results In infant monkeys, the degree of radial astigmatism increased symmetrically with eccentricity in all meridians. There were, however, initial nasal-temporal and superior-inferior asymmetries in the spherical-equivalent refractive errors. Specifically, the refractions in the temporal and superior fields were similar to the central ametropia, but the refractions in the nasal and inferior fields were more myopic than the central ametropia and the relative nasal field myopia increased with the degree of central hyperopia. With age, the degree of radial astigmatism decreased in all meridians and the refractions became more symmetrical along both the horizontal and vertical meridians; small degrees of relative myopia were evident in all fields. Conclusions As in adult humans, refractive error varied as a function of eccentricity in infant monkeys and the pattern of peripheral refraction varied with the central refractive error. With age, emmetropization occurred for both central and peripheral refractive errors resulting in similar refractions across the central 45 degrees of the visual field, which may reflect the actions of vision-dependent, growth-control mechanisms operating over a wide area of the posterior globe. PMID:18487366

Parametric fitting of corneal height data to a biconic surface.

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Janunts, Edgar; Kannengießer, Marc; Langenbucher, Achim

2015-03-01

As the average corneal shape can effectively be approximated by a conic section, a determination of the corneal shape by biconic parameters is desired. The purpose of the paper is to introduce a straightforward mathematical approach for extracting clinically relevant parameters of corneal surface, such as radii of curvature and conic constants for principle meridians and astigmatism. A general description for modeling the ocular surfaces in a biconic form is given, based on which an implicit parametric surface fitting algorithm is introduced. The solution of the biconic fitting is obtained by a two sequential least squares optimization approach with constrains. The data input can be raw information from any corneal topographer with not necessarily a uniform data distribution. Various simulated and clinical data are studied including surfaces with rotationally symmetric and non-symmetric geometries. The clinical data was obtained from the Pentacam (Oculus) for the patient having undergone a refractive surgery. A sub-micrometer fitting accuracy was obtained for all simulated surfaces: 0,08 μm RMS fitting error at max for rotationally symmetric and 0,125 μm for non-symmetric surfaces. The astigmatism was recovered in a sub-minutes resolution. The equality in rotational symmetric and the superiority in non-symmetric surfaces of the presented model over the widely used quadric fitting model is shown. The introduced biconic surface fitting algorithm is able to recover the apical radii of curvature and conic constants in principle meridians. This methodology could be a platform for advanced IOL calculations and enhanced contact lens fitting. Copyright © 2014. Published by Elsevier GmbH.

Results of a pediatric vision screening program in western South Dakota.

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Terveen, Daniel C; Moser, Jess M; Spencer, Terrence S

2015-03-01

South Dakota is one of eight states that do not require any vision screening for children. This study describes the results of the first children's vision screening program in the state. Children ages 6 months to 12 years were screened using the SPOT photoscreener by lay volunteers as part of the Northern Plains Eye Foundation's Western South Dakota Children's Vision Screening Initiative (CVSI). Referral criteria were based on the recommendations of the manufacturer. Data was stratified by age group, sex, and percentage of children referred for hyperopia, myopia, astigmatism, anisocoria, anisometropia, and ocular misalignment. The cost benefit of amblyopia treatment in South Dakota was also calculated. Screenings were completed on 4,784 children from August 2012 to May 2014 with 62 excluded due to age. Mean age of the 4,722 (2,373 females) subjects was 6 years 7 months. Overall, the SPOT device referred 563 (11.9 percent) children. There was no significant difference in referral rate based on sex (p = 0.598). Children aged 73-144 months had the highest referral rate (12.2 percent) and children aged 12-30 months had the lowest referral rate (7.9 percent). The suspected reasons for referral based upon the screenings were as follows: 371 (7.9 percent) astigmatism, 24 (0.5 percent) ocular misalignment, 101 (2.1 percent) anisometropia, 135 (2.9 percent) myopia, 36 (0.8 percent) hyperopia, and 16 (0.3 percent) anisocoria. The SPOT photoscreener yielded an acceptable referral rate of 11.9 percent. This study represents an effective model for pediatric vision screening in South Dakota.

Main visual symptoms associated to refractive errors and spectacle need in a Brazilian population

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Silvana Schellini

2016-12-01

Full Text Available AIM: To determine the main visual symptoms in a Brazilian population sample, associated to refractive errors (REs and spectacle need to suggest priorities in preventive programs. METHODS: A cross-sectional study was conducted in nine counties of the southeast region of Brazil, using a systematic sampling of households, between March 2004 and July 2005. The population was defined as individuals aged between 1 and 96y, inhabitants of 3600 residences to be evaluated and 3012 households were included, corresponding to 8010 subjects considered for participation in the survey, of whom 7654 underwent ophthalmic examinations. The individuals were evaluated according their demographic data, eye complaints and eye examination including the RE and the need to prescribe spectacles according to age. Statistical analysis was performed using SPSS software package and descriptive analysis using 95% confidence intervals (P<0.05. RESULTS: The main symptom detected was asthenopia, most frequent in the 2nd and 3rd decades of life, with a significant decline after the 4th decade. Astigmatism was the RE most associated with asthenopia. Reduced near vision sight was more frequent in those ≥40y with a progressive decline thereafter. Spectacles were most frequently required in subjects of ≥40 years of age. CONCLUSION: The main symptom related to the vision was asthenopia and was associated to astigmatism. The greatest need for spectacles prescription occurred after 40’s, mainly to correct near vision. Subjects of ≥40 years old were determined to be at high risk of uncorrected REs. These observations can guide intervention programs for the Brazilian population.

Three-Year Outcomes of Cross-Linking PLUS (Combined Cross-Linking with Femtosecond Laser Intracorneal Ring Segments Implantation for Management of Keratoconus

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Mohammed Iqbal Hafez Saleem

2018-01-01

Full Text Available Purpose. To analyze the results of three-year outcomes of combined epithelium-on cross-linking with femtosecond laser ICRS (cross-linking PLUS for keratoconus management. Design. A retrospective multicenter clinical study. Methods. 43 eyes of 38 patients were subjected to preoperative and postoperative UCVA, BCVA, refraction, Pentacam pachymetry, and keratometry examinations at 3-, 6-, 12-, 24-, and 36-month follow-up period. Results. The preoperative and postoperative mean UCVA was 1.30 ± 0.48 (logMAR ± SD and 0.82 ± 0.22 respectively. The preoperative and postoperative mean BCVA was 0.90 ± 0.40 and 0.60 ± 0.30, respectively. The preoperative and postoperative mean K average was 50.63 ± 0.87 (D ± SD and 45.56 ± 0.98, respectively. The preoperative and postoperative mean pachymetry was 471 ± 92.36 (μm ± SD and 423 ± 39.58, respectively. The preoperative and postoperative mean astigmatism was 7.55 ± 1.75 and 3.39 ± 1.26, respectively. One eye showed ICRS edge exposure while 6 eyes showed progression of keratoconus. Conclusion. CXL PLUS was proved to be a successful procedure to halt progression (mainly by CXL and to correct the refractive status of the keratoconic eye (mainly by ICRS. CXL PLUS performed a synergistic action correcting and maintaining the correction of both myopic and astigmatic components of keratoconus.

Optical modeling of a corneal inlay in real eyes to increase depth of focus: optimum centration and residual defocus.

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Tabernero, Juan; Artal, Pablo

2012-02-01

To determine the optimum position to center a small-aperture corneal inlay and the effect of residual defocus in the surgical eye to maximize depth of focus. Laboratorio de Óptica, Universidad de Murcia, Murcia, Spain. Cohort study. Personalized eye models were built using actual data (corneal topography, eye length, ocular aberrations, and eye alignment). A small aperture 1.6 mm in diameter was placed at the corneal plane in each model. The monochromatic and polychromatic Strehl ratios were calculated as a function of the pinhole position. Different residual defocus values were also incorporated into the models, and the through-focus Strehl ratios were calculated. Sixteen eye models were built. For most subjects, the optimum location of the aperture for distance vision was close to the corneal reflex position. For a given optimized centration of the aperture, the best compromise of depth of focus was obtained when the eyes had some residual myopic defocus (range -0.75 to -1.00 diopter [D]). Strehl ratio values were over 0.1 for far distance, which led to visual acuities better than 20/20. The depth of focus was 2.50 D with a mean near visual acuity of Jaeger 1 or better. In eyes with little astigmatism and aberrations, the optimum centration of the small aperture was near the corneal reflex position. To improve optical outcomes with the inlay, some small residual myopia and correction of corneal astigmatism might be required. Copyright © 2011 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Guiding flying-spot laser transepithelial phototherapeutic keratectomy with optical coherence tomography.

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Li, Yan; Yokogawa, Hideaki; Tang, Maolong; Chamberlain, Winston; Zhang, Xinbo; Huang, David

2017-04-01

To analyze transepithelial phototherapeutic keratectomy (PTK) results using optical coherence tomography (OCT) and develop a model to guide the laser dioptric and depth settings. Casey Eye Institute, Portland, Oregon, USA. Prospective nonrandomized case series. Patients with superficial corneal opacities and irregularities had transepithelial PTK with a flying-spot excimer laser by combining wide-zone myopic and hyperopic astigmatic ablations. Optical coherence tomography was used to calculate corneal epithelial lenticular masking effects, guide refractive laser settings, and measure opacity removal. The laser ablation efficiency and the refractive outcome were investigated using multivariate linear regression models. Twenty-six eyes of 20 patients received PTK to remove opacities and irregular astigmatism due to scar, dystrophy, radial keratotomy, or previous corneal surgeries. The uncorrected distance visual acuity and corrected distance visual acuity were significantly improved (P laser ablation depths were 31.3% (myopic ablation) and 63.0% (hyperopic ablation) deeper than the manufacturer's nomogram. The spherical equivalent of the corneal epithelial lenticular masking effect was 0.73 diopter ± 0.61 (SD). The refractive outcome highly correlated to the laser settings and epithelial lenticular masking effect (Pearson R = 0.96, P < .01). The ablation rate of granular dystrophy opacities appeared to be slower. Smoothing ablation under masking fluid was needed to prevent focal steep islands in these cases. The OCT-measured ablation depth efficiency could guide opacity removal. The corneal epithelial lenticular masking effect could refine the spherical refractive nomogram to achieve a better refractive outcome after transepithelial ablation. Copyright © 2017 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

The prevalence of refractive error in three communities of Cape Town, South Africa

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M. Otutu

2012-12-01

Full Text Available The prevalence, distribution and demographic associations of refractive error in three communities in Cape Town, South Africa were assessed. In this cross-sectional study, a clustered random sampling procedure was used to recruit participants (n=176; age=40.6±14.7 years; males=76, females=96 from Khayelitsha, Milnerton, and Mitchell’s Plain. From March to May 2010, participants underwent autore-fraction and subjective refraction eye examinations.A structured interview was used to collect data on sociodemographics, age, gender, level of education, employment and race. Participants younger than 15 years, non-residents, or residents for less than six months, who declined signing the informed consent forms were excluded from the study. In this study myopia was defined as the spherical equivalent value in the better eye of −1.00D or worse and hyperopia as the spherical equivalent value in the better eye of ≥1.00D. Astigmatism was defined as −0.50 cylinder or worse in the better eye. The prevalence of myopia was 17.4% with a 90% confidence interval (CI of 12.65-22.15, hyperopia was 13.4% (90% CI 9.13-17.67, and astigmatism was 60% (90% CI 53.86-66.14. Myopia was found to be significantly associated with race and age; while hyperopia was significantly associated with age, employment and race. The results of this study may assist in planning for eye care on district level. (S Afr Optom 2012 71(1 32-38

On-line pachymetry outcome of ablation in aberration free mode TransPRK.

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Adib-Moghaddam, Soheil; Arba-Mosquera, Samuel; Salmanian, Bahram; Omidvari, Amir-Houshang; Noorizadeh, Farsad

2014-01-01

There are many independent factors that influence the outcome of refractive surgeries, consisting of patient characteristics and environmental factors. We studied the accuracy of central ablation depth compared to online pachymetry results. A total of 153 eyes that underwent TransPRK at Bina Eye Hospital, Tehran, Iran, were evaluated from November 2010 to January 2012 in a retrospective cross-sectional study. The relevant data were registered and bivariate correlations and linear regression association were investigated statistically. The mean age was 29 ± 5 years. Distribution of refractive errors was as follows: compound myopic astigmatism 123 (80.4%), simple myopia 24 (15.7%), and mixed astigmatism 6 (3.9%). Mean ambient temperature and humidity levels intraoperatively were 23.49 ± 1.16°C and 28.91 ± 6.16%, respectively. There was a significant difference (p<0.001) between the preassumed central ablation depth (131.68 ± 32.72 µm) and the net level of ablation depth (measured by online pachymetry, 168.04 ± 41.47 µm). Temperature and humidity levels were not in any statistically significant correlation with the net amount of difference found. The backward linear regression was done to reveal the association between ablation depth and several variables. This study showed that there is deviation in optical coherence pachymetry online measurements done with SCHWIND AMARIS laser. Ambient temperature and humidity levels intraoperatively do not influence the outcome. However, basic structural characteristics of patients along with change in refractive index and corneal shrinkage because of corneal dehydration are associated with the differences.

Incidence, outcomes, and risk factors for retreatment after wavefront-optimized ablations with PRK and LASIK.

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Randleman, J Bradley; White, Alfred J; Lynn, Michael J; Hu, Michelle H; Stulting, R Doyle

2009-03-01

To analyze and compare retreatment rates after wavefront-optimized photorefractive keratectomy (PRK) and LASIK and determine risk factors for retreatment. A retrospective chart review was performed to identify patients undergoing PRK or LASIK with the wavefront-optimized WaveLight platform from January 2005 through December 2006 targeted for a piano outcome and to determine the rate and risk factors for retreatment surgery in this population. Eight hundred fifty-five eyes were analyzed, including 70 (8.2%) eyes with hyperopic refractions and 785 (91.8%) eyes with myopic refractions. After initial treatment, 72% of eyes were 20/20 or better and 99.5% were 20/40 or better. To improve uncorrected visual acuity, 54 (6.3%) eyes had retreatments performed. No significant differences in retreatment rates were noted based on age (P = .15), sex (P = .8), eye (P = .3), PRK versus LASIK (P = 1.0), room temperature (P = .1) or humidity (P = .9), and no correlation between retreatment rate and month or season of primary surgery (P = .4). There was no correlation between degree of myopia and retreatment rate. Eyes were significantly more likely to undergo retreatment if they were hyperopic (12.8% vs 6.0%, P = .006) or had astigmatism > or = 1.00 diopter (D) (9.1% vs 5.3%, P = .04). Retreatment rate was 6.3% with the WaveLight ALLEGRETTO WAVE excimer laser. This rate was not influenced by age, sex, corneal characteristics, or environmental factors. Eyes with hyperopic refractions or astigmatism > or = 1.00 D were more likely to undergo retreatment.

Microcoaxial cataract surgery outcomes: comparison of 1.8 mm system and 2.2 mm system.

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Lee, Kyung-Min; Kwon, Hyung-Goo; Joo, Choun-Ki

2009-05-01

To compare clinical outcomes of a 1.8 mm and a 2.2 mm microcoaxial cataract surgery system. Department of Ophthalmology and Visual Science, Kangnam St. Mary's Hospital, College of Medicine, Catholic University of Korea, Seoul, Korea. In a prospective study, eyes were randomly selected to have phacoemulsification using a Stellaris system or an Intrepid Infiniti system. The initial incision size was 1.8 mm and 2.2 mm, respectively. Measured intraoperative parameters included phacoemulsification time, mean cumulative dissipated ultrasound energy (CDE), change in incision size at each step of surgery, and total volume of balanced salt solution (BSS) used. The best corrected visual acuity (BCVA), corneal astigmatism, corneal thickness, and endothelial cell count were evaluated preoperatively and postoperatively. The study evaluated 86 eyes of 78 patients (43 eyes in each group). There were no significant differences in postoperative BCVA, surgically induced astigmatism, or amount of BSS used between the 2 systems (P >.05). However, for high-density cataracts, the 1.8 mm group had a greater change between the initial incision size and the incision size after phacoemulsification (P = .019, nuclear opalescence [NO] NO3; P = .001, NO4), a longer phacoemulsification time (P = .013, NO3), greater mean CDE (P = .005, NO3; P = .001, NO4), and greater corneal endothelial cell loss (P = .003, NO4). Both systems were safe and effective in microcoaxial phacoemulsification. The 1.8 mm system performed better with cortical-type cataract and the 2.2 mm system, with high-density nuclear-type cataract.

Computational adaptive optics for broadband optical interferometric tomography of biological tissue.

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Adie, Steven G; Graf, Benedikt W; Ahmad, Adeel; Carney, P Scott; Boppart, Stephen A

2012-05-08

Aberrations in optical microscopy reduce image resolution and contrast, and can limit imaging depth when focusing into biological samples. Static correction of aberrations may be achieved through appropriate lens design, but this approach does not offer the flexibility of simultaneously correcting aberrations for all imaging depths, nor the adaptability to correct for sample-specific aberrations for high-quality tomographic optical imaging. Incorporation of adaptive optics (AO) methods have demonstrated considerable improvement in optical image contrast and resolution in noninterferometric microscopy techniques, as well as in optical coherence tomography. Here we present a method to correct aberrations in a tomogram rather than the beam of a broadband optical interferometry system. Based on Fourier optics principles, we correct aberrations of a virtual pupil using Zernike polynomials. When used in conjunction with the computed imaging method interferometric synthetic aperture microscopy, this computational AO enables object reconstruction (within the single scattering limit) with ideal focal-plane resolution at all depths. Tomographic reconstructions of tissue phantoms containing subresolution titanium-dioxide particles and of ex vivo rat lung tissue demonstrate aberration correction in datasets acquired with a highly astigmatic illumination beam. These results also demonstrate that imaging with an aberrated astigmatic beam provides the advantage of a more uniform depth-dependent signal compared to imaging with a standard gaussian beam. With further work, computational AO could enable the replacement of complicated and expensive optical hardware components with algorithms implemented on a standard desktop computer, making high-resolution 3D interferometric tomography accessible to a wider group of users and nonspecialists.

Anterior stromal puncture with staining: A modified technique for preoperative reference corneal marking for toric lenses and its retrospective analyses

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Sahil Bhandari

2016-01-01

Full Text Available Introduction: Toric intraocular lenses (IOLs are an effective way of compensating preexisting corneal astigmatism during cataract surgery. To achieve success, it is imperative to align the toric IOLs in desired position and preoperative reference marking is one among the three important steps for accurate alignment. To make the marking procedure simpler and effective, we have modified the conventional three-step slit lamp-based technique. Materials and Methods: Patient is seated in front of the slit lamp and asked to keep the chin over chin rest. A 26-gauge bent needle with tip stained by sterile blue ink marker is used to make anterior stromal puncture (ASP at the edges of horizontal 180° axis near the limbus. Results: A total of 58 eyes were retrospectively evaluated. Mean (+/-SD IOL deviation on day 1 and day 30 was 5.7 ± 6.5° and 4.7 ± 5.6°, respectively. Median IOL misalignment on day 1 and day 30 was 3°. Redialing of IOL was required in 2 (3.4% eyes only, all of which were performed within 1 week of surgery. In total, 2 (3.7% eyes had a residual astigmatism of − 0.5 Dcyl and − 1.0 Dcyl, respectively. Conclusion: ASP is an effective technique for reference marking, technically simpler and can be practiced by most of the surgeons. It avoids the necessity of high-end sophisticated machinery and gives a better platform for the reference corneal marking along with the benefit of reproducibility and simplicity.

Distrofia de Reis-Bücklers: Presentación de una familia

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Daisy Flores Pérez

2003-09-01

Full Text Available Se presentan los resultados de un estudio realizado en 12 pacientes integrantes de una familia de la raza blanca. Se diagnosticaron 5 con distrofia de Reis-Bücklers. El defecto refractivo que predominó fue el astigmatismo. Se obtuvo un patrón de herencia autosómico dominante en la familia en estudio.The results of the study performed in 12 patients from a Caucasian family are presented. Five were diagnosed with Reis-BücKler dystrophy. The predominant refractory defect was astigmatism. A dominant autosomal hereditary pattern was obtained in the studied family.

Optical Aberrations and Wavefront

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Nihat Polat

2014-08-01

Full Text Available The deviation of light to create normal retinal image in the optical system is called aberration. Aberrations are divided two subgroup: low-order aberrations (defocus: spherical and cylindrical refractive errors and high-order aberrations (coma, spherical, trefoil, tetrafoil, quadrifoil, pentafoil, secondary astigmatism. Aberrations increase with aging. Spherical aberrations are compensated by positive corneal and negative lenticular spherical aberrations in youth. Total aberrations are elevated by positive corneal and positive lenticular spherical aberrations in elderly. In this study, we aimed to analyze the basic terms regarding optic aberrations which have gained significance recently. (Turk J Ophthalmol 2014; 44: 306-11

Orbital-angular-momentum photons for optical communication in non-Kolmogorov atmospheric turbulence

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Wei, Mei-Song; Wang, Jicheng; Zhang, Yixin; Hu, Zheng-Da

2018-06-01

We investigate the effects of non-Kolmogorov atmospheric turbulence on the transmission of orbital-angular-momentum single photons for different turbulence aberrations in optical communication, via the channel capacity. For non-Kolmogorov model, the characteristics of atmosphere turbulence may be determined by different cases, including the increasing altitude, the mutative index-of-refraction structure constant and the power-law exponent of non-Kolmogorov spectrum. It is found that the influences of low-order aberrations, including Z-tilt, defocus, astigmatism, and coma aberrations, are different and the turbulence Z-tilt aberration plays a more important role in the decay of the signal.

Optical vortex symmetry breakdown and decomposition of the orbital angular momentum of light beams.

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Bekshaev, A Ya; Soskin, M S; Vasnetsov, M V

2003-08-01

Two forms of the transverse energy circulation within plane-polarized paraxial light beams are specified: one inherent in wave-front singularities (optical vortices) and the other peculiar to astigmatism and asymmetry of beams with a smooth wave front. As quantitative measures of these energy flow components, the concepts of vortex and asymmetry parts of a beam's orbital angular momentum are introduced and their definitions are proposed on the basis of beam intensity moments. The properties and physical meaning of these concepts are analyzed, and their use for the study of transformations of optical vortices is demonstrated.

Optical traps with geometric aberrations

International Nuclear Information System (INIS)

Roichman, Yael; Waldron, Alex; Gardel, Emily; Grier, David G.

2006-01-01

We assess the influence of geometric aberrations on the in-plane performance of optical traps by studying the dynamics of trapped colloidal spheres in deliberately distorted holographic optical tweezers. The lateral stiffness of the traps turns out to be insensitive to moderate amounts of coma, astigmatism, and spherical aberration. Moreover holographic aberration correction enables us to compensate inherent shortcomings in the optical train, thereby adaptively improving its performance. We also demonstrate the effects of geometric aberrations on the intensity profiles of optical vortices, whose readily measured deformations suggest a method for rapidly estimating and correcting geometric aberrations in holographic trapping systems

Quality control of JEOL JBX-9500FSZ e-beam lithography system in a multi-user laboratory

DEFF Research Database (Denmark)

Greibe, Tine; Anhøj, Thomas Aarøe; Johansen, Leif

2016-01-01

designed quality control procedure characterized using a scanning electron microscope. We inspect position accuracy, dynamic focus, and dynamic astigmatism, as well as single and multi-pixel lines in thin resist. Beam shape quality is inspected in the corners of the writing field at 6 different beam...... currents between 2 and 60 nA. We use positive-tone resist AR-P6200 (CSAR 62) from All Resist. With our quality control procedure, we routinely write 11 nm lines on a 40 nm pitch, and obtain a field stitching accuracy better than 3 nm and overlay accuracy less than 7 nm....

2. Basis of measurement of plasma flow. 2.3 Plasma flow measurements. Spectroscopic methods

International Nuclear Information System (INIS)

Kado, Shinichiro

2007-01-01

The construction of optical system, optical fiber incident system, reciprocal linear dispersion, grating smile and astigmatism of the reflection plane diffraction grating spectrometer are explained in order to measure the plasma flow. The specification of flow measurement and evaluation of 0 point of velocity are stated. For examples of measurements, the fine structures of He II (Δn = 3 - 4) in material and plasma(MAP)-II of Tokyo University, plasma flow measurement by the charge exchange recombination spectroscopy using Large Helical Device and by Zeeman spectroscopy using TRIAM-1M tokamak plasma are stated. (S.Y.)

Change in corneal aberrations after cataract surgery with 2 types of aspherical intraocular lenses.

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Marcos, Susana; Rosales, Patricia; Llorente, Lourdes; Jiménez-Alfaro, Ignacio

2007-02-01

To study the effect of cataract surgery through 3.2 mm superior incisions on corneal aberrations with 2 types of monofocal intraocular lenses (IOLs) with an aspherical design. Instituto de Optica, Consejo Superior de Investigaciones Científicas, and Fundación Jiménez Díaz, Madrid, Spain. Corneal topography of 43 eyes was obtained before and after small corneal incision cataract surgery. Twenty-two eyes had implantation of a Tecnis Z9000 silicone IOL (Advanced Medical Optics) and 21 had implantation of an AcrySof IQ SN60WF acrylic IOL (Alcon Research Labs) using the recommended injector for each IOL type. The intended incision size (3.2 mm) was similar in the 2 groups. Corneal aberrations were estimated using custom-developed algorithms (based on ray tracing) for 10.0 mm and 5.0 mm pupils. Comparisons between preoperative and postoperative measurements and across the groups were made for individual Zernike terms and root-mean-square (RMS) wavefront error. The RMS (excluding tilt and defocus) did not change in the AcrySof IQ group and increased significantly in the Tecnis group with the 10.0 mm and 5.0 mm pupil diameters. Spherical aberration and coma-like terms did not change significantly; however, vertical astigmatism, vertical trefoil, and vertical tetrafoil changed significantly with surgery with the 10.0 mm and 5.0 mm pupil diameters (Porder aberrations consistently showed a superior lobe, resulting from a combination of positive vertical trefoil (Z(3)(-3)) and negative tetrafoil (Z(4)(4)). The mean vertical astigmatism increased by 2.47 microm +/- 1.49 (SD) and 1.74 +/- 1.44 microm, vertical trefoil increased by 1.81 +/- 1.19 microm and 1.20 +/- 1.34 microm, and tetrafoil increased by -1.10 +/- 0.78 microm and -0.89 +/- 0.68 microm in the Tecnis group and AcrySof IQ group, respectively. There were no significant differences between the corneal aberrations in the 2 postoperative groups, although there was a tendency toward more terms or orders changing

Acute Corneal Hydrops in Children with Primary Infantile Glaucoma: A Report of 31 Cases over 23 Years at the LVPEI.

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Anil K Mandal

Full Text Available Relatively little data exist regarding the outcomes of children with primary infantile glaucoma presenting with acute corneal hydrops. The aim of our study was to determine the surgical outcome of children of infantile glaucoma who presented with acute corneal hydrops.In total, 38 eyes of 31 consecutive children of infantile glaucoma presented with acute corneal hydrops who underwent primary combined trabeculotomy-trabeculectomy (CTT by a single surgeon from January 1990 to December 2012 at the LV Prasad Eye Institute (LVPEI, a tertiary eye care centre in Southern India were enrolled in this retrospective study. Primary outcome measures were intraocular pressure (IOP control (IOP ≤ 16 mmHg under anaesthesia or IOP ≤ 21 mmHg without anaesthesia and clearance of corneal edema. Secondary outcome measures were visual acuity (VA, corneal diameter, bleb appearance, intraoperative and postoperative complications.Mean age at presentation was 6.4 months (range, 2-11 months and seven eyes (23% had bilateral affliction. At presentation, all eyes (100% had moderate to severe degree of corneal edema with a mean preoperative IOP of 25.6 ±5.1 mmHg. Postoperatively, the IOP reduced to 12.0 ± 3.8 mmHg (difference = -13.6, 95% CI = -15.7 to -11.5, t = -13.18, p<0.0001, and the percentage reduction in IOP was 53.05%. Preoperatively 83% of the eyes were on antiglaucoma medication, and postoperatively 2 eyes (5.3% required 1 antiglaucoma medication for control of IOP. Preoperatively, corneal edema was present in all eyes and postoperatively it cleared in all of them. Significant myopic astigmatism was present in 28 eyes (74%, the commonest being compound myopic astigmatism (75% followed by simple myopic astigmatism (21%. Normal VA (best-corrected VA; BCVA ≥ 20/60 was achieved in 44.4% of the eyes and 22.2% eyes had low vision (BCVA, <20/60 to 20/400. Complete success (IOP control and clearance of corneal oedema was obtained in 94.7% eyes. There were no

Prevalência das ametropias e oftalmopatias em crianças pré-escolares e escolares em favelas do Alto da Boa Vista, Rio de Janeiro, Brasil Prevalence of the ametropias and eye diseases in preschool and school children of Alto da Boa Vista favelas, Rio de Janeiro, Brazil

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Abelardo de Souza Couto Júnior

2007-10-01

prevalence was 3.50% (hyperopia and astigmatism hyperopic were 1.78%, myopia and astigmatism myopic 1.06%, mixed astigmatism 0.67%.The eyes diseases prevalence was 3.50% (amblyopia was 2.00%, manifest strabismus was 1.72% and others causes was 1.11%. CONCLUSION: It was shown the prevalence of the main ophthalmologic children disorders. It also points out the need of ocular health campaigns thus achieve remarkably the development of the children visual acuity.

Intraocular lens power selection and positioning with and without intraoperative aberrometry.

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Hatch, Kathryn M; Woodcock, Emily C; Talamo, Jonathan H

2015-04-01

To determine the value of intraoperative aberrometry in cases of toric intraocular lens (IOL) implantation and positioning. In this non-randomized retrospective comparative trial, two groups of eyes underwent cataract extraction with toric IOL implantation: the aberrometry group (n = 37 eyes), where toric IOL power and alignment were determined before surgery with automated keratometry, standard optical biometry, and an online calculator and then refined using intraoperative aberrometry, and the toric calculator group (n = 27 eyes), where IOL selection was performed in a similar manner but without intraoperative aberrometry. The primary outcome measure was mean postoperative residual refractive astigmatism (RRA). Mean RRA measured at follow-up after surgery was 0.46 ± 0.42 and 0.68 ± 0.34 diopters (D) in the aberrometry and toric calculator groups, respectively (P = .0153). A 75% and 57% reduction in cylinder was noted between preoperative keratometric astigmatism and postoperative RRA in the aberrometry and toric calculator groups, respectively (P = .0027). RRA of 0.25 D or less, 0.50 D or less, 0.75 D or less, and 1.00 D or less was seen 38%, 78%, 86%, and 95% of the time, respectively, in the aberrometry group and 22%, 33%, 74%, and 89% of the time, respectively, in the toric calculator group. These data show that the chance of a patient being in a lower postoperative RRA range increased when intraoperative aberrometry was used (P = .0130). Patients undergoing cataract extraction with toric IOL placement aided by intraoperative aberrometry were 2.4 times more likely to have less than 0.50 D of RRA compared to standard methods. Copyright 2015, SLACK Incorporated.

Results of photorefractive keratectomy in keratoconus suspects at 4 years.

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Bilgihan, K; Ozdek, S C; Konuk, O; Akata, F; Hasanreisoglu, B

2000-01-01

We studied the long-term results of photorefractive keratectomy (PRK) in keratoconus suspects detected by videokeratography (TMS). Bilateral inferior corneal steepening was detected in 6 candidates for PRK presenting with moderate myopia or astigmatism. Mean follow-up was 44.5 +/- 4.4 months (range, 38 to 54 mo). Mean spherical equivalent refraction was -5.18 +/- 1.60 D (mean sphere, -4.73 D; mean cyclinder, -0.92 D) which was stable for at least the preceding year. The quantitative measurement of inferior corneal steepening (I-S value) was greater than +1.60 (mean, 1.83 +/- 0.11) in all eyes. An Aesculap Meditec Mel 60 excimer laser was used for the PRK procedures and mean follow-up was 44.5 months. Postoperative pachymetric measurements were also performed in 6 eyes. Postoperative uncorrected visual acuity was 20/20 in 8 eyes (66.6%) and 20/32 or better in all eyes with a mean postoperative spherical equivalent refraction of -0.70 +/- 0.74 D (mean sphere, -0.63 D; mean cyclinder, -0.39 D). Five eyes (41.6%) were within +/- 0.50 D spherical equivalent refraction. Inferior steepening was associated with thinning of the inferior cornea which was statistically significantly thinner than the superior thickness (Student's t-test, P < .05). There were no wound healing problems or any sign that the excimer laser adversely affected the cornea during follow-up. Photorefractive keratectomy seems to be a safe procedure for reducing or eliminating myopia or astigmatism in keratoconus suspect eyes-most probably forme fruste keratoconus-with a stable refraction, but this may be different in eyes with early keratoconus, known to be a progressive disease.

Nano-Structuring of Solid Surface by EUV Ar8+ Laser

International Nuclear Information System (INIS)

Kolacek, K.; Prukner, V.; Schmidt, J

2013-01-01

Requirement of increased resolution is at present most loudly pronounced in microelectronics, which, following Moore´s law (doubling every two years the transistorcount that can be placed inexpensively on integrated circuit), commands a continuous upgrade of micro-/nano-lithography. Such upgrade indirectly influences processing speed, memory capacity, number and size of pixels in sensors, etc. The submitted paper demonstrates our first attempt for “direct (i.e. ablation) patterning” of PMMA by pulse, high-current, capillary-discharge-pumped Ar 8+ ion laser (λ = 46,9 nm). For focusing a long-focal spherical mirror (R = 2100 mm) covered by 14 double-layer Sc-Si coating was used. The ablated focal spots demonstrate not only that the energy of our laser is sufficient for such experiments, but also that the design of focusing optics must be more sophisticated: severe aberrations have been revealed – an irregular spot shape and strong astigmatism with astigmatic difference as large as 16 mm. Moreover, on the bottom of ablated spots a laserinduced periodic surface structure (LIPSS) has appeared. Finally, a direct patterning of quadratic hole 7,5x7,5 µm, standing in contact with PMMA substrate, has shown a strongly developed 2D diffraction pattern (period in the centre ∼125 nm). In conclusion there will be shown the design of a new (grazing incidence) focusing optics, and a new “nano-patterning” tool – grazing incidence interferometer, which enable to ablate a regular, in advance defined pattern. It is believed that this is the first step to application of this technique not only to nanolithography,but also e.g. to study of electron dynamics in superlattices. (author)

Heritability of myopia and ocular biometrics in Koreans: the healthy twin study.

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Kim, Myung Hun; Zhao, Di; Kim, Woori; Lim, Dong-Hui; Song, Yun-Mi; Guallar, Eliseo; Cho, Juhee; Sung, Joohon; Chung, Eui-Sang; Chung, Tae-Young

2013-05-01

To estimate the heritabilities of myopia and ocular biometrics among different family types among a Korean population. We studied 1508 adults in the Healthy Twin Study. Spherical equivalent, axial length, anterior chamber depth, and corneal astigmatism were measured by refraction, corneal topography, and A-scan ultrasonography. To see the degree of resemblance among different types of family relationships, intraclass correlation coefficients (ICC) were calculated. Variance-component methods were applied to estimate the genetic contributions to eye phenotypes as heritability based on the maximum likelihood estimation. Narrow sense heritability was calculated as the proportion of the total phenotypic variance explained by additive genetic effects, and linear and nonlinear effects of age, sex, and interactions between age and sex were adjusted. A total of 240 monozygotic twin pairs, 45 dizygotic twin pairs, and 938 singleton adult family members who were first-degree relatives of twins in 345 families were included in the study. ICCs for spherical equivalent from monozygotic twins, pooled first-degree pairs, and spouse pairs were 0.83, 0.34, and 0.20, respectively. The ICCs of other ocular biometrics were also significantly higher in monozygotic twins compared with other relative pairs, with greater consistency and conformity. The estimated narrow sense heritability (95% confidence interval) was 0.78 (0.71-0.84) for spherical equivalent; 0.86 (0.82-0.90) for axial length; 0.83 (0.76-0.91) for anterior chamber depth; and 0.70 (0.63-0.77) for corneal astigmatism. The estimated heritability of spherical equivalent and ocular biometrics in the Korean population suggests the compelling evidence that all traits are highly heritable.

PREVALENCE OF REFRACTIVE ERRORS AMONG CHILDREN IN RURA L AREAS OF CHITTOOR DISTRICT, A . P

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Sadana

2015-08-01

Full Text Available BACKGROUND: The uncorrected refractive errors are the main cause of low vision which hampers performance at school, reduces productivity and impairs quality of life. It is considered to be one of the most important priorities in the global initiation for the elimination of avoidable blindness. The refractive errors are especially common among children as they do not complain and adjust with circumstances. School children constitute an ideal group for study of refractive errors because most of them go to school, easily accessible and offer excellent opportunity for services and health education. MATERIAL & METHODS: This is a cross sectional study conducted among 2,568 children attending various government schools in the rural areas of Chittoor district. The study was carried out during January to June 2015. A preliminary examination of visual acuity was determined by Snellen’s chart and those with defective vision were subjected to detailed eye examination by a specialist. The results were analyzed using MS excel software and Epiinfo 7 software version using percentages and Chi - square test. RESULTS: The overall prevalence of refractive errors among children was found to be 11.3%. (Astigmatism - 5.8%; myopia - 4.2%; hypermetropia - 1.4%. The prevalence of refractive errors increased steadily from 5.7% in 5 - 7 years age group to 14.7% in 14 - 16 years group. The prevalence was found to be similar in male and female children. The prevalence of myopia and astigmatism was found to increase steadily with age while hypermetropia showed an inverse trend CONCLUSIONS: Examination of school children for refractive errors is a useful strategy for early diagnosis and intervention.

Refractive Outcomes, Contrast Sensitivity, HOAs, and Patient Satisfaction in Moderate Myopia: Wavefront-Optimized Versus Tissue-Saving PRK.

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Nassiri, Nader; Sheibani, Kourosh; Azimi, Abbas; Khosravi, Farinaz Mahmoodi; Heravian, Javad; Yekta, Abasali; Moghaddam, Hadi Ostadi; Nassiri, Saman; Yasseri, Mehdi; Nassiri, Nariman

2015-10-01

To compare refractive outcomes, contrast sensitivity, higher-order aberrations (HOAs), and patient satisfaction after photorefractive keratectomy for correction of moderate myopia with two methods: tissue saving versus wavefront optimized. In this prospective, comparative study, 152 eyes (80 patients) with moderate myopia with and without astigmatism were randomly divided into two groups: the tissue-saving group (Technolas 217z Zyoptix laser; Bausch & Lomb, Rochester, NY) (76 eyes of 39 patients) or the wavefront-optimized group (WaveLight Allegretto Wave Eye-Q laser; Alcon Laboratories, Inc., Fort Worth, TX) (76 eyes of 41 patients). Preoperative and 3-month postoperative refractive outcomes, contrast sensitivity, HOAs, and patient satisfaction were compared between the two groups. The mean spherical equivalent was -4.50 ± 1.02 diopters. No statistically significant differences were detected between the groups in terms of uncorrected and corrected distance visual acuity and spherical equivalent preoperatively and 3 months postoperatively. No statistically significant differences were seen in the amount of preoperative to postoperative contrast sensitivity changes between the two groups in photopic and mesopic conditions. HOAs and Q factor increased in both groups postoperatively (P = .001), with the tissue-saving method causing more increases in HOAs (P = .007) and Q factor (P = .039). Patient satisfaction was comparable between both groups. Both platforms were effective in correcting moderate myopia with or without astigmatism. No difference in refractive outcome, contrast sensitivity changes, and patient satisfaction between the groups was observed. Postoperatively, the tissue-saving method caused a higher increase in HOAs and Q factor compared to the wavefront-optimized method, which could be due to larger optical zone sizes in the tissue-saving group. Copyright 2015, SLACK Incorporated.

Results of endocapsular phacofracture debulking of hard cataracts

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Davison JA

2015-07-01

Full Text Available James A Davison Wolfe Eye Clinic, Marshalltown, IA, USA Purpose/aim of the study: To present a phacoemulsification technique for hard cataracts and compare postoperative results using two different ultrasonic tip motions during quadrant removal.Materials and methods: A phacoemulsification technique which employs in situ fracture and endocapsular debulking for hard cataracts is presented. The prospective study included 56 consecutive cases of hard cataract (LOCS III NC [Lens Opacification Classification System III, nuclear color], average 4.26, which were operated using the Infiniti machine and the Partial Kelman tip. Longitudinal tip movement was used for sculpting for all cases which were randomized to receive longitudinal or torsional/interjected longitudinal (Intelligent Phaco [IP] strategies for quadrant removal. Measurements included cumulative dissipated energy (CDE, 3 months postoperative surgically induced astigmatism (SIA, and corneal endothelial cell density (ECD losses.Results: No complications were recorded in any of the cases. Respective overall and longitudinal vs IP means were as follows: CDE, 51.6±15.6 and 55.7±15.5 vs 48.6±15.1; SIA, 0.36±0.2 D and 0.4±0.2 D vs 0.3±0.2 D; and mean ECD loss, 4.1%±10.8% and 5.9%±13.4% vs 2.7%±7.8%. The differences between longitudinal and IP were not significant for any of the three categories.Conclusion: The endocapsular phacofracture debulking technique is safe and effective for phacoemulsification of hard cataracts using longitudinal or torsional IP strategies for quadrant removal with the Infiniti machine and Partial Kelman tip. Keywords: astigmatism, cataract, corneal endothelium, phacoemulsification, viscoelastic

Estimating variability in placido-based topographic systems.

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Kounis, George A; Tsilimbaris, Miltiadis K; Kymionis, George D; Ginis, Harilaos S; Pallikaris, Ioannis G

2007-10-01

To describe a new software tool for the detailed presentation of corneal topography measurements variability by means of color-coded maps. Software was developed in Visual Basic to analyze and process a series of 10 consecutive measurements obtained by a topographic system on calibration spheres, and individuals with emmetropic, low, high, and irregular astigmatic corneas. Corneal surface was segmented into 1200 segments and the coefficient of variance of each segment's keratometric dioptric power was used as the measure of variability. The results were presented graphically in color-coded maps (Variability Maps). Two topographic systems, the TechnoMed C-Scan and the TOMEY Topographic Modeling System (TMS-2N), were examined to demonstrate our method. Graphic representation of coefficient of variance offered a detailed representation of examination variability both in calibration surfaces and human corneas. It was easy to recognize an increase in variability, as the irregularity of examination surfaces increased. In individuals with high and irregular astigmatism, a variability pattern correlated with the pattern of corneal topography: steeper corneal areas possessed higher variability values compared with flatter areas of the same cornea. Numerical data permitted direct comparisons and statistical analysis. We propose a method that permits a detailed evaluation of the variability of corneal topography measurements. The representation of the results both graphically and quantitatively improves interpretability and facilitates a spatial correlation of variability maps with original topography maps. Given the popularity of topography based custom refractive ablations of the cornea, it is possible that variability maps may assist clinicians in the evaluation of corneal topography maps of patients with very irregular corneas, before custom ablation procedures.

Refractive accuracy with light-adjustable intraocular lenses.

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Villegas, Eloy A; Alcon, Encarna; Rubio, Elena; Marín, José M; Artal, Pablo

2014-07-01

To evaluate efficacy, predictability, and stability of refractive treatments using light-adjustable intraocular lenses (IOLs). University Hospital Virgen de la Arrixaca, Murcia, Spain. Prospective nonrandomized clinical trial. Eyes with a light-adjustable IOL (LAL) were treated with spatial intensity profiles to correct refractive errors. The effective changes in refraction in the light-adjustable IOL after every treatment were estimated by subtracting those in the whole eye and the cornea, which were measured with a Hartmann-Shack sensor and a corneal topographer, respectively. The refractive changes in the whole eye and light-adjustable IOL, manifest refraction, and visual acuity were obtained after every light treatment and at the 3-, 6-, and 12-month follow-ups. The study enrolled 53 eyes (49 patients). Each tested light spatial pattern (5 spherical; 3 astigmatic) produced a different refractive change (Plight adjustments induced a maximum change in spherical power of the light-adjustable IOL of between -1.98 diopters (D) and +2.30 D and in astigmatism of up to -2.68 D with axis errors below 9 degrees. Intersubject variability (standard deviation) ranged between 0.10 D and 0.40 D. The 2 required lock-in procedures induced a small myopic shift (range +0.01 to +0.57 D) that depended on previous adjustments. Light-adjustable IOL implantation achieved accurate refractive outcomes (around emmetropia) with good uncorrected distance visual acuity, which remained stable over time. Further refinements in nomograms and in the treatment's protocol would improve the predictability of refractive and visual outcomes with these IOLs. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2014 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Visual acuity and refraction by age for children of three different ethnic groups in Paraguay

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Marissa Janine Carter

2013-04-01

Full Text Available PURPOSE: To characterize refractive errors in Paraguayan children aged 5-16 years and investigate effect of age, gender, and ethnicity. METHODS:The study was conducted at 3 schools that catered to Mennonite, indigenous, and mixed race children. Children were examined for presenting visual acuity, autorefraction with and without cycloplegia, and retinoscopy. Data were analyzed for myopia and hyperopia (SE ≤-1 D or -0.5 D and ≥2 D or ≥3 D and astigmatism (cylinder ≥1 D. Spherical equivalent (SE values were calculated from right eye cycloplegic autorefraction data and analyzed using general linear modelling. RESULTS: There were 190, 118, and 168 children of Mennonite, indigenous and mixed race ethnicity, respectively. SE values between right/left eyes were nonsignificant. Mean visual acuity (VA without correction was better for Mennonites compared to indigenous or mixed race children (right eyes: 0.031, 0.090, and 0.102 logMAR units, respectively; P<0.000001. There were 2 cases of myopia in the Mennonite group (1.2% and 2 cases in the mixed race group (1.4% (SE ≤-0.5 D. The prevalence of hyperopia (SE ≥2 D was 40.6%, 34.2%, and 46.3% for Mennonite, indigenous and mixed race children. Corresponding astigmatism rates were 3.2%, 9.5%, and 12.7%. Females were slightly more hyperopic than males, and the 9-11 years age group was the most hyperopic. Mennonite and mixed race children were more hyperopic than indigenous children. CONCLUSIONS: Paraguayan children were remarkably hyperopic and relatively free of myopia. Differences with regard to gender, age, and ethnicity were small.

Refractive state of the Spanish Thoroughbred horse: a comparison with the Crossbred horse.

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Rull-Cotrina, Jorge; Molleda, Jose M; Gallardo, José; Martín-Suárez, Eva

2013-01-01

To assess the refractive state of the equine eye utilizing retinoscopy. To compare the refractive state of Spanish Thoroughbred horses with the refractive state of Crossbred horses. The refractive state of 135 horses (264 eyes) was assessed utilizing streak retinoscopy. Two perpendicular meridians were examined in order to assess astigmatism at a working distance of approximately 67 cm. A group of 81 Spanish Thoroughbred horses was compared with a group of 54 Crossbred horses. Cyclopentolate ophthalmic solution was instilled in the eyes of a group of 18 horses to determine if accommodation has any influence on the assessment of the refractive state.   Mean ± SE refractive state of all horses examined was -0.17 ± 0.04 D. The mean refractive state of the Spanish Thoroughbred was -0.28 ± 0.06 D while that of the Crossbred was -0.01 ± 0.05 D. The refractive state of the Spanish Thoroughbred was found to be statistically different to that of the Crossbred. The most prevalent refractive state was emmetropia in all cases, followed by hyperopia for the Crossbred, and myopia for the Spanish Thoroughbred. Astigmatism ≥0.50 D present in both eyes from the same individual was found in 21.7% of all horses examined. Anisometropia ≥1.00 D was diagnosed in 4 out of 129 horses with both visual eyes. Cycloplegia did not statistically affect the refractive state of the evaluated eyes. The equine eye has a refractive state close to emmetropia. Myopia is higher among Spanish Thoroughbred horses than among Crossbred horses. © 2012 American College of Veterinary Ophthalmologists.

Comparison of FDA safety and efficacy data for KAMRA and Raindrop corneal inlays

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Majid Moshirfar

2017-09-01

Full Text Available AIM: To provide a side-by-side analysis of the summary of safety and effectiveness data (SSED submitted to the FDA for the KAMRA and Raindrop corneal inlays for the correction of presbyopia. METHODS: SSED reports submitted to the FDA for KAMRA and Raindrop were compared with respect to loss of corrected distance visual acuity (CDVA, adverse event rates, induction of astigmatism, retention of contrast sensitivity, stability of manifest refractive spherical equivalent (MRSE, and achieved monocular uncorrected near visual acuity (UNVA at 24mo. RESULTS: Totally 442/508 of KAMRA patients and 344/373 Raindrop patients remained enrolled in the clinical trials at 24mo. The proportion of KAMRA and Raindrop patients who lost ≥2 lines of CDVA at 24mo was 3.4% and 1%, respectively. The adverse event rate was comparable between the devices. No significant inductions of astigmatism were noted. Both technologies induced a transient myopic shift in MRSE followed by a hyperopic shift and subsequent stabilization. Totally 87% of KAMRA and 98% of Raindrop patients attained a monocular UNVA of J5 (20/40 or better at 24mo, 28% of KAMRA and 67% of Raindrop patients attained a monocular UNVA of J1 (20/20 or better at 24mo. CONCLUSION: Both devices can be considered safe and effective, however, the results of corneal inlay implantation are mixed, and long-term patient satisfaction will likely depend on subjective expectations about the capabilities of the inlays. Variability in surgical technique and postoperative care within and between the two clinical trials diminishes the comparative power of this article.

Corrective Techniques and Future Directions for Treatment of Residual Refractive Error Following Cataract Surgery

Science.gov (United States)

Moshirfar, Majid; McCaughey, Michael V; Santiago-Caban, Luis

2015-01-01

Postoperative residual refractive error following cataract surgery is not an uncommon occurrence for a large proportion of modern-day patients. Residual refractive errors can be broadly classified into 3 main categories: myopic, hyperopic, and astigmatic. The degree to which a residual refractive error adversely affects a patient is dependent on the magnitude of the error, as well as the specific type of intraocular lens the patient possesses. There are a variety of strategies for resolving residual refractive errors that must be individualized for each specific patient scenario. In this review, the authors discuss contemporary methods for rectification of residual refractive error, along with their respective indications/contraindications, and efficacies. PMID:25663845

Vortex Airy beams directly generated via liquid crystal q-Airy-plates

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Wei, Bing-Yan; Liu, Sheng; Chen, Peng; Qi, Shu-Xia; Zhang, Yi; Hu, Wei; Lu, Yan-Qing; Zhao, Jian-Lin

2018-03-01

Liquid crystal q-Airy-plates with director distributions integrated by q-plates and polarization Airy masks are proposed and demonstrated via the photoalignment technique. Single/dual vortex Airy beams of opposite topological charges and orthogonal circular polarizations are directly generated with polarization-controllable characteristic. The singular phase of the vortex part is verified by both astigmatic transformation and digital holography. The trajectory of vortex Airy beams is investigated, manifesting separate propagation dynamics of optical vortices and Airy beams. Meanwhile, Airy beams still keep their intrinsic transverse acceleration, self-healing, and nondiffraction features. This work provides a versatile candidate for generating high-quality vortex Airy beams.

High resolution projection X-ray microscope equipped with fluorescent X-ray analyzer and its applications

International Nuclear Information System (INIS)

Minami, K; Saito, Y; Kai, H; Shirota, K; Yada, K

2009-01-01

We have newly developed an open type fine-focus X-ray tube 'TX-510' to realize a spatial resolution of 50nm and to radiate low energy characteristic X-rays for giving high absorption contrast to images of microscopic organisms. The 'TX-510' employs a ZrO/W(100) Schottky emitter and an 'In-Lens Field Emission Gun'. The key points of the improvements are (1) reduced spherical aberration coefficient of magnetic objective lens, (2) easy and accurate focusing, (3) newly designed astigmatism compensator, (4) segmented thin film target for interchanging the target materials by electron beam shift and (5) fluorescent X-ray analysis system.

Femtosecond laser-assisted cataract surgery and implantable miniature telescope

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Randal Pham

2017-09-01

Conclusions and importance: To our knowledge and confirmed by the manufacturer of the implantable miniature telescope this is the first case ever reported of a patient who has undergone femtosecond laser cataract surgery with corneal astigmatism correction and implantation of the implantable miniature telescope. This is also the first case report of the preoperative use of microperimetry and visual electrophysiology to evaluate a patient's postoperative potential visual acuity. The success of the procedure illustrated the importance of meticulous preoperative planning, the combined use of state-of-the-art technologies and the seamless teamwork in order to achieve the best clinical outcome for patients who undergo implantation of the implantable miniature telescope.

Rigorous description of holograms of particles illuminated by an astigmatic elliptical Gaussian beam

Energy Technology Data Exchange (ETDEWEB)

Yuan, Y J; Ren, K F; Coetmellec, S; Lebrun, D, E-mail: fang.ren@coria.f [UMR 6614/CORIA, CNRS and Universite et INSA de Rouen Avenue de l' Universite BP 12, 76801 Saint Etienne du Rouvray (France)

2009-02-01

The digital holography is a non-intrusive optical metrology and well adapted for the measurement of the size and velocity field of particles in the spray of a fluid. The simplified model of an opaque disk is often used in the treatment of the diagrams and therefore the refraction and the third dimension diffraction of the particle are not taken into account. We present in this paper a rigorous description of the holographic diagrams and evaluate the effects of the refraction and the third dimension diffraction by comparison to the opaque disk model. It is found that the effects are important when the real part of the refractive index is near unity or the imaginary part is non zero but small.

A STUDY ON EFFICACY OF MANUAL SMALL INCISION CATARACT SURGERY BY TEMPORAL APPROACH

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Vinodhini Kannan

2018-01-01

Full Text Available BACKGROUND Manual Small Incision Cataract Surgery (MSICS is a well-known technique of cataract surgery owing to its advantage of a selfsealing suture less incision with least surgically induced astigmatism at a low cost. It is a safe, simple, consistent, stable and cost-effective technique with various modifications that involve site, size, type of incision and method of nucleus delivery. One such modification is Temporal Incision MSICS, where the cataract surgery is done by a temporal approach, which is equally good compared to the superior incision. This study was done retrospectively to analyse the visual outcome of patients operated by Manual SICS - Temporal Approach, using the WHO criteria and to establish its efficacy as a good surgical technique. MATERIALS AND METHODS Records of patients operated for senile cataract by a single surgeon by Temporal MSICS using a temporal sclerocorneal incision of 6-6.5 mm, during a 1-year period, were analysed retrospectively. Post-operative followup records of POD-1 and subsequent follow-ups at 1 st week and 6 th week were recorded for visual outcome. RESULTS Out of the 83 cases analysed retrospectively, majority of them were found to be between 61-70 years with a female Preponderance. Most of the cases were found to have senile immature cataract (55 patients, with Grade III nuclear sclerosis (52 cases. The pre-operative visual acuity was poor <6/60 in 72 cases (86.7% and borderline in 11 cases (14.5%. 55 cases (66.3% had a 6.5 mm scleral incision and the remaining 28 cases (33.7% had a 6 mm incision. Average duration of surgery noted was 8.35 minutes. Striate Keratopathy was the most common 1 st POD complication followed by corneal oedema. Striate keratopathy was the most common complication at the 1 st week followup followed by pigment dispersion. Majority of cases (76 cases were found to have been complication free at the end of 6 weeks. At the end of 6 weeks post-operatively as per records, 80 cases

Wave aberrations in rhesus monkeys with vision-induced ametropias

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Ramamirtham, Ramkumar; Kee, Chea-su; Hung, Li-Fang; Qiao-Grider, Ying; Huang, Juan; Roorda, Austin; Smith, Earl L.

2007-01-01

The purpose of this study was to investigate the relationship between refractive errors and high-order aberrations in infant rhesus monkeys. Specifically, we compared the monochromatic wave aberrations measured with a Shack-Hartman wavefront sensor between normal monkeys and monkeys with vision-induced refractive errors. Shortly after birth, both normal monkeys and treated monkeys reared with optically induced defocus or form deprivation showed a decrease in the magnitude of high-order aberrations with age. However, the decrease in aberrations was typically smaller in the treated animals. Thus, at the end of the lens-rearing period, higher than normal amounts of aberrations were observed in treated eyes, both hyperopic and myopic eyes and treated eyes that developed astigmatism, but not spherical ametropias. The total RMS wavefront error increased with the degree of spherical refractive error, but was not correlated with the degree of astigmatism. Both myopic and hyperopic treated eyes showed elevated amounts of coma and trefoil and the degree of trefoil increased with the degree of spherical ametropia. Myopic eyes also exhibited a much higher prevalence of positive spherical aberration than normal or treated hyperopic eyes. Following the onset of unrestricted vision, the amount of high-order aberrations decreased in the treated monkeys that also recovered from the experimentally induced refractive errors. Our results demonstrate that high-order aberrations are influenced by visual experience in young primates and that the increase in high-order aberrations in our treated monkeys appears to be an optical byproduct of the vision-induced alterations in ocular growth that underlie changes in refractive error. The results from our study suggest that the higher amounts of wave aberrations observed in ametropic humans are likely to be a consequence, rather than a cause, of abnormal refractive development. PMID:17825347

Higher-order aberrations and visual acuity after LASEK.

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Urgancioglu, Berrak; Bilgihan, Kamil; Ozturk, Sertac

2008-08-01

To determine ocular higher-order aberrations (HOAs) in eyes with supernormal vision after myopic astigmatic laser subepithelial keratomileusis (LASEK) and to compare the findings with those in eyes with natural supernormal vision. Ocular HOAs were measured after LASEK in 20 eyes of 12 myopic astigmatic patients with postoperative uncorrected visual acuity (UCVA) of >20/16 (group 1). Patients who were included in the study had no visual symptoms like glare, halo or double vision. The measurements were taken 8.3 +/- 3 months after LASEK surgery. In group 2 ocular HOAs were examined in 20 eyes of 10 subjects with natural UCVA of >20/16 as a control. Measurements were taken across a pupil with a diameter of 4.0 mm and 6.0 mm. Root-mean-square (RMS) values of HOAs, Z(3)-1, Z(3)1, Z(4)0, Z(5)-1, Z(5)1 and Z(6)0 were analyzed. The mean RMS values for each order were higher in group 1 when compared with group 2 at 4.0 mm and 6.0 mm pupil diameters. There was no statistically significant difference between groups in spherical and coma aberrations (P > 0.05). Mean RMS values for total HOAs were 0.187 +/- 0.09 microm at 4.0 mm and 0.438 +/- 0.178 microm at 6.0 mm pupil in group 1 and 0.120 +/- 0.049 microm at 4.0 mm and 0.344 +/- 0.083 microm at 6.0 mm pupil in group 2. The difference between groups in total HOAs was statistically significant at 4.0 mm and 6.0 mm pupil diameters (P < 0.05). Ocular HOAs exist in eyes with supernormal vision. After LASEK, the amount of HOAs of the eye increases under both mesopic and photopic conditions. However the amount of HOA increase does not seem to be consistent with visual symptoms.

Assessment of multifocal contact lens over-refraction using an infrared, open-field autorefractor: A preliminary study.

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Giner, Anna; Aldaba, Mikel; Arjona, Montserrat; Vilaseca, Meritxell; Pujol, Jaume

2015-10-01

To evaluate the usefulness of an infrared open-field autorefractor as a predictor of the refractive error when fitting multifocal contact lenses (MCL). Objective and subjective measurements of the non-cycloplegic distance refractive error were compared in patients wearing MCL. We used the Grand Seiko WAM-5500 autorefractor for the objective measurements. Three commercially available MCL were tested. Twenty-one eyes of sixteen healthy adults were included in the study. Over-refraction was evaluated in terms of spherical equivalent (SE) and astigmatic vectors (J0 and J45). The mean difference±SD of each parameter was calculated. The Kolmogorov-Smirnov test was used to verify the normal distribution. Pearson's correlation, Bland and Altman plot and paired sample t test were used to compare the results obtained with both methods. The mean difference between objective and subjective results of the SE over-refraction was 0.13±0.42D; for astigmatic vectors J0 and J45 were 0.03±0.32D and -0.00±0.17D, respectively. The Kolmogorov-Smirnov test showed a normal distribution for all parameters. The highest Pearson's correlation coefficients were obtained for the SE with values of 0.98 without MCL and 0.97 with MCL. The lowest were obtained for J45 with values of 0.65 without MCL and 0.75 with MCL. Significant correlations were obtained for each parameter. The paired sample t test failed to show significant differences in analyzed parameters except for J0 without MCL. The Grand Seiko WAM-5500 can be used as a screening method of over-refraction in the clinical fitting of MCL. Copyright © 2015 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

A Comparative Study of Clear Corneal Phacoemulsification with Rigid IOL Versus SICS; the Preferred Surgical Technique in Low Socio-economic group Patients of Rural Areas.

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Devendra, Jaya; Agarwal, Smita; Singh, Pankaj Kumar

2014-11-01

Low socio-economic group patients from rural areas often opt for free cataract surgeries offered by charitable organisations. SICS continues to be a time tested technique for cataract removal in such patients. In recent times, camp patients are sometimes treated by clear corneal phacoemulsification with implantation of a rigid IOL, which being more cost effective is often provided for camp patients. This study was undertaken to find out which surgical technique yielded better outcomes and was more suited for high volume camp surgery. To find the better surgical option- phacoemulsification with rigid IOL or SICS, in poor patients from rural areas. A prospective randomised controlled trial of cataract patients operated by two different techniques. One hundred and twelve eyes were selected and were randomly allocated into two groups of 56 eyes each. At completion of the study, data was analysed for 52 eyes operated by clear corneal phacoemulsification and implantation of a rigid IOL, and 56 eyes operated by SICS. Unpaired t-test was used to calculate the p- value. The results were evaluated on the following criteria. The mean post-operative astigmatism at the end of four weeks - was significantly higher in phacoemulsification group as compared to SICS group The BCVA (best corrected visual acuity) at the end of four weeks - was comparable in both groups. Subjective complaints and/ or complications: In phaco group two patients required sutures and seven had striate keratitis , while none in SICS group. Complaint of irritation was similar in both groups. Surgical time- was less for SICS group as compared to phaco group. SICS by virtue of being a faster surgery with more secure wound and significantly less astigmatism is a better option in camp patients from rural areas as compared to phacoemulsification with rigid IOL.

A practical femtosecond laser procedure for DLEK endothelial transplantation: cadaver eye histology and topography.

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Terry, Mark A; Ousley, Paula J; Will, Brian

2005-05-01

The manual dissection technique for deep lamellar endothelial keratoplasty (DLEK) surgery is technically difficult and may not be smooth enough for consistently optimal postoperative vision. We evaluated the feasibility and efficacy of using a femtosecond laser to perform the dissections in the DLEK procedure. The Intralase femtosecond laser (with standard LASIK surgery spot settings) was used to create a 9.4-mm wide, 400-microm deep lamellar pocket dissection and a 5.0-mm wide side cut near-exit incision in 10 "recipient" whole cadaver eyes and in 10 "donor" cadaver corneal-scleral caps mounted onto an artificial anterior chamber. Recipient and donor disks were resected with special scissors, and the donor tissue was transplanted using the small incision (5.0-mm) DLEK technique. Topography of the recipient eyes was measured pre- and postlaser dissection, and the recipient and donor tissues were sent for scanning electron microscopy (SEM) analysis of the smoothness of the dissections. Successful lamellar dissections were obtained in all tissues. The mean recipient topographic corneal curvature postoperatively was 43.3 +/- 1.7 diopters, which was not a significant change from the preoperative curvature of 44.0 +/- 0.8 diopters (P = 0.430). The mean recipient topographic astigmatism postoperatively was 1.7 +/- 0.8 diopters, which was not a significant change from the preoperative recipient astigmatism of 1.6 +/- 0.7 diopters (P = 0.426). Comparison of the histology of the laser-formed stromal dissections by scanning electron microscopy, however, did not appear significantly better than histology after manual DLEK dissections in either the recipient or the donor tissues. A femtosecond laser can create the lamellar dissections for the DLEK procedure, making this procedure easier and faster. As in the manual technique, corneal topography is unchanged by this surgery. More work will need to be done, however, to optimize the laser settings to provide even smoother

Comparison of optical quality after implantable collamer lens implantation and wavefront-guided laser in situ keratomileusis.

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Liu, Hong-Ting; Zhou, Zhou; Luo, Wu-Qiang; He, Wen-Jing; Agbedia, Owhofasa; Wang, Jiang-Xia; Huang, Jian-Zhong; Gao, Xin; Kong, Min; Li, Min; Li, Li

2018-01-01

To compare the optical quality after implantation of implantable collamer lens (ICL) and wavefront-guided laser in situ keratomileusis (WG-LASIK). The study included 40 eyes of 22 patients with myopia who accepted ICL implantation and 40 eyes of 20 patients with myopia who received WG-LASIK. Before surgery and three months after surgery, the objective scattering index (OSI), the values of modulation transfer function (MTF) cutoff frequency, Strehl ratio, and the Optical Quality Analysis System (OQAS) values (OVs) were accessed. The higher order aberrations (HOAs) data including coma, trefoil, spherical, 2 nd astigmatism and tetrafoil were also obtained. For patients with pupil size LASIK group, significant improvements in visual acuities were found postoperatively, with a significant reduction in spherical equivalent ( P LASIK group, the OSI significantly increased from 0.68±0.43 preoperatively to 0.91±0.53 postoperatively (Wilcoxon signed ranks test, P =0.000). None of the mean MTF cutoff frequency, Strehl ratio, OVs showed statistically significant changes in both ICL and WG-LASIK groups. In the ICL group, there were no statistical differences in the total HOAs for either 4 mm-pupil or 6 mm-pupil. In the WG-LASIK group, the HOA parameters increased significantly at 4 mm-pupil. The total ocular HOAs, coma, spherical and 2 nd astigmatism were 0.12±0.06, 0.06±0.03, 0.00±0.03, 0.02±0.01, respectively. After the operation, these values were increased into 0.16±0.07, 0.08±0.05, -0.04±0.04, 0.03±0.01 respectively (Wilcoxon signed ranks test, all P LASIK group. ICL implantation has a less disturbance to optical quality than WG-LASIK. The OQAS is a valuable complementary measurement to the wavefront aberrometers in evaluating the optical quality.

Risk factors of regression and undercorrection in photorefractive keratectomy:a case-control study

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Seyed-Farzad Mohammadi

2015-10-01

Full Text Available AIM:To determine risk factors of regression and undercorrection following photorefractive keratectomy (PRK in myopia or myopic astigmatism.METHODS: A case-control study was designed in which eyes with an indication for re-treatment (RT were defined as cases; primary criteria for RT indication, as assessed at least 9mo postoperatively, included an uncorrected distance visual acuity (UDVA of 20/30 or worse and a stable refraction for more than 3mo. Additional considerations included optical quality symptoms and significant higher order aberrations (HOAs. Controls were chosen from the same cohort of operated eyes which had complete post-operative follow up data beyond 9mo and did not need RT. The cohort included patients who had undergone PRK by the Tissue-Saving (TS ablation profile of Technolas 217z100 excimer laser (Bausch & Lomb, Rochester, NY, USA. Mitomycin C had been used in all of the primary procedures.RESULTS:We had 70 case eyes and 158 control eyes, and they were comparable in terms of age, sex and follow-up time (P values:0.58, 1.00 and 0.89, respectively. Pre-operative spherical equivalent of more than -5.00 diopter (D, intended optical zone (OZ diameter of less than 6.00 mm and ocular fixation instability during laser ablation were associated with RT indications (all P values <0.001. These factors maintained their significance in the multiple logistic regression model with odd ratios of 6.12, 6.71 and 7.89, respectively.CONCLUSION:Higher refractive correction (>-5.00 D, smaller OZ (<6.00 mm and unstable fixation during laser ablation of PRK for myopia and myopic astigmatism were found to be strong predictors of undercorrection and regression.

The application of excimer lasers for corneal sculpturing

International Nuclear Information System (INIS)

King, M.C.

1990-01-01

Of the broad selection of lasers available for surgery, the argon fluoride excimer laser offers a set of attributes that make it uniquely suited for the removal of corneal tissue. With ultraviolet radiation at 193mm, the energy of an individual photon (6.3 electron volts) is sufficient to break bonds in protein molecules without generating molecular vibration (heat). A single laser pulse is capable of removing 0.25 microns of corneal tissue over a well defined area 80 mm 2 in extent. This excision with a lateral precision to a fraction of a micron causes no discernible damage to neighboring cells. The smooth surface left after the tissue is removed promotes a quick and predictable regrowth of the epithelium. The penetration of radiation into the underlying tissue is the order of a micron so there is no potential harm to the lens or retinal tissue. Insignificant mutagenesis or unscheduled DNA synthesis has been detected as a result of tissue irradiation at this wavelength. In the past few years major progress has been made towards developing ophthalmic procedures which utilize the unique properties of this laser. To date there are FDA IDE's (Investigational Device Exemptions) for the following procedures: Photorefractive Keratectomy (PRK) or corneal reshaping for correcting near-sightedness, far-sightedness and astigmatism without the need for eye glasses, contact lenses or conventional refractive surgery (Radial Keratotomy); Partial Excimer Trabeculectomy for relieving the pressure build-up caused by glaucoma; T-Excisons for reducing astigmatism; Myopic Keratomileusis (MKM) for the refractive correction of severe myopia; superficial Keratectomy (corneal smoothing) for treating various corneal scars, dystrophies, recurrent corneal erosion etc. In this paper the fundamentals of beam tissue interaction at 193nm will be discussed

Clinical Outcomes after Uncomplicated Cataract Surgery with Implantation of the Tecnis Toric Intraocular Lens

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Wojciech Lubiński

2016-01-01

Full Text Available Purpose. To evaluate the clinical outcomes after uncomplicated cataract surgery with implantation of an aspheric toric intraocular lens (IOL during a 6-month follow-up. Methods. Prospective study including 27 consecutive eyes of 18 patients (mean age: 66.1±11.4 years with a visually significant cataract and corneal astigmatism ≥ 0.75 D and undergoing uncomplicated cataract surgery with implantation of the Tecnis ZCT toric IOL (Abbott Medical Optics. Visual, refractive, and keratometric outcomes as well as IOL rotation were evaluated during a 6-month follow-up. At the end of the follow-up, patient satisfaction and perception of optical/visual disturbances were also evaluated using a subjective questionnaire. Results. At 6 months after surgery, mean LogMAR uncorrected (UDVA and corrected distance visual acuity (CDVA were 0.19±0.12 and 0.14±0.10, respectively. Postoperative UDVA of 20/40 or better was achieved in 92.6% of eyes. Mean refractive cylinder decreased significantly from −3.73±1.96 to −1.42±0.88 D (p<0.001, while keratometric cylinder did not change significantly (p=0.44. Mean absolute IOL rotation was 1.1±2.4°, with values of more than 5° in only 2 eyes (6.9%. Mean patient satisfaction score was 9.70±0.46, using a scale from 0 (not at all satisfied to 10 (very satisfied. No postoperative optical/visual disturbances were reported. Conclusion. Cataract surgery with implantation of the Tecnis toric IOL is an effective method of refractive correction in eyes with corneal astigmatism due to the good IOL positional stability, providing high levels of patient’s satisfaction.

Surface ablation with iris recognition and dynamic rotational eye tracking-based tissue saving treatment with the Technolas 217z excimer laser.

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Prakash, Gaurav; Agarwal, Amar; Kumar, Dhivya Ashok; Jacob, Soosan; Agarwal, Athiya; Maity, Amrita

2011-03-01

To evaluate the visual and refractive outcomes and expected benefits of Tissue Saving Treatment algorithm-guided surface ablation with iris recognition and dynamic rotational eye tracking. This prospective, interventional case series comprised 122 eyes (70 patients). Pre- and postoperative assessment included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refraction, and higher order aberrations. All patients underwent Tissue Saving Treatment algorithm-guided surface ablation with iris recognition and dynamic rotational eye tracking using the Technolas 217z 100-Hz excimer platform (Technolas Perfect Vision GmbH). Follow-up was performed up to 6 months postoperatively. Theoretical benefit analysis was performed to evaluate the algorithm's outcomes compared to others. Preoperative spherocylindrical power was sphere -3.62 ± 1.60 diopters (D) (range: 0 to -6.75 D), cylinder -1.15 ± 1.00 D (range: 0 to -3.50 D), and spherical equivalent -4.19 ± 1.60 D (range: -7.75 to -2.00 D). At 6 months, 91% (111/122) of eyes were within ± 0.50 D of attempted correction. Postoperative UDVA was comparable to preoperative CDVA at 1 month (P=.47) and progressively improved at 6 months (P=.004). Two eyes lost one line of CDVA at 6 months. Theoretical benefit analysis revealed that of 101 eyes with astigmatism, 29 would have had cyclotorsion-induced astigmatism of ≥ 10% if iris recognition and dynamic rotational eye tracking were not used. Furthermore, the mean percentage decrease in maximum depth of ablation by using the Tissue Saving Treatment was 11.8 ± 2.9% over Aspheric, 17.8 ± 6.2% over Personalized, and 18.2 ± 2.8% over Planoscan algorithms. Tissue saving surface ablation with iris recognition and dynamic rotational eye tracking was safe and effective in this series of eyes. Copyright 2011, SLACK Incorporated.

Refractive errors in 3-6 year-old Chinese children: a very low prevalence of myopia?

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Weizhong Lan

Full Text Available PURPOSE: To examine the prevalence of refractive errors in children aged 3-6 years in China. METHODS: Children were recruited for a trial of a home-based amblyopia screening kit in Guangzhou preschools, during which cycloplegic refractions were measured in both eyes of 2480 children. Cycloplegic refraction (from 3 to 4 drops of 1% cyclopentolate to ensure abolition of the light reflex was measured by both autorefraction and retinoscopy. Refractive errors were defined as followed: myopia (at least -0.50 D in the worse eye, hyperopia (at least +2.00 D in the worse eye and astigmatism (at least 1.50 D in the worse eye. Different definitions, as specified in the text, were also used to facilitate comparison with other studies. RESULTS: The mean spherical equivalent refractive error was at least +1.22 D for all ages and both genders. The prevalence of myopia for any definition at any age was at most 2.5%, and lower in most cases. In contrast, the prevalence of hyperopia was generally over 20%, and declined slightly with age. The prevalence of astigmatism was between 6% and 11%. There was very little change in refractive error with age over this age range. CONCLUSIONS: Previous reports of less hyperopic mean spherical equivalent refractive error, and more myopia and less hyperopia in children of this age may be due to problems with achieving adequate cycloplegia in children with dark irises. Using up to 4 drops of 1% cyclopentolate may be necessary to accurately measure refractive error in paediatric studies of such children. Our results suggest that children from all ethnic groups may follow a similar pattern of early refractive development, with little myopia and a hyperopic mean spherical equivalent over +1.00 D up to the age of 5-6 years in most conditions.

[Visual outcomes 5 years after small incision lenticule extraction (SMILE), surgery on spherocylindrical myopia eyes, from 616 eyes].

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Burazovitch, J; Ferguene, H; Naguszewski, D

2018-05-15

Determine if the visual criteria of the technique of surgery refractive by Femtosecond Laser-assisted duckweed Extraction - Small Lenticule Extraction (FLEx-Smile ® ), realized in the laser femtosecond VisuMax ® (Carl Zeiss Meditec, Jena, Germany), are stable, secure, effective and predictable in the long term, to the nearsighted and astigmatic. Retrospective study, monocentric with data collected between March 2012 and March 2017. The study included 616 eyes of 309 nearsighted and astigmatic patients (spherical equivalent from 1 to 11 D). They were followed in postoperative immediate (D+1), in 3 months, in 1 year and in 5 years. The taken measures include the refraction, the uncorrected visual acuteness (UVAC) and the best visual corrected acuteness (BVAC). The criteria of evaluation were based on the BVAC, the refractive stability, the index of security (IS: MAVC to preoperative D+1/BVAC before operation) and the predictability (percentage of eyes in±1 D of SE target). UVAC was better 5th year than after the intervention (P=0.001) and 88% of the operated eyes had an UVAC in 8/10 (logMAR=0.1). For the stability refractive, the patients became nearsighted between the intervention and 5th year (P=0.001), with a regression of 0.240 D. The indication of safety was better 5th year than the day after the intervention (P=0.001), 92% of eyes operated in 5 years were 0.5 D of SE target and 77% of eyes had lost no line. SMILE is a good technique of surgery refractive stable, secure, effective and predictable on the long term. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

Visual and refractive outcomes with ReLEx® SMILE in 600 eyes

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Sri Ganesh

2016-02-01

Full Text Available AIM:To study the outcomes of ReLEx® small incision lenticule extraction(SMILEfor correction of myopia or myopic astigmatism in terms of visual acuity, contrast sensitivity, aberrations, and dry eye.METHODS: In this prospective, non-randomized clinical study, done at Nethradhama Super Speciality Eye Hospital, a total of 600 eyes that met the inclusion criteria underwent a thorough preoperative examination, including corrected distance visual acuity(CDVA, contrast sensitivity, aberrometry, and dry eye assessment. VisuMax femtosecond laser system was used to perform SMILE. Patients were followed up on 1, 15d and 3mo. Pre and postoperative uncorrected visual acuity(UCVA, CDVA, aberrations, dry eye, and contrast sensitivity during 3mo of follow-up were recorded. Data analysis was done with the help of a computer using SPSS for Windows Software(version 17.0, SPSS, Inc., New York, USA. A paired t-test was used to test the significance of difference between quantitative variables and Yate's Chi-square test for qualitative variables. P value less than 0.05 denoted a significant relationship.RESULTS: The study enrolled 600 eyes of 305 patients, of which 10 patients underwent SMILE in 1 eye only due to anisometropia. At 3mo, 98.83% of eyes had attained a UCVA of 20/20 or better. No patient had a loss of CDVA, and 37 eyes(6.17%showed a gain in 1 line in postoperative CDVA. Postoperative induction of coma and spherical aberrations was minimal. Contrast sensitivity reduced immediate postoperatively(PP=0.43, 0.47, 0.46CONCLUSION:Our results demonstrate the high refractive accuracy and safety of ReLEx® SMILE for the treatment of myopia and myopic astigmatism. Increase in postoperative dryness and aberrations, both accepted drawbacks of any corneal refractive surgery were observed, while decrease in contrast sensitivity was insignificant at lower spatial frequencies.

Corneal injection track:an unusual complication of intraocular lens implantation and review

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Julie Y.C. Lok

2015-06-01

Full Text Available Phacoemulsification is the main gold standard for cataract operation in the developed world together with foldable intraocular lens (IOL implantation by injection, allowing for stable wound construction and less postoperative astigmatism. It is a safe procedure with high success rate with the advancement in machines, improvement of IOL injection systems and further maturation of surgeons’ techniques. Despite the large number of operations performed every day, foldable IOL injection leading to an intra-stromal corneal track is a very rare complication. We report a case of this unusual finding in a 70-year-old gentleman who has undergone cataract operation in November 2011 in our hospital and will review on the complications related to foldable IOL injection.

[The eye, the optic system and its anomalies].

Science.gov (United States)

Cohen, S Y

1993-09-15

The eye is a perceptive system with extremely complex physiology, although its optical properties can be assimilated to those of spherical diopters. Various approximations make it possible to reduce the eyeball to a single convex diopter. With a normal eye the image of an object situated ad infinitum focuses on the retina. The normal eye is called emmetropic. Otherwise, the eye is called ametropic. Several types of ametropy exist. When the image focuses in front of the retina the eye is said to be myopic. When the image focuses behind the retina the eye is called hypermetropic (or hyperopic). When the image of an object differs according to various focusing axes, the eye is said to be astigmatic.

Multiple passage cells theory

International Nuclear Information System (INIS)

Riva, R.

1983-01-01

A review of the main concepts envolved in non astigmatic multiple passes cells is presented. It is shown that these concepts can be extended to ring cavities in which the analysis of the ray propagation (in the paraxial approaching) in two separated plans is accomplished. The concepts developed are applyed to a simple ring cavity (one curve mirror and two plane ones) showing that the acquired pattern of the rays on the mirrors is the one of a Lissajours figure which allows a better use of the mirror's area and consequently a larger number of passes. The cavity has applications in optical delay lines, measurements of mirrors reflectivities and possibly in passive optical gyroscopes. (Author) [pt

Influence factors of visual quality after phacoemulsification for cataract

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Zhen-Lin Lin

2017-12-01

Full Text Available Cataract refers to the degenerative changes in lens quality caused by various causes of reduced transparency or color change. Surgical treatment is the main treatment modality at present. Among them, phacoemulsification has become the main surgical treatment for cataract because of its advantages such as short operation time, small incision and quicker healing. Today, cataract surgery has gradually shift to refractive surgery, and is no longer simply as cataract surgery. But after cataract phacoemulsification, the symptoms and visual quality are different. The main causes include refractive error, postoperative dry eyes and postoperative corneal astigmatism. This article reviews the factors that influence the visual quality of cataract phacoemulsification and its future trends.

Toric implantable collamer lens for keratoconus

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Mathew Kurian Kummelil

2013-01-01

Full Text Available Keratoconus is a progressive non-inflammatory thinning of the cornea that induces myopia and irregular astigmatism and decreases the quality of vision due to monocular diplopia, halos, or ghost images. Keratoconus patients unfit for corneal procedures and intolerant to refractive correction by spectacles or contact lenses have been implanted toric posterior chamber phakic intraocular lenses (PC pIOLs alone or combined with other surgical procedures to correct the refractive errors associated with keratoconus as an off label procedure with special informed consent from the patients. Several reports attest to the safety and efficacy of the procedure, though the associated corneal higher order aberrations would have an impact on the final visual quality.

Statistical characteristics of aberrations of human eyes after small incision lenticule extraction surgery and analysis of visual performance with individual eye model.

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Lou, Qiqi; Wang, Yan; Wang, Zhaoqi; Liu, Yongji; Zhang, Lin; Fang, Hui

2015-09-01

Preoperative and postoperative wavefront aberrations of 73 myopic eyes with small incision lenticule extraction surgery are analyzed in this paper. Twenty-eight postoperative individual eye models are constructed to investigate the visual acuity (VA) of human eyes. Results show that in photopic condition, residual defocus, residual astigmatism, and higher-order aberrations are relatively small. 100% of eyes reach a VA of 0.8 or better, and 89.3% of eyes reach a VA of 1.0 or better. In scotopic condition, the residual defocus and the higher-order aberrations are, respectively, 1.9 and 8.5 times the amount of that in photopic condition, and the defocus becomes the main factor attenuating visual performance.

High power spatial filter considerations, with special emphasis on the cyclops geometry

International Nuclear Information System (INIS)

Simmons, W.W.; Guch, S.

1974-01-01

This document presents considerations leading to location and first-cut design of a lens-pinhole-lens spatial filter for Cyclops laser chain. Small scale beam break-up is the driving phenomenon for spatial filtering, and design is predicated upon estimates of this effect's magnitude. The departure of the beam from diffraction limited performance (due to astigmatism and to whole beam self-focusing) is presented in terms of pinhole size limitations. All calculations are presented in terms of parameters associated with Cyclops, through the B stages, assuming that the spatial filter is located at this point in the chain, and that the focal length of the input spatial filter lens is 100 cm. The geometrical ray diagram is shown

Self-focusing and self-defocusing of elliptically shaped Gaussian laser beams in plasmas

Energy Technology Data Exchange (ETDEWEB)

Nayyar, V P; Soni, V S [Punjabi Univ., Patiala (India). Dept. of Physics

1979-02-14

This paper presents a study of the self-focusing and self-defocusing of elliptically shaped Gaussian laser beams in collisional and collisionless plasmas. The non-linear dependence of the dielectric constant inside a collisional plasma is due to inhomogeneous heating of energy carriers and in a collisionless plasma it is due to the ponderomotive force. It is found that the beam gets focused at different points in different planes, exhibiting the effect of astigmatism. In certain power regions considered, the beam either converges or defocuses in both the directions, while in some other regions of the power spectrum one dimension of the beam focuses while the other defocuses. The beam also propagates in an oscillatory waveguide.

High-flux normal incidence monochromator for circularly polarized synchrotron radiation

International Nuclear Information System (INIS)

Schaefers, F.; Peatman, W.; Eyers, A.; Heckenkamp, C.; Schoenhense, G.; Heinzmann, U.

1986-01-01

A 6.5-m normal incidence monochromator installed at the storage ring BESSY, which is optimized for a high throughput of circularly polarized off-plane radiation at moderate resolution is described. The monochromator employs two exit slits and is specially designed and used for low-signal experiments such as spin- and angle-resolved photoelectron spectroscopy on solids, adsorbates, free atoms, and molecules. The Monk--Gillieson mounting (plane grating in a convergent light beam) allows for large apertures with relatively little astigmatism. With two gratings, a flux of more than 10 11 photons s -1 bandwidth -1 (0.2--0.5 nm) with a circular polarization of more than 90% in the wavelength range from 35 to 675 nm is achieved

Quality descriptors of optical beams based on centred reduced moments I spot analysis

CERN Document Server

Castaneda, R; García-Sucerquia, J

2003-01-01

A method for analyzing beam spots is discussed. It is based on the central reduced moments of the spot and its associated density functions. These functions allow us to separately analyze specific spot fractions, in such a way that specific combinations of higher order moments can be interpreted as coordinates of their centre of mass and the length and orientations of their principal axis. So, the descriptors of the associated density functions deal with the quantitative estimation of spot features, such as coma-like and astigmatism-like distortions. To assure high accuracy, background noise suppression and an optimal match of the spot support onto the region [-1,1]x[- 1,1] are performed prior to the calculation of the moments. Simulations were performed for illustrating the method.

[Vision test program for ophthalmologists on Apple II, IIe and IIc computers].

Science.gov (United States)

Huber, C

1985-03-01

A microcomputer program for the Apple II family of computers on a monochrome and a color screen is described. The program draws most of the tests used by ophthalmologists, and is offered as an alternative to a projector system. One advantage of the electronic generation of drawings is that true random orientation of Pflueger's E is possible. Tests are included for visual acuity (Pflueger's E, Landolt rings, numbers and children's drawings). Colored tests include a duochrome test, simple color vision tests, a fixation help with a musical background, a cobalt blue test and a Worth figure. In the astigmatic dial a mobile pointer helps to determine the axis. New tests can be programmed by the user and exchanged on disks among collageues.

Receiving efficiency of monostatic pulsed coherent lidars. I - Theory. II - Applications

Science.gov (United States)

Zhao, Yanzeng; Post, Madison J.; Hardesty, Michael

1990-01-01

Pulsed coherent radars' receiving efficiency, eta, is presently investigated as a function of range z on the basis of a theory which relates eta(z) to both the transmitted laser intensity and the point-source receiving efficiency; this efficiency is calculated by a backward method employing the back-propagated local oscillator (BPLO) approach. The theory is applied to the ideal case, in order to study system optimization when both the transmitted and the BPLO fields at the antenna are Gaussian. In the second part of this work, eta(z) is calculated for various conditions of the NOAA/ERL Wave Propagation Laboratory CO2 Doppler lidar; the sensitivity of eta(z) to transmitted laser beam quality, telescope focal setting, telescope power, scanner astigmatism, and system misalignment.

Relaxation in Thin Polymer Films Mapped across the Film Thickness by Astigmatic Single-Molecule Imaging

KAUST Repository

Oba, Tatsuya; Vacha, Martin

2012-01-01

We have studied relaxation processes in thin supported films of poly(methyl acrylate) at the temperature corresponding to 13 K above the glass transition by monitoring the reorientation of single perylenediimide molecules doped into the films

A two-year's results of iontophoresis-assisted transepithelial corneal cross-linking for progressive keratoconus

Directory of Open Access Journals (Sweden)

Hong-Zhen Jia

2016-07-01

Full Text Available AIM: To report a two-year's results of iontophoresis-assisted transepithelial corneal cross-linking(I-CXLfor progressive keratoconus. METHODS: Thirty-four eyes in 24 patients with progressive keratoconus(mean age 21.0±5.6 years; range: 14-32 yearswere treated. After 1g/L riboflavin-distilled water solution was administered by iontophoresis-assited(current 1mAtransepithelial method for 5min in total, standard surface UVA irradiation(370nm, 3mW/cm2was performed at a 1-cm distance for 30min. The best corrected visual acuity(BCVAmeasured as LogMAR number, corneal refractive astigmatism, K1, K2, Kmean, Kmax, intraocular pressure, endothelial cell density, the thickness at corneal apex and the thinnest point were measured preoperatively and 2a postoperatively. RESULTS:At 2a after the procedure, BCVA(LogMARimproved from 0.32±0.25 to 0.25±0.19(t=2.849, P=0.015. K1 decreased from 47.12±4.33 to 46.06±4.77(t=2.652, P=0.015. K2 decreased from 51.36±5.59 to 50.40±6.16(t=2.121, P=0.047. Kmean decreased from 49.12±4.76 to 48.10±5.25(t=2.663, P=0.015. Kmax decreased from 57.57±8.30 to 55.91±8.14(t=2.398, P=0.026. The corneal apex thickness decreased from 476.90±38.71μm to 454.43±40.86μm(t=2.853, P=0.010. The thinnest thickness decreased from 464.38±39.92μm to 433.86±50.78μm(t=3.485, P=0.002. Corneal refractive astigmatism, intraocular pressure and endothelial cell density did not show significant changes. CONCLUSION: I-CXL for progressive keratoconus is safe and effective which can prevent deterioration of progressive keratoconus within 2a, but further long-term studies are necessary still.

Two-years results of small-incision lenticule extraction and wavefront-guided laser in situ keratomileusis for Myopia.

Science.gov (United States)

Kobashi, Hidenaga; Kamiya, Kazutaka; Igarashi, Akihito; Takahashi, Masahide; Shimizu, Kimiya

2018-03-01

To compare the 2-years visual and refractive outcomes between small-incision lenticule extraction (SMILE) and wavefront-guided laser in situ keratomileusis (LASIK) in eyes with myopia and myopic astigmatism. Our retrospective case-control study examined 30 eyes of 30 patients with the manifest refraction spherical equivalent (MRSE) of -3.71 ± 1.83 dioptres (D) who underwent SMILE and 30 eyes of 30 patients with MRSE of -3.81 ± 1.40 D who underwent wavefront-guided LASIK. We assessed the 2-years clinical outcomes. Logarithm of the minimal angle of resolution (LogMAR)-corrected distance visual acuity (CDVA) was -0.23 ± 0.07 in the SMILE group and -0.24 ± 0.07 in the wavefront-guided LASIK group 2 years postoperatively (p = 0.82). Logarithm of the minimal angle of resolution-uncorrected distance visual acuity (UDVA) was -0.18 ± 0.09 and -0.15 ± 0.11 (p = 0.30, respectively). In the SMILE and wavefront-guided LASIK groups 2 years postoperatively, 100% and 73% of eyes, respectively, were within 0.5 D of the prompted MRSE correction (p = 0.005). Changes in the MRSE of -0.10 ± 0.30 D and -0.23 ± 0.51 D occurred from 3 months to 2 years (p = 0.40, respectively). We found a significant correlation between myopic regression and the changes in the keratometric readings from 3 months to 2 years after wavefront-guided LASIK (r = -0.48, p = 0.002), but not after SMILE (r = -0.004, p = 0.90). Small-incision lenticule extraction offers better refractive outcomes than wavefront-guided LASIK during a 2-years follow-up for the correction of myopia and myopic astigmatism. © 2017 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Ocellar optics in nocturnal and diurnal bees and wasps.

Science.gov (United States)

Warrant, Eric J; Kelber, Almut; Wallén, Rita; Wcislo, William T

2006-12-01

Nocturnal bees, wasps and ants have considerably larger ocelli than their diurnal relatives, suggesting an active role in vision at night. In a first step to understanding what this role might be, the morphology and physiological optics of ocelli were investigated in three tropical rainforest species - the nocturnal sweat bee Megalopta genalis, the nocturnal paper wasp Apoica pallens and the diurnal paper wasp Polistes occidentalis - using hanging-drop techniques and standard histological methods. Ocellar image quality, in addition to lens focal length and back focal distance, was determined in all three species. During flight, the ocellar receptive fields of both nocturnal species are centred very dorsally, possibly in order to maximise sensitivity to the narrow dorsal field of light that enters through gaps in the rainforest canopy. Since all ocelli investigated had a slightly oval shape, images were found to be astigmatic: images formed by the major axis of the ocellus were located further from the proximal surface of the lens than images formed by the minor axis. Despite being astigmatic, images formed at either focal plane were reasonably sharp in all ocelli investigated. When compared to the position of the retina below the lens, measurements of back focal distance reveal that the ocelli of Megalopta are highly underfocused and unable to resolve spatial detail. This together with their very large and tightly packed rhabdoms suggests a role in making sensitive measurements of ambient light intensity. In contrast, the ocelli of the two wasps form images near the proximal boundary of the retina, suggesting the potential for modest resolving power. In light of these results, possible roles for ocelli in nocturnal bees and wasps are discussed, including the hypothesis that they might be involved in nocturnal homing and navigation, using two main cues: the spatial pattern of bright patches of daylight visible through the rainforest canopy, and compass information

Attention and Visual Motor Integration in Young Children with Uncorrected Hyperopia.

Science.gov (United States)

Kulp, Marjean Taylor; Ciner, Elise; Maguire, Maureen; Pistilli, Maxwell; Candy, T Rowan; Ying, Gui-Shuang; Quinn, Graham; Cyert, Lynn; Moore, Bruce

2017-10-01

Among 4- and 5-year-old children, deficits in measures of attention, visual-motor integration (VMI) and visual perception (VP) are associated with moderate, uncorrected hyperopia (3 to 6 diopters [D]) accompanied by reduced near visual function (near visual acuity worse than 20/40 or stereoacuity worse than 240 seconds of arc). To compare attention, visual motor, and visual perceptual skills in uncorrected hyperopes and emmetropes attending preschool or kindergarten and evaluate their associations with visual function. Participants were 4 and 5 years of age with either hyperopia (≥3 to ≤6 D, astigmatism ≤1.5 D, anisometropia ≤1 D) or emmetropia (hyperopia ≤1 D; astigmatism, anisometropia, and myopia each attention (sustained, receptive, and expressive), VMI, and VP. Binocular visual acuity, stereoacuity, and accommodative accuracy were also assessed at near. Analyses were adjusted for age, sex, race/ethnicity, and parent's/caregiver's education. Two hundred forty-four hyperopes (mean, +3.8 ± [SD] 0.8 D) and 248 emmetropes (+0.5 ± 0.5 D) completed testing. Mean sustained attention score was worse in hyperopes compared with emmetropes (mean difference, -4.1; P Attention score was worse in 4 to 6 D hyperopes compared with emmetropes (by -2.6, P = .01). Hyperopes with reduced near visual acuity (20/40 or worse) had worse scores than emmetropes (-6.4, P attention; -3.0, P = .004 for Receptive Attention; -0.7, P = .006 for VMI; -1.3, P = .008 for VP). Hyperopes with stereoacuity of 240 seconds of arc or worse scored significantly worse than emmetropes (-6.7, P attention; -3.4, P = .03 for Expressive Attention; -2.2, P = .03 for Receptive Attention; -0.7, P = .01 for VMI; -1.7, P visual function generally performed similarly to emmetropes. Moderately hyperopic children were found to have deficits in measures of attention. Hyperopic children with reduced near visual function also had lower scores on VMI and VP than emmetropic children.

Manifestações oculares em pacientes que tiveram desnutrição nos primeiros seis meses de vida Ocular manifestations in patients who had malnutrition in the first six months of life

Directory of Open Access Journals (Sweden)

Alessandra Pereira Dantas

2005-12-01

Full Text Available OBJETIVOS: Investigar possíveis alterações oftalmológicas em pacientes que tiveram desnutrição grave durante os primeiros seis meses de vida. MÉTODOS: Foram analisados 182 olhos de 91 crianças entre 2 e 11 anos que tiveram desnutrição grave durante os primeiros seis meses de vida (grupo estudo. Como grupo controle foram incluídas 88 crianças, selecionadas aleatoriamente segundo características similares de idade, gênero, condições econômicas e demográficas. RESULTADOS: Observou-se, de forma significante, no grupo estudo, maior freqüência de crianças com acuidade visual de 0,3 a 0,1 e menor que 0,1 (11,5% versus 0,7% - p PURPOSE: To investigate possible ophthalmologic alterations in patients who had severe malnutrition during the first six months of life. METHODS: 182 eyes of 91, 2 to 11-year-old, children who had had severe malnutrition during the first six months of life (study group were analyzed. As a control group 88 children selected according to similar characteristics of age, gender, demographic and economic conditions were included. RESULTS: In the study group, a higher frequency of children with visual acuity from 0.3 to 0.1 and less than 0.1 (11.5% versus 0.7% - p<0.0001 was observed. There was a higher frequency of astigmatism and myopia in the study group. A higher frequency of astigmatism of one diopter or more in the study group (p<0.0001 was also observed. The fundoscopic alterations were pale optic nerve (2.2%, increased disc cup (4.4%, increased vascular tortuosity (6.6%, alteration of retina color (13.2% and retinal pigment epithelium cell atrophy (12.0%. CONCLUSIONS: The present data support the concept that early malnutrition interferes in the individual's visual health. Further studies are necessary to establish a more precise cause-effect relationship.

Short-term outcomes of small incision cataract surgery provided by a regional population in the Pacific.

Science.gov (United States)

Bhikoo, Riyaz; Vellara, Hans; Lolokabaira, Salome; Murray, Neil; Sikivou, Biu; McGhee, Charles

2017-11-01

This study aims to describe patient demographics, visual and surgical outcomes of a cohort undergoing small incision cataract surgery at a Pacific regional ophthalmic training facility. This is a prospective, longitudinal study conducted at the Pacific Eye Institute, Fiji. One hundred fifty-six patients underwent small incision cataract surgery. Preoperatively, a complete ophthalmic examination, including pachymetry and macular optical coherence tomography performed by two independent investigators. Temporal small incision cataract surgery with intraocular lens insertion was performed by ophthalmologists, and trainee ophthalmologists. Follow-up occurred at day one, four weeks and 3 months. Patient characteristics, visual outcomes including surgically induced astigmatism and complications. Ninety-one per cent (142/156) attended 3-month follow-up with median age 63 years (range 19-82), 52% female (81/156) and 58% (90/156) Fijian ethnicity. In 37% (57/156), the contralateral eye was pseudophakic. Mean preoperative best spectacle-corrected visual acuity was logMAR 1.44 (6/165). At 3 months, 74% (105/142) achieved ≥6/18 unaided vision (94% [133/142] best spectacle-corrected visual acuity). Mean postoperative spherical equivalent was -0.78 (SD 0.95) D and mean surgically induced astigmatism 1.04 (0.57) D. Complications included posterior capsular rupture with vitreous loss (4% [6/156]), optical coherence tomography confirmed macular oedema (8% [12/152] at 4 weeks), significant posterior capsular opacity (23% [31/136]) and >5% increase in preoperative pachymetry (1% [1/142]) at 3 months. Reduction in preoperative best spectacle-corrected visual acuity occurred in 2% (3/142). No cases of endophthalmitis. Small incision cataract surgery provided to a regional population is effective with 94% achieving the World Health Organisation's definition of 'Good Vision' (≥6/18). Refinements in biometric and surgical techniques may allow a greater proportion of patients to

[Phacoemulsification versus manual small incision cataract surgery: Anatomic and functional results].

Science.gov (United States)

Ammous, I; Bouayed, E; Mabrouk, S; Boukari, M; Erraies, K; Zhioua, R

2017-06-01

Prospective randomised study to compare the impact of phacoemusification (PHACO) and small incision cataract surgery (SICS) on endothelial structure (cell density and morphology) and refractive results (visual acuity, induced astigmatism). Prospective study of 57 patients (63 eyes) over 20 months (May 2012-January 2014) undergoing surgery by 2 experienced surgeons. We included patients with senile or presenile cataracts, LOCS III class 2, 3 and 4. Patients were randomized into 2 groups based on their birth month (group 1: PHACO [33]; group 2: SICS [30]). All pre- intra- and postoperative data were collected prospectively. The minimum follow-up was 6 months. We used the SPSS 18.0 for statistical analysis. Statistical tests used included the test-t Student, the Anova test, the Mann-Witney non-parametric test and the Khi 2 test. A threshold of significance was set at 0.05. The mean preoperative endothelial cell density was 2447.5±225 c/mm 2 with no significant difference between the two groups (P=0.207). The mean percentage of hexagonality was 55.5±8.2% in groups 1 and 2. The most significant cell loss was during the first immediate postoperative period for both groups. At Day 15 postoperative, the decrease in cell loss was significant (P<0.001) with a mean loss of 312.9±208.9 c/mm 2 (P<10 -2 ). Postoperatively, the mean best-corrected visual acuity was 0.057 log MAR for all of our patients (P=0.170); no patient had an acuity ≤1/10. The mean astigmatism at the conclusion of follow-up was 1.08±0.42 D in group 1 and 1.51±0.55 D in group 2, with a significant difference (P=0.001). Both SICS and PHACO give excellent results, both anatomical and refractive. However, SICS appears to be more advantageous than PHACO in terms of speed, cost, and independence from technology, and appears to be better suited to dense cataracts and mass surgery. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

The Risk of Contact Lens Wear and the Avoidance of Complications

Directory of Open Access Journals (Sweden)

Farihah Tariq

2013-11-01

Full Text Available Contact lenses are lenses placed on the surface of the cornea to correct refractive errors such as myopia (short-sightedness, hypermetropia (far-sightedness and astigmatism. Lens-related complications are becoming a greater health concern as increasing number of individuals are using them as an alternative to spectacles. Contact lenses alter the natural ocular environment and reduce the efficacy of the innate defences. Although many complications are minor, microbial keratitis is potentially blinding and suspected cases should be rapidly diagnosed and referred to an ophthalmologist for treatment. Several risk factors have been identified with extended wear, poor hand hygiene, inadequate lens and lens-case care being the most significant. Promotion of good contact lens hygiene and practices are essential to reduce the adverse effects of contact lens wear.

Refraktīvā lēcas ķirurģija pie augstas pakāpes ametropijas

OpenAIRE

Šamajeva, Nataļja

2012-01-01

Ametropija ir patoloģisks redzes stāvoklis, kad gaismas stari, izejot cauri acs optiskajām vidēm, fokusējas nevis uz tīklenes, bet pirms vai aiz tās, tad apkārtējo pasauli cilvēks redz neasi. Ametropijas veidi ir miopija, hipermetropija, astigmatisms, kā arī presbopija. Izšķir vājas, vidējas un augstas pakāpes ametropiju. Pilnībā sekmīgi izārstēt augstas pakāpes ametropijas var ar dabīgās acu lēcas aizvietošanu ar multifokālo intraokulāro lēcu. Turklāt pacientiem jāņem vērā, ka šai operā...

Identification of various phases in HRTEM images of MgO-PSZ

International Nuclear Information System (INIS)

Liu, Z.; Spargo, A.E.C.

2000-01-01

Magnesia partially stabilized zirconia is one of the most commonly used engineering ceramics based on zirconia. A detailed discussion about how to identify the various phases in the high resolution transmission electron microscopy images of this material is presented. It shows that in some cases, the standard procedures of image simulation are inadequate to interpret these images. By including the effect of astigmatism in both experimental and simulated images, together with the digital Fourier transforms of the images, orthorhombic ZrO 2 in [001] orientation was identified. The δ-phase, which has a marked effect on the thermomechanical properties of MgO-PSZ, can most easily be identified by high resolution imaging in the [130] c zone which coincides with a low-index zone axis of the δ-phase

Quality descriptors of optical beams based on centred reduced moments I: spot analysis

International Nuclear Information System (INIS)

Castaneda, Roman; Garcia-Sucerquia, Jorge; Brand, Frank

2003-03-01

A method for analyzing beam spots is discussed. It is based on the central reduced moments of the spot and its associated density functions. These functions allow us to separately analyze specific spot fractions, in such a way that specific combinations of higher order moments can be interpreted as coordinates of their centre of mass and the length and orientations of their principal axis. So, the descriptors of the associated density functions deal with the quantitative estimation of spot features, such as coma-like and astigmatism-like distortions. To assure high accuracy, background noise suppression and an optimal match of the spot support onto the region [-1,1]x[- 1,1] are performed prior to the calculation of the moments. Simulations were performed for illustrating the method. (author)

Fifth-order canonical geometric aberration analysis of electrostatic round lenses

CERN Document Server

Liu Zhi Xiong

2002-01-01

In this paper the fifth-order canonical geometric aberration patterns are analyzed and a numerical example is given on the basis of the analytical expressions of fifth-order aberration coefficients derived in the present work. The fifth-order spherical aberration, astigmatism and field curvature, and distortion are similar to the third-order ones and the fifth-order coma is slightly different. Besides, there are two more aberrations which do not exist in the third-order aberration: they are peanut aberration and elliptical coma in accordance with their shapes. In the numerical example, by using a cross-check of the calculated coefficients with those computed through the differential algebraic method, it has been verified that all the expressions are correct and the computational results are reliable with high precision.

Cost-effective solar furnace system using fixed geometry Non-Imaging Focusing Heliostat and secondary parabolic concentrator

Energy Technology Data Exchange (ETDEWEB)

Chong, K.K.; Lim, C.Y.; Hiew, C.W. [Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Off Jalan Genting Kelang, Setapak, Kuala Lumpur 53300 (Malaysia)

2011-05-15

A novel cost-effective solar furnace system is proposed to be consisted of a Non-Imaging Focusing Heliostat (NIFH) and a much smaller parabolic concentrator. In order to simplify the design and hence leading to the cost reduction, a fixed geometry of the NIFH heliostat is adopted in the novel solar furnace system by omitting the requirement of continuous astigmatic correction throughout the year with the use of local controllers. The performance of this novel solar furnace configuration can be optimized when the heliostat's spinning-axis is orientated in such a way that the annual variations of incident angle and therefore the annual variations of aberrant image size are the least. To verify the new configuration, a prototype solar furnace has been constructed at Universiti Tunku Abdul Rahman. (author)

Femtosecond laser enabled keratoplasty for advanced keratoconus

Directory of Open Access Journals (Sweden)

Yathish Shivanna

2013-01-01

Full Text Available Purpose : To assess the efficacy and advantages of femtosecond laser enabled keratoplasty (FLEK over conventional penetrating keratoplasty (PKP in advanced keratoconus. Materials and Methods: Detailed review of literature of published randomized controlled trials of operative techniques in PKP and FLEK. Results: Fifteen studies were identified, analyzed, and compared with our outcome. FLEK was found to have better outcome in view of better and earlier stabilization uncorrected visual acuity (UCVA, best corrected visual acuity (BCVA, and better refractive outcomes with low astigmatism as compared with conventional PKP. Wound healing also was noticed to be earlier, enabling early suture removal in FLEK. Conclusions: Studies relating to FLEK have shown better results than conventional PKP, however further studies are needed to assess the safety and intraoperative complications of the procedure.

Image processing and analysis using neural networks for optometry area

Science.gov (United States)

Netto, Antonio V.; Ferreira de Oliveira, Maria C.

2002-11-01

In this work we describe the framework of a functional system for processing and analyzing images of the human eye acquired by the Hartmann-Shack technique (HS), in order to extract information to formulate a diagnosis of eye refractive errors (astigmatism, hypermetropia and myopia). The analysis is to be carried out using an Artificial Intelligence system based on Neural Nets, Fuzzy Logic and Classifier Combination. The major goal is to establish the basis of a new technology to effectively measure ocular refractive errors that is based on methods alternative those adopted in current patented systems. Moreover, analysis of images acquired with the Hartmann-Shack technique may enable the extraction of additional information on the health of an eye under exam from the same image used to detect refraction errors.

Vision screening of abused and neglected children by the UCLA Mobile Eye Clinic.

Science.gov (United States)

Yoo, R; Logani, S; Mahat, M; Wheeler, N C; Lee, D A

1999-07-01

The purpose of our study was to present descriptive findings of ocular abnormalities in vision screening examinations of abused and neglected children. We compared the prevalence and the nature of eye diseases and refractive error between abused and neglected boys staying at the Hathaway Home, a residential facility for abused children, and boys from neighboring Boys and Girls clubs. The children in the study received vision screening examinations through the UCLA Mobile Eye Clinic following a standard format. Clinical data were analyzed by chi-square test. The children with a history of abuse demonstrated significantly higher prevalence of myopia, astigmatism, and external eye disorders. Our study suggests that children with a history of abuse may be at higher risk for visual impairment. These visual impairments may be the long-term sequelae of child abuse.

Estudo prospectivo comparativo de duas técnicas cirúrgicas de extração extra-capsular planejada de catarata com implante de lente intra-ocular: incisão limbar e incisão escleral tunelizada Prospective comparative study of two techniques of planned extracapsular cataract extraction: limbal incision and scleral tunnel incision

Directory of Open Access Journals (Sweden)

Lincoln Lemes Freitas

2001-06-01

extraction (ECCE with posterior chamber intraocular lens implantation. This study aims to compare limbal incision and scleral tunnel incision in planned ECCE. Methods: Fifty-four consecutive patients (59 eyes with follow-up of 6 months were studied prospectively. ECCE with limbal incision was performed in 30 patients (Group I, and with scleral tunnel incision in 29 patients (Group II. Corrected visual acuity, intraocular inflammation (cells and flare, surgical time, specular microscopy, induced astigmatism and pachymetry were assessed. Results: Surgical time, endothelial cells loss and induced astigmatism were statistically greater in group I than in group II. No significant differences were found between groups when comparing the corrected visual acuity, intraocular inflammation and pachymetry. Conclusions: ECCE with scleral tunnel incision technique offers advantages regarding surgical time, endothelial cells loss and induced astigmatism if compared with limbal incision technique. Surgical steps used in this technique help in transition for phacoemulsification with low cost and a safer way.

Frecuencia de ametropías Frequency of ametropias

Directory of Open Access Journals (Sweden)

Luis Curbelo Cunill

2005-06-01

Full Text Available Se realizó un estudio con una muestra aleatoria de 9 513 pacientes seleccionados (19 026 ojos que presentaban ametropías y que asistieron a consulta de cirugía refractiva en el Instituto Cubano de Oftalmología "Ramón Pando Ferrer"; donde se encontró una mayor frecuencia de éstas en el sexo femenino con predominio en las edades entre los 21 y los 30 años. El astigmatismo miópico compuesto fue la ametropía más frecuente en la muestra, con diferencias de género a favor del sexo femenino; el astigmatismo hipermetrópico simple fue la única ametropía que no mostró diferencias entre los grupos de edades. Existió una correlación lineal positiva entre la edad y la intensidad de la hipermetropía y miopía en el grupo de pacientes entre los 18 y los 39 años. Hubo predominio de las miopías y las hipermetropías ligeras y moderadas. Entre las ametropías esféricas un 36, 8 % de ojos obtuvo un rango de severidad que excedía los criterios quirúrgicos. No se encontró relación entre la magnitud del cilindro y la edad de los casos estudiados. Los astigmatismos directo, oblicuo y oblicuo directo demostraron mayor frecuencia en la muestra, donde prevaleció el ojo derecho en el tipo directo e indirecto, mientras que en el ojo izquierdo predominaron el oblicuo directo y el oblicuo inverso. La anisometropía fue poco frecuente en la muestra y alcanzó solamente el 2,1 % del total de pacientes emétropes y predominó en el grupo de 31 a 35 aA descriptive study was conducted with a randomized sample of 9 513 patients selected (19 026 eyes that presented ametropias and that received attention at the department of refractive surgery in "Ramón Pando Ferrer" Cuban Institute of Ophthalmlogy. Ametropias were more frequent among women aged 21-30. The compound myopic astigmatism was the commonest ametropia in the sample, with difference of gender in favor of females. The simple hypermetropic astigmatism was the only ametropia that did not show

Endothelial keratoplasty using donor tissue not suitable for full-thickness penetrating keratoplasty.

Science.gov (United States)

Armour, Rebecca L; Ousley, Paula J; Wall, Jennifer; Hoar, Karen; Stoeger, Chris; Terry, Mark A

2007-06-01

To evaluate the use of corneal donor tissue deemed unsuitable for full-thickness penetrating keratoplasty (PK) for use in deep lamellar endothelial keratoplasty (DLEK) and to compare postoperative results to those of DLEK surgery using donor tissue that is suitable for PK. Small-incision DLEK surgery was performed using 39 donor corneas unsuitable for PK. Thirty-five donors had anterior scars or opacities, 3 donors had pterygia within the 8-mm zone, and 1 had prior LASIK. All donor preparation was completed by manual stromal dissection. The DLEK surgical and postoperative courses were reviewed. Preoperative and 6-month postoperative results of this study group were compared with a control group consisting of the first 55 consecutive small-incision DLEK patients receiving donor corneas that had no criteria excluding them from use in PK. Four eyes in the study group and 1 eye in the control group had the confounding variables of the presence of an anterior-chamber lens or surgical vitrectomy with macular disease in the recipient eye. There was no significant difference in preoperative measurements of best spectacle-corrected visual acuity (BSCVA; P = 0.372), donor endothelial cell density (ECD; P = 0.749), or corneal topography [surface regularity index (SRI), P = 0.485; or surface asymmetry index (SAI), P = 0.154] between the 2 groups. For the patients receiving corneas deemed unacceptable for PK, at 6 months after surgery, the vision (P = 0.002) and corneal topography measurements improved significantly from before surgery (SRI, P < 0.001; SAI, P < 0.001), and there was no significant change in refractive astigmatism (P = 0.240). There was a significant difference in the vision at 6 months postoperatively between the overall study group and the control group, with the mean vision of the study group at 20/56 and the control group at 20/43 (P = 0.015). If eyes with known cystoid macular edema (CME) and vitrectomy are removed from each group, there is no significant

Análise comparativa da refração automática objetiva e refração clínica Automatic objective refraction and clinical refraction - a comparative analysis

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Ricardo Uras

2001-02-01

automated objective refraction was performed using the automatic keratorefractor TOPCON 3000. Results: 1,001 eyes of 504 patients were studied. 45.2% were male patients and the mean age was 36.6 years. There was an overall concordance between clinical refraction and the automated objective refraction in 66.7% of the patients. The concordance of a spherical value, not considering variations of -0.50 to +0.50 SD was, approximately 90%. In simple hyperopic/myopic astigmatic eyes the concordance was 27.6%, in eyes with compound hyperopic/myopic astigmatism the concordance was 97.7%. Cycloplegia did not significantly affect this concordance. There was no significant difference regarding the axis of astigmatic eyes when using both techniques. Conclusion: Automated objective refraction is an useful tool in clinical refraction but clinical data should also be considered and the final lens prescription should never be based solely on the automated examination.

Intrastromal corneal ring implants for corneal thinning disorders: an evidence-based analysis.

Science.gov (United States)

2009-01-01

progressively thins causing a cone-like bulge or forward protrusion in response to the normal pressure of the eye. Thinning occurs primarily in the stoma layers and is believed to be a breakdown in the collagen network. This bulging can lead to an irregular shape or astigmatism of the cornea and, because the anterior part of the cornea is largely responsible for the focusing of light on the retina, results in loss of visual acuity. This can make even simple daily tasks, such as driving, watching television or reading, difficult to perform. Keratoconus (KC) is the most common form of corneal thinning disorder and is a noninflammatory chronic disease process. Although the specific causes of the biomechanical alterations that occur in KC are unknown, there is a growing body of evidence to suggest that genetic factors may play an important role. KC is a rare condition (management for this condition follows a step-wise approach depending on disease severity. Contact lenses are the primary treatment of choice when there is irregular astigmatism associated with the disease. When patients can no longer tolerate contact lenses or when lenses no longer provide adequate vision, patients are referred for corneal transplant. Keratoconus is one of the leading indications for corneal transplants and has been so for the last three decades. Yet, despite high graft survival rates of up to 20 years, there are reasons to defer receiving transplants for as long as possible. Patients with keratoconus are generally young and life-long term graft survival would be an important consideration. The surgery itself involves lengthy time off work and there are potential complications from long term steroid use following surgery, as well as the risk of developing secondary cataracts, glaucoma etc. After transplant, recurrent KC is possible with need for subsequent intervention. Residual refractive errors and astigmatism can remain challenging after transplantation and high refractive surgery rates and re

Use of the Femtosecond Lasers in Ophthalmology

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Roszkowska Anna M

2018-01-01

Full Text Available Femtosecond laser (FSL is an infrared laser with a wavelength of 1053 nm. FS laser works producing photodisruption or photoionization of the optically transparent tissue such as cornea. Currently FS lasers have a wide range of applications in ophthalmic surgery. They are used above all in corneal surgery in refractive procedures and keratoplasty, and recently in cataract surgery. The use of the FSL in corneal refractive surgery includes LASIK flap creation, astigmatic keratotomy, Femtosecond Lenticule Extraction (FLEx, Small Incision Lenticule Extraction (SMILE and channels creation for implantation of the intrastromal corneal rings. As to the corneal grafting, the FS lasers are used in laser-assisted anterior and posterior lamellar keratoplasty and customized trephination in the penetrating keratoplasty. FS Laser Assisted Cataract Surgery (FLACS includes capsulorrhexis and nuclear fragmentation that enhance safety and efficacy of the procedure.

The Genetic and Environmental Factors for Keratoconus

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Ariela Gordon-Shaag

2015-01-01

Full Text Available Keratoconus (KC is the most common cornea ectatic disorder. It is characterized by a cone-shaped thin cornea leading to myopia, irregular astigmatism, and vision impairment. It affects all ethnic groups and both genders. Both environmental and genetic factors may contribute to its pathogenesis. This review is to summarize the current research development in KC epidemiology and genetic etiology. Environmental factors include but are not limited to eye rubbing, atopy, sun exposure, and geography. Genetic discoveries have been reviewed with evidence from family-based linkage analysis and fine mapping in linkage region, genome-wide association studies, and candidate genes analyses. A number of genes have been discovered at a relatively rapid pace. The detailed molecular mechanism underlying KC pathogenesis will significantly advance our understanding of KC and promote the development of potential therapies.

Ocular Features in 16 Brazilian Patients with Williams-Beuren Syndrome.

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Viana, Melissa Machado; Frasson, Maria; Galvão, Henrique; Leão, Letícia Lima; Stofanko, Martin; Gonçalves-Dornelas, Higgor; da Silva Cunha, Pricila; Burle de Aguiar, Marcos José

2015-01-01

Williams-Beuren Syndrome (WBS) is a multisystem disorder caused by the deletion of contiguous genes on chromosome 7q11.23. Ophthalmologic abnormalities and deficits in visual motor integration are important features of WBS. Here we describe our experience with Brazilian WBS patients and their ophthalmologic features. Sixteen patients with confirmed WBS went through thorough ophthalmologic examination. The most frequent ocular findings in our group of patients were stellate iris pattern (81.2%), hyperopic astigmatism (50%), hyperopia (37.5%), tortuosity of retinal vessel (37.5%) and strabismus (18.7%). This is the second report of ophthalmologic abnormalities in a group of Brazilian individuals with WBS. It is extremely valuable that specific populations are studied so that clinical diagnosis can be refined and management of patients can be driven to the most common presentations of the disease.

Use of the Femtosecond Lasers in Ophthalmology

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Roszkowska, Anna M.; Urso, Mario; Signorino, Alberto; Aragona, Pasquale

2018-01-01

Femtosecond laser (FSL) is an infrared laser with a wavelength of 1053 nm. FS laser works producing photodisruption or photoionization of the optically transparent tissue such as cornea. Currently FS lasers have a wide range of applications in ophthalmic surgery. They are used above all in corneal surgery in refractive procedures and keratoplasty, and recently in cataract surgery. The use of the FSL in corneal refractive surgery includes LASIK flap creation, astigmatic keratotomy, Femtosecond Lenticule Extraction (FLEx), Small Incision Lenticule Extraction (SMILE) and channels creation for implantation of the intrastromal corneal rings. As to the corneal grafting, the FS lasers are used in laser-assisted anterior and posterior lamellar keratoplasty and customized trephination in the penetrating keratoplasty. FS Laser Assisted Cataract Surgery (FLACS) includes capsulorrhexis and nuclear fragmentation that enhance safety and efficacy of the procedure.

Contribution to the development of a gamma radiation camera for use in scintigraphy

International Nuclear Information System (INIS)

Felix, J.

1969-10-01

This report constitutes an attempt to study systematically the properties of the detection head of a multichannel collimating grid camera. The object has been to show the disadvantages of present equipment, and to propose possible solutions for overcoming them: firstly by improving the methods used for collecting data, and the performances of the equipment doing the collecting; secondly by devising methods for processing the data so as to reduce image distortion and, first of all, the astigmatism due to the collimator. The first part deals with the study of the formation of the image by means of the collimating grid, the second with the examination of many systems which could be used for acquiring data. The last part summarizes the experiments carried out and proposes an experimental programme for the development of a prototype. (author) [fr

Three-dimensional microbubble streaming flows

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Rallabandi, Bhargav; Marin, Alvaro; Rossi, Massimiliano; Kaehler, Christian; Hilgenfeldt, Sascha

2014-11-01

Streaming due to acoustically excited bubbles has been used successfully for applications such as size-sorting, trapping and focusing of particles, as well as fluid mixing. Many of these applications involve the precise control of particle trajectories, typically achieved using cylindrical bubbles, which establish planar flows. Using astigmatic particle tracking velocimetry (APTV), we show that, while this two-dimensional picture is a useful description of the flow over short times, a systematic three-dimensional flow structure is evident over long time scales. We demonstrate that this long-time three-dimensional fluid motion can be understood through asymptotic theory, superimposing secondary axial flows (induced by boundary conditions at the device walls) onto the two-dimensional description. This leads to a general framework that describes three-dimensional flows in confined microstreaming systems, guiding the design of applications that profit from minimizing or maximizing these effects.

PRESBYOPIA OPTOMETRY METHOD BASED ON DIOPTER REGULATION AND CHARGE COUPLE DEVICE IMAGING TECHNOLOGY.

Science.gov (United States)

Zhao, Q; Wu, X X; Zhou, J; Wang, X; Liu, R F; Gao, J

2015-01-01

With the development of photoelectric technology and single-chip microcomputer technology, objective optometry, also known as automatic optometry, is becoming precise. This paper proposed a presbyopia optometry method based on diopter regulation and Charge Couple Device (CCD) imaging technology and, in the meantime, designed a light path that could measure the system. This method projects a test figure to the eye ground and then the reflected image from the eye ground is detected by CCD. The image is then automatically identified by computer and the far point and near point diopters are determined to calculate lens parameter. This is a fully automatic objective optometry method which eliminates subjective factors of the tested subject. Furthermore, it can acquire the lens parameter of presbyopia accurately and quickly and can be used to measure the lens parameter of hyperopia, myopia and astigmatism.

Vision Problems in Homeless Children.

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Smith, Natalie L; Smith, Thomas J; DeSantis, Diana; Suhocki, Marissa; Fenske, Danielle

2015-08-01

Vision problems in homeless children can decrease educational achievement and quality of life. To estimate the prevalence and specific diagnoses of vision problems in children in an urban homeless shelter. A prospective series of 107 homeless children and teenagers who underwent screening with a vision questionnaire, eye chart screening (if mature enough) and if vision problem suspected, evaluation by a pediatric ophthalmologist. Glasses and other therapeutic interventions were provided if necessary. The prevalence of vision problems in this population was 25%. Common diagnoses included astigmatism, amblyopia, anisometropia, myopia, and hyperopia. Glasses were required and provided for 24 children (22%). Vision problems in homeless children are common and frequently correctable with ophthalmic intervention. Evaluation by pediatric ophthalmologist is crucial for accurate diagnoses and treatment. Our system of screening and evaluation is feasible, efficacious, and reproducible in other homeless care situations.

Femtosecond filaments for rapid and flexible writing of Fiber-Bragg grating (Conference Presentation)

Science.gov (United States)

Ertorer, Erden; Haque, Moez; Li, Jianzhao; Herman, Peter R.

2017-03-01

Kerr-lens self-channelling of femtosecond laser light offers a novel high-aspect geometry for laser processing inside transparent materials. In glass materials, the laser filaments enable white-light continuum generation, scribing, nanochannel formation, and refractive index modification. In the present work, refractive index matching oils were applied around optical fiber to eliminate astigmatic aberration and thereby form highly symmetric and uniform filaments selectively in the cladding or core waveguide of standard single-mode optical fibre (SMF-28). Under tight focusing, long filaments exceeding 20 um length were formed with single pulses to sub-micron diameter. Arrays of 0.5 um spaced filaments are verified by formation of strong fiber Bragg gratings (FBGs). Flexible positioning of the filament arrays within the fiber core offers wide scope for coupling to cladding and radiation modes and creating new types of in-fibre optical devices.

Concave omnidirectional imaging device for cylindrical object based on catadioptric panoramic imaging

Science.gov (United States)

Wu, Xiaojun; Wu, Yumei; Wen, Peizhi

2018-03-01

To obtain information on the outer surface of a cylinder object, we propose a catadioptric panoramic imaging system based on the principle of uniform spatial resolution for vertical scenes. First, the influence of the projection-equation coefficients on the spatial resolution and astigmatism of the panoramic system are discussed, respectively. Through parameter optimization, we obtain the appropriate coefficients for the projection equation, and so the imaging quality of the entire imaging system can reach an optimum value. Finally, the system projection equation is calibrated, and an undistorted rectangular panoramic image is obtained using the cylindrical-surface projection expansion method. The proposed 360-deg panoramic-imaging device overcomes the shortcomings of existing surface panoramic-imaging methods, and it has the advantages of low cost, simple structure, high imaging quality, and small distortion, etc. The experimental results show the effectiveness of the proposed method.

Injection seeded, diode pumped regenerative ring Nd:YAG amplifier for spaceborne laser ranging technology development

Science.gov (United States)

Coyle, D. Barry; Kay, Richard B.; Degnan, John J.; Krebs, Danny J.; Seery, Bernard D.

1992-01-01

A small, all solid state, regenerative ring amplifier designed as a prototype for space application is discussed. Novel features include dual side pumping of the Nd:YAG crystal and a triangular ring cavity design which minimizes the number of optical components and losses. The amplifier is relatively small (3 ns round trip time) even though standard optical elements are employed. The ring regeneratively amplifies a 100 ps single pulse by approximately 10(exp 5) at a repetition rate of 10 to 100 Hz. The amplifier is designed to be injection seeded with a pulsed, 100 ps laser diode at 1.06 microns, but another Nd:YAG laser system supplying higher pulse energies was employed for laboratory experiment. This system is a prototype laser oscillator for the Geoscience Laser Ranging System (GLRS) platform. Results on measurements of beam quality, astigmatism, and gain are given.

Kerr-lens mode-locked Ti:Sapphire laser pumped by a single laser diode

Science.gov (United States)

Kopylov, D. A.; Esaulkov, M. N.; Kuritsyn, I. I.; Mavritskiy, A. O.; Perminov, B. E.; Konyashchenko, A. V.; Murzina, T. V.; Maydykovskiy, A. I.

2018-04-01

The performance of a Ti:sapphire laser pumped by a single 461 nm laser diode is presented for both the continuous-wave and the mode-locked regimes of operation. We introduce a simple astigmatism correction scheme for the laser diode beam consisting of two cylindrical lenses affecting the pump beam along the fast axis of the laser diode, which provides the mode-matching between the nearly square-shaped pump beam and the cavity mode. The resulting efficiency of the suggested Ti:Sapphire oscillator pumped by such a laser diode is analyzed for the Ti:sapphire crystals of 3 mm, 5 mm and 10 mm in length. We demonstrate that such a system provides the generation of ultrashort pulses up to 15 fs in duration with the repetition rate of 87 MHz, the average power being 170 mW.

Alteraciones en el endotelio corneal después de la facoemulsificación por técnica de pre chop versus extracción tunelizada esclerocorneal del cristalino Alterations of the corneal endothelium after prechop phacoemulsification versus tunnelized scleracorneal extraction of the crystalline

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Belkys Rodríguez Suárez

2012-12-01

the crystalline through the scleracorneal tunnel. Methods: a prospective and descriptive study of 100 patients (eyes seen at “Ramón Pando Ferrer" Cuban Institute of Ophthalmology from September to December 2010 was conducted. One half was operated on by phacoemulsification whereas the other underwent scleracorneal tunnelized extraction. The analyzed variables were: best uncorrected and corrected visual acuity, endothelial cellular count, hexagonality, variability coefficient, mean induced astigmatism and effective phaco time. Results: the endothelial cellular loss for the phacoemulsification group was 9.8 % and for the scleralcorneal tunnel group was 6.8 %. Postoperative average hexagonality was better in the phacoemulsification group (53 %. The preoperative average variability coefficient of 0.32 decreased to 0.28 in the phacoemulsification group. Postoperative astigmatism in the phacoemulsification group was 1.35 diopters and the effective phaco time was less than 2 minutes. Preoperative best average uncorrected visual acuity in both groups was 0.29, rising to 0.56 for the scleracorneal tunnel extraction group and to 0.8 in the phacoemulsification patients. Conclusions: the prechop phacoemulsification is a good option for cataract surgery. Endothelial alterations are similar to those of the tunnelized extraction, but the former has the advantage of improved visual acuity without glasses, because of minor induced astigmatism.

Defectos refractivos en estudiantes de la Escuela “Pedro D. Murillo” Refractive defects found in “Pedro D. Murillo” school students

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Yaimir Estévez Miranda

2011-12-01

Full Text Available Objetivo: Caracterizar los defectos refractivos en niños de edad escolar en la escuela “Pedro Murillo” en el centro “Ciudad Escolar Libertad”. Métodos: Se realizó un estudio descriptivo, transversal con la finalidad de conocer los trastornos refractivos en niños de la primaria “Pedro Murillo” en el municipio Marianao, Ciudad de la Habana, en el periodo comprendido de septiembre 2010 a febrero de 2011. El universo estuvo formado por 422 estudiantes. Fueron 844 ojos a los que se le realizó un examen oftalmológico completo. Se distribuyeron según el defecto refractivo y su grado de severidad, edad, género y la frecuencia de la ambliopía. Resultados: El astigmatismo se presentó como la ametropía más frecuente para un 63,4 % y predominó el astigmatismo miópico compuesto. De las ametropías estudiadas prevaleció su forma leve (83 %. Se encontró una frecuencia de ambliopía de 3,7 % en los escolares. Conclusión: El comportamiento de los defectos refractivos observado, estuvo dentro de las cifras esperadas en relación a los reportes internacionales referidos al tema.Objectives: To characterize the refractive defects in children of school age in “Pedro Murillo” school in educational center Ciudad Libertad. Methods: A descriptive study and cross-sectional study was carried out to knowing the refractive disorders in elementary school children in “Pedro Murillo” school Marianao municipality, La Havana, in the from September 2010 to February, 2011. The universe was formed by 422 students. A complete ophthalmologic exam was performed on 844 eyes. They were distributed according to the refractive defect and their degree of severity, age, gender and the frequency of the amblyopia. Results: The astigmatism was the most frequent ametropia for 63.4 %, the compound myopic astigmatism prevailed. Of the studied ametropias their mild form prevailed for 83 %. The frequency of amblyopia was 3.7 % in students. Conclusions: The

[Monochromatic aberration in accommodation. Dynamic wavefront analysis].

Science.gov (United States)

Fritzsch, M; Dawczynski, J; Jurkutat, S; Vollandt, R; Strobel, J

2011-06-01

Monochromatic aberrations may influence the visual acuity of the eye. They are not stable and can be affected by different factors. The subject of the following paper is the dynamic investigation of the changes in wavefront aberration with accommodation. Dynamic measurement of higher and lower order aberrations was performed with a WASCA Wavefront Analyzer (Carl-Zeiss-Meditec) and a specially constructed target device for aligning objects in far and near distances on 25 subjects aged from 15 to 27 years old. Wavefront aberrations showed some significant changes in accommodation. In addition to the characteristic sphere reaction accompanying miosis and changes in horizontal prism (Z(1) (1)) in the sense of a convergence movement of the eyeball also occurred. Furthermore defocus rose (Z(2) (0)) and astigmatism (Z(2) (-2)) changed. In higher-order aberrations a decrease in coma-like Zernike polynomials (Z(3) (-1), Z(3) (1)) was found. The most obvious change appeared in spherical aberration (Z(4) (0)) which increased and changed from positive to negative. In addition the secondary astigmatism (Z(4) (-2)) and quadrafoil (Z(4) (4)) rise also increased. The total root mean square (RMS), as well as the higher-order aberrations (RMS-HO) significantly increased in accommodation which is associated with a theoretical reduction of visual acuity. An analysis of the influence of pupil size on aberrations showed significant increases in defocus, spherical aberration, quadrafoil, RMS and RMS HO by increasing pupil diameter. By accommodation-associated miosis, the growing aberrations are partially compensated by focusing on near objects. Temporal analysis of the accommodation process with dynamic wavefront analysis revealed significant delays in pupil response and changing of prism in relation to the sphere reaction. In accommodation to near objects a discrete time ahead of third order aberrations in relation to the sphere response was found. Using dynamic wavefront measurement

Gendered Disparities in Quality of Cataract Surgery in a Marginalised Population in Pakistan: The Karachi Marine Fishing Communities Eye and General Health Survey.

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Khabir Ahmad

Full Text Available Marine fishing communities are among the most marginalised and hard-to-reach groups and have been largely neglected in health research. We examined the quality of cataract surgery and its determinants, with an emphasis on gender, in marine fishing communities in Karachi, Pakistan, using multiple indicators of performance.The Karachi Marine Fishing Communities Eye and General Health Survey was a door-to-door, cross-sectional study conducted between March 2009 and April 2010 in fishing communities living on 7 islands and in coastal areas in Keamari, Karachi, located on the Arabian Sea. A population-based sample of 638 adults, aged ≥ 50 years, was studied. A total of 145 eyes (of 97 persons had undergone cataract surgery in this sample. Cataract surgical outcomes assessed included vision (presenting and best-corrected with a reduced logMAR chart, satisfaction with surgery, astigmatism, and pupil shape. Overall, 65.5% of the operated eyes had some form of visual loss (presenting visual acuity [PVA] < 6/12. 55.2%, 29.0%, and 15.9% of these had good, borderline, and poor visual outcomes based on presenting vision; with best correction, these values were: 68.3 %, 18.6%, and 13.1%, respectively. Of 7 covariates evaluated in the multivariable generalized estimating equations (GEE analyses, gender was the only significant independent predictor of visual outcome. Women's eyes were nearly 4.38 times more likely to have suboptimal visual outcome (PVA<6/18 compared with men's eyes (adjusted odds ratio 4.38, 95% CI 1.96-9.79; P<0.001 after adjusting for the effect of household financial status. A higher proportion of women's than men's eyes had an irregular pupil (26.5% vs. 14.8% or severe/very severe astigmatism (27.5% vs. 18.2%. However, these differences did not reach statistical significance. Overall, more than one fourth (44/144 of cataract surgeries resulted in dissatisfaction. The only significant predictor of satisfaction was visual outcome (P <0

Prevalence and risk factors for refractive errors in the South Indian adult population: The Andhra Pradesh Eye disease study

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Sannapaneni Krishnaiah

2008-12-01

Full Text Available Sannapaneni Krishnaiah1,2,3, Marmamula Srinivas1,2,3, Rohit C Khanna1,2, Gullapalli N Rao1,2,31L V Prasad Eye Institute, Banjara Hills, Hyderabad, India; 2International Center for Advancement of Rural Eye Care, L V Prasad Eye Institute, Banjara Hills, Hyderabad, India; 3Vision CRC, University of New South Wales, Sydney, NSW, AustraliaAim: To report the prevalence, risk factors and associated population attributable risk percentage (PAR for refractive errors in the South Indian adult population.Methods: A population-based cross-sectional epidemiologic study was conducted in the Indian state of Andhra Pradesh. A multistage cluster, systematic, stratified random sampling method was used to obtain participants (n = 10293 for this study.Results: The age-gender-area-adjusted prevalence rates in those ≥40 years of age were determined for myopia (spherical equivalent [SE] < −0.5 D 34.6% (95% confidence interval [CI]: 33.1–36.1, high-myopia (SE < −5.0 D 4.5% (95% CI: 3.8–5.2, hyperopia (SE > +0.5 D 18.4% (95% CI: 17.1–19.7, astigmatism (cylinder < −0.5 D 37.6% (95% CI: 36–39.2, and anisometropia (SE difference between right and left eyes >0.5 D 13.0% (95% CI: 11.9–14.1. The prevalence of myopia, astigmatism, high-myopia, and anisometropia significantly increased with increasing age (all p < 0.0001. There was no gender difference in prevalence rates in any type of refractive error, though women had a significantly higher rate of hyperopia than men (p < 0.0001. Hyperopia was significantly higher among those with a higher educational level (odds ratio [OR] 2.49; 95% CI: 1.51–3.95 and significantly higher among the hypertensive group (OR 1.24; 95% CI: 1.03–1.49. The severity of lens nuclear opacity was positively associated with myopia and negatively associated with hyperopia.Conclusions: The prevalence of myopia in this adult Indian population is much higher than in similarly aged white populations. These results confirm the previously

One-site versus two-site phacotrabeculectomy: a prospective randomized study

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Moschos MM

2015-08-01

Full Text Available Marilita M Moschos,1 Irini P Chatziralli,2 Michael Tsatsos3 1First Department of Ophthalmology, University of Athens, 2Second Department of Ophthalmology, Ophthalmiatrion Athinon, Athens, Greece; 3Department of Ophthalmology, Cambridge University Hospital NHS, Cambridge, UK Purpose: The purpose of this study is to compare the efficacy and safety of one-site and two-site combined phacotrabeculectomy with foldable posterior chamber intraocular lens implantation.Methods: Thirty-four patients (41 eyes with glaucoma and cataract were randomly assigned to undergo either a one-site (22 eyes or a two-site (19 eyes combined procedure. One-site approach consisted of a standard superior phacotrabeculectomy with a limbus-based conjunctival flap, while two-site approach consisted of a clear cornea phacoemulsification and a separate superior trabeculectomy with a limbus-based conjunctival flap.Results: Mean follow-up period was 54 months (standard deviation [SD] 2.3. Mean preoperative intraocular pressure (IOP in the one-site group was 21.3 mmHg (SD 2.8 and in the two-site group was 21.8 mmHg (SD 3.0 (P>0.1. Mean postoperative IOP significantly decreased in both groups compared to the preoperative level and was 15.6 mmHg (SD 3.5 in the one-site group and 14.9 mmHg (SD 2.7 in the two-site group. Three months later, the difference between the two groups was not statistically significant (P=0.058. The one-site group required significantly more medications than the two-site group (P=0.03. Best-corrected visual acuity (BCVA improved similarly in both groups, but there was less postoperative (induced astigmatism in the two-site group in a marginal statistical level (P=0.058. Intra- and postoperative complications were comparable in the two groups.Conclusion: Both techniques yielded similar results concerning final BCVA and IOP reduction. However, the two-site group had less induced astigmatism and a better postoperative IOP control with less required

The prevalence and causes of visual impairment in seven-year-old children.

Science.gov (United States)

Ghaderi, Soraya; Hashemi, Hassan; Jafarzadehpur, Ebrahim; Yekta, Abbasali; Ostadimoghaddam, Hadi; Mirzajani, Ali; Khabazkhoob, Mehdi

2018-05-01

To report the prevalence and causes of visual impairment in seven-year-old children in Iran and its relationship with socio-economic conditions. In a cross-sectional population-based study, first-grade students in the primary schools of eight cities in the country were randomly selected from different geographic locations using multistage cluster sampling. The examinations included visual acuity measurement, ocular motility evaluation, and cycloplegic and non-cycloplegic refraction. Using the definitions of the World Health Organization (presenting visual acuity less than or equal to 6/18 in the better eye) to estimate the prevalence of vision impairment, the present study reported presenting visual impairment in seven-year-old children. Of 4,614 selected students, 4,106 students participated in the study (response rate 89 per cent), of whom 2,127 (51.8 per cent) were male. The prevalence of visual impairment according to a visual acuity of 6/18 was 0.341 per cent (95 per cent confidence interval 0.187-0.571); 1.34 per cent (95 per cent confidence interval 1.011-1.74) of children had visual impairment according to a visual acuity of 6/18 in at least one eye. Sixty-six (1.6 per cent) and 23 (0.24 per cent) children had visual impairment according to a visual acuity of 6/12 in the worse and better eye, respectively. The most common causes of visual impairment were refractive errors (81.8 per cent) and amblyopia (14.5 per cent). Among different types of refractive errors, astigmatism was the main refractive error leading to visual impairment. According to the concentration index, the distribution of visual impairment in children from low-income families was higher. This study revealed a high prevalence of visual impairment in a representative sample of seven-year-old Iranian children. Astigmatism and amblyopia were the most common causes of visual impairment. The distribution of visual impairment was higher in children from low-income families. Cost

Effect of Cycloplegia on Corneal Biometrics and Refractive State.

Science.gov (United States)

Bagheri, Abbas; Feizi, Mohadeseh; Shafii, Aliakbar; Faramarzi, Amir; Tavakoli, Mehdi; Yazdani, Shahin

2018-01-01

To determine changes in refractive state and corneal parameters after cycloplegia with cyclopentolate hydrochloride 1% using a dual Scheimpflug imaging system. In this prospective cross-sectional study patients aged 10 to 40 years who were referred for optometric evaluation enrolled and underwent autorefraction and corneal imaging with the Galilei dual Scheimpflug system before and 30 minutes after twice instillation of medication. Changes in refraction and astigmatism were investigated. Corneal biometrics including anterior and posterior corneal curvatures, total corneal power and corneal pachymetry were compared before and after cycloplegia. Two hundred and twelve eyes of 106 subjects with mean age of 28 ± 5 years including 201 myopic and 11 hyperopic eyes were evaluated. Mean spherical equivalent refractive error before cycloplegia was -3.4 ± 2.6 D. A mean hyperopic shift of 0.4 ± 0.5 D occurred after cycloplegia ( P biometrics should be considered before cataract and refractive surgeries.

Prevalence of refraction errors and color blindness in heavy vehicle drivers.

Science.gov (United States)

Erdoğan, Haydar; Ozdemir, Levent; Arslan, Seher; Cetin, Ilhan; Ozeç, Ayşe Vural; Cetinkaya, Selma; Sümer, Haldun

2011-01-01

To investigate the frequency of eye disorders in heavy vehicle drivers. A cross-sectional type study was conducted between November 2004 and September 2006 in 200 driver and 200 non-driver persons. A complete ophthalmologic examination was performed, including visual acuity, and dilated examination of the posterior segment. We used the auto refractometer for determining refractive errors. According to eye examination results, the prevalence of the refractive error was 21.5% and 31.3% in study and control groups respectively (P<0.05). The most common type of refraction error in the study group was myopic astigmatism (8.3%) while in the control group simple myopia (12.8%). Prevalence of dyschromatopsia in the rivers, control group and total group was 2.2%, 2.8% and 2.6% respectively. A considerably high number of drivers are in lack of optimal visual acuity. Refraction errors in drivers may impair the traffic security.

[Remote results of high myopia surgical correction by tunnel keratoplasty ].

Science.gov (United States)

Dushin, N V; Beliaev, V S; Gonchar, P A; Barashkov, V I; Kravchinina, V V; Frolov, M A

2000-01-01

Remote results evidence high refraction efficiency of tunnel keratoplasty, stable results being observed for up to 15 years. A total of 104 operations (58 patients) were analyzed for a period of observation of more than 10 years. The patients' ages varied from 17 to 52 years, there were 34 women and 24 men. The main advantage of interlamellar refraction meridional keratoplasty is easiness of operation. At present it is the operation of choice for dosed reduction of eye refraction aimed at correction of high myopia and astigmatism. The possibility of correcting residual myopia after keratotomy and repair of refraction abnormalities resultant from perforating keratoplasty is particularly interesting. The possibility of regulating the corrective effect in remote periods by replacing the implants also deserves attention. Hence, low traumatism, high efficiency, and stability of the refraction effect once more confirm our recommendation to use tunnel keratoplasty in clinical practice.