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Sample records for eye institute refractive

  1. Psychometric properties of the national eye institute refractive error correction quality-of-life questionnaire among Iranian patients

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    Amir H Pakpour

    2013-01-01

    Conclusions: The Iranian version of the NEI-RQL-42 is a valid and reliable instrument to assess refractive error correction quality-of-life in Iranian patients. Moreover this questionnaire can be used to evaluate the effectiveness of interventions in patients with refractive errors.

  2. Wavefront Derived Refraction and Full Eye Biometry in Pseudophakic Eyes.

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    Xinjie Mao

    Full Text Available To assess wavefront derived refraction and full eye biometry including ciliary muscle dimension and full eye axial geometry in pseudophakic eyes using spectral domain OCT equipped with a Shack-Hartmann wavefront sensor.Twenty-eight adult subjects (32 pseudophakic eyes having recently undergone cataract surgery were enrolled in this study. A custom system combining two optical coherence tomography systems with a Shack-Hartmann wavefront sensor was constructed to image and monitor changes in whole eye biometry, the ciliary muscle and ocular aberration in the pseudophakic eye. A Badal optical channel and a visual target aligning with the wavefront sensor were incorporated into the system for measuring the wavefront-derived refraction. The imaging acquisition was performed twice. The coefficients of repeatability (CoR and intraclass correlation coefficient (ICC were calculated.Images were acquired and processed successfully in all patients. No significant difference was detected between repeated measurements of ciliary muscle dimension, full-eye biometry or defocus aberration. The CoR of full-eye biometry ranged from 0.36% to 3.04% and the ICC ranged from 0.981 to 0.999. The CoR for ciliary muscle dimensions ranged from 12.2% to 41.6% and the ICC ranged from 0.767 to 0.919. The defocus aberrations of the two measurements were 0.443 ± 0.534 D and 0.447 ± 0.586 D and the ICC was 0.951.The combined system is capable of measuring full eye biometry and refraction with good repeatability. The system is suitable for future investigation of pseudoaccommodation in the pseudophakic eye.

  3. Influence of changes in an eye's optical system on refraction

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    Bartkowska, Janina

    1998-10-01

    The optical system of eye is composed of cornea, lens, anterior chamber, and vitreous body. In the standard schematic eye there are 6 refracting surfaces. The changes of the curvature radii, of the distances between them, of the refractive indices influence the ametropia, refractive power of the eye and retinal image size. The influence of these changes can be appreciated by ray tracing or by an analytical method. There are presented simplified formulae for the differentials of ametropia and refractive power of the eye with respect to the surfaces curvatures, refracting power of cornea and lens, refractive indices. The relations are valid too for bigger changes if ametropia is measured in the cornea vertex. The formulae for the differentials with respect to distances, lens translation, eye axis length are valid if ametropia is measured in the object focus of the eye.

  4. The Eye and Refractive Geography in Pericles

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    Matei-Chesnoiu Monica

    2017-06-01

    Full Text Available The paper highlights the cultural constructedness of vision in the early modern period by drawing on heteroglossic representations of the eye in early English texts, ranging from anatomy and physiology treatises to philosophy, poetry, emblems, and geometrical perspective in astronomy and land surveying. The argument is based on the association of word and image in early modern representations of space, mirrored in Ortelius’s notion of geography as the eye of history, which shows the importance of the visual element in the system of acquisition and transmission of knowledge in the Renaissance. In the particular case of Pericles, the play unfolds over a vast international geography and creates powerful visual effects. The imaginative spatial conventions of the play can be assimilated to the system of geometrical projection on which maps depended. Locations are used according to a geometric triangulation system to refract the imaginative and spatial vision. As in emblems, the locations unfolding in the play give the action meaning in the process of involved spectatorship. Moreover, in the theatre, the lone monocular beholder of mathematical linear perspective is multiplied into a choric array of spectators.

  5. Eye laterality: a comprehensive analysis in refractive surgery candidates.

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

    2013-08-01

    To explore eye laterality (higher refractive error in one eye) and its association with refractive state, spherical/astigmatic anisometropia, age and sex in refractive surgery candidates. Medical records of 12 493 consecutive refractive surgery candidates were filtered. Refractive error (subjective and cycloplegic) was measured in each subject and correlated with eye laterality. Only subjects with corrected distance visual acuity (CDVA) of >20/22 in each eye were enrolled to exclude amblyopia. Associations between eye laterality and refractive state were analysed by means of t-test, chi-squared test, Spearman's correlation and multivariate logistic regression analysis, respectively. There was no statistically significant difference in spherical equivalent between right (-3.47 ± 2.76 D) and left eyes (-3.47 ± 2.76 D, p = 0.510; Pearson's r = 0.948, p laterality for anisometropia >2.5 D in myopic (-5.64 ± 2.5 D versus -4.92 ± 2.6 D; p = 0.001) and in hyperopic (4.44 ± 1.69 D versus 3.04 ± 1.79 D; p = 0.025) subjects, (II) a tendency for left eye cylindrical laterality in myopic subjects, and (III) myopic male subjects had a higher prevalence of left eye laterality. (IV) Age did not show any significant impact on laterality. Over the full refractive spectrum, this study confirmed previously described strong interocular refractive correlation but revealed a statistically significant higher rate of right eye laterality for anisometropia >2.5 D. In general, our results support the use of data from one eye only in studies of ocular refraction. © 2013 The Authors. Acta Ophthalmologica © 2013 Acta Ophthalmologica Scandinavica Foundation.

  6. An optomechanical model eye for ophthalmological refractive studies.

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    Arianpour, Ashkan; Tremblay, Eric J; Stamenov, Igor; Ford, Joseph E; Schanzlin, David J; Lo, Yuhwa

    2013-02-01

    To create an accurate, low-cost optomechanical model eye for investigation of refractive errors in clinical and basic research studies. An optomechanical fluid-filled eye model with dimensions consistent with the human eye was designed and fabricated. Optical simulations were performed on the optomechanical eye model, and the quantified resolution and refractive errors were compared with the widely used Navarro eye model using the ray-tracing software ZEMAX (Radiant Zemax, Redmond, WA). The resolution of the physical optomechanical eye model was then quantified with a complementary metal-oxide semiconductor imager using the image resolution software SFR Plus (Imatest, Boulder, CO). Refractive, manufacturing, and assembling errors were also assessed. A refractive intraocular lens (IOL) and a diffractive IOL were added to the optomechanical eye model for tests and analyses of a 1951 U.S. Air Force target chart. Resolution and aberrations of the optomechanical eye model and the Navarro eye model were qualitatively similar in ZEMAX simulations. Experimental testing found that the optomechanical eye model reproduced properties pertinent to human eyes, including resolution better than 20/20 visual acuity and a decrease in resolution as the field of view increased in size. The IOLs were also integrated into the optomechanical eye model to image objects at distances of 15, 10, and 3 feet, and they indicated a resolution of 22.8 cycles per degree at 15 feet. A life-sized optomechanical eye model with the flexibility to be patient-specific was designed and constructed. The model had the resolution of a healthy human eye and recreated normal refractive errors. This model may be useful in the evaluation of IOLs for cataract surgery. Copyright 2013, SLACK Incorporated.

  7. Dry Eye Epidemiology in Patients before Refractive Operations

    OpenAIRE

    S. N. Sakhnov; S. V. Yanchenko; A. V. Malyshev; Y. A. Kalantaevskaya; R. A. Ismaylova; E. M. Ehieva; M. V. Grishenko; I. V. Gorbunova; O. F. Ozhug; O. A. Klokova

    2018-01-01

    Purpose. To evaluate the prevalence, clinical severity, clinical and pathogenetic variants and etiology of dry eye (DE) in patientsbefore refractive surgery. Methods. OSDI testing, lipid interferential test, TBUT, Shirmer-1, -2 tests, compression Norn test in Korbmodification, calculation of xerosis index by Bijsterveld, tear meniscus index evaluation, LIPCOF test, evaluation of epitheliopaty and microerosion by Tseng and lid viper epitheliopaty were performed in 600 myopia (with or without a...

  8. Refractive results of cataract surgery using optical biometry and Haigis formula in eyes with refractive keratotomy

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    Juan Carlos Sánchez Caballero

    2013-04-01

    Full Text Available OBJECTIVE: To analyze refractive results in postoperative cataract surgery in eyes previously submitted to keratotomy using Haigis formula and data provided by IOL Master®optical biometer. METHODS: The measurements for IOL calculation were obtained through optical biometry by partial coherence interferometry (IOL Master®- Zeiss, 5.4 and 5.5 version that provides us with the axial length, the central keratometry of 2.5mm, white-to-white diameter and anterior chamber anatomical depth. The formula chosen was Haigis. The surgical technique applied was with the scleral incision at 1.5 mm from the limbus, with scleral-corneal tunnel of 2.2 mm wide, phacoemulsification using INFINITI Ozil®- Alcon and implantation of hydrophobic acrylic aspheric intraocular lens - SN60WF®- Alcon. RESULTS: We studied 20 eyes submitted to keratotomy in the past and currently with cataract with indication for cataract surgerywith intraocular lens implantation using phacoemulsification. Postoperative spherical equivalent was plano in 40% of the eyes and lower than -1.00 in 85% of the eyes. CONCLUSION: The optical biometry by partial coherence interferometry associated with Haigis formula is a valid alternative in IOL calculation for eyes submitted to keratotomy. The refractive results are highly predictable and reproducible.

  9. Accommodation, refractive error and eye growth in chickens.

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    Schaeffel, F; Glasser, A; Howland, H C

    1988-01-01

    We raised chickens with defocusing lenses of differing powers in front of their eyes. For this purpose, small hoods made from soft, thin leather were carefully fitted to their heads. Lenses were attached to the hoods by velcro fasteners and could be easily removed for cleaning. The powers of the lenses were such that their optical effects could be compensated for by accommodation. It was verified by infrared (IR) photoretinoscopy that the chickens could keep their retinal images in focus. Wearing a lens resulted in a consistent shift of the non cycloplegic refractive state (measured without the lens) which was in the direction to compensate for the lens. We used a sensitive technique (precision = +/- 50 micron as estimated from the variability of repeated measurements) to measure the posterior nodal distance (PND) in excised eyes of birds grown with lenses. The PND, in turn, was used to compare eyes treated with different lenses. It was found that the PND was increased in eyes which were treated with negative lenses compared to those treated with positive lenses. This effect occurs independently in both eyes and it is not due to changes in corneal curvature. We discuss our result in terms of a closed-loop feedback system for the regulation of eye growth.

  10. Fellow eye treatment in excimer photo refractive keratectomy

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    Rao Srinivas

    2000-01-01

    Full Text Available Purpose: To describe symmetry of response in fellow eyes of patients undergoing photorefractive keratectomy (PRK for myopia, analyse the risk factors leading to asymmetry in response and to determine if delayed treatment of the second eye increases safety and predictability of PRK. Methods: Retrospective review of case records of 133 patients who underwent bilateral myopic PRK and had a minimum follow up of 6 months in both eyes. Results: Postoperative uncorrected visual acuity, spherical equivalent (SE refraction within ±1D of emmetropia, best-corrected visual acuity (BCVA and corneal haze were not significantly different in fellow eyes of patients undergoing PRK for myopia. Of 87 eyes in group 1 (myopia <6D, 96.6% had uncorrected visual acuity ≥6/ 12, 89.7% were within ±1D of emmetropia, none lost ≥1 line BCVA, and none had haze ≥grade 3. Similar results for 98 eyes in group II (myopia 6 to 9.9D were 75.6%, 55.1%, 2.0% and 2.0% respectively. For 81 eyes in group III (myopia ≥ 10D the results were 42.7%, 33.3%, 8.6%, and 4.9% respectively. Among 84 patients with similar preoperative myopia in both eyes, 54 (64.3% patients had a postoperative SE difference ≤ ID in fellow eyes. Risk factors for asymmetric response among fellow eyes included increasing preoperative myopia (p<0.001 and dissimilar treatment technique in the two eyes (p=0.03. Corneal haze did not increase significantly after the third postoperative month. Conclusion: This study demonstrates that considerable symmetry of response exists in fellow eyes of patients undergoing myopic PRK. Early PRK in the fellow eye of patients with < 6 D myopia is safe and allows quick visual rehabilitation of the patient. In patients with myopia ≥6D, a 3-month interval before treating the second eye may improve the safety of the procedure.

  11. Image sensor for testing refractive error of eyes

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    Li, Xiangning; Chen, Jiabi; Xu, Longyun

    2000-05-01

    It is difficult to detect ametropia and anisometropia for children. Image sensor for testing refractive error of eyes does not need the cooperation of children and can be used to do the general survey of ametropia and anisometropia for children. In our study, photographs are recorded by a CCD element in a digital form which can be directly processed by a computer. In order to process the image accurately by digital technique, formula considering the effect of extended light source and the size of lens aperture has been deduced, which is more reliable in practice. Computer simulation of the image sensing is made to verify the fineness of the results.

  12. Investigation of retinal damage during refractive eye surgery

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    Schumacher, S.; Sander, M.; Dopke, C.; Grone, A.; Ertmer, W.; Lubatschowski, H.

    2005-04-01

    Ultrashort laser pulses are increasingly used in refractive eye surgery to cut inside transparent corneal tissue. This is exploited by the fs-LASIK procedure which affords the opportunity to correct ametropia without any mechanical effects. The cutting process is caused by the optical breakdown occurring in the laser focus. During this process only a certain amount of the pulse energy is deposited into the tissue. The remaining pulse energy propagates further through the eye and interacts with the retina and the strong absorbing tissue layers behind. Therefore this investigation shall clarify if the intensity of the remaining laser pulse and the resulting temperature field can damage the retina and the surrounding tissue. Threshold values of the retinal tissue and theoretical calculations of the temperature field will be presented.

  13. Refraction and eye anterior segment parameters in schizophrenic patients

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    Tongabay Cumurcu

    2015-06-01

    Full Text Available ABSTRACT Purpose: To evaluate the difference in terms of refractive errors and anterior segment parameters between schizophrenic patients and healthy volunteers. Methods: This study compared 70 patients (48 men who were diagnosed with schizophrenia with a control group of 60 (35 men who were similar in terms of age, gender, education, and socioeconomic level. Anterior segment examination was performed using a Scheimflug system. Axial length and lens thickness (LT were measured using optic biometry. The following tests were administered to the psychiatric patient group: Brief Psychiatric Rating Scale (BPRS, Scale for the Assessment of Negative Symptoms (SANS, and Scale for the Assessment of Positive Symptoms (SAPS. Results: Mild myopia was detected in both the schizophrenic and control groups, with no statistically significant difference (p>0.005. Corneal volume (CV, anterior chamber volume (ACV, anterior chamber depth (ACD, and central corneal thickness (CCT values were lower in the schizophrenic group, and there was a statistically significant between-group difference (p=0.026, p=0.014, p=0.048, and p=0.005, respectively. LT was greater in schizophrenics, and the difference was found to be statistically significant (p=0.006. A statistically significant negative correlation was found between SAPS and cylinder values (p=0.008. The axial eye length, cylinder value, pupil diameter, mean keratometric value, and anterior chamber angle revealed no statistically significant difference between the groups (p>0.05. Conclusion: No statistically significant difference was detected in terms of refraction disorders between schizophrenics and the healthy control group, while some differences in anterior chamber parameters were present. These results demonstrate that schizophrenics may exhibit clinical and structural differences in the eye.

  14. Preliminary study of the correlation between refractive error and corneal refractive power, corneal asphericity in myopic eye

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    Qi-Chao Han

    2014-05-01

    Full Text Available AIM: To investigate the correlation between myopic refractive error and relative factors, including the corneal refractive power, posterior refractive power, axial length, corneal asphericity coefficient Q value, central cornea thickness(CCTand intraocular pressure(IOP. METHODS:According to the degree of myopia measured by subjective refraction, 138 myopia patients were divided into three subgroups: mild group(-1.00D--3.00D, moderate group(-3.25D--6.00D, high group(>6.00D. The Pentacam anterior segment tomographer(Germany, Oculus Companywas used to measure the corneal refractive power, posterior refractive power, and corneal asphericity in the right eye. IOP, CCT and axial length were measured by a non-contact tonometer and A-scan ultrasonic, respectively. The data was analyzed with a Pearson correlation analysis and one-way ANOVA. RESULTS: The myopic refractive error was negatively correlated with the axial length(r=-0.682, Pr=0.009, P=0.925. The axial length was negatively correlated with corneal refractive power(r=-0.554, Pr=0.674, Pr=-0.375, P=0.01. There was no significantly correlation between the myopic refractive error and CCT, IOP(r=-0.138, P=0.141; r=-0.121, P=0.157. CONCLUSION:The corneal refractive power plays the role of emmetropization during the development of myopia. There is clinic significance for the correlation between Q value and refractive error, IOP to guide the corneal refractive surgery.

  15. Dry Eye Epidemiology in Patients before Refractive Operations

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    S. N. Sakhnov

    2018-01-01

    Full Text Available Purpose. To evaluate the prevalence, clinical severity, clinical and pathogenetic variants and etiology of dry eye (DE in patientsbefore refractive surgery. Methods. OSDI testing, lipid interferential test, TBUT, Shirmer-1, -2 tests, compression Norn test in Korbmodification, calculation of xerosis index by Bijsterveld, tear meniscus index evaluation, LIPCOF test, evaluation of epitheliopaty and microerosion by Tseng and lid viper epitheliopaty were performed in 600 myopia (with or without astigmatism patients (234 men, 366 women; 30.1 ± 6.26 years old before refractive surgery. The structure of the DE etiological conditions, was studied both in DE patients and non-DE subjects with calculation of the Pearson xi-square test. To estimate the strength of the connection between the etiological condition and the DE, the normalized value of the Pearson coefficient (C' was used. Results. The dry eye prevalence was 38.83% (of them, 71.76% was mild, 28.83% — moderate, by Brzhesky. Clinical and pathogenetic variants of mild DE included: lipid deficiency (53.29%; lipid-mucin deficiency (26.95%; mucin deficiency (11.38%; state without signs of lipid or mucin deficiency (8.38%. In patients with moderate DE were identified: isolated aqueous deficiency (6.06%; aqueous-lipid deficiency (34.85%; aqueous-mucin deficiency (7.58%; aqueous-lipid-mucin deficiency (51.52%. Statistically significant (р < 0.01 etiological conditions for the disease in patients with diagnosed DE include: contact lenses wearing (C' = 0.349; visual display use (C' = 0.342; the use of medication affecting tear production or tear film stability (C' = 0.41; application of cosmetics (cosmetic pencil or mascara in the intercostal space of the eyelid margin — in the area of the excretory ducts of the meibomian glands (C' = 0.44; meibomian glands dysfunction (C' = 0.782; chronic allergic conjunctivitis (C' = 0.543; the presence of gynecological pathology (C' = 0.413; thyroid

  16. Topical cyclosporine a treatment in corneal refractive surgery and patients with dry eye.

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    Torricelli, Andre A M; Santhiago, Marcony R; Wilson, Steven E

    2014-08-01

    To evaluate preoperative and postoperative dry eye and the effect of cyclosporine A treatment in patients screened for corneal refractive surgery and treated with photorefractive keratectomy (PRK) or LASIK. A consecutive case series of 1,056 patients screened for corneal refractive surgery from 2007 to 2012 was retrospectively analyzed. The level of preoperative and postoperative dry eye and the responsiveness to topical cyclosporine A treatment were assessed. One eye of each patient was randomly selected. A total of 642 eyes progressed to surgery: 524 (81.6%) and 118 (18.4%) underwent LASIK and PRK, respectively. Of 81 (7.7%) diagnosed as having dry eye, 55 were deemed potential candidates and optimized for refractive surgery. Thirty-seven patients with moderate dry eye were treated with topical cyclosporine A prior to surgery (mean duration: 3.2 ± 2.1 months; range: 1 to 12 months). After cyclosporine A treatment, 28 (75.7%) eyes underwent LASIK, 4 (10.8%) eyes underwent PRK, and 5 (13.5%) eyes were not operated on due to failed treatment of dry eye. Postoperative refractive surgery-induced neurotrophic epitheliopathy (LINE in LASIK) was noted in 132 (27.3%) and 12 (11.1%) eyes that underwent LASIK and PRK, respectively. Topical cyclosporine A was prescribed in 79 LASIK-induced and 3 PRK-induced dry eyes. After 12 months or more of cyclosporine A treatment, 5 (6.1%) eyes continued to have dry eye symptoms or signs. Topical cyclosporine A treatment is effective therapy for optimizing patients for refractive surgery and treatment of new onset or worsened dry eye after surgery. Copyright 2014, SLACK Incorporated.

  17. Interconnection between several eye biomechanical and biometric parameters in children with axial and refractive mild myopia

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    T. Ye. Tsybulskaya

    2016-08-01

    Full Text Available Aim – to study the relationship of biometric and biomechanical indicators of corneoscleral capsule of the eye in children with axial and refractive mild myopia. Materials and methods. Axial myopia was diagnosed in 32 children (64 eyes, refractive myopia – 18 (36 eyes. The control group – 16 children without ophthalmic diseases (32 eyes. Eye examination: visometry, automated refractometry, biomicroscopy, ophthalmoscopy, determination of the axial length of the eyeball and corneal hysteresis. Results. Significant differences were determined in the indicators of dioptric power of the cornea: 42.2 dpt in patients with axial and 44.7 dpt with refractive myopia (p<0.05, and also difference between patients with refractive myopia and the control group, in which the diopter power of cornea was 42.6 (p<0.05. There are also significant differences in the indicators of the axial length of eyes between axial and refractive myopia – 24.5±0.64 mm and 23.1±0.43 mm (p<0.05. Significant difference with the control group in the axial length marked only in eyes with axial myopia 22.7±0.33 mm and 24.5±0.64 mm, respectively (p<0.05. Corneal hysteresis determined significantly reduced on eyes with both the axial and refractive myopia, which was significantly lower than in the indicators of emmetropic eyes of the control group 13.7 (p<0.05. Corneal hysteresis is inversely related to the axial length of the eyeball: in patients with axial myopia r -0.32, p<0.05; with refractive myopia r -0.36, p<0.05. Сorrelation between diopter power of cornea and axial length of the eyeball: r -0.53, р<0.05 in eyes with axial myopia and r -0.42, p<0.05 refractive myopia. Comparative analysis showed no significant differences between the corneal hysteresis, the axial length of the eye and the spherical component of myopia. Conclusions. In patients with axial and refractive mild myopia corneal hysteresis is reduced on average in 1.2 and 1.1 times, in comparison with

  18. Surface refractive index of the eye lens determined with an optic fiber sensor

    International Nuclear Information System (INIS)

    Pierscionek, B.K.

    1993-01-01

    The use of a fiber optic sensor for measurement of refractive index on the surface of eye lenses is described. The technique makes use of the fact that the amount of light reflected at the interface of two media (Fresnel reflectance) depends on the refractive-index difference between them. The sample is probed with a single-mode fiber, and the refractive index is calculated from the proportion of light reflected at the probe--sample interface

  19. Modeling of mouse eye and errors in ocular parameters affecting refractive state

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    Bawa, Gurinder

    Rodents eye are particularly used to study refractive error state of an eye and development of refractive eye. Genetic organization of rodents is similar to that of humans, which makes them interesting candidates to be researched upon. From rodents family mice models are encouraged over rats because of availability of genetically engineered models. Despite of extensive work that has been performed on mice and rat models, still no one is able to quantify an optical model, due to variability in the reported ocular parameters. In this Dissertation, we have extracted ocular parameters and generated schematics of eye from the raw data from School of Medicine, Detroit. In order to see how the rays would travel through an eye and the defects associated with an eye; ray tracing has been performed using ocular parameters. Finally we have systematically evaluated the contribution of various ocular parameters, such as radii of curvature of ocular surfaces, thicknesses of ocular components, and refractive indices of ocular refractive media, using variational analysis and a computational model of the rodent eye. Variational analysis revealed that variation in all the ocular parameters does affect the refractive status of the eye, but depending upon the magnitude of the impact those parameters are listed as critical or non critical. Variation in the depth of the vitreous chamber, thickness of the lens, radius of the anterior surface of the cornea, radius of the anterior surface of the lens, as well as refractive indices for the lens and vitreous, appears to have the largest impact on the refractive error and thus are categorized as critical ocular parameters. The radii of the posterior surfaces of the cornea and lens have much smaller contributions to the refractive state, while the radii of the anterior and posterior surfaces of the retina have no effect on the refractive error. These data provide the framework for further refinement of the optical models of the rat and mouse

  20. Prevalence of refractive errors in the Slovak population calculated using the Gullstrand schematic eye model.

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    Popov, I; Valašková, J; Štefaničková, J; Krásnik, V

    2017-01-01

    A substantial part of the population suffers from some kind of refractive errors. It is envisaged that their prevalence may change with the development of society. The aim of this study is to determine the prevalence of refractive errors using calculations based on the Gullstrand schematic eye model. We used the Gullstrand schematic eye model to calculate refraction retrospectively. Refraction was presented as the need for glasses correction at a vertex distance of 12 mm. The necessary data was obtained using the optical biometer Lenstar LS900. Data which could not be obtained due to the limitations of the device was substituted by theoretical data from the Gullstrand schematic eye model. Only analyses from the right eyes were presented. The data was interpreted using descriptive statistics, Pearson correlation and t-test. The statistical tests were conducted at a level of significance of 5%. Our sample included 1663 patients (665 male, 998 female) within the age range of 19 to 96 years. Average age was 70.8 ± 9.53 years. Average refraction of the eye was 2.73 ± 2.13D (males 2.49 ± 2.34, females 2.90 ± 2.76). The mean absolute error from emmetropia was 3.01 ± 1.58 (males 2.83 ± 2.95, females 3.25 ± 3.35). 89.06% of the sample was hyperopic, 6.61% was myopic and 4.33% emmetropic. We did not find any correlation between refraction and age. Females were more hyperopic than males. We did not find any statistically significant hypermetopic shift of refraction with age. According to our estimation, the calculations of refractive errors using the Gullstrand schematic eye model showed a significant hypermetropic shift of more than +2D. Our results could be used in future for comparing the prevalence of refractive errors using same methods we used.Key words: refractive errors, refraction, Gullstrand schematic eye model, population, emmetropia.

  1. Falls and Postural Control in Older Adults With Eye Refractive Errors

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    Afsun Nodehi-Moghadam

    2016-04-01

    Conclusion: Vision impairment of older adults due to refractive error is not associated with an increase in falls. Furthermore, TUG test results did not show balance disorders in these groups. Further research, such as assessment of postural control with advanced devices and considering other falling risk factors is also needed to identify the predictors of falls in older adults with eye refractive errors.

  2. 77 FR 63845 - National Eye Institute; Notice of Closed Meetings

    Science.gov (United States)

    2012-10-17

    ... personal privacy. Name of Committee: National Eye Institute Special Emphasis Panel; NEI-RFA Stem Cell... Extramural Research, National Eye Institute, National Institutes of Health, 5635 Fishers Lane, Suite 1300... Research, National Eye Institute, National Institutes of Health, 5635 Fishers Lane, Suite 1300, MSC 9300...

  3. Effect of interface reflection in pseudophakic eyes with an additional refractive intraocular lens.

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    Schrecker, Jens; Zoric, Katja; Meßner, Arthur; Eppig, Timo

    2012-09-01

    To compare the surface reflections in a pseudophakic model eye with and without a monofocal additional refractive intraocular lens (add-on IOL). Department of Ophthalmology, Rudolf-Virchow-Klinikum Glauchau, Glauchau, and Experimental Ophthalmology, Saarland University, Homburg, Germany. Experimental study. The Liou and Brennan model eye was used to determine the retinal surface reflections in a pseudophakic model eye with and without an add-on IOL. The crystalline lens of the model eye was replaced by (1) a standard posterior chamber IOL (PC IOL) with a refractive power of 22.0 diopters (D) and (2) a PC IOL and an add-on IOL with refractive powers of 19.0 D and 2.5 D, respectively. To theoretically estimate the impact of the reflected images to visual impression, the signal-to-noise ratio (SNR) was calculated under 2 conditions: without and with straylight and double reflection effects. Compared with the pseudophakic model eye without an add-on IOL, the pseudophakic model eye with an add-on IOL showed no relevant differences in the SNR under both conditions. Findings indicate that implantation of monofocal add-on IOLs will not induce relevant additional disturbing glare compared with conventional pseudophakia. Copyright © 2012 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  4. Evaluation of refractive correction for standard automated perimetry in eyes wearing multifocal contact lenses.

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    Hirasawa, Kazunori; Ito, Hikaru; Ohori, Yukari; Takano, Yui; Shoji, Nobuyuki

    2017-01-01

    To evaluate the refractive correction for standard automated perimetry (SAP) in eyes with refractive multifocal contact lenses (CL) in healthy young participants. Twenty-nine eyes of 29 participants were included. Accommodation was paralyzed in all participants with 1% cyclopentolate hydrochloride. SAP was performed using the Humphrey SITA-standard 24-2 and 10-2 protocol under three refractive conditions: monofocal CL corrected for near distance (baseline); multifocal CL corrected for distance (mCL-D); and mCL-D corrected for near vision using a spectacle lens (mCL-N). Primary outcome measures were the foveal threshold, mean deviation (MD), and pattern standard deviation (PSD). The foveal threshold of mCL-N with both the 24-2 and 10-2 protocols significantly decreased by 2.2-2.5 dB ( P correction without additional near correction is to be recommended.

  5. Refractive shifts in four selected artificial vitreous substitutes based on Gullstrand-Emsley and Liou-Brennan schematic eyes.

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    Gao, Qianying; Chen, Xiang; Ge, Jian; Liu, Yongji; Jiang, Zhaoxin; Lin, Zhi; Liu, Yaqin

    2009-07-01

    To determine and compare the refractive shifts based on Gullstrand-Emsley and Liou-Brennan schematic eyes after filling them with four selected artificial vitreous substitutes: silicone oil, heavy silicone oil, hydrogels, and encapsuled balanced salt solution. The optical constants of artificial vitreous body-filled eyes were calculated based on Gullstrand-Emsley and Liou-Brennan schematic eyes with accommodation relaxed. The theoretical refractive shifts in these two models were compared in pars plana vitrectomy (PPV), PPV plus lensectomized and PPV plus intraocular lens (IOL) eyes after four artificial vitreous tamponades. The Gullstrand-Emsley schematic eye shows refractive shifts of +8.710, -4.544, +1.136, and -0.338 D in PPV eyes; +11.044, +20.332, +16.351, and +17.413 D in PPV plus lensectomized eyes; and the need for IOL powers of +22.195, +22.366, +22.292, and +22.312 D in PPV plus IOL eyes in silicone oil, heavy silicone oil, hydrogels, and encapsuled balanced salt solution tamponade eyes, respectively. Similarly, the Liou-Brennan schematic eye induced shifts of +6.260, -3.266, +0.817, and -0.272 D in PPV eyes; +13.181, +20.654, +17.451, and +18.305 D in PPV plus lensectomized eyes; and the need IOL powers of +13.522, +23.767, +19.389, and +20.558 D in PPV plus IOL eyes, respectively. The Gullstrand-Emsley schematic eye is a convenient and accurate model for predicting refractive shifts for hydrogels and encapsuled balanced salt solution substitutes in PPV eyes. The Liou-Brennan schematic eye is recommended for silicone oil and heavy silicone oil in PPV eyes and for all four substitutes in PPV plus lensectomized eyes and PPV plus IOL eyes. In addition, the encapsuled balanced salt solution changes the refraction little in either schematic eye.

  6. Study on the transverse chromatic aberration of the individual eye model after LASIK refractive surgery

    Science.gov (United States)

    Zhang, Mei; Wang, Zhao-Qi; Wang, Yan; Zuo, Tong

    2010-10-01

    The aim of this research is to study the properties of the transverse chromatic aberration (TCA) after the LASIK refractive surgery based on the individual eye model involving the angle between visual axis and optical axis. According to the measurements of the corneal surfaces, the optical axis lengths and the wavefront aberrations, the individual eye models before and after LASIK refractive surgery are constructed for 15 eyes by using ZEMAX optic design software, while the angle between the visual axis and optical axis is calculated from the data of the anterior corneal surface. The constructed eye models are then used to investigate the variation of the TCA after the surgery. The statistical distributions of the magnitude of the foveal TCA for 15 eyes over the visible spectrum are provided. Finally, we investigate the influence of the TCA on the visual quality and compare the results with previous research. The TCA is an indispensable criterion to evaluate the performance of the refractive surgery. This research is very meaningful for the studies of not only foveal vision but also the peripheral vision.

  7. Evaluation of refractive correction for standard automated perimetry in eyes wearing multifocal contact lenses

    Directory of Open Access Journals (Sweden)

    Kazunori Hirasawa

    2017-10-01

    Full Text Available AIM: To evaluate the refractive correction for standard automated perimetry (SAP in eyes with refractive multifocal contact lenses (CL in healthy young participants. METHODS: Twenty-nine eyes of 29 participants were included. Accommodation was paralyzed in all participants with 1% cyclopentolate hydrochloride. SAP was performed using the Humphrey SITA-standard 24-2 and 10-2 protocol under three refractive conditions: monofocal CL corrected for near distance (baseline; multifocal CL corrected for distance (mCL-D; and mCL-D corrected for near vision using a spectacle lens (mCL-N. Primary outcome measures were the foveal threshold, mean deviation (MD, and pattern standard deviation (PSD. RESULTS: The foveal threshold of mCL-N with both the 24-2 and 10-2 protocols significantly decreased by 2.2-2.5 dB CONCLUSION: Despite the induced mydriasis and the optical design of the multifocal lens used in this study, our results indicated that, when the dome-shaped visual field test is performed with eyes with large pupils and wearing refractive multifocal CLs, distance correction without additional near correction is to be recommended.

  8. Light intensity modulates corneal power and refraction in the chick eye exposed to continuous light.

    Science.gov (United States)

    Cohen, Yuval; Belkin, Michael; Yehezkel, Oren; Avni, Isaac; Polat, Uri

    2008-09-01

    Continuous exposure of chicks to light was shown to result in severe hyperopia, accompanied by anterior segment changes, such as severe corneal flattening. Since rearing chicks in complete darkness results only in mild hyperopia and minor changes in corneal curvature, we hypothesized that light intensity may play a role in the development of refractive changes under continuous light illumination. To test this hypothesis, we examined the effects of rearing chicks under various continuous light intensities. More specifically, we investigated the refractive parameters of the chicks' eyes, and avoided light cycling effects on ocular development. To this end, thirty-eight chicks were reared under 24-h incandescent illumination, at three different light intensities: 10,000 lux (n=13), 500 lux (n=12), and 50 lux (n=13). Their eyes underwent repeated retinoscopy, keratometry, and ultrasound biometry, as well as caliper measurements of enucleated eyes. Both refraction and corneal refractive power were found to be correlated with light intensity. On day 90 after hatching, exposure to light intensities of 10,000, 500, and 50 lux resulted in hyperopia of +11.97+/-3.7 (mean+/-SD) +7.9+/-4.08 and +0.63+/-3.61 diopters (D), respectively. Under those intensities, corneal refractive power was 46.10+/-3.62, 49.72+/-4.16, and 56.88+/-4.92D, respectively. Axial length did not differ significantly among the groups. The vitreous chamber was significantly deeper in the high than in the low-intensity groups. Thus, during the early life of chicks exposed to continuous lighting, light intensity affects the vitreous chamber depth as well as the anterior segment parameters, most notably the cornea. The higher the intensity, the more severe was the corneal flattening observed and the hyperopia that developed, whereas continuous illumination at low intensities resulted in emmetropia. Thus, light intensity is an important factor that should be taken into account when studying refractive

  9. 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.

  10. Multivariate correlation analysis of eye cyclotorsion degree in corneal refractive surgery

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    Xiao-Guang Niu

    2015-06-01

    Full Text Available AIM: To explore the correlation between eye cyclotorsion degrees and patient's age, gender, diopter and other factors in corneal refractive surgery. METHODS: A total of 762 wavefront-guided LASIK patients with 1524 eyes were retrospectively analyzed from January 2010 to December 2013 in our hospital. Iris recognition was accomplished successfully and eye cyclotorsion degrees were recorded intraoperatively for all the patients. The correlations between eye cyclotorsion degrees and patient's age, gender, different eye, diopter and the dominant eye or not were statistically analyzed. In which correlation analysis was used to analyze the relationship between eye cyclotorsion degrees and age and diopter, while the correlations with gender, different eye and the dominant eye or not were analyzed using t-test.RESULTS: The eye cyclotorsion degrees of patients were 0 to 9.7 degrees with an average of 3.08±2.22 degrees. Amongst the average cyclotorsion of 444 men with 888 eyes were 3.05±2.26 degrees, 318 women with 636 eyes were 3.12±2.15 degrees and there were no significant differences(t=1.905, P=0.168. The average age of all the patients was 22.6±5.4y. No significant correlation was found between cyclotorsion degrees and age(r=-0.012, P=0.748. The mean spherical equivalent was -4.76±1.77 degrees, and there was no significant correlation between the eye cyclotorsion degrees and spherical equivalent(r=0.017, P=0.633. The mean cylinder was -0.60±0.64 degrees of no significant correlation with eye cyclotorsion degrees(r=-0.004, P=0.910. The cyclotorsion of dominant eyes of all the patients was 3.0±2.17 degrees, and the non-dominant eyes were 3.11±2.12 degrees. No significant differences were found(t=-0.521,P=0.603. CONCLUSION: The eye cyclotorsion degrees occurred in LASIK surgery had no correlation with age, gender, different eye, diopter and the dominant eye or not.

  11. Effect of cycloplegia on the refractive status of children: the Shandong children eye study.

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    Yuan Yuan Hu

    Full Text Available To determine the effect of 1% cyclopentolate on the refractive status of children aged 4 to 18 years.Using a random cluster sampling in a cross-sectional school-based study design, children with an age of 4-18 years were selected from kindergardens, primary schools, junior and senior high schools in a rural county and a city. Auto-refractometry was performed before and after inducing cycloplegia which was achieved by 1% cyclopentolate eye drops.Out of 6364 eligible children, data of 5999 (94.3% children were included in the statistical analysis. Mean age was 10.0±3.3 years (range: 4-18 years. Mean difference between cycloplegic and non-cycloplegic refractive error (DIFF was 0.78±0.79D (median: 0.50D; range: -1.00D to +10.75D. In univariate analysis, DIFF decreased significantly with older age (P<0.001;correlation coefficient r:-0.24, more hyperopic non-cycloplegic refractive error (P<0.001;r = 0.13 and more hyperopic cycloplegic refractive error (P<0.001;r = 0.49. In multivariate analysis, higher DIFF was associated with higher cycloplegic refractive error (P<0.001; standardized regression coefficient beta:0.50; regression coefficient B: 0.19; 95% confidence interval (CI: 0.18, 0.20, followed by lower intraocular pressure (P<0.001; beta: -0.06; B: -0.02; 95%CI: -0.03, -0.01, rural region of habitation (P = 0.001; beta: -0.04; B: -0.07; 95%CI: -0.11, -0.03, and, to a minor degree, with age (P = 0.006; beta: 0.04; B: 0.009; 95%CI: 0.003, 0.016. 66.4% of all eyes with non-cycloplegic myopia (≤-0.50D remained myopic after cycloplegia while the remaining 33.6% of eyes became emmetropic (18.0% or hyperopic (15.7% under cycloplegia. Prevalence of emmetropia decreased from 37.5% before cycloplegia to 19.8% after cycloplegia while the remaining eyes became hyperopic under cycloplegia.The error committed by using non-cycloplegic versus cycloplegic refractometry in children with mid to dark-brown iris color decreased with older age, and in parallel

  12. Relationship between refractive error and ocular biometrics in twin children: the Guangzhou Twin Eye Study.

    Science.gov (United States)

    Wang, Decai; Liu, Bin; Huang, Shengsong; Huang, Wenyong; He, Mingguang

    2014-09-01

    A cross-sectional study was conducted to explore the relationship between refractive error and ocular biometrics in children from the Guangzhou twin eye study. Twin participants aged 7-15 years were selected from Guangzhou Twin Eye Study. Ocular examinations included visual acuity measurement, ocular motility evaluation, autorefraction under cycloplegia, and anterior segment, media, and fundus examination. Axial length (AL), anterior chamber depth (ACD), and corneal curvature radius were measured using partial coherence laser interferometry. A multivariate linear regression model was used for statistical analysis. Twin children from Guangzhou city showed a decreased spherical equivalent with age, whereas both AL and ACD were increased and corneal curvature radius remained unchanged. When adjusted by age and gender, the data from 77% of twins presenting with spherical equivalent changes indicated that these were caused by predictable variables (R2 = 0.77, P biometrics. Refractive status is largely determined by axial length as the major factor.

  13. 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

  14. The refractive state of the eye in Icelandic horses with the Silver mutation.

    Science.gov (United States)

    Johansson, Maria K; Jäderkvist Fegraeus, Kim; Lindgren, Gabriella; Ekesten, Björn

    2017-06-02

    The syndrome Multiple Congenital Ocular Anomalies (MCOA) is a congenital eye disorder in horses. Both the MCOA syndrome and the Silver coat colour in horses are caused by the same missense mutation in the premelanosome protein (PMEL) gene. Horses homozygous for the Silver mutation (TT) are affected by multiple ocular defects causing visual impairment or blindness. Horses heterozygous for the Silver mutation (CT) have less severe clinical signs, usually cysts arising from the ciliary body iris or retina temporally. It is still unknown if the vision is impaired in horses heterozygous for the Silver mutation. A recent study reported that Comtois horses carrying the Silver mutation had significantly deeper anterior chambers of the eye compared to wild-type horses. This could potentially cause refractive errors. The purpose of the present study was to investigate if Icelandic horses with the Silver mutation have refractive errors compared to wild-type horses. One hundred and fifty-two Icelandic horses were included in the study, 71 CT horses and five TT horses. All horses were genotyped for the missense mutation in PMEL. Each CT and TT horse was matched by a wild-type (CC) horse of the same age ± 1 year. Skiascopy and a brief ophthalmic examination were performed in all horses. Association between refraction and age, eye, genotype and sex was tested by linear mixed-effect model analysis. TT horses with controls were not included in the statistical analyses as they were too few. The interaction between age and genotype had a significant impact on the refractive state (P = 0.0001). CT horses older than 16 years were on average more myopic than wild-type horses of the same age. No difference in the refractive state could be observed between genotypes (CT and CC) in horses younger than 16 years. TT horses were myopic (-2 D or more) in one or both eyes regardless of age. Our results indicate that an elderly Icelandic horse (older than 16 years) carrying the Silver

  15. Three-dimensional ray tracing for refractive correction of human eye ametropies

    Science.gov (United States)

    Jimenez-Hernandez, J. A.; Diaz-Gonzalez, G.; Trujillo-Romero, F.; Iturbe-Castillo, M. D.; Juarez-Salazar, R.; Santiago-Alvarado, A.

    2016-09-01

    Ametropies of the human eye, are refractive defects hampering the correct imaging on the retina. The most common ways to correct them is by means of spectacles, contact lenses, and modern methods as laser surgery. However, in any case it is very important to identify the ametropia grade for designing the optimum correction action. In the case of laser surgery, it is necessary to define a new shape of the cornea in order to obtain the wanted refractive correction. Therefore, a computational tool to calculate the focal length of the optical system of the eye versus variations on its geometrical parameters is required. Additionally, a clear and understandable visualization of the evaluation process is desirable. In this work, a model of the human eye based on geometrical optics principles is presented. Simulations of light rays coming from a punctual source at six meter from the cornea are shown. We perform a ray-tracing in three dimensions in order to visualize the focusing regions and estimate the power of the optical system. The common parameters of ametropies can be easily modified and analyzed in the simulation by an intuitive graphic user interface.

  16. Low Vision Research at the Schepens Eye Research Institute

    National Research Council Canada - National Science Library

    D'Amore, Patricia

    2003-01-01

    This research proposal, Low Vision at the Schepens Eye Research Institute, is a collaborative effort on the part of four Investigators at the Institute whose goal is to advance the studies on low vision...

  17. 78 FR 28233 - National Eye Institute; Notice of Closed Meeting

    Science.gov (United States)

    2013-05-14

    ..., National Eye Institute, Bethesda, MD 20892, (301) 451-6763. In the interest of security, NIH has instituted stringent procedures for entrance onto the NIH campus. All visitor vehicles, including taxicabs, hotel, and...

  18. Refractive error, ocular biometry, and lens opalescence in an adult population: the Los Angeles Latino Eye Study.

    Science.gov (United States)

    Shufelt, Chrisandra; Fraser-Bell, Samantha; Ying-Lai, Mei; Torres, Mina; Varma, Rohit

    2005-12-01

    To characterize age- and gender-related differences in refractive error, ocular biometry, and lens opalescence (NOP) in a population-based sample of adult Latinos. Also assessed were the determinants of age-related refractive differences. Participants in the Los Angeles Latino Eye Study (LALES), a population-based study of Latinos aged 40 years and more, underwent an ophthalmic examination, including ultrasonic measurements of axial length (AL), vitreous chamber depth (VCD), anterior chamber depth (ACD), lens thickness (LT), and noncycloplegic automated and subjective refraction. Corneal curvature/power (CP) was measured using an autorefractor. NOP was graded at the slit lamp by an ophthalmologist using the Lens Opacity Classification System II. Age- and gender-related differences were calculated. Multiple regression models were used to identify the determinants of age-related refractive differences. Of the 6357 LALES participants, 5588 phakic individuals with biometric data were included in this analysis. Older individuals had shallower ACDs, thicker lenses, more NOP, and more hyperopia compared to younger individuals (P or = 0.05). Women had significantly shorter AL, shallower ACD and VCD, than did men (P < or = 0.01). The strongest determinants of refractive error were AL (primarily VCD) and CP. NOP was a small but significant determinant of refractive error in older individuals. Age- and gender-related differences in ocular biometric, refractive error, and NOP measurements are present in adult Latinos. While the relative contribution of NOP in determining refractive error is small, it is greater in older persons compared to younger individuals.

  19. Prevalence and risk factors of undercorrected refractive errors among Singaporean Malay adults: the Singapore Malay Eye Study.

    Science.gov (United States)

    Rosman, Mohamad; Wong, Tien Y; Tay, Wan-Ting; Tong, Louis; Saw, Seang-Mei

    2009-08-01

    To describe the prevalence and the risk factors of undercorrected refractive error in an adult urban Malay population. This population-based, cross-sectional study was conducted in Singapore in 3280 Malay adults, aged 40 to 80 years. All individuals were examined at a centralized clinic and underwent standardized interviews and assessment of refractive errors and presenting and best corrected visual acuities. Distance presenting visual acuity was monocularly measured by using a logarithm of the minimum angle of resolution (logMAR) number chart at a distance of 4 m, with the participants wearing their "walk-in" optical corrections (spectacles or contact lenses), if any. Refraction was determined by subjective refraction by trained, certified study optometrists. Best corrected visual acuity was monocularly assessed and recorded in logMAR scores using the same test protocol as was used for presenting visual acuity. Undercorrected refractive error was defined as an improvement of at least 0.2 logMAR (2 lines equivalent) in the best corrected visual acuity compared with the presenting visual acuity in the better eye. The mean age of the subjects included in our study was 58 +/- 11 years, and 52% of the subjects were women. The prevalence rate of undercorrected refractive error among Singaporean Malay adults in our study (n = 3115) was 20.4% (age-standardized prevalence rate, 18.3%). More of the women had undercorrected refractive error than the men (21.8% vs. 18.8%, P = 0.04). Undercorrected refractive error was also more common in subjects older than 50 years than in subjects aged 40 to 49 years (22.6% vs. 14.3%, P Malay adults with refractive errors was higher than that of the Singaporean Chinese adults with refractive errors. Undercorrected refractive error is a significant cause of correctable visual impairment among Singaporean Malay adults, affecting one in five persons.

  20. Optical correction of refractive error for preventing and treating eye symptoms in computer users.

    Science.gov (United States)

    Heus, Pauline; Verbeek, Jos H; Tikka, Christina

    2018-04-10

    Computer users frequently complain about problems with seeing and functioning of the eyes. Asthenopia is a term generally used to describe symptoms related to (prolonged) use of the eyes like ocular fatigue, headache, pain or aching around the eyes, and burning and itchiness of the eyelids. The prevalence of asthenopia during or after work on a computer ranges from 46.3% to 68.5%. Uncorrected or under-corrected refractive error can contribute to the development of asthenopia. A refractive error is an error in the focusing of light by the eye and can lead to reduced visual acuity. There are various possibilities for optical correction of refractive errors including eyeglasses, contact lenses and refractive surgery. To examine the evidence on the effectiveness, safety and applicability of optical correction of refractive error for reducing and preventing eye symptoms in computer users. We searched the Cochrane Central Register of Controlled Trials (CENTRAL); PubMed; Embase; Web of Science; and OSH update, all to 20 December 2017. Additionally, we searched trial registries and checked references of included studies. We included randomised controlled trials (RCTs) and quasi-randomised trials of interventions evaluating optical correction for computer workers with refractive error for preventing or treating asthenopia and their effect on health related quality of life. Two authors independently assessed study eligibility and risk of bias, and extracted data. Where appropriate, we combined studies in a meta-analysis. We included eight studies with 381 participants. Three were parallel group RCTs, three were cross-over RCTs and two were quasi-randomised cross-over trials. All studies evaluated eyeglasses, there were no studies that evaluated contact lenses or surgery. Seven studies evaluated computer glasses with at least one focal area for the distance of the computer screen with or without additional focal areas in presbyopic persons. Six studies compared computer

  1. Analysis of the effects of Eye-Tracker performance on the pulse positioning errors during refractive surgery☆

    Science.gov (United States)

    Arba-Mosquera, Samuel; Aslanides, Ioannis M.

    2012-01-01

    Purpose To analyze the effects of Eye-Tracker performance on the pulse positioning errors during refractive surgery. Methods A comprehensive model, which directly considers eye movements, including saccades, vestibular, optokinetic, vergence, and miniature, as well as, eye-tracker acquisition rate, eye-tracker latency time, scanner positioning time, laser firing rate, and laser trigger delay have been developed. Results Eye-tracker acquisition rates below 100 Hz correspond to pulse positioning errors above 1.5 mm. Eye-tracker latency times to about 15 ms correspond to pulse positioning errors of up to 3.5 mm. Scanner positioning times to about 9 ms correspond to pulse positioning errors of up to 2 mm. Laser firing rates faster than eye-tracker acquisition rates basically duplicate pulse-positioning errors. Laser trigger delays to about 300 μs have minor to no impact on pulse-positioning errors. Conclusions The proposed model can be used for comparison of laser systems used for ablation processes. Due to the pseudo-random nature of eye movements, positioning errors of single pulses are much larger than observed decentrations in the clinical settings. There is no single parameter that ‘alone’ minimizes the positioning error. It is the optimal combination of the several parameters that minimizes the error. The results of this analysis are important to understand the limitations of correcting very irregular ablation patterns.

  2. Dry Eye Disease following Refractive Surgery: A 12-Month Follow-Up of SMILE versus FS-LASIK in High Myopia

    Science.gov (United States)

    Wang, Bingjie; Chu, Renyuan; Dai, Jinhui; Qu, Xiaomei; Zhou, Hao

    2015-01-01

    Purpose. To compare dry eye disease following SMILE versus FS-LASIK. Design. Prospective, nonrandomised, observational study. Patients. 90 patients undergoing refractive surgery for myopia were included. 47 eyes underwent SMILE and 43 eyes underwent FS-LASIK. Methods. Evaluation of dry eye disease was conducted preoperatively and at 1, 3, 6, and 12 months postoperatively, using the Salisbury Eye Evaluation Questionnaire (SEEQ) and TBUT. Results. TBUT reduced following SMILE at 1 and 3 months (p dry eye disease than FS-LASIK at 6 months postoperatively but demonstrates similar degrees of dry eye disease at 12 months. PMID:26649190

  3. The prevalence of refractive conditions in Puerto Rican adults attending an eye clinic system

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    Neisha M. Rodriguez

    2014-07-01

    Conclusion: Hyperopia is the most common refractive error and its prevalence and seems to increase among the aging population who visited the clinics. Further programs and studies must be developed to address the refractive errors needs of the adult Puerto Rican population.

  4. Effects of flickering light on refraction and changes in eye axial length of C57BL/6 mice.

    Science.gov (United States)

    Yu, Ying; Chen, Hui; Tuo, Jingsheng; Zhu, Yin

    2011-01-01

    To investigate the effectiveness and feasibility of inducing myopia in mice by flickering-light (FL) stimulation. Forty-five 28-day-old C57BL/6 (B6) mice were randomly assigned to three groups: control group, FL stimulation group and form deprivation (FD) group. Mice in the control group were raised under 250 lux illumination from 8:00 a.m. to 8:00 p.m. Mice in the FL group were raised under illumination with a duty cycle of 50% at a flash rate of 2 Hz from 8:00 a.m. to 8:00 p.m. for 6 weeks. Mice in the FD group were raised under the same conditions as the control group; the right eyes of the mice were covered with semitransparent hemispherical plastic shells serving as eye diffusers. The refractive state and axial length (AL) of the right eyes were measured by eccentric infrared photorefraction and A-scan ultrasonography, respectively, before treatment and after 2, 4, 6 or 8 weeks' treatment. After 6 weeks' exposure to FL, the refraction became more myopic compared with the control group as indicated by longer AL compared with the control group (p < 0.05); the FD eyes were more myopic than the FL eyes (p < 0.05). However, some mice lost their eye diffusers, and lens opacities were found. Myopia can be induced by FL in B6 mice. The myopic shift induced by FL is less than that induced by FD, but FL causes fewer side effects, and is safery and easier to manipulate. Copyright © 2011 S. Karger AG, Basel.

  5. The Perfect Eye A Novel Model for Teaching the Theory of Refraction.

    Science.gov (United States)

    Kurtz, Daniel

    1999-01-01

    The Perfect Eye model simplifies solutions to a wide variety of optometry instructional problems by facilitating student understanding of the interaction among lenses, objects, accommodation, and ametropia. The model is based on the premise that inside every eye is a perfect (emmetropic) eye, and that the physiological eye is a combination of the…

  6. 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.

  7. Implantation of refractive multifocal intraocular lens with a surface-embedded near section for cataract eyes complicated with a coexisting ocular pathology.

    Science.gov (United States)

    Ouchi, M; Kinoshita, S

    2015-05-01

    To evaluate the postoperative outcomes of cataract eyes complicated with coexisting ocular pathologies that underwent implantation of a refractive multifocal intraocular lens (MIOL) with a surface-embedded near section. LENTIS MPlus (Oculentis GmbH) refractive MIOLs were implanted in 15 eyes with ocular pathologies other than cataract (ie, six high-myopia eyes with an axial length longer than 28 mm, two fundus albipunctatus eyes, two branch retinal-vein occlusion eyes, four glaucoma eyes (one with high myopia), and two keratoconus eyes). Uncorrected or corrected distance and near visual acuity (VA) (UDVA, UNVA, CDVA, and CNVA), contrast sensitivity, and defocus curve were measured at 1 day and 6 months postoperatively, and each patient completed a 6-month postoperative questionnaire regarding vision quality and eyeglass use. Thirteen eyes (87%) registered 0 or better in CDVA and 12 eyes (73%) registered better than 0 in CNVA. Contrast sensitivity in the eyes of all patients was comparable to that of normal healthy subjects. No patient required eyeglasses for distance vision, but three patients (20%) required them for near vision. No patient reported poor or very poor vision quality. With careful case selection, sectorial refractive MIOL implantation is effective for treating cataract eyes complicated with ocular pathologies.

  8. Visual and refractive outcomes of LASIK with the SCHWIND ESIRIS and WaveLight ALLEGRETTO WAVE Eye-q excimer lasers: a prospective, contralateral study.

    Science.gov (United States)

    Mearza, Ali A; Muhtaseb, Mohammed; Aslanides, Ioannis M

    2008-11-01

    To compare the safety, efficacy, and predictability of LASIK with the SCHWIND ESIRIS and WaveLight ALLEGRETTO WAVE Eye-Q excimer laser platforms. This prospective study comprised 44 eyes of 22 consecutive patients who were treated with LASIK using the Moria M2 microkeratome. One eye was treated with the SCHWIND ESIRIS laser and the fellow eye treated with the WaveLight ALLEGRETTO WAVE Eye-Q laser. All eyes operated with the SCHWIND ESIRIS were treated with standard aspheric ablation, whereas the eyes operated with the WaveLight ALLEGRETTO WAVE Eye-Q received treatment with three different ablation types according to the common practice at our clinic. Outcome measures were uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest refraction, and proximity to target refraction at 6-month follow-up. At 6 months postoperative, mean decimal UCVA was 0.96+/-0.22 (range: 0.3 to 1.2) for ESIRIS eyes and 0.98+/-0.17 (range: 0.6 to 1.2) for ALLEGRETTO eyes (P=.57). Mean postoperative spherical equivalent refraction was -0.02+/-0.28 diopters (D) (range: -0.75 to +0.75 D) for ESIRIS eyes and 0.11+/-0.91 D (range: -1.00 to +3.88 D) for ALLEGRETTO eyes (P=.49). Of the ESIRIS eyes, 20/22 (91%) were within +/-1.00 D of target refraction and 20/22 (91%) were within +/-0.50 D of target refraction. Of the ALLEGRETTO eyes, 20/22 (91%) and 19/22 (86%) were within +/-1.00 D and +/-0.50 D, respectively, of target refraction. No patient lost > or =2 lines of BSCVA in either group. No differences were seen in safety and efficacy outcome parameters between the SCHWIND ESIRIS and WaveLight ALLEGRETTO WAVE Eye-Q excimer lasers when used according to a previously established treatment algorithm at our clinic in the treatment of refractive error.

  9. Simulation of the Effect of Different Presbyopia-Correcting Intraocular Lenses With Eyes With Previous Laser Refractive Surgery.

    Science.gov (United States)

    Camps, Vicente J; Miret, Juan J; García, Celia; Tolosa, Angel; Piñero, David P

    2018-04-01

    To simulate the optical performance of three presbyopia-correcting intraocular lenses (IOLs) implanted in eyes with previous laser refractive surgery. A simulation of the through-focus modulation transfer function (MTF) was performed for three presbyopia-correcting IOLs (Mplus, Oculentis GmbH, Berlin, Germany; Symfony, Johnson & Johnson Vision, Santa Ana, CA; and Mini Well, SIFI S.p.A., Lavinaio, Italy) in one eye with previous myopic LASIK and another with hyperopic LASIK. Real topographic data and the wavefront aberration profile of each IOL obtained with a Hartmann-Shack sensor were used. In the eye with myopic LASIK, all IOLs lost optical quality at near and intermediate distances for 4- and 4.7-mm pupil size. For 3-mm pupil size, the Mini Well IOL showed the best intermediate and near MTF and maintained the far focus independently of the pupil. In the eye with hyperopic LASIK, the Mini Well IOL showed an intermediate, distance, and -4.00-diopter (D) foci for all pupils. The Symfony IOL showed a depth of focus at far and intermediate distance for 3-mm and a focus at -2.50 D in the rest. The Mplus showed a focus of -4.50 and -3.00 D for the 3- and 4-mm pupil, respectively. The Mini Well and Symfony IOLs seem to work better than the Mplus IOL in eyes with previous myopic LASIK. With previous hyperopic LASIK, the Mini Well IOL seems to be able to provide acceptable near, intermediate, and far foci for all pupil sizes. These findings should be confirmed in future clinical studies. [J Refract Surg. 2018;34(4):222-227.]. Copyright 2018, SLACK Incorporated.

  10. Eye Wear: MedlinePlus Health Topic

    Science.gov (United States)

    ... When You Exercise (National Institute on Aging) - PDF Topic Image MedlinePlus Email Updates Get Eye Wear updates by email What's this? GO Related Health Topics Refractive Errors National Institutes of Health The primary ...

  11. Eye Care Professionals' Perspectives on Eye Donation and an Eye Donation Registry for Research: A Single-Institution, Cross-Sectional Study.

    Science.gov (United States)

    Williams, Andrew M; Allingham, R Rand; Stamer, W Daniel; Muir, Kelly W

    2016-06-01

    A centralized eye donation registry for research could help to bridge the gap between patients interested in donating their eyes to science and scientists who conduct research on human eye tissue. Previous research has demonstrated patient and family support for such a registry. In this study, we assessed the views that eye care professionals have toward an eye donation registry for research. Surveys were distributed to all 46 clinical faculty members of the Duke University Eye Center. In addition to collecting demographic information, the surveys assessed clinicians' experience with discussing eye donation with patients, described the proposed eye donation registry for research and asked how the registry would affect the clinicians' practice. A total of 21 eye care professionals returned the survey. Thirty-three percent reported discussing eye donation with patients, and 43% reported that a patient has asked about donating their eyes for research on their disease. Eighty-six percent of eye care professionals reported that a centralized registry would improve the way they work with patients who express a desire to donate their eyes for research. The majority of eye care professionals at our academic institution indicated that an eye donation registry for research would improve how they work with patients who are interested in donating their eyes for research on their disease. Future research should examine how best to communicate this registry to ophthalmic patients.

  12. Scanning mid-IR laser apparatus with eye tracking for refractive surgery

    Science.gov (United States)

    Telfair, William B.; Yoder, Paul R., Jr.; Bekker, Carsten; Hoffman, Hanna J.; Jensen, Eric F.

    1999-06-01

    A robust, real-time, dynamic eye tracker has been integrated with the short pulse mid-infrared laser scanning delivery system previously described. This system employs a Q- switched Nd:YAG laser pumped optical parametric oscillator operating at 2.94 micrometers. Previous ablation studies on human cadaver eyes and in-vivo cat eyes demonstrated very smooth ablations with extremely low damage levels similar to results with an excimer. A 4-month healing study with cats indicated no adverse healing effects. In order to treat human eyes, the tracker is required because the eyes move during the procedure due to both voluntary and involuntary motions such as breathing, heartbeat, drift, loss of fixation, saccades and microsaccades. Eye tracking techniques from the literature were compared. A limbus tracking system was best for this application. Temporal and spectral filtering techniques were implemented to reduce tracking errors, reject stray light, and increase signal to noise ratio. The expanded-capability system (IRVision AccuScan 2000 Laser System) has been tested in the lab on simulated eye targets, glass eyes, cadaver eyes, and live human subjects. Circular targets ranging from 10-mm to 14-mm diameter were successfully tracked. The tracker performed beyond expectations while the system performed myopic photorefractive keratectomy procedures on several legally blind human subjects.

  13. A Longitudinal Study on the Effects of Laser Refractive Eye Surgery in Military Aircrew

    National Research Council Canada - National Science Library

    Hinton, Patricia; Niall, Keith K; Wainberg, Dan; Bateman, Bill; Courchesne, Cyd; Gray, Gary; Quick, Gayle; Thatcher, Bob

    2005-01-01

    .... Postoperative low contrast acuity has improved with newer laser techniques but there was still concern that vision after laser eye surgery would be not good enough for military aircrew demands...

  14. Knowledge, Attitude, and Practice of Dry Eye Treatment by Institutional Chinese Physicians in Singapore

    OpenAIRE

    Lan, Wanwen; Lee, Sze Yee; Lee, Man Xin; Tong, Louis

    2012-01-01

    Dry eye is a common health problem worldwide, causing significant discomfort and inconvenience to sufferers. The conventional treatment of dry eye via topical administration of eye drops is deemed palliative and unsatisfactory to many. Traditional Chinese medicine (TCM) has shown some promise in dry eye treatment; however, the extent of its use and acceptance is uncertain. We evaluated the knowledge, attitude, and practice of institutional TCM practitioners in the treatment of dry eye in Sing...

  15. Accommodation: The role of the external muscles of the eye: A consideration of refractive errors in relation to extraocular malfunction.

    Science.gov (United States)

    Hargrave, B K

    2014-11-01

    Speculation as to optical malfunction has led to dissatisfaction with the theory that the lens is the sole agent in accommodation and to the suggestion that other parts of the eye are also conjointly involved. Around half-a-century ago, Robert Brooks Simpkins suggested that the mechanical features of the human eye were precisely such as to allow for a lengthening of the globe when the eye accommodated. Simpkins was not an optical man but his theory is both imaginative and comprehensive and deserves consideration. It is submitted here that accommodation is in fact a twofold process, and that although involving the lens, is achieved primarily by means of a give - and - take interplay between adducting and abducting external muscles, whereby an elongation of the eyeball is brought about by a stretching of the delicate elastic fibres immediately behind the cornea. The three muscles responsible for convergence (superior, internal and inferior recti) all pull from in front backwards, while of the three abductors (external rectus and the two obliques) the obliques pull from behind forwards, allowing for an easy elongation as the eye turns inwards and a return to its original length as the abducting muscles regain their former tension, returning the eye to distance vision. In refractive errors, the altered length of the eyeball disturbs the harmonious give - and - take relationship between adductors and abductors. Such stresses are likely to be perpetuated and the error exacerbated. Speculation is not directed towards a search for a possible cause of the muscular imbalance, since none is suspected. Muscles not used rapidly lose tone, as evidenced after removal of a limb from plaster. Early attention to the need for restorative exercise is essential and results usually impressive. If flexibility of the external muscles of the eyes is essential for continuing good sight, presbyopia can be avoided and with it the supposed necessity of glasses in middle life. Early attention

  16. Refractive error, visual acuity and causes of vision loss in children in Shandong, China. The Shandong Children Eye Study.

    Directory of Open Access Journals (Sweden)

    Jian Feng Wu

    Full Text Available PURPOSE: To examine the prevalence of refractive errors and prevalence and causes of vision loss among preschool and school children in East China. METHODS: Using a random cluster sampling in a cross-sectional school-based study design, children with an age of 4-18 years were selected from kindergartens, primary schools, and junior and senior high schools in the rural Guanxian County and the city of Weihai. All children underwent a complete ocular examination including measurement of uncorrected (UCVA and best corrected visual acuity (BCVA and auto-refractometry under cycloplegia. Myopia was defined as refractive error of ≤-0.5 diopters (D, high myopia as ≤ -6.0D, and amblyopia as BCVA ≤ 20/32 without any obvious reason for vision reduction and with strabismus or refractive errors as potential reasons. RESULTS: Out of 6364 eligible children, 6026 (94.7% children participated. Prevalence of myopia (overall: 36.9 ± 0.6%;95% confidence interval (CI:36.0,38.0 increased (P<0.001 from 1.7 ± 1.2% (95%CI:0.0,4.0 in the 4-years olds to 84.6 ± 3.2% (95%CI:78.0,91.0 in 17-years olds. Myopia was associated with older age (OR:1.56;95%CI:1.52,1.60;P<0.001, female gender (OR:1.22;95%CI:1.08,1.39;P = 0.002 and urban region (OR:2.88;95%CI:2.53,3.29;P<0.001. Prevalence of high myopia (2.0 ± 0.2% increased from 0.7 ± 0.3% (95%CI:0.1,1.3 in 10-years olds to 13.9 ± 3.0 (95%CI:7.8,19.9 in 17-years olds. It was associated with older age (OR:1.50;95%CI:1.41,1.60;P<0.001 and urban region (OR:3.11;95%CI:2.08,4.66;P<0.001. Astigmatism (≥ 0.75D (36.3 ± 0.6%;95%CI:35.0,38.0 was associated with older age (P<0.001;OR:1.06;95%CI:1.04,1.09, more myopic refractive error (P<0.001;OR:0.94;95%CI:0.91,0.97 and urban region (P<0.001;OR:1.47;95%CI:1.31,1.64. BCVA was ≤ 20/40 in the better eye in 19 (0.32% children. UCVA ≤ 20/40 in at least one eye was found in 2046 (34.05% children, with undercorrected refractive error as cause in 1975 (32.9% children. Amblyopia

  17. Refractive variation under accommodative demand: curvital and scaled torsional variances and covariance across the meridians of the eye.

    Science.gov (United States)

    van Gool, R D; Harris, W F

    1997-06-01

    Autorefractor measurements were taken on the right eye of 10 students with an external target at vergences -1.00 and -3.00 D. The refractive errors in the form of sphere, cylinder, and axis were converted to vectors h and variance-covariance matrices calculated for different reference meridians. Scatter plots are drawn in symmetric dioptric power space. The profiles of curvital and scaled torsional variances, the scaled torsional fraction, and the scaled torsional-curvital correlation are shown using a polar representation. This form of representation provides a meridional pattern of variation under accommodative demand. The profile for scaled torsional variance is characteristically in the form of a pair of rabbit ears. At both target vergences curvital variance is larger than scaled torsional variance in all the meridians of the eye: the relative magnitudes are quantified by the scaled torsional fraction. An increase in accommodative demand generally results in an increase in variance. The rabbit ears usually become larger but less well divided. The correlation between curvital and torsional powers is usually positive in the first quadrant and negative in the second quadrant. Typical, atypical, and mean typical responses are discussed.

  18. Visual and Refractive Outcomes in Manual versus Femtosecond Laser-Assisted Cataract Surgery: A Single-Center Retrospective Cohort Analysis of 1838 Eyes.

    Science.gov (United States)

    Berk, Thomas A; Schlenker, Matthew B; Campos-Möller, Xavier; Pereira, Austin M; Ahmed, Iqbal Ike K

    2018-03-06

    Femtosecond laser-assisted cataract surgery (FLACS) has emerged as an alternative to manual cataract surgery (MCS) for corneal incision and capsulorhexis creation, as well as nuclear fragmentation. This study compares postoperative refractive and visual outcomes in eyes receiving MCS or FLACS. Single-center, comparative, retrospective cohort analysis. Consecutive eyes receiving FLACS and MCS from July 1, 2012, to July 31, 2015, at a single tertiary care center. Demographic data, ocular history, preoperative measurements and biometry, and postoperative surgical results were retrospectively obtained and statistically analyzed using a generalized linear mixed model adjusting for differences in baseline characteristics and within-patient correlation. A 2-tailed P value <0.05 was considered statistically significant throughout the study. Percentage of eyes achieving absolute error (AE) ≤0.5 diopters (D). Secondary outcomes included percentage of eyes with AE ≤0.25 D and ≤1.0 D, and percentage of distance-targeted eyes achieving uncorrected distance visual acuity (UDVA) of 20/20 or better, 20/25 or better, and 20/30 or better. A total of 883 eyes received MCS and 955 received FLACS among 1089 patients. Some 82.6% of FLACS eyes and 78.8% of MCS eyes had ≤0.5 D of AE at 3 weeks, representing an adjusted odds ratio (OR) of 1.28 (95% confidence interval [CI], 0.98-1.66) of FLACS relative to MCS being within target. Some 97.1% of FLACS and 97.2% of MCS eyes had ≤1.0 D of AE (OR, 0.96; 95% CI, 0.57-1.60) and 49.3% of FLACS and 46.3% of MCS eyes, ≤0.25 D of AE (OR, 1.13; 95% CI, 0.91-1.39). Factors predictive of a favorable refractive outcome included axial length between 22 and 24.8 mm, receiving a toric intraocular lens, less preoperative cylinder, and greater preoperative average keratometry. There was no significant difference in the percentage of patients targeted for distance who achieved UDVA of 20/20 or better (P = 0.30), 20/25 or better (P = 0.06), or 20

  19. Meta analysis of therapeutic effects of domestic deproteinized calf blood extract eye gel on corneal epithelial repair after laser refractive surgery

    Directory of Open Access Journals (Sweden)

    Jian Zhang

    2018-01-01

    Full Text Available AIM: To systemically evaluate the clinical efficacy and safety of domestic deproteinized calf blood extract eye gel for corneal epithelial repair after laser refractive surgery. METHODS:We performed a comprehensive search via Pubmed, Embase, Cochrane Library, VIP Chinese Science and Technology Journal Database, CNKI and Wan Fang Chinese periodical Database for the randomized controlled trials(RCTsat home and abroad about effects of the domestic deproteinized calf blood extract eye gel for corneal epithelial repair after laser corneal refractive surgery with retrieval time from January 2007 to December 2016. According to the inclusion and exclusion criteria, 2 medical researchers independently screened documents, extracted data and evaluated the quality. Review Manager 5.3 software was used for Meta analysis. RESULTS: Seven RCTs involving 1 042 eyes, including 523 eyes in the treatment group and 519 eyes in the control group, were selected for this Meta-analysis. The results showed that the clinical efficacy in the treatment group was better than that in the control group(OR=1.81, 95%CI: 1.39~2.35; PWMD=-0.33, 95%CI: -0.45 to -0.21; PWMD=-1.26, 95%CI: -1.56 to -0.97; PCONCLUSION: The domestic deproteinized calf blood extract eye gel can relieve the patients' symptoms after laser refractive surgery, improve the corneal epithelial recovery and the efficiency of treatment. Due to the limited quality and quantity of the studies these conclusions should be further validated by more well-designed randomized double blind controlled trials.

  20. Knowledge, Attitude, and Practice of Dry Eye Treatment by Institutional Chinese Physicians in Singapore

    Science.gov (United States)

    Lan, Wanwen; Lee, Sze Yee; Lee, Man Xin; Tong, Louis

    2012-01-01

    Dry eye is a common health problem worldwide, causing significant discomfort and inconvenience to sufferers. The conventional treatment of dry eye via topical administration of eye drops is deemed palliative and unsatisfactory to many. Traditional Chinese medicine (TCM) has shown some promise in dry eye treatment; however, the extent of its use and acceptance is uncertain. We evaluated the knowledge, attitude, and practice of institutional TCM practitioners in the treatment of dry eye in Singapore. A questionnaire was generated to address the study aims and sent to TCM practitioners listed in the Singapore TCM practitioners' board database. About three quarters of respondents thought that dry eye was not severe enough to be a public health burden but most thought that TCM was effective in the treatment of dry eye. Acupuncture and herbal medicine were most commonly used TCM modalities in dry eye treatment, and a single TCM treatment session would be charged S$20–50 by the practitioner. The majority of surveyed institutional TCM practitioners in Singapore believe that TCM is relevant in dry eye treatment. Public awareness should be raised regarding the availability of TCM as alternative medicine for dry eye. PMID:23213306

  1. Dry Eye

    Science.gov (United States)

    ... Eye » Facts About Dry Eye Listen Facts About Dry Eye Fact Sheet Blurb The National Eye Institute (NEI) ... and their families search for general information about dry eye. An eye care professional who has examined the ...

  2. Dry Eye Disease following Refractive Surgery: A 12-Month Follow-Up of SMILE versus FS-LASIK in High Myopia

    Directory of Open Access Journals (Sweden)

    Bingjie Wang

    2015-01-01

    Full Text Available Purpose. To compare dry eye disease following SMILE versus FS-LASIK. Design. Prospective, nonrandomised, observational study. Patients. 90 patients undergoing refractive surgery for myopia were included. 47 eyes underwent SMILE and 43 eyes underwent FS-LASIK. Methods. Evaluation of dry eye disease was conducted preoperatively and at 1, 3, 6, and 12 months postoperatively, using the Salisbury Eye Evaluation Questionnaire (SEEQ and TBUT. Results. TBUT reduced following SMILE at 1 and 3 months (p<0.001 and at 1, 3, and 6 months following FS-LASIK (p<0.001. TBUT was greater following SMILE than FS-LASIK at 3, 6, and 12 months (p<0.001, p<0.001, and p=0.009, resp.. SEEQ scores increased (greater symptoms following SMILE at 1 month (p<0.001 and 3 months (p=0.003 and at 1, 3, and 6 months following FS-LASIK (p<0.001. SMILE produced lower SEEQ scores (fewer symptoms than FS-LASIK at 1, 3, and 6 months (p<0.001. Conclusion. SMILE produces less dry eye disease than FS-LASIK at 6 months postoperatively but demonstrates similar degrees of dry eye disease at 12 months.

  3. 76 FR 24499 - National Eye Institute; Notice of Closed Meeting

    Science.gov (United States)

    2011-05-02

    ... the public as indicated below, with attendance limited to space available. Individuals who plan to... disclose confidential trade secrets or commercial property such as patentable material, and personal... discussions concerning Institute programs. Place: National Institutes of Health, 5635 Fishers Lane, Terrace...

  4. 77 FR 31032 - National Eye Institute; Notice of Closed Meeting

    Science.gov (United States)

    2012-05-24

    ... the public as indicated below, with attendance limited to space available. Individuals who plan to... disclose confidential trade secrets or commercial property such as patentable material, and personal... concerning Institute programs. Place: National Institutes of Health, 5635 Fishers Lane, Terrace Level...

  5. 77 FR 73037 - National Eye Institute; Notice of Closed Meeting

    Science.gov (United States)

    2012-12-07

    ... the public as indicated below, with attendance limited to space available. Individuals who plan to... disclose confidential trade secrets or commercial property such as patentable material, and personal... discussions concerning Institute programs. Place: National Institutes of Health, 5635 Fishers Lane, Terrace...

  6. 77 FR 55852 - National Eye Institute; Notice of Closed Meeting

    Science.gov (United States)

    2012-09-11

    ... the public as indicated below, with attendance limited to space available. Individuals who plan to... disclose confidential trade secrets or commercial property such as patentable material, and personal... concerning Institute programs. Place: National Institutes of Health, 5635 Fishers Lane, Terrace Level...

  7. 75 FR 76474 - National Eye Institute; Notice of Closed Meeting

    Science.gov (United States)

    2010-12-08

    ... the public as indicated below, with attendance limited to space available. Individuals who plan to... disclose confidential trade secrets or commercial property such as patentable material, and personal... concerning Institute programs. Place: National Institutes of Health, 5635 Fishers Lane, Terrace Level...

  8. 76 FR 53687 - National Eye Institute Notice of Closed Meeting

    Science.gov (United States)

    2011-08-29

    ... the public as indicated below, with attendance limited to space available. Individuals who plan to... disclose confidential trade secrets or commercial property such as patentable material, and personal... concerning Institute programs. Place: National Institutes of Health, 5635 Fishers Lane, Terrace Level...

  9. 78 FR 25458 - National Eye Institute; Notice of Meeting

    Science.gov (United States)

    2013-05-01

    ... public as indicated below, with attendance limited to space available. Individuals who plan to attend and... secrets or commercial property such as patentable material, and personal information concerning... be presentations by the staff of the Institute and discussions concerning Institute programs. Place...

  10. 78 FR 73867 - National Eye Institute; Notice of Meeting

    Science.gov (United States)

    2013-12-09

    ... open to the public as indicated below, with attendance limited to space available. Individuals who plan... discussions could disclose confidential trade secrets or commercial property such as patentable material, and... concerning Institute programs. Place: National Institutes of Health, Rockledge II Building, Room 9100/9104...

  11. 77 FR 2076 - National Eye Institute; Notice of Closed Meeting

    Science.gov (United States)

    2012-01-13

    ... the public as indicated below, with attendance limited to space available. Individuals who plan to... disclose confidential trade secrets or commercial property such as patentable material, and personal... concerning Institute programs. Place: National Institutes of Health, 5635 Fishers Lane, Terrace Level...

  12. Laser Eye Surgery: MedlinePlus Health Topic

    Science.gov (United States)

    ... corneal surgery - discharge (Medical Encyclopedia) Also in Spanish Topic Image MedlinePlus Email Updates Get Laser Eye Surgery ... surgery - what to ask your doctor Related Health Topics Refractive Errors National Institutes of Health The primary ...

  13. 77 FR 8266 - National Eye Institute; Notice of Closed Meeting

    Science.gov (United States)

    2012-02-14

    ... interest of security, NIH has instituted stringent procedures for entrance onto the NIH campus. All visitor vehicles, including taxicabs, hotel, and airport shuttles will be inspected before being allowed on campus...

  14. 76 FR 2914 - National Eye Institute; Notice of Closed Meeting

    Science.gov (United States)

    2011-01-18

    ... interest of security, NIH has instituted stringent procedures for entrance onto the NIH campus. All visitor vehicles, including taxicabs, hotel, and airport shuttles will be inspected before being allowed on campus...

  15. 75 FR 57968 - National Eye Institute; Notice of Closed Meeting

    Science.gov (United States)

    2010-09-23

    ... interest of security, NIH has instituted stringent procedures for entrance onto the NIH campus. All visitor vehicles, including taxicabs, hotel, and airport shuttles will be inspected before being allowed on campus...

  16. 77 FR 55852 - National Eye Institute; Notice of Closed Meeting

    Science.gov (United States)

    2012-09-11

    ... interest of security, NIH has instituted stringent procedures for entrance onto the NIH campus. All visitor vehicles, including taxicabs, hotel, and airport shuttles will be inspected before being allowed on campus...

  17. 75 FR 54642 - National Eye Institute; Notice of Meeting

    Science.gov (United States)

    2010-09-08

    ... public as indicated below, with attendance limited to space available. Individuals who plan to attend and... disclose confidential trade secrets or commercial property such as patentable material, and personal... concerning Institute programs. Place: Melrose Hotel, 2430 Pennsylvania Ave., NW., Washington, DC 20037...

  18. Questionnaires for Measuring Refractive Surgery Outcomes.

    Science.gov (United States)

    Kandel, Himal; Khadka, Jyoti; Lundström, Mats; Goggin, Michael; Pesudovs, Konrad

    2017-06-01

    To identify the questionnaires used to assess refractive surgery outcomes, assess the available questionnaires in regard to their psychometric properties, validity, and reliability, and evaluate the performance of the available questionnaires in measuring refractive surgery outcomes. An extensive literature search was done on PubMed, MEDLINE, Scopus, CINAHL, Cochrane, and Web of Science databases to identify articles that described or used at least one questionnaire to assess refractive surgery outcomes. The information on content quality, validity, reliability, responsiveness, and psychometric properties was extracted and analyzed based on an extensive set of quality criteria. Eighty-one articles describing 27 questionnaires (12 refractive error-specific, including 4 refractive surgery-specific, 7 vision-but-non-refractive, and 8 generic) were included in the review. Most articles (56, 69.1%) described refractive error-specific questionnaires. The Quality of Life Impact of Refractive Correction (QIRC), the Quality of Vision (QoV), and the Near Activity Visual Questionnaire (NAVQ) were originally constructed using Rasch analysis; others were developed using the Classical Test Theory. The National Eye Institute Refractive Quality of Life questionnaire was the most frequently used questionnaire, but it does not provide a valid measurement. The QoV, QIRC, and NAVQ are the three best existing questionnaires to assess visual symptoms, quality of life, and activity limitations, respectively. This review identified three superior quality questionnaires for measuring different aspects of quality of life in refractive surgery. Clinicians and researchers should choose a questionnaire based on the concept being measured with superior psychometric properties. [J Refract Surg. 2017;33(6):416-424.]. Copyright 2017, SLACK Incorporated.

  19. Integrated model of primary and secondary eye care for underserved rural areas: The L V Prasad Eye Institute experience

    Directory of Open Access Journals (Sweden)

    Gullapalli N Rao

    2012-01-01

    Full Text Available Blindness is a major global public health problem and recent estimates from World Health Organization (WHO showed that in India there were 62 million visually impaired, of whom 8 million are blind. The Andhra Pradesh Eye Disease Study (APEDS provided a comprehensive estimate for prevalence and causes of blindness for the state of Andhra Pradesh (AP. It also highlighted that uptake of services was also an issue, predominantly among lower socio-economic groups, women, and rural populations. On the basis of this analysis, L V Prasad Eye Institute (LVPEI developed a pyramidal model of eye care delivery. This article describes the LVPEI eye care delivery model. The article discusses infrastructure development, human resource development, and service delivery (including prevention and promotion in the context of primary and secondary care service delivery in rural areas. The article also alludes to opportunities for research at these levels of service delivery and the amenability of the evidence generated at these levels of the LVPEI eye health pyramid for advocacy and policy planning. In addition, management issues related to the sustainability of service delivery in rural areas are discussed. The article highlights the key factors required for the success of the LVPEI rural service delivery model and discusses challenges that need to be overcome to replicate the model. The article concludes by noting the potential to convert these challenges into opportunities by integrating certain aspects of the existing healthcare system into the model. Examples include screening of diabetes and diabetic retinopathy in order to promote higher community participation. The results of such integration can serve as evidence for advocacy and policy.

  20. A web-based information system for management and analysis of patient data after refractive eye surgery.

    Science.gov (United States)

    Zuberbuhler, Bruno; Galloway, Peter; Reddy, Aravind; Saldana, Manuel; Gale, Richard

    2007-12-01

    The aim was to develop a software tool for refractive surgeons using a standard user-friendly web-based interface, providing the user with a secure environment to protect large volumes of patient data. The software application was named "Internet-based refractive analysis" (IBRA), and was programmed with the computer languages PHP, HTML and JavaScript, attached to the opensource MySQL database. IBRA facilitated internationally accepted presentation methods including the stability chart, the predictability chart and the safety chart; it was able to perform vector analysis for the course of a single patient or for group data. With the integrated nomogram calculation, treatment could be customised to reduce the postoperative refractive error. Multicenter functions permitted quality-control comparisons between different surgeons and laser units.

  1. A randomized clinical evaluation of the safety of Systane® Lubricant Eye Drops for the relief of dry eye symptoms following LASIK refractive surgery

    Directory of Open Access Journals (Sweden)

    Daniel Durrie

    2008-12-01

    Full Text Available Daniel Durrie, Jason StahlDurrie Vision, Overland Park, Kansas, USAPurpose: To evaluate the safety of Systane® Lubricant Eye Drops in relieving the symptoms of dry eye following laser-assisted in situ keratomileusis (LASIK surgery.Methods: This was a randomized, double-masked, single-center, placebo-controlled, contralateral eye study of 30 patients undergoing LASIK surgery. The mean age of patients was 42.4 ± 10.7 years, and the mean spherical equivalent was −3.29 (range, +1.75 to −7.38. Patients’ right and left eyes were randomized to receive either Systane® or placebo – a preserved, thimerosal-free saline solution – beginning from the day of surgery and ending 30 days following surgery. Outcome measures included tear film break up time (TFBUT, visual acuity, degree of corneal and conjunctival staining, and treatment-related adverse events.Results: Preoperatively, placebo-treated eyes had statistically significantly higher sum corneal staining score than Systane®-treated eyes (p = 0.0464; however, the difference was clinically insignificant (p = 0.27. Two weeks post operatively, the average TFBUT in the Systane®-treated eyes was 1.23 seconds longer than that of the placebo-treated eyes (p = 0.028. All other evaluated variables were comparable between the two treatments. No adverse events were reported in the study.Conclusion: Systane® Lubricant Eye Drops are safe for use following LASIK surgery to relieve the discomfort symptoms of dry eye associated with the procedure.Keywords: Systane®, safety, dry eye, LASIK

  2. The effect of Nd:YAG laser treatment of posterior capsule opacification on anterior chamber depth and refraction in pseudophakic eyes

    Directory of Open Access Journals (Sweden)

    Khambhiphant B

    2015-03-01

    Full Text Available Bharkbhum Khambhiphant,1 Chayata Liumsirijarern,2 Piyada Saehout1 1Department of Ophthalmology, King Chulalongkorn Memorial Hospital, Thai Red Cross Society, 2Department of Ophthalmology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand Purpose: This was a prospective descriptive study to determine the changes in intraocular lens (IOL position after neodymium-doped yttrium–aluminum–garnet (Nd:YAG laser posterior capsulotomy by measuring anterior chamber depth (ACD and refraction, including the spherical equivalent (SE and cylinder. Materials and methods: Forty-seven pseudophakic eyes with posterior capsule opacification of 29 patients were included. Nd:YAG laser posterior capsulotomy was performed. Patients’ ACD and refraction were measured before the treatment, as well as after the treatment at 1 week and 3 months. IOLMaster® and an automated refractometer were used at the Department of Ophthalmology, King Chulalongkorn Memorial Hospital, Bangkok, Thailand. Results: There were no statistically significant differences in ACD and SE before and after laser treatment at 1 week and 3 months (repeated analysis of variance, P=0.582 and P=0.269, respectively. Both backward IOL movement (number [n]=29 and forward IOL movement (n=18 were found. Some changes in cylindrical refraction were found at 1 week, but decreased at 3 months after capsulotomy (baseline cylinder: -1.16; cylinder at 1 week and 3 months: -1.00 and -1.14, respectively; P=0.012. These changes were the same with one-piece and three-piece IOLs. Conclusion: Nd:YAG laser posterior capsulotomy did not significantly change ACD and SE. It led to cylinder change at 1 week after laser, but the effect decreased at 3 months. This effect was small and may not be clinically significant. Keywords: posterior capsule opacification, neodymium-doped yttrium–aluminum–garnet, anterior chamber depth, pseudophakia, refraction

  3. Residencies at The Eye Institute of the Pennsylvania College of Optometry.

    Science.gov (United States)

    Alexander, Arthur H.; Klopfer, Joann

    1983-01-01

    An optometric residency program at The Eye Institute of the Pennsylvania College of Optometry that focuses on clinical training in the areas of low vision rehabilitation, pediatric optometry, visual training, behavioral vision, primary care optometry and hospital based optometry is discussed. (MSW)

  4. The KwaZulu-Natal Child Eye Care Programme: Delivering refractive error services to primary school learners

    Directory of Open Access Journals (Sweden)

    Y. I. Mahraj

    2011-12-01

    sion screeners screened 239 606 primary school children from February 2007 to May 2008. Seven percent (15 944 of the children failed the vision screening and were referred for optometric assessments. Of the 15 944 children that failed the vision screening, 10 707 children were examined by optometrists and 1083 were found to have a refractive error and were therefore supplied with spectacles. The study indicates that a short-term programme to address a backlog of services can reach many underserved children. This programme identified many challenges of implementing a vision screening programme such as poor uptake of refractive services by learners in the absence of an appropriate referral system and high attrition of trained vision screeners. (S Afr Optom 2011 70(2 61-68

  5. Resources for eye care at secondary and tertiary level government institutions in Saudi Arabia.

    Science.gov (United States)

    Al Motowa, Saeed; Khandekar, Rajiv; Al-Towerki, Abdulelah

    2014-01-01

    To evaluate the number of healthcare personnel and equipment resources for eye care at government institutions in different administrative zones of the Kingdom of Saudi Arabia (KSA) and to recommend measures for increasing resources to address deficiencies. Data on resources (personnel and equipment) for eye care were collected from all governmental eye units in 2012. The data was regrouped by zones and administrative areas. The mid-2012 population projections were used to calculate the ophthalmologist to population ratio and optometrist to population ratio. The equipment available for eye care was reviewed. All 60 institutions in 13 administrative areas and five zones of KSA participated in this study. There were 407 ophthalmologists and 147 optometrists. The ophthalmologist to population ratio was 1:43,000 (1:12,900 in the northern zone to 1:80,300 in the western zone). By 2015, 700 ophthalmologists will be required, and by 2020, 1,100 ophthalmologists will be required. The optometrist to population ratio was 1:95,000 (1:34,100 in the northern zone to 1:146,700 in the western zone). Nearly 2,800 and 4,400 allied eye care personnel will be needed by 2015 and 2020. Diagnostic and treatment equipment such as lasers, electrophysiologic and ultrasound equipment, and fundus cameras were not available at all institutions. Data from the private sector need to be included to draw conclusions on the human resource index for eye care in the Kingdom. An unequal distribution of resources in different zones and administrative areas requires attention. Better utilization of available resources is recommended before fulfilling the demand for additional resources.

  6. Counter-Democratic Surveillance: The Watchful Eye of a Local Institution

    DEFF Research Database (Denmark)

    Hjelholt, Morten

    2014-01-01

    mechanisms similar to those described by Foucault, but in the service of society. From this perspective democracy is seen as a composite of two realms – a sphere of electoral representation and a constellation of counter-democratic organizations – in constant tension with each other (Rosanvallon 2008......). The watchful eyes of counter-democratic organizations are particularly made powerful by the rise of the Internet with its spontaneous adaption of watchful functions. However increased awareness and mistrust have led not to broader participation in traditional liberal institutions but to a greater social...... in the interest of the national overseers but correspondingly given as responds to fulfill legal requirements or more loosely defined public concerns. Consequently the watchful eye of a local institution form a counter-democratic sight aimed at the strategic intentions of the Government. The paper introduces...

  7. The history of keratoprosthetics in the S. Fyodorov Eye Microsurgery Federal State Institution

    OpenAIRE

    Z.I. Moroz; V.A. Vlasova; E.V. Kovshun

    2013-01-01

    ABSTRACT The article highlights a 45-year experience in keratoprosthetics at the S. Fyodorov Eye Microsurgery Federal State Institution. During this period, more than 1,000 keratoprostheses of different types has been implanted. The design features, advantages and disadvantages of foreign keratoprosthesis – Choyce-1, Choyce-2, H. Cardona «bolt-nut», which were used in the clinic in the first stages of prosthetics of the cornea, are described. There are presented the...

  8. What Is Dry Eye?

    Medline Plus

    Full Text Available ... Ophthalmology/Strabismus Ocular Pathology/Oncology Oculoplastics/Orbit Refractive Management/Intervention Retina/Vitreous Uveitis Focus On ... Dry Eye Sections What Is Dry Eye? Dry Eye Symptoms Causes of ...

  9. Aquaporin 0 plays a pivotal role in refractive index gradient development in mammalian eye lens to prevent spherical aberration

    International Nuclear Information System (INIS)

    Kumari, S. Sindhu; Varadaraj, Kulandaiappan

    2014-01-01

    Highlights: • Intact AQP0 functions as fiber cell-to-fiber cell adhesion protein. • AQP0 facilitates reduction in extracellular space and lens water content. • AQP0 adhesion function aids in lens refractive index gradient (RING) formation. • AQP0 prevents lens spherical aberration by establishing RING. • AQP0 is critical for lens transparency and homeostasis. - Abstract: Aquaporin 0 (AQP0) is a transmembrane channel that constitutes ∼45% of the total membrane protein of the fiber cells in mammalian lens. It is critical for lens transparency and homeostasis as mutations and knockout cause autosomal dominant lens cataract. AQP0 functions as a water channel and as a cell-to-cell adhesion (CTCA) molecule in the lens. Our recent in vitro studies showed that the CTCA function of AQP0 could be crucial to establish lens refractive index gradient (RING). However, there is a lack of in vivo data to corroborate the role of AQP0 as a fiber CTCA molecule which is critical for creating lens RING. The present investigation is undertaken to gather in vivo evidence for the involvement of AQP0 in developing lens RING. Lenses of wild type (WT) mouse, AQP0 knockout (heterozygous, AQP0 +/− ) and AQP0 knockout lens transgenically expressing AQP1 (heterozygous AQP0 +/− /AQP1 +/− ) mouse models were used for the study. Data on AQP0 protein profile of intact and N- and/or C-terminal cleaved AQP0 in the lens by MALDI-TOF mass spectrometry and SDS–PAGE revealed that outer cortex fiber cells have only intact AQP0 of ∼28 kDa, inner cortical and outer nuclear fiber cells have both intact and cleaved forms, and inner nuclear fiber cells have only cleaved forms (∼26–24 kDa). Knocking out of 50% of AQP0 protein caused light scattering, spherical aberration (SA) and cataract. Restoring the lost fiber cell membrane water permeability (P f ) by transgene AQP1 did not reinstate complete lens transparency and the mouse lenses showed light scattering and SA. Transmission and

  10. Aquaporin 0 plays a pivotal role in refractive index gradient development in mammalian eye lens to prevent spherical aberration

    Energy Technology Data Exchange (ETDEWEB)

    Kumari, S. Sindhu [Physiology and Biophysics, Stony Brook University, Stony Brook, NY (United States); Varadaraj, Kulandaiappan, E-mail: kulandaiappan.varadaraj@stonybrook.edu [Physiology and Biophysics, Stony Brook University, Stony Brook, NY (United States); SUNY Eye Institute, New York, NY (United States)

    2014-10-03

    Highlights: • Intact AQP0 functions as fiber cell-to-fiber cell adhesion protein. • AQP0 facilitates reduction in extracellular space and lens water content. • AQP0 adhesion function aids in lens refractive index gradient (RING) formation. • AQP0 prevents lens spherical aberration by establishing RING. • AQP0 is critical for lens transparency and homeostasis. - Abstract: Aquaporin 0 (AQP0) is a transmembrane channel that constitutes ∼45% of the total membrane protein of the fiber cells in mammalian lens. It is critical for lens transparency and homeostasis as mutations and knockout cause autosomal dominant lens cataract. AQP0 functions as a water channel and as a cell-to-cell adhesion (CTCA) molecule in the lens. Our recent in vitro studies showed that the CTCA function of AQP0 could be crucial to establish lens refractive index gradient (RING). However, there is a lack of in vivo data to corroborate the role of AQP0 as a fiber CTCA molecule which is critical for creating lens RING. The present investigation is undertaken to gather in vivo evidence for the involvement of AQP0 in developing lens RING. Lenses of wild type (WT) mouse, AQP0 knockout (heterozygous, AQP0{sup +/−}) and AQP0 knockout lens transgenically expressing AQP1 (heterozygous AQP0{sup +/−}/AQP1{sup +/−}) mouse models were used for the study. Data on AQP0 protein profile of intact and N- and/or C-terminal cleaved AQP0 in the lens by MALDI-TOF mass spectrometry and SDS–PAGE revealed that outer cortex fiber cells have only intact AQP0 of ∼28 kDa, inner cortical and outer nuclear fiber cells have both intact and cleaved forms, and inner nuclear fiber cells have only cleaved forms (∼26–24 kDa). Knocking out of 50% of AQP0 protein caused light scattering, spherical aberration (SA) and cataract. Restoring the lost fiber cell membrane water permeability (P{sub f}) by transgene AQP1 did not reinstate complete lens transparency and the mouse lenses showed light scattering and SA

  11. Analysis of the effects of Eye-Tracker performance on the pulse positioning errors during refractive surgery

    Directory of Open Access Journals (Sweden)

    Samuel Arba-Mosquera

    2012-01-01

    Conclusions: The proposed model can be used for comparison of laser systems used for ablation processes. Due to the pseudo-random nature of eye movements, positioning errors of single pulses are much larger than observed decentrations in the clinical settings. There is no single parameter that ‘alone’ minimizes the positioning error. It is the optimal combination of the several parameters that minimizes the error. The results of this analysis are important to understand the limitations of correcting very irregular ablation patterns.

  12. Cataract Surgery Visual Outcomes and Associated Risk Factors in Secondary Level Eye Care Centers of L V Prasad Eye Institute, India.

    Science.gov (United States)

    Matta, Sumathi; Park, Jiwon; Palamaner Subash Shantha, Ghanshyam; Khanna, Rohit C; Rao, Gullapalli N

    2016-01-01

    To evaluate cataract surgery visual outcomes and associated risk factors in rural secondary level eye care centers of L V Prasad Eye Institute (LVPEI), India. The Eye Health pyramid of LVPEI has a network of rural secondary care centres (SCs) and attached vision centres (VCs) that provide high quality comprehensive eye care with permanent infrastructure to the most disadvantaged sections of society. The most common procedure performed at SCs is cataract surgery. We audited the outcome of a random sample of 2,049 cataract surgeries done from October 2009-March 2010 at eight rural SCs. All patients received a comprehensive ophthalmic examination, both before and after surgery. The World Health Organization recommended cataract surgical record was used for data entry. Visual outcomes were measured at discharge, 1-3 weeks and 4-11 weeks follow up visits. Poor outcome was defined as best corrected visual acuity gender discrimination in terms of outcome continues to be an issue and needs further investigation.

  13. Effect of a pulsed magnetic field on permeability of the cornea and sorption properties of the tissue structures and refractive media of the eye

    International Nuclear Information System (INIS)

    Skrinnik, A.V.

    1986-01-01

    The author attempts to obtain direct proof of increased permeability of the cornea and enhanced sorption properties of the tissue structures and refractive media of the eye under the influence of a pulsed magnetic field (MF). In the course of the investigation, the method of radioactive indication of two substances ( 35 S-streptomycin and 75 Se-methionine), widely used in opthalmologic practice, was used. The radioactivity of the working solution of the preparations was 300,000 cpm in 0.1 ml. Changes in the permeability of the cornea were assessed on the basis of changes in radioactivity of the aqueous humor. The concentration of 35 S-streptomycin in aqueous humor of the animals immediately after exposure to MF was significantly higher than in the control. Analysis of permeability of the cornea for 75 Se-methionine also showed increased penetration of radioactivity into the aqueous. The results are evidence of the greater penetrating power of 75 Se-methionine

  14. Refractive outcomes after multifocal intraocular lens exchange.

    Science.gov (United States)

    Kim, Eric J; Sajjad, Ahmar; Montes de Oca, Ildamaris; Koch, Douglas D; Wang, Li; Weikert, Mitchell P; Al-Mohtaseb, Zaina N

    2017-06-01

    To evaluate the refractive outcomes after multifocal intraocular lens (IOL) exchange. Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA. Retrospective case series. Patients had multifocal IOL explantation followed by IOL implantation. Outcome measures included type of IOL, surgical indication, corrected distance visual acuity (CDVA), and refractive prediction error. The study comprised 29 patients (35 eyes). The types of IOLs implanted after multifocal IOL explantation included in-the-bag IOLs (74%), iris-sutured IOLs (6%), sulcus-fixated IOLs with optic capture (9%), sulcus-fixated IOLs without optic capture (9%), and anterior chamber IOLs (3%). The surgical indication for exchange included blurred vision (60%), photic phenomena (57%), photophobia (9%), loss of contrast sensitivity (3%), and multiple complaints (29%). The CDVA was 20/40 or better in 94% of eyes before the exchange and 100% of eyes after the exchange (P = .12). The mean refractive prediction error significantly decreased from 0.22 ± 0.81 diopter (D) before the exchange to -0.09 ± 0.53 D after the exchange (P exchange to 0.23 D after the exchange (P exchange can be performed safely with good visual outcomes using different types of IOLs. A lower refractive prediction error and a higher likelihood of 20/40 or better vision can be achieved with the implantation of the second IOL compared with the original multifocal IOL, regardless of the final IOL position. Copyright © 2017 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  15. Surgical removal of eyes in a tertiary institution in North eastern ...

    African Journals Online (AJOL)

    Background Surgical eye removal is performed for various end-stage eye diseases to provide adequate comfort, replace volume and give good functional and cosmetic appearance. The pattern of eye removal is unknown for North Eastern Nigeria. Objective To determine the indications for eye removal in the study ...

  16. Indications and Visual Outcome of Penetrating Keratoplasty in Tertiary Eye Care Institute in Uttarakhand

    Science.gov (United States)

    Gupta, Neeti; Dhasmana, Renu; Nagpal, Ramesh Chander; Bahadur, Harsh; Maitreya, Amit

    2016-01-01

    Introduction Corneal blindness forms significant proportion of visual blindness in developing countries and penetrating keratoplasty (PK) can restore vision for this. The prognosis of PK is dependent on the corneal diseases responsible for corneal blindness. Aim To evaluate the indications and visual outcome of PK in tertiary eye care institute in Uttarakhand. Materials and Methods Data was reviewed from the medical records of 145 PK done in Department of Ophthalmology, Himalayan Institute of Medical Sciences from January 2012 to October 2014. Analysis of data was done for evaluation of the indications and visual outcome by Paired student’s t-test for hypothesis testing of grouped values of preoperative and last follow-up best corrected visual acuity in cases of optical and therapeutic grafts. A p-value < 0.05 was considered statistically significant. Results In this study data of 145 eyes of 138 patients was reviewed. The most common indication for keratoplasty was corneal scarring including adherent leucoma 48 (33.10%). Therapeutic keratoplasty was done for 33 cases with maximum 30(20.68%) cases of infectious keratitis. One case of tectonic graft was included in therapeutic keratoplasty group for analysis. There was statistically significant difference (p=.0001) in best corrected visual acuity improvement from 1.39 logMAR+ 0.022(SD) preoperatively to 0.367 logMAR+0.44(SD) postoperatively and 1.4 logMAR+.000(SD) preoperatively to 0.16 logMAR+0.57(SD) postoperatively for optical and therapeutic grafts respectively. Conclusion Infective keratitis either active or healed was the major indication for keratoplasty. Poor prognosis indications were most common in this part of the country. The visual outcome following corneal transplantation was encouraging particularly in cases of optical keratoplasty. PMID:27504319

  17. Development of a preference-based index from the National Eye Institute Visual Function Questionnaire-25.

    Science.gov (United States)

    Rentz, Anne M; Kowalski, Jonathan W; Walt, John G; Hays, Ron D; Brazier, John E; Yu, Ren; Lee, Paul; Bressler, Neil; Revicki, Dennis A

    2014-03-01

    Understanding how individuals value health states is central to patient-centered care and to health policy decision making. Generic preference-based measures of health may not effectively capture the impact of ocular diseases. Recently, 6 items from the National Eye Institute Visual Function Questionnaire-25 were used to develop the Visual Function Questionnaire-Utility Index health state classification, which defines visual function health states. To describe elicitation of preferences for health states generated from the Visual Function Questionnaire-Utility Index health state classification and development of an algorithm to estimate health preference scores for any health state. Nonintervention, cross-sectional study of the general community in 4 countries (Australia, Canada, United Kingdom, and United States). A total of 607 adult participants were recruited from local newspaper advertisements. In the United Kingdom, an existing database of participants from previous studies was used for recruitment. Eight of 15,625 possible health states from the Visual Function Questionnaire-Utility Index were valued using time trade-off technique. A θ severity score was calculated for Visual Function Questionnaire-Utility Index-defined health states using item response theory analysis. Regression models were then used to develop an algorithm to assign health state preference values for all potential health states defined by the Visual Function Questionnaire-Utility Index. Health state preference values for the 8 states ranged from a mean (SD) of 0.343 (0.395) to 0.956 (0.124). As expected, preference values declined with worsening visual function. Results indicate that the Visual Function Questionnaire-Utility Index describes states that participants view as spanning most of the continuum from full health to dead. Visual Function Questionnaire-Utility Index health state classification produces health preference scores that can be estimated in vision-related studies that

  18. Refractive error in school children in Agona Swedru, Ghana

    Directory of Open Access Journals (Sweden)

    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

  19. Five years of proton therapy of tumours of the eye at Hahn-Meitner Institute, Berlin

    International Nuclear Information System (INIS)

    Heufelder, J.; Cordini, D.; Heese, J.; Homeyer, H.; Kluge, H.; Morgenstern, H.; Fuchs, H.; Hoecht, S.; Nausner, M.; Hinkelbein, W.; Bechrakis, N.E.; Foerster, M.H.

    2004-01-01

    Eye tumors (choroidal melanomas, iris melanomas, and choroidal hemangiomas) are being treated with 68 MeV protons since 1998 at the Ion Beam Laboratory of the Hahn-Meitner Institute of Berlin (Germany's first proton therapy center), in cooperation with the Charite University Hospital in Berlin, Campus Benjamin Franklin. The proton beam, generated via a combination of Van de Graaff accelerator and cyclotron, is prepared by passive shaping for conformal tumor irradiation. A digital X-ray verification of the tumor location with the patient in sitting position limits the position uncertainties to a maximum of 0,3 mm. The treatment planning is performed using the program EYEPLAN. OCTOPUS, a CT-based planning program developed in cooperation with the German Cancer Research Center of Heidelberg, is under pre-clinical testing. Thus far, more than 400 patients have been irradiated. The first results are comparable to those obtained in other proton therapy centers. At the end of 2002, the University Hospital of Essen has also become a cooperation partner of the Hahn-Meitner Institute. (orig.) [de

  20. [Correction of refractive errors in patients with strabismus. Part I. Clinical problems associated with refraction, accommodation and convergence].

    Science.gov (United States)

    Tokarz-Sawińska, Ewa

    2012-01-01

    In Part I the problems associated with refraction, accommodation and convergence and their role in proper eye position/visual alignment of the eyes as well as convergent, divergent and vertical alignment of the eyes have been described.

  1. What Is Dry Eye?

    Medline Plus

    Full Text Available ... Payment Meetings and Deadlines Museum of Vision Ophthalmology Job Center Our Sites EyeWiki International Society of Refractive ... Payment Meetings and Deadlines Museum of Vision Ophthalmology Job Center Our Sites EyeWiki International Society of Refractive ...

  2. Crystalline lens power and refractive error.

    Science.gov (United States)

    Iribarren, Rafael; Morgan, Ian G; Nangia, Vinay; Jonas, Jost B

    2012-02-01

    To study the relationships between the refractive power of the crystalline lens, overall refractive error of the eye, and degree of nuclear cataract. All phakic participants of the population-based Central India Eye and Medical Study with an age of 50+ years were included. Calculation of the refractive lens power was based on distance noncycloplegic refractive error, corneal refractive power, anterior chamber depth, lens thickness, and axial length according to Bennett's formula. The study included 1885 subjects. Mean refractive lens power was 25.5 ± 3.0 D (range, 13.9-36.6). After adjustment for age and sex, the standardized correlation coefficients (β) of the association with the ocular refractive error were highest for crystalline lens power (β = -0.41; P lens opacity grade (β = -0.42; P lens power (β = -0.95), lower corneal refractive power (β = -0.76), higher lens thickness (β = 0.30), deeper anterior chamber (β = 0.28), and less marked nuclear lens opacity (β = -0.05). Lens thickness was significantly lower in eyes with greater nuclear opacity. Variations in refractive error in adults aged 50+ years were mostly influenced by variations in axial length and in crystalline lens refractive power, followed by variations in corneal refractive power, and, to a minor degree, by variations in lens thickness and anterior chamber depth.

  3. Axial Length/Corneal Radius of Curvature Ratio and Refractive ...

    African Journals Online (AJOL)

    2017-06-14

    Jun 14, 2017 ... of individuals,[2,5-8] the relationship between CR and refractive status ... the relationship between refractive error and ocular .... AG, 07740 Jena Germany). ..... adult population in rural Myanmar: The Meiktila eye study. Clin.

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

    NARCIS (Netherlands)

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

    2014-01-01

    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

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

    NARCIS (Netherlands)

    Linden, J.W.M. van der; Vrijman, V.; El-Saady, R.; Meulen, I.J. van der; Mourits, M.P.; Lapid-Gortzak, R.

    2014-01-01

    PURPOSE: To evaluate whether the automated refraction (AR) correlates with subjective manifest (MR) refraction in eyes implanted with radially asymmetric multifocal intraocular lens (IOLs). METHODS: This retrospective study evaluated 52 eyes (52 patients) implanted with a radially asymmetric

  6. Significant Axial Elongation with Minimal Change in Refraction in 3- to 6-Year-Old Chinese Preschoolers: The Shenzhen Kindergarten Eye Study.

    Science.gov (United States)

    Guo, Xinxing; Fu, Min; Ding, Xiaohu; Morgan, Ian G; Zeng, Yangfa; He, Mingguang

    2017-12-01

    To document the distribution of ocular biometry and to evaluate its associations with refraction in a group of Chinese preschoolers. Population-based cross-sectional study. A total of 1133 preschoolers 3 to 6 years of age from 8 representative kindergartens. Biometric measurements including axial length (AL), anterior chamber depth (ACD), and corneal radius of curvature (CR) were obtained from partial-coherence laser interferometry (IOL Master; Carl Zeiss Meditec, Oberkochen, Germany) before cycloplegia. Lens power (LP) and AL-to-CR ratio were calculated. Cycloplegic refraction (3 drops of 1% cyclopentolate) was measured using an autorefractor (KR8800; Topcon Corp., Tokyo, Japan), and spherical equivalent refraction (SER) was calculated. Biometric and refractive parameters were assessed as a function of age and gender. Multiple regression analysis was performed to explore the associations between refraction and ocular biometry. Ocular biometric distributions and their relationships to refraction. Among the 1127 children (99.5%) with successful cycloplegic refraction, mean SER was 1.37±0.63 diopters (D). Prevalence of myopia increased from 0% at 3 years of age to 3.7% (95% confidence interval, 1.0%-6.5%) at 6 years of age. Biometric parameters followed Gaussian distributions with means of 22.39±0.68 mm for AL, 7.79±0.25 mm for CR, and 24.61±1.42 D for calculated LP; and non-Gaussian distributions with means of 3.34±0.24 mm for ACD and 2.88±0.06 for AL-to-CR ratio. Axial length, ACD, and AL-to-CR ratio increased from 3 to 6 years of age, CR remained stable, whereas LP declined. Overall, SER declined slightly. For the SER variance, AL explained 18.6% and AL-to-CR ratio explained 39.8%, whereas AL, CR, and LP accounted for 80.0% after adjusting for age and gender. Young Chinese children are predominantly mildly hyperopic, with a low prevalence of myopia by the age of 6 years. An increase of 1 mm in AL was associated with only 0.45 D of myopic change. Decreases in

  7. Emmetropisation and the aetiology of refractive errors

    Science.gov (United States)

    Flitcroft, D I

    2014-01-01

    The distribution of human refractive errors displays features that are not commonly seen in other biological variables. Compared with the more typical Gaussian distribution, adult refraction within a population typically has a negative skew and increased kurtosis (ie is leptokurtotic). This distribution arises from two apparently conflicting tendencies, first, the existence of a mechanism to control eye growth during infancy so as to bring refraction towards emmetropia/low hyperopia (ie emmetropisation) and second, the tendency of many human populations to develop myopia during later childhood and into adulthood. The distribution of refraction therefore changes significantly with age. Analysis of the processes involved in shaping refractive development allows for the creation of a life course model of refractive development. Monte Carlo simulations based on such a model can recreate the variation of refractive distributions seen from birth to adulthood and the impact of increasing myopia prevalence on refractive error distributions in Asia. PMID:24406411

  8. Cataract Surgery Visual Outcomes and Associated Risk Factors in Secondary Level Eye Care Centers of L V Prasad Eye Institute, India.

    Directory of Open Access Journals (Sweden)

    Sumathi Matta

    Full Text Available To evaluate cataract surgery visual outcomes and associated risk factors in rural secondary level eye care centers of L V Prasad Eye Institute (LVPEI, India.The Eye Health pyramid of LVPEI has a network of rural secondary care centres (SCs and attached vision centres (VCs that provide high quality comprehensive eye care with permanent infrastructure to the most disadvantaged sections of society. The most common procedure performed at SCs is cataract surgery. We audited the outcome of a random sample of 2,049 cataract surgeries done from October 2009-March 2010 at eight rural SCs. All patients received a comprehensive ophthalmic examination, both before and after surgery. The World Health Organization recommended cataract surgical record was used for data entry. Visual outcomes were measured at discharge, 1-3 weeks and 4-11 weeks follow up visits. Poor outcome was defined as best corrected visual acuity <6/18.Mean age was 61.8 years (SD: 8.9 years and 1,133 (55.3% surgeries were performed on female patients. Pre-existing ocular co-morbidity was present in 165 patients (8.1%. The most common procedure was small incision cataract surgery (SICS with intraocular lens (IOL implantation (91.8%. Intraoperative complications were seen in 29 eyes (1.4%. At the 4-11 weeks follow-up visit, based on presenting visual acuity (PVA, 61.8% had a good outcome and based on best-corrected visual acuity (BCVA, 91.7% had a good outcome. Based on PVA and BCVA, those with less than 6/60 were only 2.9% and 1.6% respectively. Using multivariable analysis, poor visual outcomes were significantly higher in patients aged ≥70 (OR 4.63; 95% CI 1.61, 13.30, in females (OR 1.58; 95% CI 1.04, 2.41, those with preoperative comorbidities (odds ratio 4.68; 95% CI 2.90, 7.57, with intraoperative complications (OR 8.01; 95% CI 2.91, 22.04, eyes that underwent no IOL or anterior chamber-IOL (OR 12.63; 95% CI 2.65, 60.25 and those undergoing extracapsular cataract extraction (OR 9

  9. Perfect imaging without negative refraction

    OpenAIRE

    Leonhardt, Ulf

    2009-01-01

    Perfect imaging has been believed to rely on negative refraction, but here we show that an ordinary positively-refracting optical medium may form perfect images as well. In particular, we establish a mathematical proof that Maxwell's fish eye in two-dimensional integrated optics makes a perfect instrument with a resolution not limited by the wavelength of light. We also show how to modify the fish eye such that perfect imaging devices can be made in practice. Our method of perfect focusing ma...

  10. Perfect imaging without negative refraction

    Energy Technology Data Exchange (ETDEWEB)

    Leonhardt, Ulf [School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS (United Kingdom)], E-mail: ulf@st-andrews.ac.uk

    2009-09-15

    Perfect imaging has been believed to rely on negative refraction, but here we show that an ordinary positively refracting optical medium may form perfect images as well. In particular, we establish a mathematical proof that Maxwell's fish eye in two-dimensional (2D) integrated optics makes a perfect instrument with a resolution not limited by the wavelength of light. We also show how to modify the fish eye such that perfect imaging devices can be made in practice. Our method of perfect focusing may also find applications outside of optics, in acoustics, fluid mechanics or quantum physics, wherever waves obey the 2D Helmholtz equation.

  11. Fish eye optics

    Science.gov (United States)

    Hudec, R.; Michalova, S.

    2017-07-01

    We report on small student (high—school) project of the Czech Academy of Sciences dealing with animal (fish) eyes and possible application in science and technology. Albeit most fishes have refractive eyes, the recent discoveries confirm that some fishes have reflective eyes with strange arrangements as well.

  12. Development of an Arabic version of the National Eye Institute Visual Function Questionnaire as a tool to study eye diseases patients in Egypt

    Directory of Open Access Journals (Sweden)

    Nizar Saleh Abdelfattah

    2014-10-01

    Full Text Available AIM:To develop and test an Arabic version of the National Eye Institute Visual Function Questionnaire-25 (NEI-VFQ-25.METHODS:NEI-VFQ-25 was translated into Arabic according to WHO translation guidelines. We enrolled adult consenting patients with bilateral chronic eye diseases who presented to 14 hospitals across Egypt from October to December 2012, and documented their clinical findings. Psychometric properties were then tested using STATA.RESULTS:We recruited 379 patients, whose mean age was (54.5±15y. Of 46.2% were males, 227 had cataract, 31 had glaucoma, 23 had retinal detachment, 37 had diabetic retinopathy, and 61 had miscellaneous visual defects. Non-response rate and the floor and ceiling numbers of the Arabic version (ARB-VFQ-25 were calculated. Internal consistency was high in all subscales (except general health, with Cronbach-α ranging from 0.702-0.911. Test-retest reliability was high (intraclass correlation coefficient 0.79.CONCLUSION:ARB-VFQ-25 is a reliable and valid tool for assessing visual functions of Arabic speaking patients. However, some questions had high non-response rates and should be substituted by available alternatives. Our results support the importance of including self-reported visual functions as part of routine ophthalmologic examination.

  13. EVALUATION OF DRY EYES IN DIABETES MELLITUS

    Directory of Open Access Journals (Sweden)

    Anshu Sharma

    2017-12-01

    Full Text Available BACKGROUND According to the National Eye Institute, dry eye is a condition in which the eye does not produce tears properly. It can also involve tears not having the right consistency or evaporating too quickly. Tears are necessary to help maintain moisture on the surface of the eye and for clear vision. Diabetes is often associated with several significant ocular conditions such as retinopathy, refractive changes, cataracts, glaucoma and macular oedema. However, one of the most common ocular complications associated with diabetes is dry eye. The aim of the study is to study the prevalence of dry eyes in diabetes mellitus and to evaluate ocular and other risk factors relevant to diabetic dry eyes. MATERIALS AND METHODS A hospital-based cross-sectional clinical study of 100 diabetic patients who presented to the Department of Ophthalmology, Santosh Medical College and Hospital, Ghaziabad, between January 2016 to June 2017 was conducted. Detailed diabetic history was recorded. Assessment of anterior segment via slit-lamp biomicroscopy was done. The examinations for dry eyes included Schirmer's test, tear breakup time, fluorescein and rose Bengal staining. RESULTS Sixty two (62% diabetic patients had dry eye. The prevalence in type I was 3% and prevalence in type II was 59%. Dry eye prevalence was maximum in those above 40 years of age. Symptoms like reduced corneal sensation (44% and meibomitis (20% were major attributable risk factors. Ocular surface damage was predominantly superficial punctate keratitis. Retinopathy was not statistically associated with the prevalence of dry eyes. CONCLUSION Diabetes and dry eye appears to be a common association. Reduction in the modifiable risk factors of dry eye is essential to reduce its prevalence. No significant statistical correlation was found between retinopathy and dry eyes. However, examination for dry eyes should be an integral part of the assessment of diabetic eye disease.

  14. REFLECTION AND REFRACTION, VOLUME 2.

    Science.gov (United States)

    KLAUS, DAVID J.; AND OTHERS

    THIS VOLUME 2 OF A TWO-VOLUME SET PROVIDES AUTOINSTRUCTION IN PHYSICS. THE UNITS COVERED IN THIS VOLUME ARE (1) REFLECTION OF LIGHT, (2) PHOTOMETRY, (3) POLARIZATION, (4) REFRACTION OF LIGHT, (5) SNELL'S LAW, (6) LENSES, FOCUS, AND FOCAL POINTS, (7) IMAGE FORMATION, AND (8) ABERRATIONS, THE EYE, AND MAGNIFICATION. THE INTRODUCTION AND UNITS ON…

  15. A mathematical model for describing the retinal nerve fiber bundle trajectories in the human eye: average course, variability, and influence of refraction, optic disc size and optic disc position.

    Science.gov (United States)

    Jansonius, Nomdo M; Schiefer, Julia; Nevalainen, Jukka; Paetzold, Jens; Schiefer, Ulrich

    2012-12-01

    Previously we developed a mathematical model for describing the retinal nerve fiber bundle trajectories in the superior-temporal and inferior-temporal regions of the human retina, based on traced trajectories extracted from fundus photographs. Aims of the current study were to (i) validate the existing model, (ii) expand the model to the entire retina and (iii) determine the influence of refraction, optic disc size and optic disc position on the trajectories. A new set of fundus photographs was collected comprising 28 eyes of 28 subjects. From these 28 photographs, 625 trajectories were extracted. Trajectories in the temporal region of the retina were compared to the existing model. In this region, 347 of 399 trajectories (87%) were within the 95% central range of the existing model. The model was extended to the nasal region. With this extension, the model can now be applied to the entire retina that corresponds to the visual field as tested with standard automated perimetry (up to approximately 30° eccentricity). There was an asymmetry between the superior and inferior hemifields and a considerable location-specific inter-subject variability. In the nasal region, we found two "singularities", located roughly at the one and five o'clock positions for the right optic disc. Here, trajectories from relatively widespread areas of the retina converge. Associations between individual deviations from the model and refraction, optic disc size and optic disc position were studied with multiple linear regression. Refraction (P = 0.021) and possibly optic disc inclination (P = 0.09) influenced the trajectories in the superior-temporal region. Copyright © 2012 Elsevier Ltd. All rights reserved.

  16. What Is Dry Eye?

    Medline Plus

    Full Text Available ... Ophthalmology/Strabismus Ocular Pathology/Oncology Oculoplastics/Orbit Refractive Management/Intervention Retina/Vitreous Uveitis ... Eye Health A-Z Symptoms Glasses & Contacts Tips & ...

  17. Peripheral refractive correction and automated perimetric profiles.

    Science.gov (United States)

    Wild, J M; Wood, J M; Crews, S J

    1988-06-01

    The effect of peripheral refractive error correction on the automated perimetric sensitivity profile was investigated on a sample of 10 clinically normal, experienced observers. Peripheral refractive error was determined at eccentricities of 0 degree, 20 degrees and 40 degrees along the temporal meridian of the right eye using the Canon Autoref R-1, an infra-red automated refractor, under the parametric conditions of the Octopus automated perimeter. Perimetric sensitivity was then undertaken at these eccentricities (stimulus sizes 0 and III) with and without the appropriate peripheral refractive correction using the Octopus 201 automated perimeter. Within the measurement limits of the experimental procedures employed, perimetric sensitivity was not influenced by peripheral refractive correction.

  18. Refractive aim and visual outcome after phacoemulsification: A 2 ...

    African Journals Online (AJOL)

    2016-03-24

    Mar 24, 2016 ... was met, 21 eyes (14.3%) did not meet their refractive aim, 20 eyes (12.7%) were ... countries, where blindness is associated with considerable ... and better, the total range of refractive errors postoperatively ... required intraocular lenses (IOL), medical record efficiency, ..... problem that can be alleviated.

  19. Determination of Risk Factors and Treatment of Dry Eye Disease in Type 1 Diabetes Before Corneal Complications at Sindh Institute of Ophthalmology And Visual Sciences.

    Science.gov (United States)

    Shujaat, Shehnilla; Jawed, Muhammad; Memon, Shahzad; Talpur, Khalid Iqbal

    2017-01-01

    The objective of this study was to assess and determine the risk factors and treatment of dry eye disease in type 1 diabetes before any ocular surface or corneal complication occurs. This study was conducted at Sindh Institute of Ophthalmology And Visual Sciences, Hyderabad, Pakistan. Subjects and methods for observational study were undertaken at the Department of Ophthalmology Sindh Institute Of Ophthalmology And Visual Sciences, Hyderabad, Pakistan. Hundred confirmed cases of type 1 diabetes were included in the study by non probability convenience sampling. Tear film breakup time and schrimer test were carried out to determine dry eye disease. Data was collected by self-prepared questionnaire and entered and analyzed by using Statistical Program for Social Sciences (SPSS, version 20.0). The frequencies and percentage were recorded and any associations with predisposing factors were statistically analyzed by t test. Out of hundred patients, 71 (71%) were found to have dry eyes (Pdry eye disease (Pdry eyes in males and females. Long duration was found to be related with increased occurrence of dry eyes (Pdry eyes. There is marked increase in frequency/ risk of developing dry eye disease in type 1 diabetes patients. Therefore, it is recommended to have periodic ophthalmic examination for type 1 diabetic patients.

  20. Eye Injuries at Work

    Science.gov (United States)

    ... National Standards Institute (ANSI) to meet their eye protection standards. If an eye injury occurs, see an ophthalmologist or go to the emergency room immediately, even if the eye injury appears minor. Delaying medical attention can result in permanent vision ...

  1. Photorefraction of the Eye

    Science.gov (United States)

    Colicchia, Giuseppe; Wiesner, Hartmut; Zollman, Dean

    2015-01-01

    Photorefraction is a method to easily estimate the refractive state of the eye. The principle of photorefraction involves projecting light into the eye during flash photography and then examining the paths of light that emerge from the pupil after scattering on the back portion of the interior of the eyeball (fundus). We will explain the optical…

  2. Five years of proton therapy of tumours of the eye at Hahn-Meitner Institute, Berlin; Fuenf Jahre Protonentherapie von Augentumoren am Hahn-Meitner-Institut Berlin

    Energy Technology Data Exchange (ETDEWEB)

    Heufelder, J.; Cordini, D.; Heese, J.; Homeyer, H.; Kluge, H.; Morgenstern, H. [Hahn-Meitner-Inst. Berlin, Augentumortherapie (Germany); Fuchs, H. [Hahn-Meitner-Inst. Berlin, Augentumortherapie (Germany); Augenklinik, Charite - Universitaetsmedizin Berlin, Campus Benjamin Franklin (Germany); Hoecht, S.; Nausner, M.; Hinkelbein, W. [Klinik fuer Radioonkologie und Strahlentherapie, Charite - Universitaetsmedizin Berlin, Campus Benjamin Franklin (Germany); Bechrakis, N.E.; Foerster, M.H. [Augenklinik, Charite - Universitaetsmedizin Berlin, Campus Benjamin Franklin (Germany)

    2004-07-01

    Eye tumors (choroidal melanomas, iris melanomas, and choroidal hemangiomas) are being treated with 68 MeV protons since 1998 at the Ion Beam Laboratory of the Hahn-Meitner Institute of Berlin (Germany's first proton therapy center), in cooperation with the Charite University Hospital in Berlin, Campus Benjamin Franklin. The proton beam, generated via a combination of Van de Graaff accelerator and cyclotron, is prepared by passive shaping for conformal tumor irradiation. A digital X-ray verification of the tumor location with the patient in sitting position limits the position uncertainties to a maximum of 0,3 mm. The treatment planning is performed using the program EYEPLAN. OCTOPUS, a CT-based planning program developed in cooperation with the German Cancer Research Center of Heidelberg, is under pre-clinical testing. Thus far, more than 400 patients have been irradiated. The first results are comparable to those obtained in other proton therapy centers. At the end of 2002, the University Hospital of Essen has also become a cooperation partner of the Hahn-Meitner Institute. (orig.) [German] Seit 1998 werden am Ionenstrahllabor des Hahn-Meitner-Instituts Berlin (Deutschlands erster Einrichtung zur Protonentherapie) im Rahmen eines Kooperationsvertrages mit der Charite - Universitaetsmedizin Berlin, Campus Benjamin Franklin, Augentumoren (Aderhautmelanome, Irismelanome und Aderhauthaemangiome) mit 68-MeV-Protonen bestrahlt. Der mittels einer Kombination aus Van de Graaff-Beschleuniger und Zyklotron erzeugte Protonenstrahl wird passiv fuer eine konformale Bestrahlung des Tumors aufbereitet. Eine digitale Roentgenkontrolle der Lagerung des sitzenden Patienten beschraenkt die Lagerungsunsicherheit auf maximal 0,3 mm. Fuer die Bestrahlungsplanung wird das modellbasierte Planungsprogramm EYEPLAN verwendet. In vorklinischer Erprobung befindet sich das mit dem Deutschen Krebsforschungszentrum Heidelberg entwickelte CT-basierte Planungsprogramm OCTOPUS. Bisher wurden

  3. Differences between wavefront and subjective refraction for infrared light.

    Science.gov (United States)

    Teel, Danielle F W; Jacobs, Robert J; Copland, James; Neal, Daniel R; Thibos, Larry N

    2014-10-01

    To determine the accuracy of objective wavefront refractions for predicting subjective refractions for monochromatic infrared light. Objective refractions were obtained with a commercial wavefront aberrometer (COAS, Wavefront Sciences). Subjective refractions were obtained for 30 subjects with a speckle optometer validated against objective Zernike wavefront refractions on a physical model eye (Teel et al., Design and validation of an infrared Badal optometer for laser speckle, Optom Vis Sci 2008;85:834-42). Both instruments used near-infrared (NIR) radiation (835 nm for COAS, 820 nm for the speckle optometer) to avoid correction for ocular chromatic aberration. A 3-mm artificial pupil was used to reduce complications attributed to higher-order ocular aberrations. For comparison with paraxial (Seidel) and minimum root-mean-square (Zernike) wavefront refractions, objective refractions were also determined for a battery of 29 image quality metrics by computing the correcting lens that optimizes retinal image quality. Objective Zernike refractions were more myopic than subjective refractions for 29 of 30 subjects. The population mean discrepancy was -0.26 diopters (D) (SEM = 0.03 D). Paraxial (Seidel) objective refractions tended to be hyperopically biased (mean discrepancy = +0.20 D, SEM = 0.06 D). Refractions based on retinal image quality were myopically biased for 28 of 29 metrics. The mean bias across all 31 measures was -0.24 D (SEM = 0.03). Myopic bias of objective refractions was greater for eyes with brown irises compared with eyes with blue irises. Our experimental results are consistent with the hypothesis that reflected NIR light captured by the aberrometer originates from scattering sources located posterior to the entrance apertures of cone photoreceptors, near the retinal pigment epithelium. The larger myopic bias for brown eyes suggests that a greater fraction of NIR light is reflected from choroidal melanin in brown eyes compared with blue eyes.

  4. Perfect imaging without refraction?

    Science.gov (United States)

    Blaikie, R. J.

    2011-12-01

    Recent work suggesting that ‘perfect’ far-field imaging is possible using Maxwell's fish-eye lens (Leonhardt 2009 New J. Phys. 11 093040) has raised a number of questions and controversies about the nature of imaging and field localization in inhomogeneous media. In this brief paper we present analogous results for a purely reflector-based imaging system—an elliptical cavity. With a source at one focus of the ellipse we show that sub-wavelength field localization can be achieved at the other focus when an active ‘drain’ is present there, but not without it. Does this show that far-field ‘perfect’ imaging is possible even without refraction (negative or positive)? Unfortunately not, giving further evidence that these are solely drain-induced effects.

  5. Perfect imaging without refraction?

    International Nuclear Information System (INIS)

    Blaikie, R J

    2011-01-01

    Recent work suggesting that ‘perfect’ far-field imaging is possible using Maxwell's fish-eye lens (Leonhardt 2009 New J. Phys. 11 093040) has raised a number of questions and controversies about the nature of imaging and field localization in inhomogeneous media. In this brief paper we present analogous results for a purely reflector-based imaging system—an elliptical cavity. With a source at one focus of the ellipse we show that sub-wavelength field localization can be achieved at the other focus when an active ‘drain’ is present there, but not without it. Does this show that far-field ‘perfect’ imaging is possible even without refraction (negative or positive)? Unfortunately not, giving further evidence that these are solely drain-induced effects. (paper)

  6. 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.

  7. Improving the efficiency of copper indium gallium (Di-)selenide (CIGS) solar cells through integration of a moth-eye textured resist with a refractive index similar to aluminum doped zinc oxide

    Energy Technology Data Exchange (ETDEWEB)

    Burghoorn, M.; Kniknie, B.; Deelen, J. van; Ee, R. van [The Netherlands Organisation for Applied Scientific Research (TNO), De Rondom 1, 5612 AP, Eindhoven (Netherlands); Xu, M. [The Netherlands Organisation for Applied Scientific Research (TNO), De Rondom 1, 5612 AP, Eindhoven (Netherlands); Delft University of Technology, Optics Group, Van der Waalsweg 8, 2628 CH, Delft (Netherlands); Vroon, Z. [The Netherlands Organisation for Applied Scientific Research (TNO), De Rondom 1, 5612 AP, Eindhoven (Netherlands); Zuyd Hogeschool, Nieuw Eyckholt 300, 6419 DJ, Heerlen (Netherlands); Belt, R. van de [Kriya Materials BV, Urmonderbaan 22, 6167 RD, Geleen (Netherlands); Buskens, P., E-mail: pascal.buskens@tno.nl, E-mail: buskens@dwi.rwth-aachen.de [The Netherlands Organisation for Applied Scientific Research (TNO), De Rondom 1, 5612 AP, Eindhoven (Netherlands); DWI – Leibniz Institute for Interactive Materials, Forckenbeckstrasse 50, 52056, Aachen (Germany)

    2014-12-15

    Textured transparent conductors are widely used in thin-film silicon solar cells. They lower the reflectivity at interfaces between different layers in the cell and/or cause an increase in the path length of photons in the Si absorber layer, which both result in an increase in the number of absorbed photons and, consequently, an increase in short-circuit current density (J{sub sc}) and cell efficiency. Through optical simulations, we recently obtained strong indications that texturing of the transparent conductor in copper indium gallium (di-)selenide (CIGS) solar cells is also optically advantageous. Here, we experimentally demonstrate that the J{sub sc} and efficiency of CIGS solar cells with an absorber layer thickness (d{sub CIGS}) of 0.85 μm, 1.00 μm and 2.00 μm increase through application of a moth-eye textured resist with a refractive index that is sufficiently similar to AZO (n{sub resist} = 1.792 vs. n{sub AZO} = 1.913 at 633 nm) to avoid large optical losses at the resist-AZO interface. On average, J{sub sc} increases by 7.2%, which matches the average reduction in reflection of 7.0%. The average relative increase in efficiency is slightly lower (6.0%). No trend towards a larger relative increase in J{sub sc} with decreasing d{sub CIGS} was observed. Ergo, the increase in J{sub sc} can be fully explained by the reduction in reflection, and we did not observe any increase in J{sub sc} based on an increased photon path length.

  8. Improving the efficiency of copper indium gallium (Di-selenide (CIGS solar cells through integration of a moth-eye textured resist with a refractive index similar to aluminum doped zinc oxide

    Directory of Open Access Journals (Sweden)

    M. Burghoorn

    2014-12-01

    Full Text Available Textured transparent conductors are widely used in thin-film silicon solar cells. They lower the reflectivity at interfaces between different layers in the cell and/or cause an increase in the path length of photons in the Si absorber layer, which both result in an increase in the number of absorbed photons and, consequently, an increase in short-circuit current density (Jsc and cell efficiency. Through optical simulations, we recently obtained strong indications that texturing of the transparent conductor in copper indium gallium (di-selenide (CIGS solar cells is also optically advantageous. Here, we experimentally demonstrate that the Jsc and efficiency of CIGS solar cells with an absorber layer thickness (dCIGS of 0.85 μm, 1.00 μm and 2.00 μm increase through application of a moth-eye textured resist with a refractive index that is sufficiently similar to AZO (nresist = 1.792 vs. nAZO = 1.913 at 633 nm to avoid large optical losses at the resist-AZO interface. On average, Jsc increases by 7.2%, which matches the average reduction in reflection of 7.0%. The average relative increase in efficiency is slightly lower (6.0%. No trend towards a larger relative increase in Jsc with decreasing dCIGS was observed. Ergo, the increase in Jsc can be fully explained by the reduction in reflection, and we did not observe any increase in Jsc based on an increased photon path length.

  9. Comment on 'Perfect imaging without negative refraction'

    Science.gov (United States)

    Blaikie, R. J.

    2010-05-01

    The prediction of 'perfect' imaging without negative refraction for Maxwell's fish-eye lens (Leonhardt U 2009 New J. Phys. 11 093040) is a consequence of imposing an active localized 'drain' at the image point rather than being a general property of the lens. This work then becomes analogous to other work using time-reversal symmetry and/or structured antennae to achieve super-resolution, which can be applied to many types of imaging system beyond the fish-eye lens.

  10. Comment on 'Perfect imaging without negative refraction'

    International Nuclear Information System (INIS)

    Blaikie, R J

    2010-01-01

    The prediction of 'perfect' imaging without negative refraction for Maxwell's fish-eye lens (Leonhardt U 2009 New J. Phys. 11 093040) is a consequence of imposing an active localized 'drain' at the image point rather than being a general property of the lens. This work then becomes analogous to other work using time-reversal symmetry and/or structured antennae to achieve super-resolution, which can be applied to many types of imaging system beyond the fish-eye lens.

  11. Post-LASIK dry eye

    Science.gov (United States)

    Shtein, Roni M

    2011-01-01

    Laser-assisted in situ keratomileusis (LASIK) is a frequently performed corneal refractive surgery with excellent refractive outcomes. The most common complication of LASIK is dry eyes, with virtually all patients developing some degree of dryness in the immediate postoperative period. Identifying preoperative dry eyes, and conscientious attention and treatment in the perioperative time period, can lead to enhanced patient satisfaction and more accurate visual outcomes. Improved understanding of the development of dry eyes after LASIK will advance our understanding of the complex pathophysiology of dry eye disease. PMID:22174730

  12. Comparison of objective refraction in darkness to cycloplegic refraction: a pilot study.

    Science.gov (United States)

    Vasudevan, Balamurali; Ciuffreda, Kenneth J; Meehan, Kelly; Grk, Dejana; Cox, Misty

    2016-03-01

    The aim was to assess non-cycloplegic objective refraction in darkness using an open-field auto-refractor, and furthermore to compare it with distance cycloplegic subjective refraction and distance cycloplegic retinoscopy in the light, in children and young adults. Twenty-three, visually-normal, young-adults (46 eyes) ages 23 to 31 years, and five children (10 eyes) ages five to 12 years, participated in the study. The spherical component of their refraction ranged from -2.25 D to +3.75 D with a mean of +1.80 D, and a mean cylinder of -0.70 D. Three techniques were used to assess refractive error. An objective measure of the non-cycloplegic refractive state was obtained using an open-field autorefractor (WAM-5500) after five minutes in the dark to allow for dissipation of accommodative transients and relaxation of accommodation. In addition, both distance retinoscopy and subjective distance refraction were performed following cycloplegia (Cyclopentolate, 1%) using conventional clinical procedures. All measurements were obtained on the same day within a single session. The spherical component of the refraction was compared among the three techniques in both the children and adults. There was no significant difference in spherical refraction among the three techniques: non-cycloplegic objective refraction in the dark, distance cycloplegic retinoscopy and distance cycloplegic subjective refraction, in either the adults [F(2, 137) = 0.79, p = 0.45] or the children [F(2, 27) = 0.47, p = 0.62]. Mean difference in the spherical component between refraction in the dark and the cycloplegic distance retinoscopy was -0.34 D (r = 0.89) in the adults and +0.14 D (r = 0.96) in the children. The mean difference in spherical component between refraction in the dark and the cycloplegic distance subjective refraction was -0.25 D (r = 0.92) in the adults and -0.05 D (r = 0.95) in the children. Comparison of the spherical refractive component between the three techniques was not

  13. National Eye Institute

    Science.gov (United States)

    ... NEI Intranet (Employees Only) *PDF files require the free Adobe® Reader® software for viewing. This website is maintained by the NEI Office of Science Communications, Public Liaison, and Education. Technical questions about this website can be addressed ...

  14. Post-LASIK dry eye

    OpenAIRE

    Shtein, Roni M

    2011-01-01

    Laser-assisted in situ keratomileusis (LASIK) is a frequently performed corneal refractive surgery with excellent refractive outcomes. The most common complication of LASIK is dry eyes, with virtually all patients developing some degree of dryness in the immediate postoperative period. Identifying preoperative dry eyes, and conscientious attention and treatment in the perioperative time period, can lead to enhanced patient satisfaction and more accurate visual outcomes. Improved understanding...

  15. Indications for and outcomes of tertiary referrals in refractive surgery

    NARCIS (Netherlands)

    Patryn, Eliza K.; Vrijman, Violette; Nieuwendaal, Carla P.; van der Meulen, Ivanka J. E.; Mourits, Maarten P.; Lapid-Gortzak, Ruth

    2014-01-01

    To review the spectrum of disease, symptomatology, and management offered to patients referred for a second opinion after refractive surgery. A prospective cohort study was done on all patients referred from October 1, 2006, to September 30, 2011, to a tertiary eye clinic after refractive surgery of

  16. Prevalence of Refractive Error and Visual Impairment among Rural ...

    African Journals Online (AJOL)

    Refractive error was the major cause of visual impairment accounting for 54% of all causes in the study group. No child was found wearing ... So, large scale community level screening for refractive error should be conducted and integrated with regular school eye screening programs. Effective strategies need to be devised ...

  17. Personalized pseudophakic model for refractive assessment.

    Directory of Open Access Journals (Sweden)

    Filomena J Ribeiro

    Full Text Available PURPOSE: To test a pseudophakic eye model that allows for intraocular lens power (IOL calculation, both in normal eyes and in extreme conditions, such as post-LASIK. METHODS: PARTICIPANTS: The model's efficacy was tested in 54 participants (104 eyes who underwent LASIK and were assessed before and after surgery, thus allowing to test the same method in the same eye after only changing corneal topography. MODELLING: The Liou-Brennan eye model was used as a starting point, and biometric values were replaced by individual measurements. Detailed corneal surface data were obtained from topography (Orbscan® and a grid of elevation values was used to define corneal surfaces in an optical ray-tracing software (Zemax®. To determine IOL power, optimization criteria based on values of the modulation transfer function (MTF weighted according to contrast sensitivity function (CSF, were applied. RESULTS: Pre-operative refractive assessment calculated by our eye model correlated very strongly with SRK/T (r = 0.959, p0.05. Comparison of post-operative refractive assessment obtained using our eye model with the average of currently used formulas showed a strong correlation (r = 0.778, p0.05. CONCLUSIONS: Results suggest that personalized pseudophakic eye models and ray-tracing allow for the use of the same methodology, regardless of previous LASIK, independent of population averages and commonly used regression correction factors, which represents a clinical advantage.

  18. Personalized pseudophakic model for refractive assessment.

    Science.gov (United States)

    Ribeiro, Filomena J; Castanheira-Dinis, António; Dias, João M

    2012-01-01

    To test a pseudophakic eye model that allows for intraocular lens power (IOL) calculation, both in normal eyes and in extreme conditions, such as post-LASIK. The model's efficacy was tested in 54 participants (104 eyes) who underwent LASIK and were assessed before and after surgery, thus allowing to test the same method in the same eye after only changing corneal topography. MODELLING: The Liou-Brennan eye model was used as a starting point, and biometric values were replaced by individual measurements. Detailed corneal surface data were obtained from topography (Orbscan®) and a grid of elevation values was used to define corneal surfaces in an optical ray-tracing software (Zemax®). To determine IOL power, optimization criteria based on values of the modulation transfer function (MTF) weighted according to contrast sensitivity function (CSF), were applied. Pre-operative refractive assessment calculated by our eye model correlated very strongly with SRK/T (r = 0.959, p0.05). Comparison of post-operative refractive assessment obtained using our eye model with the average of currently used formulas showed a strong correlation (r = 0.778, p0.05). Results suggest that personalized pseudophakic eye models and ray-tracing allow for the use of the same methodology, regardless of previous LASIK, independent of population averages and commonly used regression correction factors, which represents a clinical advantage.

  19. Dark refraction shift with allowance for astigmatism

    Directory of Open Access Journals (Sweden)

    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.

  20. RADIO REFRACTIVITY RADIO REFRACTIVITY STUDY IN AKURE ...

    African Journals Online (AJOL)

    eobe

    Propagation of waves in a microwave link is through the troposphere which is the non-ionized lowest portion of the atmosphere [5]. The refractive index is defined as [5]. (1). Where εr is the dielectric constant of the troposphere. C is the speed of light and V is the phase velocity of the wave in the medium. The refractive index ...

  1. Refractive neutron lens

    International Nuclear Information System (INIS)

    Petrov, P.V.; Kolchevsky, N.N.

    2013-01-01

    Model of the refractive neutron lens is proposed. System of N lenses acts as one thin lens with a complex refraction index n*. The maximum number N max of individual lenses for 'thick' neutron lens is calculated. Refractive neutron lens properties (resolution, focal depth) as function of resolution factor F 0 =ρbc/μ and depth of field factor dF 0 =λF 0 =λρbc/μ are calculated. It is shown that micro resolution of the refractive neutron optics is far from the wavelength in size and its open possibilities for progress in refractive neutron optics. (authors)

  2. LASIK - Laser Eye Surgery

    Science.gov (United States)

    ... Refractive Surgery Procedures What Is Photorefractive Keratectomy (PRK)? LASIK — Laser Eye Surgery Leer en Español: LASIK—Cirugía ocular con láser ... loss of close-up focusing power. How the LASIK procedure works LASIK is performed while the patient ...

  3. The quality of systematic reviews about interventions for refractive error can be improved: a review of systematic reviews.

    Science.gov (United States)

    Mayo-Wilson, Evan; Ng, Sueko Matsumura; Chuck, Roy S; Li, Tianjing

    2017-09-05

    Systematic reviews should inform American Academy of Ophthalmology (AAO) Preferred Practice Pattern® (PPP) guidelines. The quality of systematic reviews related to the forthcoming Preferred Practice Pattern® guideline (PPP) Refractive Errors & Refractive Surgery is unknown. We sought to identify reliable systematic reviews to assist the AAO Refractive Errors & Refractive Surgery PPP. Systematic reviews were eligible if they evaluated the effectiveness or safety of interventions included in the 2012 PPP Refractive Errors & Refractive Surgery. To identify potentially eligible systematic reviews, we searched the Cochrane Eyes and Vision United States Satellite database of systematic reviews. Two authors identified eligible reviews and abstracted information about the characteristics and quality of the reviews independently using the Systematic Review Data Repository. We classified systematic reviews as "reliable" when they (1) defined criteria for the selection of studies, (2) conducted comprehensive literature searches for eligible studies, (3) assessed the methodological quality (risk of bias) of the included studies, (4) used appropriate methods for meta-analyses (which we assessed only when meta-analyses were reported), (5) presented conclusions that were supported by the evidence provided in the review. We identified 124 systematic reviews related to refractive error; 39 met our eligibility criteria, of which we classified 11 to be reliable. Systematic reviews classified as unreliable did not define the criteria for selecting studies (5; 13%), did not assess methodological rigor (10; 26%), did not conduct comprehensive searches (17; 44%), or used inappropriate quantitative methods (3; 8%). The 11 reliable reviews were published between 2002 and 2016. They included 0 to 23 studies (median = 9) and analyzed 0 to 4696 participants (median = 666). Seven reliable reviews (64%) assessed surgical interventions. Most systematic reviews of interventions for

  4. Investigation of the refractive status of preschool children in Xiantao, Hubei Province

    OpenAIRE

    Nian Guan; Hao-Ming Chen; Zhi-Guang Hu

    2014-01-01

    AIM: To investigate the refractive status of the preschool children in Xiantao, Hubei Province in order to find out the abnormal refraction error beyond the physiological range. METHODS: In this cross-sectional study, we investigated preschool children in kindergartens and the scattered ones were 12 716(25 432 eyes)ranging from 6mo~6 years old. 1 581 children(3 162 eyes)were diagnosed ametropia by Suresight refractive screening instrument, which were confirmed again after mydriasis optometry....

  5. Equivalent refractive index of the human lens upon accommodative response

    NARCIS (Netherlands)

    Hermans, E.A.; Dubbelman, M.; van der Heijde, R.G.L.; Heethaar, R.M.

    2008-01-01

    PURPOSE.: To experimentally verify the suggestion of Gullstrand (1909), i.e., that the equivalent refractive index of the human lens increases with accommodation. METHODS.: The left eye of five subjects was focused on different accommodation stimuli, while the right eye was imaged with Scheimpflug

  6. Analysis of refractive state in 708 children with ametropic amblyopia

    Directory of Open Access Journals (Sweden)

    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.

  7. Crystalline lens and refractive development.

    Science.gov (United States)

    Iribarren, Rafael

    2015-07-01

    Individual refractive errors usually change along lifespan. Most children are hyperopic in early life. This hyperopia is usually lost during growth years, leading to emmetropia in adults, but myopia also develops in children during school years or during early adult life. Those subjects who remain emmetropic are prone to have hyperopic shifts in middle life. And even later, at older ages, myopic shifts are developed with nuclear cataract. The eye grows from 15 mm in premature newborns to approximately 24 mm in early adult years, but, in most cases, refractions are maintained stable in a clustered distribution. This growth in axial length would represent a refractive change of more than 40 diopters, which is compensated by changes in corneal and lens powers. The process which maintains the balance between the ocular components of refraction during growth is still under study. As the lens power cannot be measured in vivo, but can only be calculated based on the other ocular components, there have not been many studies of lens power in humans. Yet, recent studies have confirmed that the lens loses power during growth in children, and that hyperopic and myopic shifts in adulthood may be also produced by changes in the lens. These studies in children and adults give a picture of the changing power of the lens along lifespan. Other recent studies about the growth of the lens and the complexity of its internal structure give clues about how these changes in lens power are produced along life. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. Corneal polarimetry after LASIK refractive surgery

    Science.gov (United States)

    Bueno, Juan M.; Berrio, Esther; Artal, Pablo

    2006-01-01

    Imaging polarimetry provides spatially resolved information on the polarization properties of a system. In the case of the living human eye, polarization could be related to the corneal biomechanical properties, which vary from the normal state as a result of surgery or pathologies. We have used an aberro-polariscope, which we recently developed, to determine and to compare the spatially resolved maps of polarization parameters across the pupil between normal healthy and post-LASIK eyes. The depolarization distribution is not uniform across the pupil, with post-surgery eyes presenting larger levels of depolarization. While retardation increases along the radius in normal eyes, this pattern becomes irregular after LASIK refractive surgery. The maps of slow axis also differ in normal and post-surgery eyes, with a larger disorder in post-LASIK eyes. Since these changes in polarization indicate subtle structural modifications of the cornea, this approach can be useful in a clinical environment to follow the biomechanical and optical changes of the cornea after refractive surgery or for the early diagnosis of different corneal pathologies.

  9. Experiencing Light's Properties within Your Own Eye

    Science.gov (United States)

    Mauser, Michael

    2011-01-01

    Seeing the reflection, refraction, dispersion, absorption, polarization, and scattering or diffraction of light within your own eye makes these properties of light truly personal. There are practical aspects of these within the eye phenomena, such as eye tracking for computer interfaces. They also offer some intriguing diversions, for example,…

  10. Refractive Errors in State Junior High School Students in Bandung

    Directory of Open Access Journals (Sweden)

    Sabila Tasyakur Nikmah

    2016-12-01

    Full Text Available Background: Uncorrected refractive error is one of the avoidable causes of vision impairment in children and adults. Vision problem in children has been shown to affect their psychological and academic performance. This study aims at identifying and gaining more insights on the characteristic of the refractive errors in state junior high school students in Bandung to avoid uncorrected refractive errors. Methods: A cross-sectional study was conducted in September–November 2015 in state junior high schools in Bandung, West Java, Indonesia. Sample was selected using multistage random sampling technique. Children were examined using tumbling E examination; then students with visual acuity worse than 6/12 underwent Snellen Chart test, refractometry without pupil dilatation, correction with trial lens, then was followed by direct ophthalmoscopy. Results: From a total of 435 children who completed all the examination, 80 children (18.39% had refractive errors; consisted of 151 eyes (94.38% with myopia and 9 eyes (5.62% with astigmatism. Refractive errors were found to be more common in female children (73.7% than male children (26.3%. Among those with refractive errors, 45 children (56.3% did not use any corrective glasses before the examination. Conclusions: Routine refractive error test in vision screening examination is needed for students. It is equally important to raise more awareness toward eye disease in community.

  11. Theoretical investigation of aberrations upon ametropic human eyes

    Science.gov (United States)

    Tan, Bo; Chen, Ying-Ling; Lewis, J. W. L.; Baker, Kevin

    2003-11-01

    The human eye aberrations are important for visual acuity and ophthalmic diagnostics and surgical procedures. Reported monochromatic aberration data of the normal 20/20 human eyes are scarce. There exist even fewer reports of the relation between ametropic conditions and aberrations. We theoretically investigate the monochromatic and chromatic aberrations of human eyes for refractive errors of -10 to +10 diopters. Schematic human eye models are employed using optical design software for axial, index, and refractive types of ametropia.

  12. Dwarf Eye Disorder

    Science.gov (United States)

    Science Teacher, 2005

    2005-01-01

    Johns Hopkins researchers at the Wilmer Eye Institute have discovered what appears to be the first human gene mutation that causes extreme farsightedness. The researchers report that nanophthalmos, Greek for "dwarf eye," is a rare, potentially blinding disorder caused by an alteration in a gene called MFRP that helps control eye growth and…

  13. Intravitreal injection analysis at the Bascom Palmer Eye Institute: evaluation of clinical indications for the treatment and incidence rates of endophthalmitis

    Directory of Open Access Journals (Sweden)

    Ludimila L Cavalcante

    2010-05-01

    Full Text Available Ludimila L Cavalcante, Milena L Cavalcante, Timothy G Murray, Michael M Vigoda, Yolanda Piña, Christina L Decatur, R Prince Davis, Lisa C Olmos, Amy C Schefler, Michael B Parrott, Kyle J Alliman, Harry W Flynn, Andrew A MoshfeghiBascom Palmer Eye Institute, Department of Ophthalmology, University of Miami Miller School of Medicine, Miami, FL, USAObjective: To report the incidence of endophthalmitis, in addition to its clinical and microbiological aspects, after intravitreal injection of vascular-targeting agents.Methods: A retrospective review of a consecutive series of 10,142 intravitreal injections of vascular targeting agents (bevacizumab, ranibizumab, triamcinolone acetonide, and preservative-free triamcinolone acetonide between June 1, 2007 and January 31, 2010, performed by a single service (TGM at the Bascom Palmer Eye Institute.Results: One case of clinically-suspected endophthalmitis was identified out of a total of 10,142 injections (0.009%, presenting within three days of injection of bevacizumab. The case was culture-positive for Staphylococcus epidermidis. Final visual acuity was 20/40 after pars plana vitrectomy surgery.Conclusions: In this series, the incidence of culture-positive endophthalmitis after intravitreal injection of vascular agents in an outpatient setting was very low. We believe that following a standardized injection protocol, adherence to sterile techniques and proper patient follow-up are determining factors for low incidence rates.Keywords: endophthalmitis, intravitreal injections, vascular targeting agents 

  14. Sources of medical error in refractive surgery.

    Science.gov (United States)

    Moshirfar, Majid; Simpson, Rachel G; Dave, Sonal B; Christiansen, Steven M; Edmonds, Jason N; Culbertson, William W; Pascucci, Stephen E; Sher, Neal A; Cano, David B; Trattler, William B

    2013-05-01

    To evaluate the causes of laser programming errors in refractive surgery and outcomes in these cases. In this multicenter, retrospective chart review, 22 eyes of 18 patients who had incorrect data entered into the refractive laser computer system at the time of treatment were evaluated. Cases were analyzed to uncover the etiology of these errors, patient follow-up treatments, and final outcomes. The results were used to identify potential methods to avoid similar errors in the future. Every patient experienced compromised uncorrected visual acuity requiring additional intervention, and 7 of 22 eyes (32%) lost corrected distance visual acuity (CDVA) of at least one line. Sixteen patients were suitable candidates for additional surgical correction to address these residual visual symptoms and six were not. Thirteen of 22 eyes (59%) received surgical follow-up treatment; nine eyes were treated with contact lenses. After follow-up treatment, six patients (27%) still had a loss of one line or more of CDVA. Three significant sources of error were identified: errors of cylinder conversion, data entry, and patient identification error. Twenty-seven percent of eyes with laser programming errors ultimately lost one or more lines of CDVA. Patients who underwent surgical revision had better outcomes than those who did not. Many of the mistakes identified were likely avoidable had preventive measures been taken, such as strict adherence to patient verification protocol or rigorous rechecking of treatment parameters. Copyright 2013, SLACK Incorporated.

  15. Refractive state of the Spanish Thoroughbred horse: a comparison with the Crossbred horse.

    Science.gov (United States)

    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.

  16. Atmospheric refraction : a history

    NARCIS (Netherlands)

    Lehn, WH; van der Werf, S

    2005-01-01

    We trace the history of atmospheric refraction from the ancient Greeks up to the time of Kepler. The concept that the atmosphere could refract light entered Western science in the second century B.C. Ptolemy, 300 years later, produced the first clearly defined atmospheric model, containing air of

  17. 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.

  18. Iterative supervirtual refraction interferometry

    KAUST Repository

    Al-Hagan, Ola

    2014-05-02

    In refraction tomography, the low signal-to-noise ratio (S/N) can be a major obstacle in picking the first-break arrivals at the far-offset receivers. To increase the S/N, we evaluated iterative supervirtual refraction interferometry (ISVI), which is an extension of the supervirtual refraction interferometry method. In this method, supervirtual traces are computed and then iteratively reused to generate supervirtual traces with a higher S/N. Our empirical results with both synthetic and field data revealed that ISVI can significantly boost up the S/N of far-offset traces. The drawback is that using refraction events from more than one refractor can introduce unacceptable artifacts into the final traveltime versus offset curve. This problem can be avoided by careful windowing of refraction events.

  19. Parsimonious refraction interferometry

    KAUST Repository

    Hanafy, Sherif

    2016-09-06

    We present parsimonious refraction interferometry where a densely populated refraction data set can be obtained from just two shot gathers. The assumptions are that the first arrivals are comprised of head waves and direct waves, and a pair of reciprocal shot gathers is recorded over the line of interest. The refraction traveltimes from these reciprocal shot gathers can be picked and decomposed into O(N2) refraction traveltimes generated by N virtual sources, where N is the number of geophones in the 2D survey. This enormous increase in the number of virtual traveltime picks and associated rays, compared to the 2N traveltimes from the two reciprocal shot gathers, allows for increased model resolution and better condition numbers in the normal equations. Also, a reciprocal survey is far less time consuming than a standard refraction survey with a dense distribution of sources.

  20. Parsimonious refraction interferometry

    KAUST Repository

    Hanafy, Sherif; Schuster, Gerard T.

    2016-01-01

    We present parsimonious refraction interferometry where a densely populated refraction data set can be obtained from just two shot gathers. The assumptions are that the first arrivals are comprised of head waves and direct waves, and a pair of reciprocal shot gathers is recorded over the line of interest. The refraction traveltimes from these reciprocal shot gathers can be picked and decomposed into O(N2) refraction traveltimes generated by N virtual sources, where N is the number of geophones in the 2D survey. This enormous increase in the number of virtual traveltime picks and associated rays, compared to the 2N traveltimes from the two reciprocal shot gathers, allows for increased model resolution and better condition numbers in the normal equations. Also, a reciprocal survey is far less time consuming than a standard refraction survey with a dense distribution of sources.

  1. Iterative supervirtual refraction interferometry

    KAUST Repository

    Al-Hagan, Ola; Hanafy, Sherif M.; Schuster, Gerard T.

    2014-01-01

    In refraction tomography, the low signal-to-noise ratio (S/N) can be a major obstacle in picking the first-break arrivals at the far-offset receivers. To increase the S/N, we evaluated iterative supervirtual refraction interferometry (ISVI), which is an extension of the supervirtual refraction interferometry method. In this method, supervirtual traces are computed and then iteratively reused to generate supervirtual traces with a higher S/N. Our empirical results with both synthetic and field data revealed that ISVI can significantly boost up the S/N of far-offset traces. The drawback is that using refraction events from more than one refractor can introduce unacceptable artifacts into the final traveltime versus offset curve. This problem can be avoided by careful windowing of refraction events.

  2. Are 3-D Movies Bad for Your Eyes?

    Medline Plus

    Full Text Available ... Payment Meetings and Deadlines Museum of Vision Ophthalmology Job Center Our Sites EyeWiki International Society of Refractive ... Payment Meetings and Deadlines Museum of Vision Ophthalmology Job Center Our Sites EyeWiki International Society of Refractive ...

  3. Parsimonious Refraction Interferometry and Tomography

    KAUST Repository

    Hanafy, Sherif; Schuster, Gerard T.

    2017-01-01

    We present parsimonious refraction interferometry and tomography where a densely populated refraction data set can be obtained from two reciprocal and several infill shot gathers. The assumptions are that the refraction arrivals are head waves

  4. Refractive accuracy with light-adjustable intraocular lenses.

    Science.gov (United States)

    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.

  5. Refractive Surgery: Malpractice Litigation Outcomes.

    Science.gov (United States)

    Custer, Benjamin L; Ballard, Steven R; Carroll, Robert B; Barnes, Scott D; Justin, Grant A

    2017-10-01

    To review data on malpractice claims related to refractive surgery to identify common allegations and injuries and financial outcomes. The WestlawNext database was reviewed for all malpractice lawsuits/settlements related to refractive eye surgery. Data evaluated included patient demographics, type of operation performed, plaintiff allegation, nature of injury, and litigation outcomes. A total of 167 cases met the inclusion criteria, of which 108 cases (64.7%) were found to be favorable and 59 cases (35.3%) unfavorable to the defendant. A total of 141 cases were tried by a jury with 108 cases (76.4%) favorable and 33 cases (23.6%) unfavorable to the defendant. Laser in situ keratomileusis was performed in 127 cases (76%). The most common allegations were negligence in treatment or surgery in 127 cases (76%) and lack of informed consent in 83 cases (49.7%). For all cases, the need for future surgery (P = 0.0001) and surgery resulting in keratoconus (P = 0.05) were more likely to favor the plaintiff. In jury verdict decisions, cases in which failure to diagnose a preoperative condition was alleged favored the defendant (P = 0.03), whereas machine malfunction (P = 0.05) favored the plaintiff. After adjustment for inflation, the overall mean award was $1,287,872. Jury verdicts and settlements led to mean awards of $1,604,801 and $826,883, respectively. Malpractice litigation in refractive surgery tends to favor the defendant. However, large awards and settlements were given in cases that were favorable to the plaintiff. The need for future surgery and surgery leading to keratoconus increased the chance of an unfavorable outcome.

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

    Science.gov (United States)

    2009-01-01

    .6 per 10,000 people in Canada have low vision. The 2001 Participation and Activity Limitation Survey (PALS) found that 594,350 (2.5%) Canadians had "difficulty seeing ordinary newsprint or clearly seeing the face of someone from 4 m," and the Canadian National Institute for the Blind (CNIB) registry classified 105,000 (.35%) Canadians as visually disabled. PHAKIC INTRAOCULAR LENSES (PIOL): A phakic intraocular lens (pIOL) is a supplementary lens that is inserted into the anterior or posterior chamber of the eye to correct refractive errors (myopia, hyperopia, and astigmatism). Unlike in cataract surgery, the eye's natural crystalline lens is not removed when the pIOL is inserted, so the eye retains its accommodative ability. In Canada and the United States, iris-fixated (anterior chamber lenses that are anchored to the iris with a claw) and posterior chamber lenses are the only types of pIOLs that are licensed by Health Canada and the Food and Drug Administration, respectively. EVIDENCE-BASED ANALYSIS METHOD: RESEARCH QUESTIONS #ENTITYSTARTX00026; What are the effectiveness, cost-effectiveness, and safety of pIOLs for the treatment of myopia, hyperopia, and astigmatism?Do certain subgroups (e.g. high myopia and low vision) benefit more from pIOLs?How do pIOLs compare with alternative surgical treatment options (LASIK, PRK, and CLE)?Using appropriate keywords, a literature search was conducted up to January 2009. Systematic reviews, meta-analyses, randomized controlled trials, and observational studies with more than 20 eyes receiving pIOLs were eligible for inclusion. The primary outcomes of interest were uncorrected visual acuity (UCVA), predictability of manifest refraction spherical equivalent (MRSE), and adverse events. The GRADE approach was used to systematically and explicitly evaluate the quality of evidence. The search identified 1,131 citations published between January 1, 2003, and January 16, 2009. Including a health technology assessment (HTA) identified in

  7. Retina Image Analysis and Ocular Telehealth: The Oak Ridge National Laboratory-Hamilton Eye Institute Case Study

    Energy Technology Data Exchange (ETDEWEB)

    Karnowski, Thomas Paul [ORNL; Giancardo, Luca [ORNL; Li, Yaquin [University of Tennessee, Knoxville (UTK); Tobin Jr, Kenneth William [ORNL; Chaum, Edward [University of Tennessee, Knoxville (UTK)

    2013-01-01

    Automated retina image analysis has reached a high level of maturity in recent years, and thus the question of how validation is performed in these systems is beginning to grow in importance. One application of retina image analysis is in telemedicine, where an automated system could enable the automated detection of diabetic retinopathy and other eye diseases as a low-cost method for broad-based screening. In this work we discuss our experiences in developing a telemedical network for retina image analysis, including our progression from a manual diagnosis network to a more fully automated one. We pay special attention to how validations of our algorithm steps are performed, both using data from the telemedicine network and other public databases.

  8. REFRACTIVE ANOMALIES OF AMBLYOPIC CHILDREN WITH AND WITHOUT STRABISMUS

    Directory of Open Access Journals (Sweden)

    Ljiljana Otašević

    2003-04-01

    Full Text Available Refractive anomalies occur when the ratio of the refraction ability and the eye length is distrurbed. Amblyopia isunderstood as dimness of vision without detectable lesions of the eye.The aim of the paper is to analyze refractive anomalies occurring in amblyopic children without of with strabismus. The cards of the children suffering from amblyopia and of five of more years of age have been singled out. The number of children obtained in that way is 243. Under special observation were bilateral and unilateral amblyopias and refractive anomalies in children both with and without strabismus. Out of 243 children there are 153 without strabismus (the majority of them reported for examination at the age of seven and 90 with strabismus (the majority of them reported at the age of five. In both the groups bilateral and unilateral amblyopia was registered so that the overall number of the observed amblyopic eyes was 369. In the children without strabismus we mostly found light amblyopia while in the froup of children with strabismus we found, in a great number, medium serious amblyopia while the presence of serious amblypia was also detected. As for refractive anomalies in both the groups of amblyopic children the most freqent were hypermetropic astigmatism and hypermetropia. Because of refractive anomalies as well as with strabismus with small angle, amblyopias are often discovered only when sharpness if vision is being checked; therefore, of great importance are regular systematic examinations of vision sharpness of younger children.

  9. Comparison of monochromatic aberrations in young adults with different visual acuity and refractive errors.

    Science.gov (United States)

    Yazar, Seyhan; Hewitt, Alex W; Forward, Hannah; McKnight, Charlotte M; Tan, Alex; Mountain, Jenny A; Mackey, David A

    2014-03-01

    To compare the monochromatic aberrations in a large cohort of 20-year-old Australians with differing levels of visual acuity and explore the relationship between these aberrations and refractive error. Lions Eye Institute, Perth, Western Australia, Australia. Cross-sectional analysis of a population-based cohort. Monochromatic aberrations were measured using a Zywave II wavefront aberrometer with natural pupils in a dark room. The logMAR corrected distance visual acuity (CDVA) was measured monocularly under normal illumination. Cycloplegic autorefraction was also performed. The study enrolled 2039 eyes of 1040 participants. Data from 1007 right eyes were analyzed. The median CDVA and spherical equivalent were -0.06 logMAR (interquartile range [IQR], -0.10 to 0.00) and +0.25 diopters (D) (IQR, -0.38 to 0.63), respectively. The median 6.0 mm higher-order aberration (HOA) was 0.58 μm (IQR, 0.44 to 0.79). Coma-like aberrations and 3rd-, 4th-, and 5th-order HOAs were significantly different between subjects with a CDVA of -0.10 logMAR or better and those with a CDVA worse than -0.10 logMAR. Fourth-order aberrations Z(4,-4) (P=.024) and Z(4,-2) (P=.029) and 2nd-order aberration Z(2,0) (Peyes, emmetropic eyes, and hyperopic eyes. Subjects with higher myopia had slightly higher total HOAs. The HOAs in this population were marginally higher than previously reported values. The findings confirm there is a difference in monochromatic aberrations between different vision and refractive groups. Results in this study will benefit decision-making processes in the clinical setting. Copyright © 2014 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  10. Uncorrected refractive errors.

    Science.gov (United States)

    Naidoo, Kovin S; Jaggernath, Jyoti

    2012-01-01

    Global estimates indicate that more than 2.3 billion people in the world suffer from poor vision due to refractive error; of which 670 million people are considered visually impaired because they do not have access to corrective treatment. Refractive errors, if uncorrected, results in an impaired quality of life for millions of people worldwide, irrespective of their age, sex and ethnicity. Over the past decade, a series of studies using a survey methodology, referred to as Refractive Error Study in Children (RESC), were performed in populations with different ethnic origins and cultural settings. These studies confirmed that the prevalence of uncorrected refractive errors is considerably high for children in low-and-middle-income countries. Furthermore, uncorrected refractive error has been noted to have extensive social and economic impacts, such as limiting educational and employment opportunities of economically active persons, healthy individuals and communities. The key public health challenges presented by uncorrected refractive errors, the leading cause of vision impairment across the world, require urgent attention. To address these issues, it is critical to focus on the development of human resources and sustainable methods of service delivery. This paper discusses three core pillars to addressing the challenges posed by uncorrected refractive errors: Human Resource (HR) Development, Service Development and Social Entrepreneurship.

  11. Uncorrected refractive errors

    Directory of Open Access Journals (Sweden)

    Kovin S Naidoo

    2012-01-01

    Full Text Available Global estimates indicate that more than 2.3 billion people in the world suffer from poor vision due to refractive error; of which 670 million people are considered visually impaired because they do not have access to corrective treatment. Refractive errors, if uncorrected, results in an impaired quality of life for millions of people worldwide, irrespective of their age, sex and ethnicity. Over the past decade, a series of studies using a survey methodology, referred to as Refractive Error Study in Children (RESC, were performed in populations with different ethnic origins and cultural settings. These studies confirmed that the prevalence of uncorrected refractive errors is considerably high for children in low-and-middle-income countries. Furthermore, uncorrected refractive error has been noted to have extensive social and economic impacts, such as limiting educational and employment opportunities of economically active persons, healthy individuals and communities. The key public health challenges presented by uncorrected refractive errors, the leading cause of vision impairment across the world, require urgent attention. To address these issues, it is critical to focus on the development of human resources and sustainable methods of service delivery. This paper discusses three core pillars to addressing the challenges posed by uncorrected refractive errors: Human Resource (HR Development, Service Development and Social Entrepreneurship.

  12. Juvenile eye growth, when completed?

    DEFF Research Database (Denmark)

    Fledelius, Hans C; Christensen, Anders S; Fledelius, Christian

    2014-01-01

    PURPOSE: To test Sorsby's classical statement of axial eye growth as completed at the age of 13 years, with a view also to differentiating between basic eye growth and juvenile elongation associated with eventual refractive change towards myopia. METHODS: (i) A total of 160 healthy eyes close...... about age 13 as general limit found support from the cross-sectional data, which suggested stable emmetropic eye size from about 11-12 years, with an average apparently outgrown male emmetropic value of 23.5 mm versus females' 22.9 mm. The longitudinal data, however, showed emmetropic growth also beyond...

  13. Knowledge, attitude and associated factors among primary school teachers regarding refractive error in school children in Gondar city, Northwest Ethiopia.

    Science.gov (United States)

    Alemayehu, Abiy Maru; Belete, Gizchewu Tilahun; Adimassu, Nebiyat Feleke

    2018-01-01

    Refractive error is an important cause of correctable visual impairment in the worldwide with a global distribution of 1.75% to 20.7% among schoolchildren. Teacher's knowledge about refractive error play an important role in encouraging students to seek treatment that helps in reducing the burden of visual impairment. To determine knowledge, attitude and associated factors among primary school teachers regarding refractive error in school children in Gondar city. Institution based cross-sectional study was conducted on 565 primary school teachers in Gondar city using pretested and structured self-administered questionnaire. For processing and analysis, SPSS version 20 was used and variables which had a P value of attitude towards refractive error. History of spectacle use [AOR = 2.13 (95% CI: 1.32, 3.43)], history of eye examination [AOR = 1.67 (95% CI: 1.19, 2.34)], training on eye health [AOR = 1.94 (95% CI; 1.09, 3.43)] and 11-20 years of experience [AOR = 2.53 (95% CI: 1.18, 5.43)] were positively associated with knowledge. Whereas being male [AOR = 2.03 (95% CI: 1.37, 3.01)], older age [AOR = 3.05 (95% CI: 1.07, 8.72)], 31-40 years of experience [AOR = 0.23 (95% CI: 0.07, 0.72)], private school type [AOR = 1.76 (95% CI: 1.06, 2.93)] and 5th -8th teaching category [AOR = 1.54 (95% CI: 1.05, 2.24)] were associated with attitude. Knowledge and attitude of study subjects were low which needs training of teachers about the refractive error.

  14. Knowledge, attitude and associated factors among primary school teachers regarding refractive error in school children in Gondar city, Northwest Ethiopia

    Science.gov (United States)

    2018-01-01

    Introduction Refractive error is an important cause of correctable visual impairment in the worldwide with a global distribution of 1.75% to 20.7% among schoolchildren. Teacher’s knowledge about refractive error play an important role in encouraging students to seek treatment that helps in reducing the burden of visual impairment. Objective To determine knowledge, attitude and associated factors among primary school teachers regarding refractive error in school children in Gondar city. Methods Institution based cross-sectional study was conducted on 565 primary school teachers in Gondar city using pretested and structured self-administered questionnaire. For processing and analysis, SPSS version 20 was used and variables which had a P value of attitude towards refractive error. History of spectacle use [AOR = 2.13 (95% CI: 1.32, 3.43)], history of eye examination [AOR = 1.67 (95% CI: 1.19, 2.34)], training on eye health [AOR = 1.94 (95% CI; 1.09, 3.43)] and 11–20 years of experience [AOR = 2.53 (95% CI: 1.18, 5.43)] were positively associated with knowledge. Whereas being male [AOR = 2.03 (95% CI: 1.37, 3.01)], older age [AOR = 3.05 (95% CI: 1.07, 8.72)], 31–40 years of experience [AOR = 0.23 (95% CI: 0.07, 0.72)], private school type [AOR = 1.76 (95% CI: 1.06, 2.93)] and 5th -8th teaching category [AOR = 1.54 (95% CI: 1.05, 2.24)] were associated with attitude. Conclusion Knowledge and attitude of study subjects were low which needs training of teachers about the refractive error. PMID:29447172

  15. Correction of refractive errors

    Directory of Open Access Journals (Sweden)

    Vladimir Pfeifer

    2005-10-01

    Full Text Available Background: Spectacles and contact lenses are the most frequently used, the safest and the cheapest way to correct refractive errors. The development of keratorefractive surgery has brought new opportunities for correction of refractive errors in patients who have the need to be less dependent of spectacles or contact lenses. Until recently, RK was the most commonly performed refractive procedure for nearsighted patients.Conclusions: The introduction of excimer laser in refractive surgery has given the new opportunities of remodelling the cornea. The laser energy can be delivered on the stromal surface like in PRK or deeper on the corneal stroma by means of lamellar surgery. In LASIK flap is created with microkeratome in LASEK with ethanol and in epi-LASIK the ultra thin flap is created mechanically.

  16. Eye Allergies

    Science.gov (United States)

    ... Español Eye Health / Eye Health A-Z Eye Allergies Sections What Are Eye Allergies? Eye Allergy Symptoms ... allergy diagnosis Eye allergy treatment What Are Eye Allergies? Leer en Español: ¿Qué son las alergias de ...

  17. Performance of Photoscreener in Detection of Refractive Error in All Age Groups and Amblyopia Risk Factors in Children in a Tribal District of Odisha: The Tribal Odisha Eye Disease Study (TOES) # 3

    Science.gov (United States)

    Panda, Lapam; Barik, Umasankar; Nayak, Suryasmita; Barik, Biswajit; Behera, Gyanaranjan; Kekunnaya, Ramesh

    2018-01-01

    Purpose To evaluate effectiveness of Welch Allyn Spot Vision Screener in detecting refractive error in all age groups and amblyopia risk factors in children in a tribal district of India. Methods All participants received dry retinoscopy and photorefraction; children also received cycloplegic retinoscopy. Statistical analysis included Bland-Altman and coefficient of determination (R2). Results Photoscreener could not elicit a response in 113 adults and 5 children of 580 recruited participants. In Bland-Altman analysis mean difference of Spot screener spherical equivalent (SSSE) and dry retinoscopy spherical equivalent (DRSE) was 0.32 diopters (D) in adults and 0.18 D in children; this was an overestimation of hyperopia and underestimation of myopia. In Bland-Altman analysis of SSSE and cycloplegic retinoscopy spherical equivalent (CRSE) the mean difference was −0.30 D in children; this was an overestimation of myopia and underestimation of hyperopia. In regression analysis the relationship between SSSE and DRSE was poor in adults (R2 = 0.50) and good in children (R2 = 0.92). Cubic regression model for Spot versus cycloretinoscopy in children was: CRSE = 0.34 + 0.85 SSSE − 0.01 SSSE2 + 0.006 SSSE3. It was 87% accurate. Sensitivity and specificity of Spot in detecting amblyopia risk factors (2013 American Association for Pediatric Ophthalmology and Strabismus [AAPOS] criteria) was 93.3% and 96.9% respectively. Sensitivity of Spot screener in detection of amblyopia was 72%. Conclusions Photoscreener has 87% accuracy in refraction in children. Its value could be used for subjective correction tests. Translational Relevance Photoscreening could complement traditional retinoscopy to address refractive error in children in a resource-limited facility region. PMID:29881649

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

    Science.gov (United States)

    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.

  19. Resident and young physician experience with complex cataract surgery and new cataract and refractive technology: Results of the ASCRS 2016 Young Eye Surgeons survey.

    Science.gov (United States)

    Schallhorn, Julie M; Ciralsky, Jessica B; Yeu, Elizabeth

    2017-05-01

    A survey was offered to attendees of the 2016 annual meeting of the American Society of Cataract and Refractive Surgery (ASCRS) as well as online to ASCRS members. Of the 429 self-identified surgeons in training or those with fewer than 5 years in practice, 83% had performed complex cataract surgery using iris expansion devices or capsular tension rings (63%) and 70% had implanted a toric intraocular lens (IOL). A minority of respondents had performed laser-assisted cataract surgery (27%) or implanted presbyopia-correcting IOLs (39%), and only half (50%) had performed laser vision correction (LVC). Comfort with complex cataract and IOL procedures improved with increasing number of cases performed until greater than 10 cases. From this we can conclude that young surgeons have adequate exposure to complex cataracts but lack experience in refractive surgery and new IOL technology. Reported surgeon confidence improved with increased experience and exposure. Copyright © 2017 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  20. 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.

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

    Directory of Open Access Journals (Sweden)

    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.

  2. 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.

  3. Bioinspired adaptive gradient refractive index distribution lens

    Science.gov (United States)

    Yin, Kezhen; Lai, Chuan-Yar; Wang, Jia; Ji, Shanzuo; Aldridge, James; Feng, Jingxing; Olah, Andrew; Baer, Eric; Ponting, Michael

    2018-02-01

    Inspired by the soft, deformable human eye lens, a synthetic polymer gradient refractive index distribution (GRIN) lens with an adaptive geometry and focal power has been demonstrated via multilayer coextrusion and thermoforming of nanolayered elastomeric polymer films. A set of 30 polymer nanolayered films comprised of two thermoplastic polyurethanes having a refractive index difference of 0.05 were coextruded via forced-assembly technique. The set of 30 nanolayered polymer films exhibited transmission near 90% with each film varying in refractive index by 0.0017. An adaptive GRIN lens was fabricated from a laminated stack of the variable refractive index films with a 0.05 spherical GRIN. This lens was subsequently deformed by mechanical ring compression of the lens. Variation in the optical properties of the deformable GRIN lens was determined, including 20% variation in focal length and reduced spherical aberration. These properties were measured and compared to simulated results by placido-cone topography and ANSYS methods. The demonstration of a solid-state, dynamic focal length, GRIN lens with improved aberration correction was discussed relative to the potential future use in implantable devices.

  4. 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.

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

    Directory of Open Access Journals (Sweden)

    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.

  6. Connecting eye to eye

    DEFF Research Database (Denmark)

    Dau, Susanne; Rask, Anders Bindslev

    2017-01-01

    Computer Supported Collaborative Learning (CSCL) is used a frame for supporting online and blended learning in educations. The online communication and collaboration are afforded by the social collaboration. However, the social collaboration is based on the establishment of direct eye contact...... (Khalid, Deska & Hugenberg, 2016), but direct eye contact is challenged by the position of the digital devices and thus CSCL. Lack of eye contact is the chief contributor to the negative effects of online disinhibition (Lapidot-Lefler & Barak, 2012) and the problem is the location of the web camera...... at the computer. Eye contact is challenged by the displacement between the senders´ and receivers´ focus on the screen picture and the camera's location at the top or bottom of screens on all digital devices. The aim of this paper is accordingly to investigate the influence of the displacement in eye contact...

  7. Contribution of refractive errors to visual impairment in patients at ...

    African Journals Online (AJOL)

    Objective: To determine the contribution of refractive error to visual impairment in visually impaired patients attending Korle-Bu Teaching Hospital, Ghana. Method: This study was conducted over a period of 1 year beginning October 2002 at Korle-Bu Teaching Hospital. Every 4th consecutive new case attending the eye ...

  8. Refractive errors in presbyopic patients in Kano, Nigeria

    African Journals Online (AJOL)

    Annals of African Medicine, Vol. ... Information extracted includes patient's age, sex, and types of refractive error. ... All patients had basic eye examination and streak retinoscopy at two third meter working distance. ... symptoms may start earlier or later than this age .... presbyopia was associated with reduced workers'.

  9. 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.

  10. Poor vision, refractive errors and barriers to treatment among ...

    African Journals Online (AJOL)

    Poor vision, refractive errors and barriers to treatment among commercial vehicle drivers in the Cape Coast municipality. ... were also administered to the participants to collect demographic data, history of driving and RTAs and utilization of eye care services as well as identification of the colours of the traffic light. Results: A ...

  11. Refractive Errors Affect the Vividness of Visual Mental Images

    Science.gov (United States)

    Palermo, Liana; Nori, Raffaella; Piccardi, Laura; Zeri, Fabrizio; Babino, Antonio; Giusberti, Fiorella; Guariglia, Cecilia

    2013-01-01

    The hypothesis that visual perception and mental imagery are equivalent has never been explored in individuals with vision defects not preventing the visual perception of the world, such as refractive errors. Refractive error (i.e., myopia, hyperopia or astigmatism) is a condition where the refracting system of the eye fails to focus objects sharply on the retina. As a consequence refractive errors cause blurred vision. We subdivided 84 individuals according to their spherical equivalent refraction into Emmetropes (control individuals without refractive errors) and Ametropes (individuals with refractive errors). Participants performed a vividness task and completed a questionnaire that explored their cognitive style of thinking before their vision was checked by an ophthalmologist. Although results showed that Ametropes had less vivid mental images than Emmetropes this did not affect the development of their cognitive style of thinking; in fact, Ametropes were able to use both verbal and visual strategies to acquire and retrieve information. Present data are consistent with the hypothesis of equivalence between imagery and perception. PMID:23755186

  12. [Use of Plusoptix as a screening method for refractive ambliopia].

    Science.gov (United States)

    Bogdănici, T; Tone, Silvia; Miron, Mihaela; Boboc, Mihaela; Bogdănici, Camelia

    2012-01-01

    Highlighting the differences in the objective refraction using the Plusoptix AO9 comparing them with the refraction performed with TOPCON KR-8900 autorefractor. Prospective study for 3 months held in the Ophthalmology Clinic in Iasi, Hospital Sf. Spiridon on a total of 39 children (21 girls and 18 boys) with mean age of 10.61 +/- 5.67 years. Clinical parameters: sex, age, objective refraction obtained with Plusoptix and with autorefractor corrected visual acuity (with different methods depending on each patient age), ortoptic examination (strabic deviation, binocular vision), the presence of symetry/asymetry while measuring with Plusoptix. The results were statistically processed by F-TEST calculating the correlation coefficient, standard deviation, significance level (using the spherical equivalent of the obtained values). Age limits of the studied cases ranged between 2-23 years. Visual acuity of children who had cooperate was between 0.2-1 with correction, achieving best values on right eye than left eye. 8 cases (20.51%) had large differences between measurements made with Plusoptix and autorefractor, half of that (4 cases) had strabismus. Three of these cases were with small hypermetropia and one with small myopia (Plusoptix shows a lower value). In 2 cases occurred higher differences (about 2-2,5D) between the 2 measurements, in patients with average hypermetropia. Plusoptix refraction was not possible at high hypermetropia or high myopia. This type of determining objective refraction using Plusoptix is a useful method of screening for discovery of refractive errors that can cause refractive amblyopia in young children and in those cases with a difficult collaboration. Because there are differences betweeti this 2 methods, for children with refractive errors are recommended further exploration to determine the appropriate optical correction. Plusoptix is a limited method because it cannot detect the exact values in those cases with high hypermetropia or high

  13. Human resources for refraction services in Central Nepal.

    Science.gov (United States)

    Kandel, Himal; Murthy, G V S; Bascaran, Covadonga

    2015-07-01

    Uncorrected refractive error is a public health problem globally and in Nepal. Planning of refraction services is hampered by a paucity of data. This study was conducted to determine availability and distribution of human resources for refraction, their efficiency, the type and extent of their training; the current service provision of refraction services and the unmet need in human resources for refraction in Central Nepal. This was a descriptive cross-sectional study. All refraction facilities in the Central Region were identified through an Internet search and interviews of key informants from the professional bodies and parent organisations of primary eye centres. A stratified simple random sampling technique was used to select 50 per cent of refraction facilities. The selected facilities were visited for primary data collection. Face-to-face interviews were conducted with the managers and the refractionists available in the facilities using a semi-structured questionnaire. Data was collected in 29 centres. All the managers (n=29; response rate 100 per cent) and 50 refractionists (Response rate 65.8 per cent) were interviewed. Optometrists and ophthalmic assistants were the main providers of refraction services (n=70, 92.11 per cent). They were unevenly distributed across the region, highly concentrated around urban areas. The median number of refractions per refractionist per year was 3,600 (IQR: 2,400 - 6,000). Interviewed refractionists stated that clients' knowledge, attitude and practice related factors such as lack of awareness of the need for refraction services and/or availability of existing services were the major barriers to the output of refraction services. The total number of refractions carried out in the Central Region per year was 653,176. An additional 170 refractionists would be needed to meet the unmet need of 1,323,234 refractions. The study findings demand a major effort to develop appropriately trained personnel when planning

  14. About the Eye

    Medline Plus

    Full Text Available ... The Visual System Your Eyes’ Natural Defenses Eye Health and Safety First Aid Tips Healthy Vision Tips ... addressed to the NEI Website Manager . Department of Health and Human Services | The National Institutes of Health | ...

  15. About the Eye

    Medline Plus

    Full Text Available ... Contact Us Visiting the NIH Campus Mission Statement As part of the federal government’s National Institutes of ... Did You Know? Vision depends on your brain as much as it does on your eyes. NEI ...

  16. Eye and orbit ultrasound

    Science.gov (United States)

    ... Images Head and eye echoencephalogram References Coleman DJ, Silverman RH, Lloyd HO, Daly S. Evaluation of the posterior ... Vision Institute, La Jolla, CA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial ...

  17. About the Eye

    Medline Plus

    Full Text Available ... Campus Mission Statement As part of the federal government’s National Institutes of Health (NIH), the National Eye ... Publications Catalog Photos and Images Spanish Language Information Grants and Funding Extramural Research Division of Extramural Science ...

  18. Refractive index based measurements

    DEFF Research Database (Denmark)

    2014-01-01

    In a method for performing a refractive index based measurement of a property of a fluid such as chemical composition or temperature, a chirp in the local spatial frequency of interference fringes of an interference pattern is reduced by mathematical manipulation of the recorded light intensity...

  19. Conceptualization of Light Refraction

    Science.gov (United States)

    Sokolowski, Andrzej

    2013-01-01

    There have been a number of papers dealing quantitatively with light refraction. Yet the conceptualization of the phenomenon that sets the foundation for a more rigorous math analysis is minimized. The purpose of this paper is to fill that gap. (Contains 3 figures.)

  20. Assessing the test-retest repeatability of the Vietnamese version of the National Eye Institute 25-item Visual Function Questionnaire among bilateral cataract patients for a Vietnamese population.

    Science.gov (United States)

    To, Kien Gia; Meuleners, Lynn; Chen, Huei-Yang; Lee, Andy; Do, Dung Van; Duong, Dat Van; Phi, Tien Duy; Tran, Hoang Huy; Nguyen, Nguyen Do

    2014-06-01

    To determine the test-retest repeatability of the National Eye Institute 25-item Visual Function Questionnaire (NEI VFQ-25) for use with older Vietnamese adults with bilateral cataract. The questionnaire was translated into Vietnamese and back-translated into English by two independent translators. Patients with bilateral cataract aged 50 and older completed the questionnaire on two separate occasions, one to two weeks after first administration of the questionnaire. Test-retest repeatability was assessed using the Cronbach's α and intraclass correlation coefficients. The average age of participants was 67 ± 8 years and most participants were female (73%). Internal consistency was acceptable with the α coefficient above 0.7 for all subscales and intraclass correlation coefficients were 0.6 or greater in all subscales. The Vietnamese NEI VFQ-25 is reliable for use in studies assessing vision-related quality of life in older adults with bilateral cataract in Vietnam. We propose some modifications to the NEI-VFQ questions to reflect activities of older people in Vietnam. © 2013 ACOTA.

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

    Directory of Open Access Journals (Sweden)

    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

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

    OpenAIRE

    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...

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

    Science.gov (United States)

    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.

  4. Effective spectral dispersion of refractive index modulation

    Czech Academy of Sciences Publication Activity Database

    Vojtíšek, Petr; Květoň, M.; Richter, I.

    2017-01-01

    Roč. 19, č. 4 (2017), č. článku 045603. ISSN 2040-8978 R&D Projects: GA MŠk(CZ) LO1206 Institutional support: RVO:61389021 Keywords : volume gratings * holography * dispersion * refractive index modulation Subject RIV: BH - Optics, Masers, Lasers OBOR OECD: Optics (including laser optics and quantum optics) Impact factor: 1.741, year: 2016 http://iopscience.iop.org/article/10.1088/2040-8986/aa6092/meta

  5. Refractive errors in Cameroonians diagnosed with complete oculocutaneous albinism

    Directory of Open Access Journals (Sweden)

    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

  6. Refractive outcomes of intraoperative wavefront aberrometry versus optical biometry alone for intraocular lens power calculation

    Directory of Open Access Journals (Sweden)

    Zina Zhang

    2017-01-01

    Full Text Available Purpose: To compare the outcomes of intraoperative wavefront aberrometry versus optical biometry alone for intraocular lens (IOL power calculation in eyes undergoing cataract surgery with monofocal IOL implantation. Methods: Preoperative data were obtained with the IOLMaster. Intraoperative aphakic measurements and IOL power calculations were obtained in some patients with the optiwave refractive analysis (ORA system. Analysis was performed to determine the accuracy of monofocal IOL power prediction and postoperative manifest refraction at 1 month of the ORA versus IOLMaster. Results: Two hundred and ninety-five eyes reviewed, 61 had only preoperative IOLMaster measurements and 234 had both IOLMaster and ORA measurements. Of these 234 eyes, 6 were excluded, 107 had the same recommended IOL power by ORA and IOLMaster. Sixty-four percent of these eyes were within ±0.5D. 95 eyes had IOL power implantation based on ORA instead of IOLMaster. Seventy percent of these eyes were within ±0.5D of target refraction. 26 eyes had IOL power chosen based on IOLMaster predictions instead of ORA. Sixty-five percent were within ±0.5D. In the group with IOLMaster without ORA measurements, 80% of eyes were within ±0.5D of target refraction. The absolute error was statistically smaller in those eyes where the ORA and IOLMaster recommended the same IOL power based on preoperative target refraction compared to instances in which IOL selection was based on ORA or IOLMaster alone. Neither prediction errors were statistically different between the ORA and IOLMaster alone. Conclusion: Intraoperative wavefront aberrometry with the ORA system provides postoperative refractive results comparable to conventional biometry with the IOLMaster for monofocal IOL selection.

  7. The Tromsø Eye Study

    DEFF Research Database (Denmark)

    Bertelsen, Geir; Erke, Maja G; von Hanno, Therese

    2013-01-01

    Purpose:  To describe the study design and methodology of the Tromsø Eye Study (TES), and to describe visual acuity and refractive error in the study population. Methods:  The Tromsø Eye Study is a sub-study of the Tromsø Study, a population-based multipurpose longitudinal study in the municipality...... of Tromsø, Norway. The Tromsø Eye Study was a part of the sixth survey of the Tromsø Study, conducted from October 2007 through December 2008. The eye examination included information on self-reported eye diseases, assessment of visual acuity and refractive errors, retinal photography and optical coherence...

  8. Ultraviolet light induced refractive index structures in germanosilica

    DEFF Research Database (Denmark)

    Svalgaard, Mikael

    1997-01-01

    The focus of the research presented in this ph.d. thesis is refractive index structures photoinduced in germanonsilica waveguides with ultra-violet (UV) radiation. The physical mechanisms involved in photosensitivity and applications of a wide range of UV induced refractive index structures in both...... application of a scanning near-field optical microscope to obtain high resolution images of UV induced refractive index structures and by monitoring the dynamics of UV induced index changes and luminescence. During part of my ph.d. project I have worked at the National Institute of Standards and Technolgy...

  9. Are 3-D Movies Bad for Your Eyes?

    Medline Plus

    Full Text Available ... Ophthalmology/Strabismus Ocular Pathology/Oncology Oculoplastics/Orbit Refractive Management/Intervention Retina/Vitreous Uveitis Focus ... Eye Health A-Z Symptoms Glasses & Contacts Tips & ...

  10. Are 3-D Movies Bad for Your Eyes?

    Medline Plus

    Full Text Available ... Privacy Policy Terms of Service For Advertisers For Media Ophthalmology Job Center © American Academy of Ophthalmology 2018 Our Sites EyeWiki International Society of Refractive Surgery * Required * First Name: * Last Name: ...

  11. Are 3-D Movies Bad for Your Eyes?

    Medline Plus

    Full Text Available ... Privacy Policy Terms of Service For Advertisers For Media Ophthalmology Job Center © American Academy of Ophthalmology 2018 Our Sites EyeWiki International Society of Refractive Surgery * Required * First ...

  12. Association between Ocular Sensory Dominance and Refractive Error Asymmetry.

    Directory of Open Access Journals (Sweden)

    Feng Jiang

    Full Text Available To investigate the association between ocular sensory dominance and interocular refractive error difference (IRED.A total of 219 subjects were recruited. The refractive errors were determined by objective refraction with a fixation target located 6 meters away. 176 subjects were myopic, with 83 being anisometropic (IRED ≥ 0.75 D. 43 subjects were hyperopic, with 22 being anisometropic. Sensory dominance was measured with a continuous flashing technique with the tested eye viewing a Gabor increasing in contrast and the fellow eye viewing a Mondrian noise decreasing in contrast. The log ratio of Mondrian to Gabor's contrasts was recorded when a subject just detected the tilting direction of the Gabor during each trial. T-test was used to compare the 50 values collected from each eye, and the t-value was used as a subject's ocular dominance index (ODI to quantify the degree of ocular dominance. A subject with ODI ≥ 2 (p < 0.05 had clear dominance and the eye with larger mean ratio was the dominant one. Otherwise, a subject had an unclear dominance.The anisometropic subjects had stronger ocular dominance in comparison to non-anisometropic subjects (rank-sum test, p < 0.01 for both myopic and hyperopic subjects. In anisometropic subjects with clear dominance, the amplitude of the anisometropia was correlated with ODI values (R = 0.42, p < 0.01 in myopic anisometropic subjects; R = 0.62, p < 0.01 in hyperopic anisometropic subjects. Moreover, the dominant eyes were more myopic in myopic anisometropic subjects (sign-test, p < 0.05 and less hyperopic in hyperopic anisometropic subjects (sign-test, p < 0.05.The degree of ocular sensory dominance is associated with interocular refractive error difference.

  13. Management of digital eye strain.

    Science.gov (United States)

    Coles-Brennan, Chantal; Sulley, Anna; Young, Graeme

    2018-05-23

    Digital eye strain, an emerging public health issue, is a condition characterised by visual disturbance and/or ocular discomfort related to the use of digital devices and resulting from a range of stresses on the ocular environment. This review aims to provide an overview of the extensive literature on digital eye strain research with particular reference to the clinical management of symptoms. As many as 90 per cent of digital device users experience symptoms of digital eye strain. Many studies suggest that the following factors are associated with digital eye strain: uncorrected refractive error (including presbyopia), accommodative and vergence anomalies, altered blinking pattern (reduced rate and incomplete blinking), excessive exposure to intense light, closer working distance, and smaller font size. Since a symptom may be caused by one or more factors, a holistic approach should be adopted. The following management strategies have been suggested: (i) appropriate correction of refractive error, including astigmatism and presbyopia; (ii) management of vergence anomalies, with the aim of inducing or leaving a small amount of heterophoria (~1.5 Δ Exo); (iii) blinking exercise/training to maintain normal blinking pattern; (iv) use of lubricating eye drops (artificial tears) to help alleviate dry eye-related symptoms; (v) contact lenses with enhanced comfort, particularly at end-of-day and in challenging environments; (vi) prescription of colour filters in all vision correction options, especially blue light-absorbing filters; and (vii) management of accommodative anomalies. Prevention is the main strategy for management of digital eye strain, which involves: (i) ensuring an ergonomic work environment and practice (through patient education and the implementation of ergonomic workplace policies); and (ii) visual examination and eye care to treat visual disorders. Special consideration is needed for people at a high risk of digital eye strain, such as computer

  14. Refractive lens exchange in younger and older presbyopes: comparison of complication rates, 3 months clinical and patient-reported outcomes

    Directory of Open Access Journals (Sweden)

    Schallhorn SC

    2017-08-01

    Full Text Available Steven C Schallhorn,1–3 Julie M Schallhorn,1 Martina Pelouskova,3 Jan A Venter,3 Keith A Hettinger,3 Stephen J Hannan,3 David Teenan3 1Department of Ophthalmology, University of California, San Francisco, CA, USA; 2Roski Eye Institute, University of Southern California, Los Angeles, CA, USA; 3Optical Express, Glasgow UK Purpose: To compare refractive and visual outcomes, patient satisfaction, and complication rates among different age categories of patients who underwent refractive lens exchange (RLE. Methods: A stratified, simple random sample of patients matched on preoperative sphere and cylinder was selected for four age categories: 45–49 years (group A, 50–54 years (group B, 55–59 years (group C, and 60–65 years (group D. Each group contained 320 patients. All patients underwent RLE with a multifocal intraocular lens at least in one eye. Three months postoperative refractive/visual and patient-reported outcomes are presented. Results: The percentage of patients that achieved binocular uncorrected distance visual acuity 20/20 or better was 91.6% (group A, 93.8% (group B, 91.6% (group C, 88.8% (group D, P=0.16. Binocularly, 80.0% of patients in group A, 84.7% in group B, 78.9% in group C, and 77.8% in group D achieved 20/30 or better uncorrected near visual acuity (P=0.13. The proportion of eyes within 0.50 D of emmetropia was 84.4% in group A, 86.8% in group B, 85.7% in group C, and 85.8% in group D (P=0.67. There was no statistically significant difference in postoperative satisfaction, visual phenomena, dry eye symptoms, distance or near vision activities. Apart from higher rate of iritis in the age group 50–55 years, there was no statistically significant difference in postoperative complication rates. Conclusion: RLE can be safely performed in younger as well as older presbyopes. No significant difference was found in clinical or patient-reported outcomes. Keywords: refractive lens exchange, multifocal IOLs, younger

  15. Eye Protection

    OpenAIRE

    Pashby, Tom

    1986-01-01

    Eye injuries frequently occur in the home, at work and at play. Many result in legally blind eyes, and most are preventable. Awareness of potential hazards is essential to preventing eye injuries, particularly in children. In addition, protective devices must be used appropriately. We have developed eye protectors that have proved effective in reducing both the overall incidence and the severity of sports eye injuries.

  16. Refractive index based measurements

    DEFF Research Database (Denmark)

    2014-01-01

    In a method for performing a refractive index based measurement of a property of a fluid such as chemical composition or temperature by observing an apparent angular shift in an interference fringe pattern produced by back or forward scattering interferometry, ambiguities in the measurement caused...... by the apparent shift being consistent with one of a number of numerical possibilities for the real shift which differ by 2n are resolved by combining measurements performed on the same sample using light paths therethrough of differing lengths....

  17. Refractive error assessment: influence of different optical elements and current limits of biometric techniques.

    Science.gov (United States)

    Ribeiro, Filomena; Castanheira-Dinis, Antonio; Dias, Joao Mendanha

    2013-03-01

    To identify and quantify sources of error on refractive assessment using exact ray tracing. The Liou-Brennan eye model was used as a starting point and its parameters were varied individually within a physiological range. The contribution of each parameter to refractive error was assessed using linear regression curve fits and Gaussian error propagation analysis. A MonteCarlo analysis quantified the limits of refractive assessment given by current biometric measurements. Vitreous and aqueous refractive indices are the elements that influence refractive error the most, with a 1% change of each parameter contributing to a refractive error variation of +1.60 and -1.30 diopters (D), respectively. In the phakic eye, axial length measurements taken by ultrasound (vitreous chamber depth, lens thickness, and anterior chamber depth [ACD]) were the most sensitive to biometric errors, with a contribution to the refractive error of 62.7%, 14.2%, and 10.7%, respectively. In the pseudophakic eye, vitreous chamber depth showed the highest contribution at 53.7%, followed by postoperative ACD at 35.7%. When optic measurements were considered, postoperative ACD was the most important contributor, followed by anterior corneal surface and its asphericity. A MonteCarlo simulation showed that current limits of refractive assessment are 0.26 and 0.28 D for the phakic and pseudophakic eye, respectively. The most relevant optical elements either do not have available measurement instruments or the existing instruments still need to improve their accuracy. Ray tracing can be used as an optical assessment technique, and may be the correct path for future personalized refractive assessment. Copyright 2013, SLACK Incorporated.

  18. Nine Loci for Ocular Axial Length Identified through Genome-wide Association Studies, Including Shared Loci with Refractive Error

    NARCIS (Netherlands)

    Cheng, Ching-Yu; Schache, Maria; Ikram, M. Kamran; Young, Terri L.; Guggenheim, Jeremy A.; Vitart, Veronique; Macgregor, Stuart; Verhoeven, Virginie J. M.; Barathi, Veluchamy A.; Liao, Jiemin; Hysi, Pirro G.; Bailey-Wilson, Joan E.; St Pourcain, Beate; Kemp, John P.; McMahon, George; Timpson, Nicholas J.; Evans, David M.; Montgomery, Grant W.; Mishra, Aniket; Wang, Ya Xing; Wang, Jie Jin; Rochtchina, Elena; Polasek, Ozren; Wright, Alan F.; Amin, Najaf; van Leeuwen, Elisabeth M.; Wilson, James F.; Pennell, Craig E.; van Duijn, Cornelia M.; de Jong, Paulus T. V. M.; Vingerling, Johannes R.; Zhou, Xin; Chen, Peng; Li, Ruoying; Tay, Wan-Ting; Zheng, Yingfeng; Chew, Merwyn; Burdon, Kathryn P.; Craig, Jamie E.; Iyengar, Sudha K.; Igo, Robert P.; Lass, Jonathan H.; Chew, Emily Y.; Haller, Toomas; Mihailov, Evelin; Metspalu, Andres; Wedenoja, Juho; Simpson, Claire L.; Wojciechowski, Robert; Chen, Wei

    2013-01-01

    Refractive errors are common eye disorders of public health importance worldwide. Ocular axial length (AL) is the major determinant of refraction and thus of myopia and hyperopia. We conducted a meta-analysis of genome-wide association studies for AL, combining 12,531 Europeans and 8,216 Asians. We

  19. Do Peripheral Refraction and Aberration Profiles Vary with the Type of Myopia? - An Illustration Using a Ray-Tracing Approach

    Directory of Open Access Journals (Sweden)

    Ravi C. Bakaraju

    2009-01-01

    Conclusion: This study has indicated that myopic eyes with primarily an axial component may have a greater risk of progression than their refractive counterparts albeit with the same degree of refractive error. This prediction emerges from the presented theoretical ray tracing model and, therefore, requires clinical confirmation.

  20. Intraocular lens calculation adjustment after laser refractive surgery using Scheimpflug imaging.

    Science.gov (United States)

    Schuster, Alexander K; Schanzlin, David J; Thomas, Karin E; Heichel, Christopher W; Purcell, Tracy L; Barker, Patrick D

    2016-02-01

    To test a new method of intraocular lens (IOL) calculation after corneal refractive surgery using Scheimpflug imaging (Pentacam HR) and partial coherence interferometry (PCI) (IOLMaster) that does not require historical data; that is, the Schuster/Schanzlin-Thomas-Purcell (SToP) IOL calculator. Shiley Eye Center, San Diego, California, and Walter Reed National Military Medical Center, Bethesda, Maryland, USA. Retrospective data analysis and validation study. Data were retrospectively collected from patient charts including data from Scheimpflug imaging and refractive history. Target refraction was calculated using PCI and the Holladay 1 and SRK/T formulas. Regression analysis was performed to explain the deviation of the target refraction, taking into account the following influencing factors: ratio of posterior-to-anterior corneal radius, axial length (AL), and anterior corneal radius. The regression analysis study included 61 eyes (39 patients) that had laser in situ keratomileusis (57 eyes) or photorefractive keratectomy (4 eyes) and subsequent cataract. Two factors were found that explained the deviation of the target refraction using the Holladay 1 formula; that is, the ratio of the corneal radii and the AL and the ratio of corneal radii for the SRK/T formula. A new IOL adjustment calculator was derived and validated at a second center using 14 eyes (10 patients). The error in IOL calculation for normal eyes after laser refractive treatment was related to the ratio of posterior-to-anterior corneal radius. A formula requiring Scheimpflug data and suggested IOL power only yielded an improved postoperative result for patients with previous corneal laser refractive surgery having cataract surgery. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2016 ASCRS and ESCRS. All rights reserved.

  1. Role of the treating surgeon in the consent process for elective refractive surgery

    Directory of Open Access Journals (Sweden)

    Schallhorn SC

    2016-11-01

    Full Text Available Steven C Schallhorn,1–3 Stephen J Hannan,3 David Teenan,3 Julie M Schallhorn1 1Department of Ophthalmology, University of California, San Francisco, San Francisco, 2Roski Eye Institute, University of Southern California, Los Angeles, CA, USA; 3Optical Express, Glasgow, UK Purpose: To compare patient’s perception of consent quality, clinical and quality-of-life outcomes after laser vision correction (LVC and refractive lens exchange (RLE between patients who met their treating surgeon prior to the day of surgery (PDOS or on the day of surgery (DOS. Design: Retrospective, comparative case series. Setting: Optical Express, Glasgow, UK. Methods: Patients treated between October 2015 and June 2016 (3972 LVC and 979 RLE patients who attended 1-day and 1-month postoperative aftercare and answered a questionnaire were included in this study. All patients had a thorough preoperative discussion with an optometrist, watched a video consent, and were provided with written information. Patients then had a verbal discussion with their treating surgeon either PDOS or on the DOS, according to patient preference. Preoperative and 1-month postoperative visual acuity, refraction, preoperative, 1-day and 1-month postoperative questionnaire were compared between DOS and PDOS patients. Multivariate regression model was developed to find factors associated with patient’s perception of consent quality. Results: Preoperatively, 8.0% of LVC and 17.1% of RLE patients elected to meet their surgeon ahead of the surgery day. In the LVC group, 97.5% of DOS and 97.2% of PDOS patients indicated they were properly consented for surgery (P=0.77. In the RLE group, 97.0% of DOS and 97.0% of PDOS patients stated their consent process for surgery was adequate (P=0.98. There was no statistically significant difference between DOS and PDOS patients in most of the postoperative clinical or questionnaire outcomes. Factors predictive of patient’s satisfaction with consent quality

  2. Fish eye optics

    Czech Academy of Sciences Publication Activity Database

    Hudec, René; Michalová, S.

    2017-01-01

    Roč. 47, č. 2 (2017), s. 94-99 ISSN 1335-1842. [INTEGRAL/BART Workshop /14./. Karlovy Vary, 03.04.2017-07.04.2017] Grant - others:GA ČR(CZ) GA13-33324S Institutional support: RVO:67985815 Keywords : fish eye optics * lobster eye optics * X-ray monitoring Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics OBOR OECD: Astronomy (including astrophysics,space science) Impact factor: 0.336, year: 2016

  3. Refraction and the axial length of the eyeball in patients with the optic disc drusen.

    Science.gov (United States)

    Obuchowska, Iwona; Mariak, Zofia

    2009-01-01

    The aim of the study was to demonstrate the relationship between the optic disc drusen (ODD) and the axial length of the eyeball as well as refractive error. We examined prospectively 40 patients with ODD, 18 men and 22 women, age range from 34 to 69 years. All subjects underwent full ophthalmic examination, visual field testing and color-coded duplex sonography of the ocular vessels. Refraction was determined with an autorefractometer (Topcon RM-8000B) and further refined subjectively. Spherical equivalent refraction was calculated as the spherical dioptre plus one half of the cylindrical dioptre. Axial lengths were measured with a Sonomed ultrasound scanner model E-Z Scan AB5500. Clinical signs were observed in 65% of the eyes with drusen, among them, 38% had symptoms of visual acuity loss and all had visual fields defects. There were 21 eyes (18 eyes with and 3 without drusen), with a recorded refractive error. Significant differences in hyperopia were observed between the eyes with and without drusen (p = 0.048). The rate of occurrence of myopia did not differ significantly between affected and unaffected eyes (p = 0.06). The mean spherical equivalent refraction and axial dimensions of the eye differed significantly among the groups of eyes with and without drusen (p < 0.05). Significant differences in mean values of peak-systolic and end-diastolic velocities (p < 0.001) as well as in the resistivity index (p = 0.047) were observed between eyes with and without drusen. The optic disc drusen are often associated with shorter and hyperopic eyes. This anatomical conditions and vascular factors may contribute to pathogenesis of drusen.

  4. 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.

  5. Changes in refractive characteristics in Japanese children with Down syndrome.

    Science.gov (United States)

    Horio, Junna; Kaneko, Hiroki; Takayama, Kei; Tuzuki, Kinichi; Kakihara, Hiroko; Iwami, Miou; Kawase, Yoshikatsu; Tsunekawa, Taichi; Yamaguchi, Naoko; Nonobe, Norie; Terasaki, Hiroko

    2018-03-01

    To investigate the refractive characteristics of Japanese children with Down syndrome. Retrospective study. The clinical records of refractive errors and ocular manifestations in children with Down syndrome who visited the Aichi Children's Health and Medical Center between November 2001 and January 2016 were retrospectively reviewed. The children were divided into the 3 following groups depending on their age: group 1 (≤ 6 years), group 2 (7-12 years), and group 3 (13-19 years). The collection of refractive error data was performed only for the right eyes and only once for each child, when the children were last examined with their pupils dilated. The study included 416 children (224 boys, 192 girls; average age, 6.1 ± 4.1 years). Group 3 had significantly stronger myopia than did groups 1 and 2. The mean cylindrical power in all the children was - 2.1 ± 1.2 diopters (D), and cylindrical power ≤ - 1.0 D (stronger than - 1.0 D) was seen in 366 eyes (88%). No significant difference in cylindrical power was found among the 3 groups. The spherical equivalent refraction showed an age-dependent myopic shift. Given that the amount of astigmatism did not show age-dependent differences, the age-dependent myopic shift could be due mainly to the change in spherical power.

  6. Refractive Development in the “ROP Rat”

    Directory of Open Access Journals (Sweden)

    Toco Y. P. Chui

    2012-01-01

    Full Text Available Although retinopathy of prematurity (ROP is clinically characterized by abnormal retinal vessels at the posterior pole of the eye, it is also commonly characterized by vascular abnormalities in the anterior segment, visual dysfunction which is based in retinal dysfunction, and, most commonly of all, arrested eye growth and high refractive error, particularly (and paradoxically myopia. The oxygen-induced retinopathy rat model of ROP presents neurovascular outcomes similar to the human disease, although it is not yet known if the “ROP rat” also models the small-eyed myopia characteristic of ROP. In this study, magnetic resonance images (MRIs of albino (Sprague-Dawley and pigmented (Long-Evans ROP rat eyes, and age- and strain-matched room-air-reared (RAR controls, were examined. The positions and curvatures of the various optical media were measured and the refractive state (℞ of each eye estimated based on a previously published model. Even in adulthood (postnatal day 50, Sprague-Dawley and Long-Evans ROP rats were significantly myopic compared to strain-matched controls. The myopia in the Long-Evans ROP rats was more severe than in the Sprague-Dawley ROP rats, which also had significantly shorter axial lengths. These data reveal the ROP rat to be a novel and potentially informative approach to investigating physiological mechanisms in myopia in general and the myopia peculiar to ROP in particular.

  7. Blue Light Protects Against Temporal Frequency Sensitive Refractive Changes.

    Science.gov (United States)

    Rucker, Frances; Britton, Stephanie; Spatcher, Molly; Hanowsky, Stephan

    2015-09-01

    Time spent outdoors is protective against myopia. The outdoors allows exposure to short-wavelength (blue light) rich sunlight, while indoor illuminants can be deficient at short-wavelengths. In the current experiment, we investigate the role of blue light, and temporal sensitivity, in the emmetropization response. Five-day-old chicks were exposed to sinusoidal luminance modulation of white light (with blue; N = 82) or yellow light (without blue; N = 83) at 80% contrast, at one of six temporal frequencies: 0, 0.2, 1, 2, 5, 10 Hz daily for 3 days. Mean illumination was 680 lux. Changes in ocular components and corneal curvature were measured. Refraction, eye length, and choroidal changes were dependent on the presence of blue light (P light, refraction did not change across frequencies (mean change -0.24 [diopters] D), while in the absence of blue light, we observed a hyperopic shift (>1 D) at high frequencies, and a myopic shift (>-0.6 D) at low frequencies. With blue light there was little difference in eye growth across frequencies (77 μm), while in the absence of blue light, eyes grew more at low temporal frequencies and less at high temporal frequencies (10 vs. 0.2 Hz: 145 μm; P light. Illuminants rich in blue light can protect against myopic eye growth when the eye is exposed to slow changes in luminance contrast as might occur with near work.

  8. Comment on ``Perfect imaging with positive refraction in three dimensions''

    Science.gov (United States)

    Merlin, R.

    2010-11-01

    Leonhardt and Philbin [Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.81.011804 81, 011804(R) (2010)] have recently constructed a mathematical proof that the Maxwell's fish-eye lens provides perfect imaging of electromagnetic waves without negative refraction. In this comment, we argue that the unlimited resolution is an artifact of having introduced an unphysical drain at the position of the geometrical image. The correct solution gives focusing consistent with the standard diffraction limit.

  9. Comment on ''Perfect imaging with positive refraction in three dimensions''

    International Nuclear Information System (INIS)

    Merlin, R.

    2010-01-01

    Leonhardt and Philbin [Phys. Rev. A 81, 011804(R) (2010)] have recently constructed a mathematical proof that the Maxwell's fish-eye lens provides perfect imaging of electromagnetic waves without negative refraction. In this comment, we argue that the unlimited resolution is an artifact of having introduced an unphysical drain at the position of the geometrical image. The correct solution gives focusing consistent with the standard diffraction limit.

  10. 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.

  11. Refractive index based measurements

    DEFF Research Database (Denmark)

    2014-01-01

    A refractive index based measurement of a property of a fluid is measured in an apparatus comprising a variable wavelength coherent light source (16), a sample chamber (12), a wavelength controller (24), a light sensor (20), a data recorder (26) and a computation apparatus (28), by - directing...... coherent light having a wavelength along an input light path, - producing scattering of said light from each of a plurality of interfaces within said apparatus including interfaces between said fluid and a surface bounding said fluid, said scattering producing an interference pattern formed by said...... scattered light, - cyclically varying the wavelength of said light in said input light path over a 1 nm to 20nm wide range of wavelengths a rate of from 10Hz to 50 KHz, - recording variation of intensity of the interfering light with change in wavelength of the light at an angle of observation...

  12. Eye Cancer

    Science.gov (United States)

    Cancer of the eye is uncommon. It can affect the outer parts of the eye, such as the eyelid, which are made up ... and nerves. If the cancer starts inside the eyeball it's called intraocular cancer. The most common intraocular ...

  13. Black Eye

    Science.gov (United States)

    ... Your Eyes Sep 20, 2017 Eye Injuries from Laundry Packets On the Rise Jun 30, 2017 ... Medical Disclaimer Privacy Policy Terms of Service For Advertisers For Media Ophthalmology Job Center © American ...

  14. Eye Anatomy

    Science.gov (United States)

    ... News About Us Donate In This Section Eye Anatomy en Español email Send this article to a ... You at Risk For Glaucoma? Childhood Glaucoma Eye Anatomy Five Common Glaucoma Tests Glaucoma Facts and Stats ...

  15. Eye Emergencies

    Science.gov (United States)

    ... The Marfan Foundation Marfan & Related Disorders What is Marfan Syndrome? What are Related Disorders? What are the Signs? ... Emergencies Eye Emergencies Lung Emergencies Surgeries Eye Emergencies Marfan syndrome significantly increases your risk of retinal detachment, a ...

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

    Science.gov (United States)

    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.

  17. Your Eyes

    Science.gov (United States)

    ... away? If you guessed the eye, you're right! Your eyes are at work from the moment you wake up to the ... the eye is seeing. A Muscle Makes It Work The lens is suspended in ... of the lens. That's right — the lens actually changes shape right inside your ...

  18. Advanced personalized nomogram for myopic laser surgery: First 100 eyes

    NARCIS (Netherlands)

    Lapid-Gortzak, Ruth; van der Linden, Jan Willem; van der Meulen, Ivanka J. E.; Nieuwendaal, Carla P.

    2008-01-01

    PURPOSE: To report the results in the first 100 eyes treated for myopia using a new advanced nomogram. SETTING: Private refractive surgery clinic. METHODS: This prospective interventional case series comprised 58 patients (100 eyes) consecutively treated for myopia with laser in situ keratomileusis

  19. Public sector refraction and spectacle dispensing in low-resource countries of the Western Pacific.

    Science.gov (United States)

    Ramke, Jacqueline; du Toit, Rènée; Palagyi, Anna; Williams, Carmel; Brian, Garry

    2008-05-01

    Given that uncorrected refractive error is a frequent cause of vision impairment, and that there is a high unmet need for spectacles, an appraisal of public sector arrangements for the correction of refractive error was conducted in eight Pacific Island countries. Mixed methods (questionnaire and semi-structured interviews) were used to collect information from eye care personnel (from Fiji, Papua New Guinea, Solomon Islands, Vanuatu, Cook Islands, Samoa, Tonga and Tuvalu) attending a regional eye health workshop in 2005. Fiji, Tonga and Vanuatu had Vision 2020 eye care plans that included refraction services, but not spectacle provision. There was wide variation in public sector spectacle dispensing services, but, except in Samoa, ready-made spectacles and a full cost recovery pricing strategy were the mainstay. There were no systems for the registration of personnel, nor guidelines for clinical or systems management. The refraction staff to population ratio varied considerably. Solomon Islands, Tuvalu and Vanuatu had the best coverage by services, either fixed or outreach. Most services had little promotional activity or community engagement. To be successful, it would seem that public sector refraction services should answer a real and perceived need, fit within prevailing policy and legislation, value, train, retain and equip employees, be well managed, be accessible and affordable, be responsive to consumers, and provide ongoing good quality outcomes. To this end, a checklist to aid the initiation and maintenance of refraction and spectacle systems in low-resource countries has been constructed.

  20. Optics of the human cornea influence the accuracy of stereo eye-tracking methods: a simulation study

    NARCIS (Netherlands)

    Barsingerhorn, A.D.; Boonstra, F.N.; Goossens, H.H.L.M.

    2017-01-01

    Current stereo eye-tracking methods model the cornea as a sphere with one refractive surface. However, the human cornea is slightly aspheric and has two refractive surfaces. Here we used ray-tracing and the Navarro eye-model to study how these optical properties affect the accuracy of different

  1. Intraocular lens calculations in atypical eyes

    Directory of Open Access Journals (Sweden)

    Aazim A Siddiqui

    2017-01-01

    Full Text Available Cataract surgery is the most performed surgical procedure in the field of ophthalmology. The process of intraocular lens (IOL calculations is a critical step to achieving successful outcomes. Many IOL formulae exist to guide surgeons through the difficult process of picking the most appropriate lens to achieve a certain target refraction. However, these formulae reach within 0.50 diopters of the target refraction only 75% of the time, leaving 25% of the eyes with a significant refractive surprise. A literature review was performed to investigate all the relevant published material on the history, progress, and recent advancements of IOL calculations. Based on this review, the appropriate history, evolution, progress, limitations, and recent advancements are analyzed and explained. Although the modern IOL formulae and biometric devices perform well for average eyes, they are suboptimal for eyes with atypical biometric parameters and also those that are postrefractive and keratoconic. There has not been a single, perfect formula that can resolve the complexities of this process. Various methods of formula optimization and newer generation of IOL formulae and devices may hold the key to improving outcomes in both typical and atypical eyes. These solutions minimize refractive error by introducing new input parameters and complex mathematical techniques to better estimate postoperative lens position.

  2. [Incidence of refractive errors with corrective aids subsequent selection].

    Science.gov (United States)

    Benes, P; Synek, S; Petrová, S; Sokolová, Sidlová J; Forýtková, L; Holoubková, Z

    2012-02-01

    This study follows the occurrence of refractive errors in population and the possible selection of the appropriate type of corrective aids. Objective measurement and subsequent determination of the subjective refraction of the eye is on essential act in opotmetric practice. The file represented by 615 patients (1230 eyes) is divided according to the refractive error of myopia, hyperopia and as a control group are listed emetropic clients. The results of objective and subjective values of refraction are compared and statistically processed. The study included 615 respondents. To determine the objective refraction the autorefraktokeratometer with Placido disc was used and the values of spherical and astigmatic correction components, including the axis were recorded. These measurements were subsequently verified and tested subjectively using the trial lenses and the projection optotype to the normal investigative distance of 5 meters. After this the appropriate corrective aids were then recommended. Group I consists of 123 men and 195 women with myopia (n = 635) of clients with an average age 39 +/- 18,9 years. Objective refraction - sphere: -2,57 +/- 2,46 D, cylinder: -1,1 +/- 1,01 D, axis of: 100 degrees +/- 53,16 degrees. Subjective results are as follows--the value of sphere: -2,28 +/- 2,33 D, cylinder -0,63 +/- 0,80 D, axis of: 99,8 degrees +/- 56,64 degrees. Group II is represented hyperopic clients and consists of 67 men and 107 women (n = 348). The average age is 58,84 +/- 16,73 years. Objective refraction has values - sphere: +2,81 +/- 2,21 D, cylinder: -1,0 +/- 0,94 D; axis 95 degree +/- 45,4 degrees. Subsequent determination of subjective refraction has the following results - sphere: +2,28 +/- 2,06 D; cylinder: -0,49 +/- 0,85 D, axis of: 95,9 degrees +/- 46,4 degrees. Group III consists from emetropes whose final minimum viasual acuity was Vmin = 1,0 (5/5) or better. Overall, this control group is represented 52 males and 71 females (n = 247). The average

  3. Improvement of visual acuity by refraction in a low-vision population.

    Science.gov (United States)

    Sunness, Janet S; El Annan, Jaafar

    2010-07-01

    Refraction often may be overlooked in low-vision patients, because the main cause of vision decrease is not refractive, but rather is the result of underlying ocular disease. This retrospective study was carried out to determine how frequently and to what extent visual acuity is improved by refraction in a low-vision population. Cross-sectional study. Seven hundred thirty-nine low-vision patients seen for the first time. A database with all new low-vision patients seen from November 2005 through June 2008 recorded presenting visual acuity using an Early Treatment Diabetic Retinopathy Study chart; it also recorded the best-corrected visual acuity (BCVA) if it was 2 lines or more better than the presenting visual acuity. Retinoscopy was carried out on all patients, followed by manifest refraction. Improvement in visual acuity. Median presenting acuity was 20/80(-2) (interquartile range, 20/50-20/200). There was an improvement of 2 lines or more of visual acuity in 81 patients (11% of all patients), with 22 patients (3% of all patients) improving by 4 lines or more. There was no significant difference in age or in presenting visual acuity between the group that did not improve by refraction and the group that did improve. When stratified by diagnosis, the only 2 diagnoses with a significantly higher rate of improvement than the age-related macular degeneration group were myopic degeneration and progressive myopia (odds ratio, 4.8; 95% confidence interval [CI], 3.0-6.7) and status post-retinal detachment (odds ratio, 7.1; 95% CI, 5.2-9.0). For 5 patients (6% of those with improvement), the eye that was 1 line or more worse than the fellow eye at presentation became the eye that was 1 line or more better than the fellow eye after refraction. A significant improvement in visual acuity was attained by refraction in 11% of the new low-vision patients. Improvement was seen across diagnoses and the range of presenting visual acuity. The worse-seeing eye at presentation may

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

    Science.gov (United States)

    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.

  5. The relationship between refractive and biometric changes during Edinger–Westphal stimulated accommodation in rhesus monkeys

    Science.gov (United States)

    Vilupuru, Abhiram S.; Glasser, Adrian

    2010-01-01

    Experiments were undertaken to understand the relationship between dynamic accommodative refractive and biometric (lens thickness (LT), anterior chamber depth (ACD) and anterior segment length (ASL=ACD+LT)) changes during Edinger–Westphal stimulated accommodation in rhesus monkeys. Experiments were conducted on three rhesus monkeys (aged 11·5, 4·75 and 4·75 years) which had undergone prior, bilateral, complete iridectomies and implantation of a stimulating electrode in the Edinger–Westphal (EW) nucleus. Accommodative refractive responses were first measured dynamically with video-based infrared photorefraction and then ocular biometric responses were measured dynamically with continuous ultrasound biometry (CUB) during EW stimulation. The same stimulus amplitudes were used for the refractive and biometric measurements to allow them to be compared. Main sequence relationships (ratio of peak velocity to amplitude) were calculated. Dynamic accommodative refractive changes are linearly correlated with the biometric changes and accommodative biometric changes in ACD, ASL and LT show systematic linear correlations with increasing accommodative amplitudes. The relationships are relatively similar for the eyes of the different monkeys. Dynamic analysis showed that main sequence relationships for both biometry and refraction are linear. Although accommodative refractive changes in the eye occur primarily due to changes in lens surface curvature, the refractive changes are well correlated with A-scan measured accommodative biometric changes. Accommodative changes in ACD, LT and ASL are all well correlated over the full extent of the accommodative response. PMID:15721617

  6. Optical models of the human eye.

    Science.gov (United States)

    Atchison, David A; Thibos, Larry N

    2016-03-01

    Optical models of the human eye have been used in visual science for purposes such as providing a framework for explaining optical phenomena in vision, for predicting how refraction and aberrations are affected by change in ocular biometry and as computational tools for exploring the limitations imposed on vision by the optical system of the eye. We address the issue of what is understood by optical model eyes, discussing the 'encyclopaedia' and 'toy train' approaches to modelling. An extensive list of purposes of models is provided. We discuss many of the theoretical types of optical models (also schematic eyes) of varying anatomical accuracy, including single, three and four refracting surface variants. We cover the models with lens structure in the form of nested shells and gradient index. Many optical eye models give accurate predictions only for small angles and small fields of view. If aberrations and image quality are important to consider, such 'paraxial' model eyes must be replaced by 'finite model' eyes incorporating features such as aspheric surfaces, tilts and decentrations, wavelength-dependent media and curved retinas. Many optical model eyes are population averages and must become adaptable to account for age, gender, ethnicity, refractive error and accommodation. They can also be customised for the individual when extensive ocular biometry and optical performance data are available. We consider which optical model should be used for a particular purpose, adhering to the principle that the best model is the simplest fit for the task. We provide a glimpse into the future of optical models of the human eye. This review is interwoven with historical developments, highlighting the important people who have contributed so richly to our understanding of visual optics. © 2016 The Authors. Clinical and Experimental Optometry © 2016 Optometry Australia.

  7. Computed estimation of visual acuity after laser refractive keratectomy

    Science.gov (United States)

    Rol, Pascal O.; Parel, Jean-Marie A.; Hanna, Khalil

    1991-06-01

    A number of surgical techniques has been developed to correct ametropia (refractive defaults) of the eye by changing the anterior corneal radius. Because the air-cornea interface makes up for about two-third of the refractive power of the eye, a refractive correction is obtained by a suitable photoablation of the cornea. For this purpose, e.g., an ArF excimer laser which emits a wavelength of 193 nm is being used. After a mechanical removal of the epithelium, the Bowman's layer and the corneal stroma are photoablated on typically 50% of the central surface of the cornea with various precomputed shapes. Methods using a variable diaphragm1 or a scanning slit2 are being utilized. After regrowth of the epithelium, a smooth interface with air develops itself, which can be attributed to a mechanical equilibration. Yet, SEM studies have shown that with such kind of treatments, irregularities can remain in the new stromal surface (Fig. 1). A possible explanation for this effect is associated with an inhomogeneous energy distribution of the laser beam profile3. To some extent, the stromal surface is equalized by the epithelial layer during healing& However, as the corneal epithelium and stroma have different refractive indices, a scatter of the incident light may result causing a haze in the cornea and a blur of the image at the retina. In such a case the resolution and the contrast performance of the eye which is expected from a successful operation, may be reduced. This study is an attempt to quantify the vision blur as a function of the deformation observed at the epithelium-stroma interface.

  8. Christoph Scheiner's eye studies.

    Science.gov (United States)

    Daxecker, F

    1992-01-01

    Christoph Scheiner was born in 1573 or 1575. In 1595 he entered into the Order of the Jesuits; he died in 1650. In 1619 his book Oculus, dealing with the optics of the eye, appeared in Innsbruck. The invention of the telescope was of utmost importance for progress in astronomical and physical research. Scheiner himself built telescopes and discovered the sunspots. As a result, an unpleasant priority dispute with Galilei ensued. From 1624 onwards, Scheiner was in Rome, where his main work Rosa Ursina was published in 1630. A part of this book deals with the physiological optics of the eye as well. Some of his discoveries and experiments are taken from these two books: determination of the radius of curvature of the cornea, discovery of the nasal exit of the optic nerve, increase in the radius of curvature of the lens in case of accommodation, Scheiner's procedure (double images with ametropia), refractive indices of various parts of the eye, Scheiner's experiment. Without any doubt, Christoph Scheiner belongs to the foremost scientists of the first half of the 17th century.

  9. The uncorrected refractive error challenge

    Directory of Open Access Journals (Sweden)

    Kovin Naidoo

    2016-11-01

    Full Text Available Refractive error affects people of all ages, socio-economic status and ethnic groups. The most recent statistics estimate that, worldwide, 32.4 million people are blind and 191 million people have vision impairment. Vision impairment has been defined based on distance visual acuity only, and uncorrected distance refractive error (mainly myopia is the single biggest cause of worldwide vision impairment. However, when we also consider near visual impairment, it is clear that even more people are affected. From research it was estimated that the number of people with vision impairment due to uncorrected distance refractive error was 107.8 million,1 and the number of people affected by uncorrected near refractive error was 517 million, giving a total of 624.8 million people.

  10. School eye health – going beyond refractive errors

    Directory of Open Access Journals (Sweden)

    Sumrana Yasmin Regional

    2015-06-01

    Full Text Available Health, including visual health, is inextricably linked to school achievement, quality of life, and economic productivity. Introducing health education in schools is essential as knowledge and good habits acquired at an early age are likely to persist.

  11. Parsimonious Refraction Interferometry and Tomography

    KAUST Repository

    Hanafy, Sherif

    2017-02-04

    We present parsimonious refraction interferometry and tomography where a densely populated refraction data set can be obtained from two reciprocal and several infill shot gathers. The assumptions are that the refraction arrivals are head waves, and a pair of reciprocal shot gathers and several infill shot gathers are recorded over the line of interest. Refraction traveltimes from these shot gathers are picked and spawned into O(N2) virtual refraction traveltimes generated by N virtual sources, where N is the number of geophones in the 2D survey. The virtual traveltimes can be inverted to give the velocity tomogram. This enormous increase in the number of traveltime picks and associated rays, compared to the many fewer traveltimes from the reciprocal and infill shot gathers, allows for increased model resolution and a better condition number with the system of normal equations. A significant benefit is that the parsimonious survey and the associated traveltime picking is far less time consuming than that for a standard refraction survey with a dense distribution of sources.

  12. Seguridad del paciente en la cirugía refractiva con láser Safety of the patients in the refractive surgery with laser

    Directory of Open Access Journals (Sweden)

    Yureisi Labarrere Cruz

    2012-06-01

    Full Text Available Objetivo: Describir aspectos relacionados con la seguridad del paciente en la cirugía refractiva con láser y enumerar las medidas para disminuir el riesgo de complicaciones. Métodos: Se realizó un estudio descriptivo transversal. El universo de estudio y la muestra se conformó por 11 720 ojos correspondientes a 5 955 pacientes que fueron intervenidos de cirugía refractiva con láser de excímeros entre los años 2005 y 2009 en el salón de cirugía refractiva del Instituto Cubano de Oftalmología "Ramón Pando Ferrer". Los datos se presentaron en tablas y gráficos, procesados en el paquete estadístico Statgraph Plus 50. Resultados: El número de ojos operados tuvo un aumento progresivo y su mayor representación en los años 2008 y 2009 (24,5 % y 25,1 %, respectivamente. Las complicaciones representaron 0,74 % del total de ojos intervenidos y con tendencia a la disminución en el tiempo. Conclusión: Existe un aumento en la demanda de la cirugía refractiva por láser en nuestro medio para la corrección de los defectos refractivos. Es necesario cumplir un conjunto de medidas que disminuyen la presencia de complicaciones, así se brinda mayor seguridad al paciente.Objective: To Identify and to describe aspects of the patient's safety in the refractive surgery with laser, as well as the measures to reduce the risk of complications. Methods: A cross-sectional descriptive study was undertaken. The universe of study was the sample of 11 720 eyes from 5 955 patients who had undergone refractive surgery with excímer laser from 2005 to 2009 in Refractive Surgery service of ¨Ramón Pando Ferrer¨ Cuban Institute of Ophthalmology. Data was processed by Statgraph Plus 50 package and presented in charts and graphics. Results: The number of operated eyes progressively increased and the biggest figure was reached in 2008 and 2009, accounting for 24.5% and 25.1% respectively. The complications occurred in 0.74 % of the total of operated eyes, with a

  13. Eyes on the Solar System

    Data.gov (United States)

    National Aeronautics and Space Administration — Eyes on the Solar System is a software package developed by NASA Jet Propulsion Laboratory and the California Institute of Technology using data provided by NASA's...

  14. [Macroeconomic costs of eye diseases].

    Science.gov (United States)

    Hirneiß, C; Kampik, A; Neubauer, A S

    2014-05-01

    Eye diseases that are relevant regarding their macroeconomic costs and their impact on society include cataract, diabetic retinopathy, age-related maculopathy, glaucoma and refractive errors. The aim of this article is to provide a comprehensive overview of direct and indirect costs for major eye disease categories for Germany, based on existing literature and data sources. A semi-structured literature search was performed in the databases Medline and Embase and in the search machine Google for relevant original papers and reviews on costs of eye diseases with relevance for or transferability to Germany (last research date October 2013). In addition, manual searching was performed in important national databases and information sources, such as the Federal Office of Statistics and scientific societies. The direct costs for these diseases add up to approximately 2.6 billion Euros yearly for the Federal Republic of Germany, including out of the pocket payments from patients but excluding optical aids (e.g. glasses). In addition to those direct costs there are also indirect costs which are caused e.g. by loss of employment or productivity or by a reduction in health-related quality of life. These indirect costs can only be roughly estimated. Including the indirect costs for the eye diseases investigated, a total yearly macroeconomic cost ranging between 4 and 12 billion Euros is estimated for Germany. The costs for the eye diseases cataract, diabetic retinopathy, age-related maculopathy, glaucoma and refractive errors have a macroeconomic relevant dimension. Based on the predicted demographic changes with an ageing society an increase of the prevalence and thus also an increase of costs for eye diseases is expected in the future.

  15. A Model of the Effect of Lens Development on Refraction in Schoolchildren.

    Science.gov (United States)

    He, Ji C

    2017-12-01

    The study provides a new theory on the mechanism underlying myopia development, and it could be useful in clinical practice to control myopia development in schoolchildren. To model the effect of the crystalline lens on refractive development in schoolchildren. The Zemax 13 was used to calculate Zernike aberrations and refractions across 50° horizontal visual fields. Optical effects of the anterior chamber depth, lens thickness, and radii of curvature of the lens surfaces on refractions were modeled. Refractive changes induced by lens development in emmetropic and myopic eyes, based on a previous longitudinal study from literature, were calculated. A lens thickness reduction with an anterior chamber depth deepening caused a hyperopic shift over the visual fields and even more at the periphery. Opposite effects were found when the lens was thinned without any change of the anterior chamber depth. While a flattening of the anterior lens surface produced hyperopic refractions overall, a posterior lens flattening caused a myopic shift at the periphery, but a hyperopic shift of the central refraction. In the myopic eye, lens development induced refractive change toward more hyperopic over the visual fields and more at the periphery. Lens thinning and lens axial movement participate in peripheral refractive development in schoolchildren, and lens development with a deeper anterior chamber depth and a flatter lens surface in the myopic eye could generate extra hyperopia over visual fields. The myopic lens development could be due to a backward movement of the lens, driven by a backward growth of the ciliary process, which might be a causative factor of myopia development.

  16. ASSOCIATION BETWEEN REFRACTIVE ERRORS AND SENILE CATARACT IN RURAL AREA OF WESTERN MAHARASHTRA

    Directory of Open Access Journals (Sweden)

    Chaudhari Sagar V, Shelke Sanjay T, BangalSurekha V, Bhandari Akshay J, Kulkarni Ameya A

    2015-04-01

    Full Text Available Purpose: To study the association between refractive errors and senile cataract in rural area of western MaharashtraMaterials & Methods: It is a prospective cross sectional study carried out on 420 eyes of 210 patients with senile cataract was included in the study. The age and sex of the patient, grade and the refractive status of the cataract of the eyes were recorded. The grade of the cataract was recorded by the LOCS III (Lens Opacities Classification System, version III. Refractive status was measured subjectively using retinoscope and refractive error for each eye was converted into spherical equivalent units. Results: The age variation in the study was between 60-85 years.The maximum number of patients was in the age group of 60-65 years.The spherical equivalent ranged between -3.0 D to +4.25D.45.95% of the study population had a spherical equivalent between -2 to -1.73.81 % of the study population had a myopic refraction.20% had a hypermetropic refraction. Percentage of patients with a score of nuclear opalescence and colour between 1.0-2.0 was 41.90%, between 2.1-3.0 was 26.67% and above 3.0 was 31.43%.Percentage of patients with a score of cortical cataract between 0.1-1.0 was 69.76% and with a grade between 2.1-3.0 was 26.91 %. Percentage of patients with a score of posterior subcapsular cataract between 0.1-1.0 was 53.57% and with a grade between 2.1-3.0 was 39.05%. Conclusion: The myopic refraction was associated with nuclear, cortical and posterior subcapsular cataract and this refractive error was stastically significant with nuclear, cortical and posterior subcapsular cataract.

  17. Diabetes eye exams

    Science.gov (United States)

    Diabetic retinopathy - eye exams; Diabetes - eye exams; Glaucoma - diabetic eye exam; Macular edema - diabetic eye exam ... if the doctor who takes care of your diabetes checks your eyes, you need an eye exam ...

  18. simEye: computer-based simulation of visual perception under various eye defects using Zernike polynomials

    OpenAIRE

    Fink, Wolfgang; Micol, Daniel

    2006-01-01

    We describe a computer eye model that allows for aspheric surfaces and a three-dimensional computer-based ray-tracing technique to simulate optical properties of the human eye and visual perception under various eye defects. Eye surfaces, such as the cornea, eye lens, and retina, are modeled or approximated by a set of Zernike polynomials that are fitted to input data for the respective surfaces. A ray-tracing procedure propagates light rays using Snell’s law of refraction from an input objec...

  19. Refractive surgery trends and practice style changes in Germany over a 3-year period.

    Science.gov (United States)

    Schmack, Ingo; Auffarth, Gerd U; Epstein, Daniel; Holzer, Mike P

    2010-03-01

    To study the current practice styles and preferences of refractive surgeons in Germany. In February 2008, a seven-item questionnaire regarding the practice of refractive surgery was mailed to 282 members of the German Society of Intra-ocular Lens Implantation, Interventional, and Refractive Surgery (DGII) and the Commission of Refractive Surgery (KRC). Most questions were identical to our 2005 German refractive surgery survey. All data were analyzed in a masked fashion. The response rate was 42.2%. The majority (68%) of respondents reported that they perform refractive surgery in laser centers (exclusively or partially) followed by general hospitals (19.4%) and universities (12.6%). Although LASIK was the predominant type of refractive surgery performed (80.6%), other refractive procedures included refractive lens exchange (60.2%), photorefractive keratectomy (47.6%), phakic intraocular lens implants (45.6%), laser-assisted subepithelial keratectomy (36.9%), epithelial laser in situ keratomileusis (15.5%), intracorneal rings (5.8%), and limbal relaxing incisions (2.9%). The volume of refractive surgery procedures and the preferred type of excimer laser systems, microkeratomes, and diagnostic devices varied at different institutions. Most respondents performed either wavefront-guided custom ablation or wavefront-optimized ablation (63.1%) compared with conventional excimer laser correction (36.9%). Refractive surgery practice styles and preferences in Germany are comparable to trends in other European countries. Although LASIK is the most commonly performed refractive procedure, the numbers of various surface ablation techniques and refractive intraocular lens procedures are increasing. Copyright 2010, SLACK Incorporated.

  20. Intraocular camera for retinal prostheses: Refractive and diffractive lens systems

    Science.gov (United States)

    Hauer, Michelle Christine

    The focus of this thesis is on the design and analysis of refractive, diffractive, and hybrid refractive/diffractive lens systems for a miniaturized camera that can be surgically implanted in the crystalline lens sac and is designed to work in conjunction with current and future generation retinal prostheses. The development of such an intraocular camera (IOC) would eliminate the need for an external head-mounted or eyeglass-mounted camera. Placing the camera inside the eye would allow subjects to use their natural eye movements for foveation (attention) instead of more cumbersome head tracking, would notably aid in personal navigation and mobility, and would also be significantly more psychologically appealing from the standpoint of personal appearances. The capability for accommodation with no moving parts or feedback control is incorporated by employing camera designs that exhibit nearly infinite depth of field. Such an ultracompact optical imaging system requires a unique combination of refractive and diffractive optical elements and relaxed system constraints derived from human psychophysics. This configuration necessitates an extremely compact, short focal-length lens system with an f-number close to unity. Initially, these constraints appear highly aggressive from an optical design perspective. However, after careful analysis of the unique imaging requirements of a camera intended to work in conjunction with the relatively low pixellation levels of a retinal microstimulator array, it becomes clear that such a design is not only feasible, but could possibly be implemented with a single lens system.

  1. Magnitude and Causes of Low Vision Disability (Moderate and Severe Visual Impairment among Students of Al-Noor Institute for the Blind in Al-Hassa, Saudi Arabia; A case series

    Directory of Open Access Journals (Sweden)

    Fahad Al-Wadani

    2012-02-01

    Full Text Available Objectives: This study aimed to estimate the magnitude and causes of low vision disability (severe visual impairment [SVI] and moderate visual impairment [MVI] among students at Al-Noor Institute for the Blind (NIB in Al-Hassa, Saudi Arabia in 2006. Methods: An optometrist conducted refraction of 122 eyes of the 61 students (27 boys and 34 girls with MVI (vision <6/18 to 6/60 and SVI (vision <6/60 to 3/60. Ophthalmologists examined the anterior and posterior segments, and analysed the outcomes of additional investigations to finalise the diagnosis. The results were categorised as ‘preventable’, ‘treatable’ and ‘not amenable to treatment’. The low vision care was also reviewed. Results: In 12 (9.8% eyes, visual acuity was ≥6/18 and in 28 (23% eyes, it was <3/60. MVI and SVI were found in 82 eyes (67.2%. Hereditary retinal disorders were found in 68 (55.7% eyes. Although refractive errors were found in 112 (91.8% eyes, isolated refractive error was found in only 9 students. Congenital glaucoma and cataract were responsible for visual impairment in 16 (13.1% and 9 (7.4% eyes. These students were prescribed optical and non-optical low vision aids. Conclusion: Retinal disease was the main cause of SVI and MVI in our series. Some students at Al-Noor Institute for the Blind have curable low vision conditions. Rehabilitation of low vision disability should be different from that offered to the absolutely blind.

  2. Refractive errors in 3-6 year-old Chinese children: a very low prevalence of myopia?

    Directory of Open Access Journals (Sweden)

    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.

  3. Comparing the relative peripheral refraction effect of single vision and multifocal contact lenses measured using an autorefractor and an aberrometer: A pilot study

    Directory of Open Access Journals (Sweden)

    Ravi C. Bakaraju

    2015-07-01

    Conclusion: For most test conditions, distinct differences were observed between the RPR measures obtained with the two modified instruments. The differences varied with CL design and centration. Although the pilot study supports the interchangeable use of the two instruments for on- and off-axis refraction in unaided eyes or eyes corrected with low/no spherical aberration; we advocate the use of the COAS-HD over the SN for special purposes like refracting through multifocal CLs.

  4. Characterizing conical refraction optical tweezers

    Science.gov (United States)

    McDonald, C.; McDougall, C.; Rafailov, E.; McGloin, D.

    2014-12-01

    Conical refraction occurs when a beam of light travels through an appropriately cut biaxial crystal. By focussing the conically refracted beam through a high numerical aperture microscope objective, conical refraction optical tweezers can be created, allowing for particle manipulation in both Raman spots and in the Lloyd/Poggendorff rings. We present a thorough quantification of the trapping properties of such a beam, focussing on the trap stiffness and how this varies with trap power and trapped particle location. We show that the lower Raman spot can be thought of as a single-beam optical gradient force trap, while radiation pressure dominates in the upper Raman spot, leading to optical levitation rather than trapping. Particles in the Lloyd/Poggendorff rings experience a lower trap stiffness than particles in the lower Raman spot but benefit from rotational control.

  5. Long-Term Changes in Refractive Error and Clinical Evaluation in Partially Accommodative Esotropia after Surgery.

    Directory of Open Access Journals (Sweden)

    Shin Yeop Oh

    Full Text Available We investigate the changes in refractive error and clinical evaluation in partially accommodative esotropia(PAET after surgery. A total of 68 patients PAET who received at least 2 years of follow-up after surgery were enrolled in this study. We performed a retrospective study in patients who underwent unilateral or bilateral medial rectus recession for a non-accommodative component of PAET between January 2005 and March 2013. Patients were divided into groups according to the presence of dominancy (dominant, non-dominant, alternative eye, and presence of amblyopia (amblyopic, fellow, normal eye. Changes and changing pattern in SE refractive error were analyzed in all patients and compared between groups. Patients were divided into two groups, those weaned off of hyperopic glasses and those who continued using them, then factors that significantly influenced the continued use of glasses were analyzed. The changes and changing pattern in SE refractive error according to time after operation and presence of amblyopia or dominancy. The mean length of follow-up was 4.89±1.74 years after surgery and the mean change in SE refractive error rate per year was -0.284±0.411 diopters (D. The pattern of changes in the mean SE refractive error for those with dominant, non-dominant, and alternative eyes was not significantly different (p = 0.292. The pattern of changes in the mean SE refractive error for those with amblyopic, fellow, and normal eyes was significantly different (p = 0.0002. Patients were successfully weaned off of hyperopic glasses at an average age of 9.41±2.74 years. The average SE refractive error in the group weaned off of hyperopic glasses was significantly lower than that in the group maintained on hyperopic glasses (p = 0.0002. The change of SE refractive error in amblyopic eyes decreased less than that in fellow or normal eyes, which may be correlated with the presence of amblyopia. Patients with a smaller esodeviated angle without

  6. [Refractive errors among schoolchildren in the central region of Togo].

    Science.gov (United States)

    Nonon Saa, K B; Atobian, K; Banla, M; Rédah, T; Maneh, N; Walser, A

    2013-11-01

    Untreated refractive errors represent the main visual impairment in the world but also the easiest to avoid. The goal of this survey is to use clinical and epidemiological data to efficiently plan distribution of corrective glasses in a project supported by the Swiss Red Cross in the central region of Togo. To achieve this goal, 66 primary schools were identified randomly in the catchment area of the project. The teachers at these schools were previously trained to test visual acuity (VA). The schoolchildren referred by these teachers were examined by eye care professionals. The schoolchildren with ametropia (VA≤7/10 in at least one eye) underwent cycloplegic autorefraction. Of a total of 19,252 registered schoolchildren, 13,039 underwent VA testing by the teachers (participation rate=68%). Among them, 366 cases of ametropia were identified (prevalence about 3%). The average age of the schoolchildren examined was 10.7±2.3years, with a sex ratio of 1.06. Autorefraction, which was performed for 37% of the schoolchildren with ametropia allowed them to be classified into three groups: hyperopia (4%), myopia (5%) and astigmatism of all types (91%). Regardless of the type of ametropia, the degree of severity was mild in 88%. The results of this survey have highlighted the importance of the teachers' contribution to eye care education in the struggle against refractive errors within the school environment, as well as helping to efficiently plan actions against ametropia. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

  7. Refractive errors in patients attending a private hospital in Jos, Nigeria

    African Journals Online (AJOL)

    2013-05-02

    May 2, 2013 ... of 6/9 or less and showed improvement in distance vision of one or more ... ninety eight patients were seen at the hospital for various eye problems. ... Two hundred twenty one (36.8%) of patients with refractive error were ... Other risk factors are ..... Myopia profile in Copenhagen medical students 1996‑98.

  8. Refractive changes after vitrectomy and phacovitrectomy for macular hole and epiretinal membrane

    DEFF Research Database (Denmark)

    Hamoudi, Hassan; La Cour, Morten

    2013-01-01

    a role in refraction, including measurement of the axial length, changes in the effective lens position and the anterior chamber depth, the use of intraocular gas tamponade, the formula for intraocular lens (IOL) power calculation, and the IOL type. Most phakic eyes with macular hole or epiretinal...

  9. THE OPTICS OF REFRACTIVE SUBSTRUCTURE

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Michael D.; Narayan, Ramesh, E-mail: mjohnson@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

    2016-08-01

    Newly recognized effects of refractive scattering in the ionized interstellar medium have broad implications for very long baseline interferometry (VLBI) at extreme angular resolutions. Building upon work by Blandford and Narayan, we present a simplified, geometrical optics framework, which enables rapid, semi-analytic estimates of refractive scattering effects. We show that these estimates exactly reproduce previous results based on a more rigorous statistical formulation. We then derive new expressions for the scattering-induced fluctuations of VLBI observables such as closure phase, and we demonstrate how to calculate the fluctuations for arbitrary quantities of interest using a Monte Carlo technique.

  10. Trial frame refraction versus autorefraction among new patients in a low-vision clinic.

    Science.gov (United States)

    DeCarlo, Dawn K; McGwin, Gerald; Searcey, Karen; Gao, Liyan; Snow, Marsha; Waterbor, John; Owsley, Cynthia

    2013-01-02

    To determine the relationship between refractive error as measured by autorefraction and that measured by trial frame refraction among a sample of adults with vision impairment seen in a university-based low-vision clinic and to determine if autorefraction might be a suitable replacement for trial frame refraction. A retrospective chart review of all new patients 19 years or older seen over an 18-month period was conducted and the following data collected: age, sex, primary ocular diagnosis, entering distance visual acuity, habitual correction, trial frame refraction, autorefraction, and distance visual acuity measured after trial frame refraction. Trial frame refraction and autorefraction were compared using paired t-tests, intraclass correlations, and Bland-Altman plots. Final analyses included 440 patients for whom both trial frame refraction and autorefraction data were available for the better eye. Participants were mostly female (59%) with a mean age of 68 years (SD = 20). Age-related macular degeneration was the most common etiology for vision impairment (44%). Values for autorefraction and trial frame refraction were statistically different, but highly correlated for the spherical equivalent power (r = 0.92), the cylinder power (r = 0.80) and overall blurring strength (0.89). Although the values of the cross-cylinders J(0) and J(45) were similar, they were poorly correlated (0.08 and 0.15, respectively). The range of differences in spherical equivalent power was large (-8.6 to 4.9). Autorefraction is highly correlated with trial frame refraction. Differences are sometimes substantial, making autorefraction an unsuitable substitute for trial frame refraction.

  11. Use of preservative-free hyaluronic acid (Hylabak® for a range of patients with dry eye syndrome: experience in Russia

    Directory of Open Access Journals (Sweden)

    Brzhesky VV

    2014-06-01

    Full Text Available Vladimir Vsevolodovich Brjesky,1 Yury Fedorovich Maychuk,2 Alexey Vladimirovich Petrayevsky,3 Peter Gerrievich Nagorsky41Department of Ophthalmology, Pediatric State Medical Academy, Saint Petersburg, 2Moscow Research Institute of Eye Diseases, Moscow, 3Department of Ophthalmology, Volgograd State Medical University, Volgograd, 4Novosibirsk Branch of the Federal State Institute MNTK Eye Microsurgery, Novosibirsk, Russian Federation, RussiaAbstract: Artificial tear preparations are important in the management of dry eye syndrome. We present the findings from four recently published studies conducted in Russia assessing Hylabak® (marketed as Hyabak® in Europe, a preservative-free hyaluronic acid preparation, for the treatment of dry eye syndrome. All studies had an open, noncomparative design, but one compared the findings with those from 25 patients treated with Tear Naturale® in previous studies. A total of 134 children and adults were enrolled, and the etiologies of dry eye syndrome included contact lens use, intensive office work, adenovirus eye infection, postmenopausal status, persistent meibomian blepharitis, Sjögren's syndrome, phacoemulsification with intraocular lens implantation, and refractive surgery. The patients were treated with Hylabak for 2 weeks to 2 months. All studies showed that Hylabak resulted in marked improvement as assessed by subjective sensations/complaints, Schirmer's test, Norn’s test, impression cytology and biomicroscopy, staining, and tear osmolarity. Greater benefits were also reported compared with Tear Naturale, including a faster onset of action. Hylabak was well tolerated. In conclusion, Hylabak provided rapid and safe relief from the signs and symptoms of dry eye syndrome, as well as improvement in objective measures, in a wide range of patients.Keywords: dry eye, eye drops, artificial tears, hyaluronic acid, Hylabak®, preservative-free

  12. Piggyback intraocular lens implantation to correct pseudophakic refractive error after segmental multifocal intraocular lens implantation.

    Science.gov (United States)

    Venter, Jan A; Oberholster, Andre; Schallhorn, Steven C; Pelouskova, Martina

    2014-04-01

    To evaluate refractive and visual outcomes of secondary piggyback intraocular lens implantation in patients diagnosed as having residual ametropia following segmental multifocal lens implantation. Data of 80 pseudophakic eyes with ametropia that underwent Sulcoflex aspheric 653L intraocular lens implantation (Rayner Intraocular Lenses Ltd., East Sussex, United Kingdom) to correct residual refractive error were analyzed. All eyes previously had in-the-bag zonal refractive multifocal intraocular lens implantation (Lentis Mplus MF30, models LS-312 and LS-313; Oculentis GmbH, Berlin, Germany) and required residual refractive error correction. Outcome measurements included uncorrected distance visual acuity, corrected distance visual acuity, uncorrected near visual acuity, distance-corrected near visual acuity, manifest refraction, and complications. One-year data are presented in this study. The mean spherical equivalent ranged from -1.75 to +3.25 diopters (D) preoperatively (mean: +0.58 ± 1.15 D) and reduced to -1.25 to +0.50 D (mean: -0.14 ± 0.28 D; P < .01). Postoperatively, 93.8% of eyes were within ±0.50 D and 98.8% were within ±1.00 D of emmetropia. The mean uncorrected distance visual acuity improved significantly from 0.28 ± 0.16 to 0.01 ± 0.10 logMAR and 78.8% of eyes achieved 6/6 (Snellen 20/20) or better postoperatively. The mean uncorrected near visual acuity changed from 0.43 ± 0.28 to 0.19 ± 0.15 logMAR. There was no significant change in corrected distance visual acuity or distance-corrected near visual acuity. No serious intraoperative or postoperative complications requiring secondary intraocular lens removal occurred. Sulcoflex lenses proved to be a predictable and safe option for correcting residual refractive error in patients diagnosed as having pseudophakia. Copyright 2014, SLACK Incorporated.

  13. Eye Injuries

    Science.gov (United States)

    ... that you could lose your vision. Most eye injuries are preventable. If you play sports or work in certain jobs, you may need protection. The most common type of injury happens when something irritates the ...

  14. Eyes - bulging

    Science.gov (United States)

    ... different ages. In: Lambert SR, Lyons CJ, eds. Taylor and Hoyt's Pediatric Ophthalmology and Strabismus . 5th ed. Philadelphia, PA: Elsevier; 2017:chap 96. Orge FH, Grigorian F. Examination and common problems of the neonatal eye. ...

  15. Combining zonal refractive and diffractive aspheric multifocal intraocular lenses.

    Science.gov (United States)

    Muñoz, Gonzalo; Albarrán-Diego, César; Javaloy, Jaime; Sakla, Hani F; Cerviño, Alejandro

    2012-03-01

    To assess visual performance with the combination of a zonal refractive aspheric multifocal intraocular lens (MIOL) (Lentis Mplus, Oculentis GmbH) and a diffractive aspheric MIOL (Acri.Lisa 366, Acri.Tech GmbH). This prospective interventional cohort study comprised 80 eyes from 40 cataract patients (mean age: 65.5±7.3 years) who underwent implantation of the Lentis Mplus MIOL in one eye and Acri.Lisa 366 MIOL in the fellow eye. The main outcome measures were refraction; monocular and binocular uncorrected and corrected distance, intermediate, and near visual acuities; monocular and binocular defocus curves; binocular photopic contrast sensitivity function compared to a monofocal intraocular lens (IOL) control group (40 age-matched pseudophakic patients implanted with the AR-40e [Abbott Medical Optics]); and quality of vision questionnaire. Binocular uncorrected visual acuities were 0.12 logMAR (0.76 decimal) or better at all distances measured between 6 m and 33 cm. The Lentis Mplus provided statistically significant better vision than the Acri.Lisa at distances between 2 m and 40 cm, and the Acri.Lisa provided statistically significant better vision than the Lentis Mplus at 33 cm. Binocular defocus curve showed little drop-off at intermediate distances. Photopic contrast sensitivity function for distance and near were similar to the monofocal IOL control group except for higher frequencies. Moderate glare (15%), night vision problems (12.5%), and halos (10%) were reported. Complete independence of spectacles was achieved by 92.5% of patients. The combination of zonal refractive aspheric and diffractive aspheric MIOLs resulted in excellent uncorrected binocular distance, intermediate, and near vision, with low incidence of significant photic phenomena and high patient satisfaction. Copyright 2012, SLACK Incorporated.

  16. What Is Dry Eye?

    Medline Plus

    Full Text Available ... Stories Español Eye Health / Eye Health A-Z Dry Eye Sections What Is Dry Eye? Dry Eye Symptoms ... of Dry Eye Dry Eye Treatment What Is Dry Eye? Leer en Español: ¿Qué es el ojo seco? ...

  17. What Is Dry Eye?

    Medline Plus

    Full Text Available ... Español Eye Health / Eye Health A-Z Dry Eye Sections What Is Dry Eye? Dry Eye Symptoms ... Dry Eye Dry Eye Treatment What Is Dry Eye? Leer en Español: ¿Qué es el ojo seco? ...

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

    Science.gov (United States)

    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.

  19. Refractive Status at Birth: Its Relation to Newborn Physical Parameters at Birth and Gestational Age

    Science.gov (United States)

    Varghese, Raji Mathew; Sreenivas, Vishnubhatla; Puliyel, Jacob Mammen; Varughese, Sara

    2009-01-01

    Background Refractive status at birth is related to gestational age. Preterm babies have myopia which decreases as gestational age increases and term babies are known to be hypermetropic. This study looked at the correlation of refractive status with birth weight in term and preterm babies, and with physical indicators of intra-uterine growth such as the head circumference and length of the baby at birth. Methods All babies delivered at St. Stephens Hospital and admitted in the nursery were eligible for the study. Refraction was performed within the first week of life. 0.8% tropicamide with 0.5% phenylephrine was used to achieve cycloplegia and paralysis of accommodation. 599 newborn babies participated in the study. Data pertaining to the right eye is utilized for all the analyses except that for anisometropia where the two eyes were compared. Growth parameters were measured soon after birth. Simple linear regression analysis was performed to see the association of refractive status, (mean spherical equivalent (MSE), astigmatism and anisometropia) with each of the study variables, namely gestation, length, weight and head circumference. Subsequently, multiple linear regression was carried out to identify the independent predictors for each of the outcome parameters. Results Simple linear regression showed a significant relation between all 4 study variables and refractive error but in multiple regression only gestational age and weight were related to refractive error. The partial correlation of weight with MSE adjusted for gestation was 0.28 and that of gestation with MSE adjusted for weight was 0.10. Birth weight had a higher correlation to MSE than gestational age. Conclusion This is the first study to look at refractive error against all these growth parameters, in preterm and term babies at birth. It would appear from this study that birth weight rather than gestation should be used as criteria for screening for refractive error, especially in developing

  20. Refractive status at birth: its relation to newborn physical parameters at birth and gestational age.

    Directory of Open Access Journals (Sweden)

    Raji Mathew Varghese

    Full Text Available Refractive status at birth is related to gestational age. Preterm babies have myopia which decreases as gestational age increases and term babies are known to be hypermetropic. This study looked at the correlation of refractive status with birth weight in term and preterm babies, and with physical indicators of intra-uterine growth such as the head circumference and length of the baby at birth.All babies delivered at St. Stephens Hospital and admitted in the nursery were eligible for the study. Refraction was performed within the first week of life. 0.8% tropicamide with 0.5% phenylephrine was used to achieve cycloplegia and paralysis of accommodation. 599 newborn babies participated in the study. Data pertaining to the right eye is utilized for all the analyses except that for anisometropia where the two eyes were compared. Growth parameters were measured soon after birth. Simple linear regression analysis was performed to see the association of refractive status, (mean spherical equivalent (MSE, astigmatism and anisometropia with each of the study variables, namely gestation, length, weight and head circumference. Subsequently, multiple linear regression was carried out to identify the independent predictors for each of the outcome parameters.Simple linear regression showed a significant relation between all 4 study variables and refractive error but in multiple regression only gestational age and weight were related to refractive error. The partial correlation of weight with MSE adjusted for gestation was 0.28 and that of gestation with MSE adjusted for weight was 0.10. Birth weight had a higher correlation to MSE than gestational age.This is the first study to look at refractive error against all these growth parameters, in preterm and term babies at birth. It would appear from this study that birth weight rather than gestation should be used as criteria for screening for refractive error, especially in developing countries where the

  1. Evidence for subwavelength imaging with positive refraction

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Yun Gui [Temasek Laboratories, National University of Singapore, Singapore 119260 (Singapore); Sahebdivan, Sahar; Tyc, Tomas; Leonhardt, Ulf [School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS (United Kingdom); Ong, C K, E-mail: ulf@st-andrews.ac.uk [Centre for Superconducting and Magnetic Materials, Department of Physics, National University of Singapore, Singapore 117542 (Singapore)

    2011-03-15

    The resolution of lenses is normally limited by the wave nature of light. Imaging with perfect resolution was believed to rely on negative refraction, but here we present experimental evidence for subwavelength imaging with positive refraction.

  2. Evidence for subwavelength imaging with positive refraction

    International Nuclear Information System (INIS)

    Ma, Yun Gui; Sahebdivan, Sahar; Tyc, Tomas; Leonhardt, Ulf; Ong, C K

    2011-01-01

    The resolution of lenses is normally limited by the wave nature of light. Imaging with perfect resolution was believed to rely on negative refraction, but here we present experimental evidence for subwavelength imaging with positive refraction.

  3. Evidence for subwavelength imaging with positive refraction

    OpenAIRE

    Ma, Yun Gui; Sahebdivan, Sahar; Ong, C. K.; Tyc, Tomas; Leonhardt, Ulf

    2011-01-01

    The resolution of lenses is normally limited by the wave nature of light. Imaging with perfect resolution was believed to rely on negative refraction, but here we present experimental evidence for subwavelength imaging with positive refraction. Publisher PDF Peer reviewed

  4. Control-matched comparison of refractive and visual outcomes between small incision lenticule extraction and femtosecond laser-assisted LASIK

    Directory of Open Access Journals (Sweden)

    Kataoka T

    2018-05-01

    Full Text Available Takahiro Kataoka,1 Tomoya Nishida,1 Azusa Murata,1 Mayuka Ito,1 Naoki Isogai,1 Rie Horai,1 Takashi Kojima,1,2 Yoko Yoshida,1 Tomoaki Nakamura1 1Nagoya Eye Clinic, Nagoya, Japan; 2Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan Purpose: This retrospective case-matched study aimed to compare visual and refractive outcomes between small incision lenticule extraction (SMILE and LASIK. Patients and methods: Patients who underwent SMILE (34 eyes of 23 patients or LASIK (34 eyes of 24 patients were enrolled and matched according to preoperative manifest refractive spherical equivalents. The mean preoperative manifest refractive spherical equivalent was −4.69±0.6 and −4.67±0.64 D in the SMILE and LASIK groups, respectively. The safety, efficacy, and predictability were compared 3 months after surgery. Changes in corneal refractive power from the center to peripheral points and their maintenance ratios were analyzed and compared between the two groups. Results: In the SMILE and LASIK groups, 82.4% and 85.3% of patients, respectively, achieved 20/13 or better uncorrected distance visual acuity (p=1.00. There were no eyes that lost two or more lines of corrected distance visual acuity in either group. The maintenance ratios of corneal refractive power changes at the peripheral points in the SMILE group were significantly higher than those in the LASIK group (p<0.05. Conclusion: Both groups achieved similar high efficacy and safety. SMILE surgery resulted in higher refractive power correction in the peripheral cornea than LASIK surgery. Keywords: small incision lenticule extraction, LASIK, corneal refractive power, refractive power correction efficiency, corneal topography

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

    Directory of Open Access Journals (Sweden)

    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.

  6. Dry eye after laser in-situ keratomileusis.

    Science.gov (United States)

    Raoof, Duna; Pineda, Roberto

    2014-01-01

    Laser-assisted in-situ keratomileusis (LASIK) is one of the most commonly performed refractive procedures with excellent visual outcomes. Dry eye syndrome is one of the most frequently seen complications after LASIK, with most patients developing at least some mild dry eye symptoms postoperatively. To achieve improved visual outcomes and greater patient satisfaction, it is essential to identify patients prone to dry eyes preoperatively, and initiate treatment early in the course. Enhanced understanding of the pathophysiology of post-LASIK dry eye will help advance our approach to its management.

  7. Past and present of corneal refractive surgery

    DEFF Research Database (Denmark)

    Vestergaard, Anders Højslet

    Surgical correction of refractive errors is becoming increasingly popular. In the 1990s, the excimer laser revolutionized the field of corneal refractive surgery with PRK and LASIK, and lately refractive lenticule extraction (ReLEx) of intracorneal tissue, using only a femtosecond laser, has become...

  8. Refracting surface plasmon polaritons with nanoparticle arrays

    DEFF Research Database (Denmark)

    Radko, I.P.; Evlyukhin, A.B.; Boltasseva, Alexandra

    2008-01-01

    Refraction of surface plasmon polaritons (SPPs) by various structures formed by a 100-nm-period square lattice of gold nanoparticles on top of a gold film is studied by leakage radiation microscopy. SPP refraction by a triangular-shaped nanoparticle array indicates that the SPP effective refractive...... to design nanoparticle arrays for specific applications requiring in-plane SPP manipulation....

  9. Modification of Low Refractive Index Polycarbonate for High Refractive Index Applications

    Directory of Open Access Journals (Sweden)

    Gunjan Suri

    2009-01-01

    Full Text Available Polycarbonates and polythiourethanes are the most popular materials in use today, for optical applications. Polycarbonates are of two types which fall in the category of low refractive index and medium refractive index. The present paper describes the conversion of low refractive index polycarbonates into high refractive index material by the use of a high refractive index monomer, polythiol, as an additive. Novel polycarbonates, where the properties of refractive index and Abbe number can be tailor made, have been obtained. Thermal studies and refractive index determination indicate the formation of a new polymer with improved properties and suitable for optical applications.

  10. Amplitude of Accommodation and its Relation to Refractive Errors

    Directory of Open Access Journals (Sweden)

    Abraham Lekha

    2005-01-01

    Full Text Available Aims: To evaluate the relationship between amplitude of accommodation and refractive errors in the peri-presbyopic age group. Materials and Methods: Three hundred and sixteen right eyes of 316 consecutive patients in the age group 35-50 years who attended our outpatient clinic were studied. Emmetropes, hypermetropes and myopes with best-corrected visual acuity of 6/6 J1 in both eyes were included. The amplitude of accommodation (AA was calculated by measuring the near point of accommodation (NPA. In patients with more than ± 2 diopter sphere correction for distance, the NPA was also measured using appropriate soft contact lenses. Results: There was a statistically significant difference in AA between myopes and hypermetropes ( P P P P P P >0.5. Conclusion: Our study showed higher amplitude of accommodation among myopes between 35 and 44 years compared to emmetropes and hypermetropes

  11. Super-Virtual Refraction Interferometric Redatuming: Enhancing the Refracted Energy

    KAUST Repository

    Aldawood, Ali

    2012-02-26

    onshore seismic data processing. Refraction tomography is becoming a common way to estimate an accurate near surface velocity model. One of the problems with refraction tomography is the low signal to noise ration in far offset data. To improve, we propose using super-virtual refraction interferometry to enhance the weak energy at far offsets. We use Interferometric Green\\'s functions to redatum sources by cross-correlating two traces recorded at receiver stations, A and B, from a source at location W. The result is a redatumed trace with a virtual source at A and a receiver at B, which can also be obtained by correlating two traces recorded at A and B from different shots. Stacking them would enhance the signal-to-noise ratio of this "virtual" trace. We next augment redatuming with convolution and stacking. The trace recorded at B from a virtual source at A is convolved with the original trace recorded at A from a source at W. The result is a "super-virtual" trace at B in the far-offset from a source at W. Stacking N traces gives a vN-improvement. We applied our method to noisy synthetic and field data recorded over a complex near-surface and we could pick more traces at far offsets. It was possible to accommodate more picks resulting in a better subsurface coverage

  12. Super-Virtual Refraction Interferometric Redatuming: Enhancing the Refracted Energy

    KAUST Repository

    Aldawood, Ali; Alshuhail, Abdulrahman Abdullatif Abdulrahman; Hanafy, Sherif

    2012-01-01

    onshore seismic data processing. Refraction tomography is becoming a common way to estimate an accurate near surface velocity model. One of the problems with refraction tomography is the low signal to noise ration in far offset data. To improve, we propose using super-virtual refraction interferometry to enhance the weak energy at far offsets. We use Interferometric Green's functions to redatum sources by cross-correlating two traces recorded at receiver stations, A and B, from a source at location W. The result is a redatumed trace with a virtual source at A and a receiver at B, which can also be obtained by correlating two traces recorded at A and B from different shots. Stacking them would enhance the signal-to-noise ratio of this "virtual" trace. We next augment redatuming with convolution and stacking. The trace recorded at B from a virtual source at A is convolved with the original trace recorded at A from a source at W. The result is a "super-virtual" trace at B in the far-offset from a source at W. Stacking N traces gives a vN-improvement. We applied our method to noisy synthetic and field data recorded over a complex near-surface and we could pick more traces at far offsets. It was possible to accommodate more picks resulting in a better subsurface coverage

  13. Refractive lens exchange with a multifocal diffractive aspheric intraocular lens

    Directory of Open Access Journals (Sweden)

    Teresa Ferrer-Blasco

    2012-06-01

    Full Text Available PURPOSE: To evaluate the safety, efficacy and predictability after refractive lens exchange with multifocal diffractive aspheric intraocular lens implantation. METHODS: Sixty eyes of 30 patients underwent bilateral implantation with AcrySof® ReSTOR® SN6AD3 intraocular lens with +4.00 D near addition. Patients were divided into myopic and hyperopic groups. Monocular best corrected visual acuity at distance and near and monocular uncorrected visual acuity at distance and near were measured before and 6 months postoperatively. RESULTS: After surgery, uncorrected visual acuity was 0.08 ± 0.15 and 0.11 ± 0.14 logMAR for the myopic and hyperopic groups, respectively (50% and 46.67% of patients had an uncorrected visual acuity of 20/20 or better in the myopic and hyperopic groups, respectively. The safety and efficacy indexes were 1.05 and 0.88 for the myopic and 1.01 and 0.86 for the hyperopic groups at distance vision. Within the myopic group, 20 eyes remained unchanged after the surgery, and 3 gained >2 lines of best corrected visual acuity. For the hyperopic group, 2 eyes lost 2 lines of best corrected visual acuity, 21 did not change, and 3 eyes gained 2 lines. At near vision, the safety and efficacy indexes were 1.23 and 1.17 for the myopic and 1.16 and 1.13 for the hyperopic groups. Best corrected near visual acuity improved after surgery in both groups (from 0.10 logMAR to 0.01 logMAR in the myopic group, and from 0.10 logMAR to 0.04 logMAR in the hyperopic group. CONCLUSIONS: The ReSTOR® SN6AD3 intraocular lens in refractive lens exchange demonstrated good safety, efficacy, and predictability in correcting high ametropia and presbyopia.

  14. Magnitude and Causes of Low Vision Disability (Moderate and Severe Visual Impairment) among Students of Al-Noor Institute for the Blind in Al-Hassa, Saudi Arabia: A case series.

    Science.gov (United States)

    Al-Wadani, Fahad; Khandekar, Rajiv; Al-Hussain, Muneera A; Alkhawaja, Ahmed A; Khan, Mohammed Sarfaraz; Alsulaiman, Ramzy A

    2012-02-01

    This study aimed to estimate the magnitude and causes of low vision disability (severe visual impairment [SVI] and moderate visual impairment [MVI]) among students at Al-Noor Institute for the Blind (NIB) in Al-Hassa, Saudi Arabia in 2006. An optometrist conducted refraction of 122 eyes of the 61 students (27 boys and 34 girls) with MVI (vision visual acuity was ≥6/18 and in 28 (23%) eyes, it was visual impairment in 16 (13.1%) and 9 (7.4%) eyes. These students were prescribed optical and non-optical low vision aids. Retinal disease was the main cause of SVI and MVI in our series. Some students at Al-Noor Institute for the Blind have curable low vision conditions. Rehabilitation of low vision disability should be different from that offered to the absolutely blind.

  15. Optical refraction index and polarization profile of ferroelectric thin films

    Czech Academy of Sciences Publication Activity Database

    Glinchuk, M. D.; Eliseev, E. A.; Deineka, Alexander; Jastrabík, Lubomír; Suchaneck, G.; Sandner, T.; Gerlach, G.; Hrabovský, Miroslav

    2001-01-01

    Roč. 38, 1-4 (2001), s. 101-110 ISSN 1058-4587 R&D Projects: GA MŠk LN00A015; GA ČR GA202/00/1425 Institutional research plan: CEZ:AV0Z1010914 Keywords : thin film * refraction index * polarization * film thickness Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.512, year: 2001

  16. Vision in semi-aquatic snakes: Intraocular morphology, accommodation, and eye: Body allometry

    Science.gov (United States)

    Plylar, Helen Bond

    Vision in vertebrates generally relies on the refractive power of the cornea and crystalline lens to facilitate vision. Light from the environment enters the eye and is refracted by the cornea and lens onto the retina for production of an image. When an animal with a system designed for air submerges underwater, the refractive power of the cornea is lost. Semi-aquatic animals (e.g., water snakes, turtles, aquatic mammals) must overcome this loss of corneal refractive power through visual accommodation. Accommodation relies on change of the position or shape of the lens to change the focal length of the optical system. Intraocular muscles and fibers facilitate lenticular displacement and deformation. Snakes, in general, are largely unstudied in terms of visual acuity and intraocular morphology. I used light microscopy and scanning electron microscopy to examine differences in eye anatomy between five sympatric colubrid snake species (Nerodia cyclopion, N. fasciata, N. rhombifer, Pantherophis obsoletus, and Thamnophis proximus) from Southeast Louisiana. I discovered previously undescribed structures associated with the lens in semi-aquatic species. Photorefractive methods were used to assess refractive error. While all species overcame the expected hyperopia imposed by submergence, there was interspecific variation in refractive error. To assess scaling of eye size with body size, I measure of eye size, head size, and body size in Nerodia cyclopion and N. fasciata from the SLU Vertebrate Museum. In both species, body size increases at a significantly faster rate than head size and eye size (negative allometry). Small snakes have large eyes relative to body size, and large snakes have relatively small eyes. There were interspecific differences in scaling of eye size with body size, where N. fasciata had larger eye diameter, but N. cyclopion had longer eyes (axial length).

  17. Anatomically accurate, finite model eye for optical modeling.

    Science.gov (United States)

    Liou, H L; Brennan, N A

    1997-08-01

    There is a need for a schematic eye that models vision accurately under various conditions such as refractive surgical procedures, contact lens and spectacle wear, and near vision. Here we propose a new model eye close to anatomical, biometric, and optical realities. This is a finite model with four aspheric refracting surfaces and a gradient-index lens. It has an equivalent power of 60.35 D and an axial length of 23.95 mm. The new model eye provides spherical aberration values within the limits of empirical results and predicts chromatic aberration for wavelengths between 380 and 750 nm. It provides a model for calculating optical transfer functions and predicting optical performance of the eye.

  18. 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

  19. Turbulent effective absorptivity and refractivity

    International Nuclear Information System (INIS)

    Rax, J.M.

    1984-09-01

    The problem of wave propagation in a turbulent magnetized plasma is investigated. Considering small scale, low frequency density fluctuations we solve the Maxwell equations and show that the eikonal approximation remains valid with an effective refractivity and an effective absorptivity taking into account the energy diffusion due to the turbulent motion. Then the result is applied to the problem of lower hybrid waves scattering by drift waves density fluctuations in tokamaks

  20. Perfect antireflection via negative refraction

    International Nuclear Information System (INIS)

    Monzon, Juan J.; Barriuso, Alberto G.; Sanchez-Soto, Luis L.

    2006-01-01

    We suggest a geometrical framework to discuss the action of slabs of negatively refracting materials. We show that these slabs generate the same orbits as normal materials, but traced out in opposite directions. This property allows us to confirm that the action of any lossless multilayer can be optically canceled by putting it together with the multilayer constructed as the inverted mirror image, with ε and μ reversed in sign

  1. What is refractive optical bistability

    International Nuclear Information System (INIS)

    Dzhehov, Tomislav

    1993-01-01

    The basic elements of the theory of refractive optical bistability, assuming mediums with linear absorption are given. Special attention is paid to bistable etalons of semiconductor materials an oxide glasses, since some of them are considered as promising components for optical bistability applications. The design optimization of such devices for minimum switching intensity is analyzed. Computer simulation of the transfer characteristic recording for two InSb etalons is presented. (author)

  2. Eye emergencies

    Science.gov (United States)

    ... eye can be caused by a work-related accident. It can also be caused by common household ... hammers, or other striking tools Working with toxic chemicals Cycling or when in windy and ... A.D.A.M.'s editorial policy , editorial process and privacy policy . A.D.A.M. is ...

  3. Eye Cancer

    Science.gov (United States)

    ... layer of tissue underneath the retina that contains connective tissue and melanocytes, which are pigmented (colored) cells, and nourishes the inside of the eye. The choroid is the most common site for a tumor. Types of intraocular cancer The most common intraocular cancer in adults is ...

  4. Eye trauma

    African Journals Online (AJOL)

    2011-02-02

    Feb 2, 2011 ... Note your findings in an orderly fashion: orbit, lids, conjunctiva, cornea, anterior chamber, iris, pupil reaction, lens, fundus. • Stain cornea with fluorescein. It is advisable to examine the eye as soon as possible since a delay will invariably lead to lid swelling, making the examination far more difficult. This can ...

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

    Directory of Open Access Journals (Sweden)

    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.

  6. Influence of corneal asphericity on the refractive outcome of intraocular lens implantation in cataract surgery.

    Science.gov (United States)

    Savini, Giacomo; Hoffer, Kenneth J; Barboni, Piero

    2015-04-01

    To evaluate the possible influence of anterior corneal surface asphericity on the refractive outcomes in eyes having intraocular lens (IOL) implantation after cataract surgery. Fondazione G.B. Bietti IRCCS, Rome, Italy. Retrospective comparative case series. Intraocular lens power was calculated using the Haigis, Hoffer Q, Holladay 1, and SRK/T formulas. Asphericity (Q-value) was measured at 8.0 mm with a Placido-disk corneal topographer (Keratron), a rotating Scheimpflug camera (Pentacam), and a rotating Scheimpflug camera combined with Placido-disk corneal topography (Sirius). The relationship between the error in refraction prediction (ie, difference between expected refraction and refraction measured 1 month after surgery) and the Q-value was assessed by linear regression. The same IOL model (Acrysof SA60AT) was implanted in 115 eyes of 115 consecutive patients. Regression analysis showed a statistically significant relationship between the error in refraction prediction and the Q-value with all formulas and all devices. In all cases, a more negative Q-value (prolate cornea) was associated with a myopic outcome, whereas a more positive Q-value (oblate cornea) was associated with a hyperopic outcome. The highest coefficient of determination was detected between the Hoffer Q formula and the Placido-disk corneal topographer (R(2) = 0.2630), for which the error in refraction prediction (y) was related to the Q-value (x) according to the formula y = -0.2641 + 1.4589 × x. Corneal asphericity influences the refractive outcomes of IOL implantation and should be taken into consideration when using third-generation IOL power formulas. Dr. Hoffer receives book royalties from Slack, Inc., Thorofare, New Jersey, and formula royalties from all manufacturers using the Hoffer Q formula. No other author has a financial or proprietary interest in any material or method mentioned. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  7. Refractive surgery for accommodative esotropia: 5-year follow-up.

    Science.gov (United States)

    Magli, Adriano; Forte, Raimondo; Gallo, Flavio; Carelli, Roberta

    2014-02-01

    To assess the long-term effectiveness and safety of refractive surgery with LASIK or photorefractive keratectomy (PRK) for treating accommodative esotropia in adults. All patients with accommodative esotropia treated with LASIK or PRK until December 2007 and with a minimum follow-up of 5 years were retrospectively included. LASIK was performed on 44 eyes of 22 patients (12 women, 10 men; mean age: 22.7 ± 2.9 years). Mean postoperative follow-up was 62.1 ± 3.2 months. PRK was performed on 16 eyes of 8 patients (4 women, 4 men; mean age: 23.7 ± 1.7 years). Mean postoperative follow-up was 61.3 ± 2.8 months. At the 5-year follow-up, the mean cycloplegic refraction was more hyperopic in the PRK group (0.3 ± 0.8 vs 0.06 ± 0.3 diopters, P = .01). Correction of esotropia to esophoria or orthotropia was present in 21 patients (95.4%) treated with LASIK and in all patients treated with PRK. Both LASIK and PRK were effective in the long-term reduction of accommodative esotropia. Copyright 2014, SLACK Incorporated.

  8. Necrotizing scleritis as a complication of cosmetic eye whitening procedure

    OpenAIRE

    Leung, Theresa G; Dunn, James P; Akpek, Esen K; Thorne, Jennifer E

    2013-01-01

    Background We report necrotizing scleritis as a serious complication of a cosmetic eye whitening procedure that involves the use of intraoperative and postoperative topical mitomycin C. Findings This is a single case report. A 59-year-old Caucasian male with a history of blepharitis status post uncomplicated LASIK refractive surgery reported chronic conjunctival hyperemia for 15 years prior to undergoing a cosmetic eye whitening procedure. He presented to our clinic 12 months after the cosmet...

  9. Wave Refraction During the May 2002 Rarefaction Event

    Science.gov (United States)

    Smith, C. W.; Mullan, D. J.; Ness, N. F.; Skoug, R. M.

    2002-12-01

    In previous work [Smith et al., 2001] we examined IMF wave refraction during the May 1999 rarefaction interval known as ``The Day The Solar Wind Disappeared.'' On that day, Alfvén speeds remained elevated over an extended region. Analysis of the recorded ACE fields and plasma data revealed depressed magnetic fluctuation levels, reduced compression in the fluctuations, and a reduced wave-like component within the region of elevated Alfvén speed, all consistent with wave refraction. The May 2002 event provides a third such period (the second identified event occured 2 weeks prior to the May 1999 period) and it again demonstrates properties which are consistent with refraction. Smith, C.~W., D.~J. Mullan, N.~F. Ness, R.~M. Skoug, and J.~Steinberg, Day the solar wind almost disappeared: Magnetic field fluctuations, wave refraction and dissipation, J. Geophys. Res., A106, 18,625--18,634, 2001. Efforts at the Bartol Research Institute were supported by CIT subcontract PC251439 under NASA grant NAG5-6912 for support of the ACE magnetic field experiment and by the NASA Delaware Space College Grant. Work at Los Alamos was performed under the auspices of the U.S. Department of Energy with financial support from the NASA ACE program.

  10. Predictability and stability of refraction with increasing optical zone diameter in hyperopic LASIK

    Directory of Open Access Journals (Sweden)

    Mostafa A El-Helw

    2010-05-01

    Full Text Available Mostafa A El-Helw, Ahmed M EmarahCairo University, Cairo, EgyptObjective: We undertook a prospective nonrandomized study to assess refractive outcome and patient satisfaction with hyperopic laser in situ keratomileusis (LASIK using variable optical zone diameters in correction of hyperopia of more than 4.00 diopters.Methods: Fourteen adults (comprising 28 hyperopic eyes underwent hyperopic LASIK correction for hyperopia of more than 4.00 diopters. The sample was divided into two groups. Group 1 included the right eyes of the 14 patients who underwent hyperopic LASIK using a 6.5 mm optical zone diameter. Group 2 comprised the left eyes of the same patients with the only difference being that the optical zone diameter was 6.0 mm.Results: The mean age of the patients was 36.42 ± 5.10 years. Group 1 eyes had a median (range preoperative uncorrected visual acuity (UCVA of 0.79 (0.52 and best-corrected visual acuity (BCVA of 0.15 (0.08. Group 2 had a median preoperative UCVA of 0.79 (0.60 and BCVA of 0.15 (0.08. The median postoperative UCVA in Group 1 was 0.17 (0.21 and BCVA was 0.15 (0.13. In Group 2, the median postoperative UCVA was 0.30 (0.32 and BCVA was 0.15 (0.26. Group 1 had a median preoperative refraction of +5.37 (1.75 diopters and the median postoperative refraction at one week was −0.23 (1.25 diopters, at three months was +0.75 (0.75 diopters, and at six months was +0.75 (1.00 diopters. Group 2 had a median preoperative refraction of +5.00 (1.75 diopters, and the median postoperative refraction at one week was +0.13 (1.5 diopters, at three months was +1.00 (0.75 diopters and at six months +1.25 (1.25 diopters. The difference was statistically significant between groups 1 and 2. The difference within each group was also significant. Group 1 eyes were stabilizing after the three-month period in contrast with Group 2 in which the refractive changes continued throughout the follow-up period.Conclusion: Larger optical zone diameter in

  11. Relationship between visual field progression and baseline refraction in primary open-angle glaucoma.

    Science.gov (United States)

    Naito, Tomoko; Yoshikawa, Keiji; Mizoue, Shiro; Nanno, Mami; Kimura, Tairo; Suzumura, Hirotaka; Umeda, Yuzo; Shiraga, Fumio

    2016-01-01

    To analyze the relationship between visual field (VF) progression and baseline refraction in Japanese patients with primary open-angle glaucoma (POAG) including normal-tension glaucoma. In this retrospective study, the subjects were patients with POAG who had undergone VF tests at least ten times with a Humphrey Field Analyzer (Swedish interactive thresholding algorithm standard, Central 30-2 program). VF progression was defined as a significantly negative value of mean deviation (MD) slope at the final VF test. Multivariate logistic regression models were applied to detect an association between MD slope deterioration and baseline refraction. A total of 156 eyes of 156 patients were included in this analysis. Significant deterioration of MD slope was observed in 70 eyes of 70 patients (44.9%), whereas no significant deterioration was evident in 86 eyes of 86 patients (55.1%). The eyes with VF progression had significantly higher baseline refraction compared to those without apparent VF progression (-1.9±3.8 diopter [D] vs -3.5±3.4 D, P=0.0048) (mean ± standard deviation). When subject eyes were classified into four groups by the level of baseline refraction applying spherical equivalent (SE): no myopia (SE > -1D), mild myopia (-1D ≥ SE > -3D), moderate myopia (-3D ≥ SE > -6D), and severe myopia (-6D ≥ SE), the Cochran-Armitage trend analysis showed a decreasing trend in the proportion of MD slope deterioration with increasing severity of myopia (P=0.0002). The multivariate analysis revealed that baseline refraction (P=0.0108, odds ratio [OR]: 1.13, 95% confidence interval [CI]: 1.03-1.25) and intraocular pressure reduction rate (P=0.0150, OR: 0.97, 95% CI: 0.94-0.99) had a significant association with MD slope deterioration. In the current analysis of Japanese patients with POAG, baseline refraction was a factor significantly associated with MD slope deterioration as well as intraocular pressure reduction rate. When baseline refraction was classified into

  12. Predicting Refractive Surgery Outcome: Machine Learning Approach With Big Data.

    Science.gov (United States)

    Achiron, Asaf; Gur, Zvi; Aviv, Uri; Hilely, Assaf; Mimouni, Michael; Karmona, Lily; Rokach, Lior; Kaiserman, Igor

    2017-09-01

    To develop a decision forest for prediction of laser refractive surgery outcome. Data from consecutive cases of patients who underwent LASIK or photorefractive surgeries during a 12-year period in a single center were assembled into a single dataset. Training of machine-learning classifiers and testing were performed with a statistical classifier algorithm. The decision forest was created by feature vectors extracted from 17,592 cases and 38 clinical parameters for each patient. A 10-fold cross-validation procedure was applied to estimate the predictive value of the decision forest when applied to new patients. Analysis included patients younger than 40 years who were not treated for monovision. Efficacy of 0.7 or greater and 0.8 or greater was achieved in 16,198 (92.0%) and 14,945 (84.9%) eyes, respectively. Efficacy of less than 0.4 and less than 0.5 was achieved in 322 (1.8%) and 506 (2.9%) eyes, respectively. Patients in the low efficacy group (differences compared with the high efficacy group (≥ 0.8), yet were clinically similar (mean differences between groups of 0.7 years, of 0.43 mm in pupil size, of 0.11 D in cylinder, of 0.22 logMAR in preoperative CDVA, of 0.11 mm in optical zone size, of 1.03 D in actual sphere treatment, and of 0.64 D in actual cylinder treatment). The preoperative subjective CDVA had the highest gain (most important to the model). Correlations analysis revealed significantly decreased efficacy with increased age (r = -0.67, P big data from refractive surgeries may be of interest. [J Refract Surg. 2017;33(9):592-597.]. Copyright 2017, SLACK Incorporated.

  13. Sensitivity of the corneal-plane refractive compensation to change in power and axial position of an intraocular lens

    Directory of Open Access Journals (Sweden)

    W. F. Harris

    2009-12-01

    Full Text Available If an intraocular lens is displaced or if its power is changed what are the consequences for the refractive compensation of the eye?  Gaussian optics is used to obtain explicit formulae for the sensitivityof the corneal-plane refractive compensation (also called the refraction, refractive state, etc to change in power and axial displacement of a thin intraocular lens implanted in a simple eye.  In particular, for a pseudophakic Gullstrand simplified eye with intraocular lens placed 5 mm behind the cornea the sensitivity to errors in the power of the intraocular lens is about  71 . 0 − 71 for an intraocular lens of power   for an intraocular lens of power 20 D, that is, the refractive compensation decreases by about 0.71 dioptres per dioptre increase in the power of the intraocular lens.  More generally the sensitivity is approximately  ( m   0037 . 0 63 . 0 F − − 0.63 ( 003 . 0 63 . 0 − − (0.0037mF where FI is the power of the intraocular lens.  Also for Gullstrand’s simplified eye the sensitivity of refractive compensation to axial displacement of the intraocular lens is approximately linear in FI about  (64D FI, in fact.  That is, for each dioptre of the power of the intraocular lens the refractive compensation increases by about 0.064 dioptres per millimetre of axial displacement towards the retina. 

  14. Role of percent peripheral tissue ablated on refractive outcomes following hyperopic LASIK

    Science.gov (United States)

    Stapleton, Fiona; Versace, Patrick

    2017-01-01

    Objectives To determine the effect of hyperopic laser in situ keratomileusis (H-LASIK) on corneal integrity, by investigating relationships between proportionate corneal tissue ablated and refractive outcomes at 3 months. Methods 18 eyes of 18 subjects treated with H-LASIK by Technolas 217c Excimer Laser were included in the study. Orbscan II Topography System was used to determine corneal volume and pachymetry 3mm temporally (3T). The volume of corneal tissue ablated was determined from the laser nomogram. Univariate associations between age, treatment, corneal volume, overall proportion of tissue removed, proportion of tissue removed at 3T, residual bed thickness at 3T and refractive outcomes 3 months post-LASIK were examined and independent factors associated with refractive outcomes determined using linear regression models. Results At 3 months post-LASIK, the mean difference to expected refractive outcome was -0.20 ± 0.64 (Range -2.00 to +1.00). In univariate analysis, difference to expected refractive outcome was associated with proportion of tissue removed at 3T (PLASIK, may present as either over or under-corrected at 3 months. The proportion of tissue removed at 3T was the single significant determinant of this outcome, suggesting unexpected biomechanical alterations resulting in corneal steepening. Future hyperopic LASIK procedures could consider proportionate volume of corneal tissue removed at 3T in addition to laser nomograms to achieve improved refractive outcomes. PMID:28151939

  15. Risk factors for refractive errors in primary school children (6-12 years old) in Nakhon Pathom Province.

    Science.gov (United States)

    Yingyong, Penpimol

    2010-11-01

    Refractive error is one of the leading causes of visual impairment in children. An analysis of risk factors for refractive error is required to reduce and prevent this common eye disease. To identify the risk factors associated with refractive errors in primary school children (6-12 year old) in Nakhon Pathom province. A population-based cross-sectional analytic study was conducted between October 2008 and September 2009 in Nakhon Pathom. Refractive error, parental refractive status, and hours per week of near activities (studying, reading books, watching television, playing with video games, or working on the computer) were assessed in 377 children who participated in this study. The most common type of refractive error in primary school children was myopia. Myopic children were more likely to have parents with myopia. Children with myopia spend more time at near activities. The multivariate odds ratio (95% confidence interval)for two myopic parents was 6.37 (2.26-17.78) and for each diopter-hour per week of near work was 1.019 (1.005-1.033). Multivariate logistic regression models show no confounding effects between parental myopia and near work suggesting that each factor has an independent association with myopia. Statistical analysis by logistic regression revealed that family history of refractive error and hours of near-work were significantly associated with refractive error in primary school children.

  16. Ocular Biometrics of Myopic Eyes With Narrow Angles.

    Science.gov (United States)

    Chong, Gabriel T; Wen, Joanne C; Su, Daniel Hsien-Wen; Stinnett, Sandra; Asrani, Sanjay

    2016-02-01

    The purpose of this study was to compare the ocular biometrics between myopic patients with and without narrow angles. Patients with a stable myopic refraction (myopia worse than -1.00 D spherical equivalent) were prospectively recruited. Angle status was assessed using gonioscopy and biometric measurements were performed using an anterior segment optical coherence tomography and an IOLMaster. A total of 29 patients (58 eyes) were enrolled with 13 patients (26 eyes) classified as having narrow angles and 16 patients (32 eyes) classified as having open angles. Baseline demographics of age, sex, and ethnicity did not differ significantly between the 2 groups. The patients with narrow angles were on average older than those with open angles but the difference did not reach statistical significance (P=0.12). The central anterior chamber depth was significantly less in the eyes with narrow angles (P=0.05). However, the average lens thickness, although greater in the eyes with narrow angles, did not reach statistical significance (P=0.10). Refractive error, axial lengths, and iris thicknesses did not differ significantly between the 2 groups (P=0.32, 0.47, 0.15). Narrow angles can occur in myopic eyes. Routine gonioscopy is therefore recommended for all patients regardless of refractive error.

  17. A prospective, randomized, fellow eye comparison of WaveLight® Allegretto Wave® Eye-Q versus VISX CustomVue™ STAR S4 IR™ in laser in situ keratomileusis (LASIK: analysis of visual outcomes and higher order aberrations

    Directory of Open Access Journals (Sweden)

    Moshirfar M

    2011-09-01

    Full Text Available Majid Moshirfar1, Brent S Betts2, Daniel S Churgin3, Maylon Hsu1, Marcus Neuffer1, Shameema Sikder4, Dane Church5, Mark D Mifflin11John A Moran Eye Center, Department of Ophthalmology and Visual Sciences, University of Utah, Salt Lake City, UT, USA; 2Temple University School of Medicine, Philadelphia, PA, USA; 3University of Arizona College of Medicine – Phoenix, Phoenix, AZ, USA; 4Wilmer Eye Institute, Johns Hopkins University, Baltimore, MD, USA; 5Virginia Commonwealth University School of Medicine, Richmond, VA, USAPurpose: To compare outcomes in visual acuity, refractive error, higher-order aberrations (HOAs, contrast sensitivity, and dry eye in patients undergoing laser in situ keratomileusis (LASIK using wavefront (WF guided VISX CustomVue and WF optimized WaveLight Allegretto platforms.Methods: In this randomized, prospective, single-masked, fellow eye study, LASIK was performed on 44 eyes (22 patients, with one eye randomized to WaveLight Allegretto, and the fellow eye receiving VISX CustomVue. Postoperative outcome measures at 3 months included uncorrected distance visual acuity (UDVA, corrected distance visual acuity (CDVA, refractive error, root-mean-square (RMS value of total and grouped HOAs, contrast sensitivity, and Schirmers testing.Results: Mean values for UDVA (logMAR were -0.067 ± 0.087 and -0.073 ± 0.092 in the WF optimized and WF guided groups, respectively (P = 0.909. UDVA of 20/20 or better was achieved in 91% of eyes undergoing LASIK with both lasers while UDVA of 20/15 or better was achieved in 64% of eyes using the Allegretto platform, and 59% of eyes using VISX CustomVue (P = 1.000. In the WF optimized group, total HOA increased 4% (P = 0.012, coma increased 11% (P = 0.065, and spherical aberration increased 19% (P = 0.214, while trefoil decreased 5% (P = 0.490. In the WF guided group, total HOA RMS decreased 9% (P = 0.126, coma decreased 18% (P = 0.144, spherical aberration decreased 27% (P = 0.713 and trefoil

  18. Diabetic Eye Disease

    Science.gov (United States)

    ... Disease, & Other Dental Problems Diabetes & Sexual & Urologic Problems Diabetic Eye Disease What is diabetic eye disease? Diabetic eye disease is a group ... eye diseases that can threaten your sight are Diabetic retinopathy The retina is the inner lining at ...

  19. About the Eye

    Medline Plus

    Full Text Available ... eye behind the iris that helps to focus light on the retina. It allows the eye to ... of the eye. It regulates the amount of light entering the eye through the pupil. Pupil (PYOO- ...

  20. Eye Movement Disorders

    Science.gov (United States)

    ... work properly. There are many kinds of eye movement disorders. Two common ones are Strabismus - a disorder ... in "crossed eyes" or "walleye." Nystagmus - fast, uncontrollable movements of the eyes, sometimes called "dancing eyes" Some ...

  1. About the Eye

    Medline Plus

    Full Text Available ... for Kids >> About the Eye Listen All About Vision About the Eye Ask a Scientist Video Series ... Eye Health and Safety First Aid Tips Healthy Vision Tips Protective Eyewear Sports and Your Eyes Fun ...

  2. Why Do Eyes Water?

    Science.gov (United States)

    ... for Educators Search English Español Why Do Eyes Water? KidsHealth / For Kids / Why Do Eyes Water? What's ... coming out of your nose. Why Do Eyes Water? Eyes water for lots of different reasons besides ...

  3. Refractions

    DEFF Research Database (Denmark)

    Hougaard, Anna Katrine; Søberg, Martin; Lorentsen, Elise

    2016-01-01

    The book focuses on new directions in architectural research, how architects develop new knowledge through their artistic design practice, working in a field between Art and Science. What new digital potentials are there in architectural media like models and drawings and how to put words...... on artistic research? The book offers theoretical articles, picture galleries of artistic projects, and interviews with senior-researchers at the Danish Academy of Architecture in Copenhagen and their built architectural projects....

  4. Pattern of Eye Diseases among Commercial Intercity Vehicle Drivers ...

    African Journals Online (AJOL)

    BOLA

    with a visual acuity (VA) of less than 3/60 in one eye. Cataract and ... to dry. Those found to require further assessment, refraction and surgery were referred to the UITH. The data .... Symptoms of ocular disease among the CIVDs examined.

  5. Causes of Adult Blindness at Ecwa Eye Hospital, Kano

    African Journals Online (AJOL)

    user

    South America, disorders of the anterior segment of the eye ... associated causes. .... checks, particularly for persons at increased risk, such as ... Cases of refractive errors were not found in this study ... West Afr J Med 2004;23(3):249-52. 8.

  6. Primary health eye care: evaluation of the competence of medical ...

    African Journals Online (AJOL)

    2009-10-17

    Oct 17, 2009 ... The ability of fifth-year medical students to perform fundoscopy on ... Keywords: primary health eye care; teaching fundoscopy; essential basic ... treatment is implemented at an early stage in the disease.3-5. Such screening and early treatment can reduce the risk of ... Students with a refractive error were.

  7. Incidence and Pattern of Retinal Detachment in a Tertiary Eye ...

    African Journals Online (AJOL)

    retinal detachment symptoms, the predisposing/precipitating factors and the need ... Sebastian N. N. Nwosu, Guinness Eye Center, PMB 1534, Onitsha, Anambra ... the temporal retina and are all associated with total ... Table 2 shows the ocular risk factors. ..... Olurin O. Refractive errors in Nigerians: A hospital clinic study.

  8. Context-Based Questions: Optics in Animal Eyes

    Science.gov (United States)

    Kaltakci, Derya; Eryilmaz, Ali

    2011-01-01

    Context is important as a motivational factor for student involvement with physics. The diversity in the types and the functions of animal eyes is an excellent context in which to achieve this goal. There exists a range of subtopics in optics including pinhole, reflection, refraction, and superposition that can be discussed in the context of the…

  9. Are 3-D Movies Bad for Your Eyes?

    Medline Plus

    Full Text Available ... Privacy Policy Terms of Service For Advertisers For Media Ophthalmology Job Center © American Academy of Ophthalmology 2018 Our Sites EyeWiki International Society of Refractive Surgery * Required * First Name: * Last Name: Member ID: * Phone Number: * Email: * Enter code: * Message: Thank you Your feedback ...

  10. The effect of instrument alignment on peripheral refraction measurements by automated optometer.

    Science.gov (United States)

    Ehsaei, Asieh; Chisholm, Catharine M; Mallen, Edward A H; Pacey, Ian E

    2011-07-01

    Interest in peripheral refraction measurement has grown in recent years in response to the insight it may provide into myopia development. In light of the likely increase in the clinical use of open-field autorefractors for peripheral refraction measurements, the question of instrument alignment and its impact on the accuracy of refraction measurements is raised. The aim of this study was to investigate the accuracy and precision when an open-field device was moved away from alignment with the corneal reflex towards the pupil margins, and to determine the optimum alignment position for peripheral refraction measurements. Autorefractions were performed on the right eyes of 10 healthy participants using the Shin-Nippon NVision-K 5001 autorefractor. At least five measurements were taken with the subject fixating a distance target in the primary position of gaze, and then four peripheral fixation targets located along the horizontal meridian (10° and 20° eccentricities in the nasal and temporal retina). Measurements were taken at seven alignment positions across the pupil for each fixation angle. Refraction was recorded as the spherical and cylindrical power. The central objective refraction achieved under cycloplegia based on the autorefraction result for the whole sample, ranged between -5.62 D and +1.85 D for the value of sphere, with a maximum astigmatism of -1.00 D. Acceptable alignment position range varied with fixation angle but was -1.0 to +1.0 mm in width across the pupil. Peripheral refraction measurements centred on the entrance pupil were as reliable as those centred on the corneal reflex. Our data suggest that for peripheral refraction measurements, there is a range of acceptable positions and operators can be confident of the validity of results obtained if aligned half way between the pupil centre and corneal reflex. The alignment becomes more critical at greater eccentricities. Ophthalmic & Physiological Optics © 2011 The College of Optometrists.

  11. Necrotizing scleritis as a complication of cosmetic eye whitening procedure.

    Science.gov (United States)

    Leung, Theresa G; Dunn, James P; Akpek, Esen K; Thorne, Jennifer E

    2013-02-22

    We report necrotizing scleritis as a serious complication of a cosmetic eye whitening procedure that involves the use of intraoperative and postoperative topical mitomycin C. This is a single case report. A 59-year-old Caucasian male with a history of blepharitis status post uncomplicated LASIK refractive surgery reported chronic conjunctival hyperemia for 15 years prior to undergoing a cosmetic eye whitening procedure. He presented to our clinic 12 months after the cosmetic eye whitening procedure with progressive bilateral necrotizing scleritis and scleral calcification. Chronic conjunctival hyperemia may prompt patients to seek surgical correction with cosmetic eye whitening procedures. However, conjunctival hyperemia secondary to tear deficiency and evaporative dry eye may predispose to poor wound healing. Serious complications including necrotizing scleritis may result from cosmetic eye whitening procedures and the use of topical mitomycin C.

  12. What Is Dry Eye?

    Medline Plus

    Full Text Available ... Eye Health A-Z Symptoms Glasses & Contacts Tips & Prevention News Ask an Ophthalmologist Patient Stories Español Eye ... Eye Symptoms Causes of Dry Eye Dry Eye Treatment What Is Dry Eye? Leer en Español: ¿Qué ...

  13. What Is Dry Eye?

    Medline Plus

    Full Text Available ... Eye? Dry Eye Symptoms Causes of Dry Eye Dry Eye Treatment What Is Dry Eye? Leer en Español: ¿Qué ... Inside of Your Eyelid Nov 29, 2017 New Dry Eye Treatment is a Tear-Jerker Jul 21, 2017 Three ...

  14. What Is Dry Eye?

    Science.gov (United States)

    ... Eye? Dry Eye Symptoms Causes of Dry Eye Dry Eye Treatment What Is Dry Eye? Leer en Español: ¿Qué ... Inside of Your Eyelid Nov 29, 2017 New Dry Eye Treatment is a Tear-Jerker Jul 21, 2017 Three ...

  15. Theory of supervirtual refraction interferometry

    KAUST Repository

    Bharadwaj, Pawan; Schuster, Gerard T.; Mallinson, Ian; Dai, Wei

    2012-01-01

    Inverting for the subsurface velocity distribution by refraction traveltime tomography is a well-accepted imaging method by both the exploration and earthquake seismology communities. A significant drawback, however, is that the recorded traces become noisier with increasing offset from the source position, and so accurate picking of traveltimes in far-offset traces is often prevented. To enhance the signal-to-noise ratio (SNR) of the far-offset traces, we present the theory of supervirtual refraction interferometry where the SNR of far-offset head-wave arrivals can be theoretically increased by a factor proportional to; here, N is the number of receiver or source positions associated with the recording and generation of the head-wave arrival. There are two steps to this methodology: correlation and summation of the data to generate traces with virtual head-wave arrivals, followed by the convolution of the data with the virtual traces to create traces with supervirtual head-wave arrivals. This method is valid for any medium that generates head-wave arrivals recorded by the geophones. Results with both synthetic traces and field data demonstrate the feasibility of this method. There are at least four significant benefits of supervirtual interferometry: (1) an enhanced SNR of far-offset traces so the first-arrival traveltimes of the noisy far-offset traces can be more reliably picked to extend the useful aperture of the data, (2) the SNR of head waves in a trace that arrive later than the first arrival can be enhanced for accurate traveltime picking and subsequent inversion by later-arrival traveltime tomography, (3) common receiver-pair gathers can be analysed to detect the presence of diving waves in the first arrivals, which can be used to assess the nature of the refracting boundary, and (4) the source statics term is eliminated in the correlation operations so that the timing of the virtual traces is independent of the source excitation time. This suggests the

  16. Risk assessment for ectasia after corneal refractive surgery.

    Science.gov (United States)

    Randleman, J Bradley; Woodward, Maria; Lynn, Michael J; Stulting, R Doyle

    2008-01-01

    To analyze the epidemiologic features of ectasia after excimer laser corneal refractive surgery, to identify risk factors for its development, and to devise a screening strategy to minimize its occurrence. Retrospective comparative and case-control study. All cases of ectasia after excimer laser corneal refractive surgery published in the English language with adequate information available through December 2005, unpublished cases seeking treatment at the authors' institution from 1998 through 2005, and a contemporaneous control group who underwent uneventful LASIK and experienced a normal postoperative course. Evaluation of preoperative characteristics, including patient age, gender, spherical equivalent refraction, pachymetry, and topographic patterns; perioperative characteristics, including type of surgery performed, flap thickness, ablation depth, and residual stromal bed (RSB) thickness; and postoperative characteristics including time to onset of ectasia. Development of postoperative corneal ectasia. There were 171 ectasia cases, including 158 published cases and 13 unpublished cases evaluated at the authors' institution. Ectasia occurred after LASIK in 164 cases (95.9%) and after photorefractive keratectomy (PRK) in 7 cases (4.1%). Compared with controls, more ectasia cases had abnormal preoperative topographies (35.7% vs. 0%; Pvs. 40.0 years; Pvs. -5.09 diopters; Pvs. 546.5 microm; Pvs. 317.3 microm; PLASIK that, if validated, represents a significant improvement over current screening strategies.

  17. Peripheral refraction in normal infant rhesus monkeys

    Science.gov (United States)

    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

  18. Impact of dry eye on work productivity

    Directory of Open Access Journals (Sweden)

    Yamada M

    2012-10-01

    Full Text Available Masakazu Yamada, Yoshinobu Mizuno, Chika ShigeyasuNational Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, JapanBackground: The purpose of this study was to evaluate the impact of dry eye on work productivity of office workers, especially in terms of presenteeism.Methods: A total of 396 individuals aged ≥20 years (258 men and 138 women, mean age 43.4 ± 13.0 years were recruited through an online survey. Data from 355 responders who did not have missing values were included in the analysis. They were classified into the following four groups according to the diagnostic status and subjective symptoms of dry eye: a definite dry eye group; a marginal dry eye group; a self-reported dry eye group; and a control group. The impact of dry eye on work productivity was evaluated using the Japanese version of the Work Limitations Questionnaire. The cost of work productivity loss associated with dry eye and the economic benefits of providing treatment for dry eye were also assessed.Results: The degree of work performance loss was 5.65% in the definite dry eye group, 4.37% in the marginal dry eye group, 6.06% in the self-reported dry eye group, and 4.27% in the control group. Productivity in the self-reported dry eye group was significantly lower than that in the control group (P < 0.05. The annual cost of work productivity loss associated with dry eye was estimated to be USD 741 per person.Conclusion: Dry eye impairs work performance among office workers, which may lead to a substantial loss to industry. Management of symptoms of dry eye by providing treatment may contribute to improvement in work productivity.Keywords: burden of disease, dry eye, presenteeism, quality of life

  19. Cover-layer with High Refractive Index for Near-Field Recording Media

    Science.gov (United States)

    Kim, Jin-Hong; Lee, Jun-Seok

    2007-06-01

    TiO2 nanoparticles are added into UV-curable resin to increase the refractive index of the cover-layer laminated for cover-layer incident near-field recording media. A high refractive index is required for the cover-layer operating with an optical head with a high numerical aperture. The eye pattern from a cover-layer coated 20 GB read-only memory disc in which the refractive index of the cover-layer is 1.75 is achieved, but the gap servo is unstable owing to the rough surface of the cover-layer. Even though the light loss due to the nanoparticles is negligible, a rough microstructure is developed by adding the nanoparticles into an organic binder material. To achieve a smooth surface for a stable gap servo, the solubility of the nanoparticles should be enhanced by the optimization of the surface of the nanoparticles.

  20. Investigation of the refractive status of preschool children in Xiantao, Hubei Province

    Directory of Open Access Journals (Sweden)

    Nian Guan

    2014-12-01

    Full Text Available AIM: To investigate the refractive status of the preschool children in Xiantao, Hubei Province in order to find out the abnormal refraction error beyond the physiological range. METHODS: In this cross-sectional study, we investigated preschool children in kindergartens and the scattered ones were 12 716(25 432 eyesranging from 6mo~6 years old. 1 581 children(3 162 eyeswere diagnosed ametropia by Suresight refractive screening instrument, which were confirmed again after mydriasis optometry. RESULTS: The incidence rate of ametropia in preschool children in Xiantao was 12.4%, and statistics showed no significant difference between boys and girls(P>0.05, but had differences of morbility rate among each age group(PCONCLUSION: The incidence rate of ametropia decreases with age increasing in the preschool children from 6mo~6 years old, which imply preschool children should have mydriasis optometry in order to find out amblyopia and other congenital eye disease.

  1. Influence of refraction index strength on the light propagation in dielectrics material with periodic refraction index

    International Nuclear Information System (INIS)

    Hidayat, Arif; Latifah, Eny; Kurniati, Diana; Wisodo, Hari

    2016-01-01

    This study investigated the influence of refraction index strength on the light propagation in refraction index-varied dielectric material. This dielectric material served as photonic lattice. The behavior of light propagation influenced by variation of refraction index in photonic lattice was investigated. Modes of the guiding light were determined numerically using squared-operator iteration method. It was found that the greater the strength of refraction index, the smaller the guiding modes.

  2. [Complications after refractive surgery abroad].

    Science.gov (United States)

    Terzi, E; Kern, T; Kohnen, T

    2008-05-01

    In this article a retrospective analysis of patients presenting at a German university following refractive surgery abroad is presented. A total of 20 cases of patients who had undergone treatment between 1998 and 2006 in China (1 case), Greece (1 case), Iran (1 case), Russia (2 cases), Switzerland (1 case), Slovakia (1 case), Spain (2 cases), South Africa (3 cases), Turkey (6 cases) and the USA (2 cases) were analyzed retrospectively. The following complications were observed: epithelial ingrowth into the interface with or without melting of the flap (6 cases), corneal ectasia (2 cases), dislocation of a phakic posterior chamber intraocular lens and prolapse into the anterior chamber with endothelial cell loss (1 case), secondary increase of intraocular pressure following implantation of a phakic intraocular lens (1 case), flap-related complications following laser-in-situ keratomileusis (LASIK) (2 cases), keratitis (1 case), dislocation of the complete flap (1 case), diffuse lamellar keratitis (DLK) grade IV (1 case), hyperopia as a consequence of radial keratotomy (1 case), and under correction/over correction and poor optical quality following laser epithelial keratomileusis (LASEK) and LASIK for high myopia (5 cases) with possible early corneal ectasia. There are four important problems arising from refractive surgery abroad, often referred to as "LASIK tourism": wrong indications, insufficient management of complications, lack of postoperative care and the health economic aspect.

  3. 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.

  4. A Comparison of the American Society of Cataract and Refractive Surgery post-myopic LASIK/PRK Intraocular Lens (IOL calculator and the Ocular MD IOL calculator

    Directory of Open Access Journals (Sweden)

    Hsu M

    2011-09-01

    Full Text Available David L DeMill1, Majid Moshirfar1, Marcus C Neuffer1, Maylon Hsu1, Shameema Sikder21John A Moran Eye Center, University of Utah, Salt Lake City, UT, USA; 2Wilmer Eye Institute, Johns Hopkins University, Baltimore, MD, USABackground: To compare the average values of the American Society of Cataract and Refractive Surgery (ASCRS and Ocular MD intraocular lens (IOL calculators to assess their accuracy in predicting IOL power in patients with prior laser-in-situ keratomileusis (LASIK or photorefractive keratectomy.Methods: In this retrospective study, data from 21 eyes with previous LASIK or photorefractive keratectomy for myopia and subsequent cataract surgery was used in an IOL calculator comparison. The predicted IOL powers of the Ocular MD SRK/T, Ocular MD Haigis, and ASCRS averages were compared. The Ocular MD average (composed of an average of Ocular MD SRK/T and Ocular MD Haigis and the all calculator average (composed of an average of Ocular MD SRK/T, Ocular MD Haigis, and ASCRS were also compared. Primary outcome measures were mean arithmetic and absolute IOL prediction error, variance in mean arithmetic IOL prediction error, and the percentage of eyes within ±0.50 and ±1.00 D.Results: The Ocular MD SRK/T and Ocular MD Haigis averages produced mean arithmetic IOL prediction errors of 0.57 and –0.61 diopters (D, respectively, which were significantly larger than errors from the ASCRS, Ocular MD, and all calculator averages (0.11, –0.02, and 0.02 D, respectively, all P < 0.05. There was no statistically significant difference between the methods in absolute IOL prediction error, variance, or the percentage of eyes with outcomes within ±0.50 and ±1.00 D.Conclusion: The ASCRS average was more accurate in predicting IOL power than the Ocular MD SRK/T and Ocular MD Haigis averages alone. Our methods using combinations of these averages which, when compared with the individual averages, showed a trend of decreased mean arithmetic IOL

  5. Eye Contricks

    Directory of Open Access Journals (Sweden)

    N Wade

    2011-04-01

    Full Text Available Icons are eye-cons: they provide a distillation of a complex object or idea into a simple pictorial shape. They create the impression of representing that which cannot be presented. Even at the level of the photograph, the links between icon and object are tenuous. The dimension of distance or depth is missing from the icon, and this alone introduces all manner of potential ambiguities. The history of art can be considered as an exploration of the missing link between icon and object. Eye-cons are more honest—they are tricks of vision so that what is seen does not necessarily correspond to what is presented. They are visual allusions rather than visual illusions, although they can display illusory effects. At its broadest, icon can be equated with image. The concept of image has thrived on its vagueness, and so attempts have been made to refine it. An icon corresponds to an optical image: it shares some of the projective characteristics of the object represented. Written words are also icons but they do not resemble the objects they represent—they are stylised or conventional rather than spatialised and projective. Words and images were set in delightful opposition by René Magritte (1898-1967 in a series of pipe paintings, and he also played on the theme of the arbitrariness of the verbal labels assigned to objects. What is surprising is that Magritte did not apply his painterly skills to transforming the word shapes he used. A similar reluctance to transform the typefaces pervades visual poetry. My interests are in the visual rather than the poetic dimension, and I will present a range of my own eye contricks which play with letter and word shapes in a variety of ways.

  6. Rotationally asymmetric multifocal IOL implantation with and without capsular tension ring: refractive and visual outcomes and intraocular optical performance.

    Science.gov (United States)

    Alió, Jorge L; Plaza-Puche, Ana B; Piñero, David P

    2012-04-01

    To ascertain whether the refractive, visual, and intraocular optical quality outcomes of a rotationally asymmetric multifocal intraocular lens (IOL) are enhanced by the use of a capsular tension ring. Ninety consecutive eyes from 53 patients (age range: 36 to 82 years) were divided into two groups: the no ring group comprised 43 eyes implanted with the multifocal rotationally asymmetric Lentis Mplus LS-312 (Oculentis GmbH) without a capsular tension ring; and the ring group comprised 47 eyes with the same IOL with a capsular tension ring. Distance and near visual acuity and refractive outcomes were evaluated pre- and postoperatively. Contrast sensitivity, intraocular aberrations, and defocus curve were evaluated postoperatively. Significant postoperative differences between groups were found in sphere, spherical equivalent refraction, and near addition (P<.02). Regarding defocus curve, significantly better visual acuity was present in eyes with the capsular tension ring for intermediate vision conditions (P<.05). Intraocular aberrometry did not differ significantly between groups (P<.09). Refractive predictability and intermediate visual outcomes with the Lentis Mplus LS-312 IOL improved significantly when implanted in combination with a capsular tension ring. Copyright 2012, SLACK Incorporated.

  7. Genome-wide meta-analyses of multiancestry cohorts identify multiple new susceptibility loci for refractive error and myopia

    NARCIS (Netherlands)

    Verhoeven, Virginie J. M.; Hysi, Pirro G.; Wojciechowski, Robert; Fan, Qiao; Guggenheim, Jeremy A.; Höhn, René; Macgregor, Stuart; Hewitt, Alex W.; Nag, Abhishek; Cheng, Ching-Yu; Yonova-Doing, Ekaterina; Zhou, Xin; Ikram, M. Kamran; Buitendijk, Gabriëlle H. S.; McMahon, George; Kemp, John P.; Pourcain, Beate St; Simpson, Claire L.; Mäkelä, Kari-Matti; Lehtimäki, Terho; Kähönen, Mika; Paterson, Andrew D.; Hosseini, S. Mohsen; Wong, Hoi Suen; Xu, Liang; Jonas, Jost B.; Pärssinen, Olavi; Wedenoja, Juho; Yip, Shea Ping; Ho, Daniel W. H.; Pang, Chi Pui; Chen, Li Jia; Burdon, Kathryn P.; Craig, Jamie E.; Klein, Barbara E. K.; Klein, Ronald; Haller, Toomas; Metspalu, Andres; Khor, Chiea-Chuen; Tai, E.-Shyong; Aung, Tin; Vithana, Eranga; Tay, Wan-Ting; Barathi, Veluchamy A.; Chen, Peng; Li, Ruoying; Liao, Jiemin; Zheng, Yingfeng; Bergen, Arthur A. B.; Chen, Wei

    2013-01-01

    Refractive error is the most common eye disorder worldwide and is a prominent cause of blindness. Myopia affects over 30% of Western populations and up to 80% of Asians. The CREAM consortium conducted genome-wide meta-analyses, including 37,382 individuals from 27 studies of European ancestry and

  8. Spherical subjective refraction with a novel 3D virtual reality based system.

    Science.gov (United States)

    Pujol, Jaume; Ondategui-Parra, Juan Carlos; Badiella, Llorenç; Otero, Carles; Vilaseca, Meritxell; Aldaba, Mikel

    To conduct a clinical validation of a virtual reality-based experimental system that is able to assess the spherical subjective refraction simplifying the methodology of ocular refraction. For the agreement assessment, spherical refraction measurements were obtained from 104 eyes of 52 subjects using three different methods: subjectively with the experimental prototype (Subj.E) and the classical subjective refraction (Subj.C); and objectively with the WAM-5500 autorefractor (WAM). To evaluate precision (intra- and inter-observer variability) of each refractive tool independently, 26 eyes were measured in four occasions. With regard to agreement, the mean difference (±SD) for the spherical equivalent (M) between the new experimental subjective method (Subj.E) and the classical subjective refraction (Subj.C) was -0.034D (±0.454D). The corresponding 95% Limits of Agreement (LoA) were (-0.856D, 0.924D). In relation to precision, intra-observer mean difference for the M component was 0.034±0.195D for the Subj.C, 0.015±0.177D for the WAM and 0.072±0.197D for the Subj.E. Inter-observer variability showed worse precision values, although still clinically valid (below 0.25D) in all instruments. The spherical equivalent obtained with the new experimental system was precise and in good agreement with the classical subjective routine. The algorithm implemented in this new system and its optical configuration has been shown to be a first valid step for spherical error correction in a semiautomated way. Copyright © 2016 Spanish General Council of Optometry. Published by Elsevier España, S.L.U. All rights reserved.

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

    Directory of Open Access Journals (Sweden)

    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.

  10. Relationship between retinal distance and object field angles for finite schematic eyes.

    Science.gov (United States)

    Suheimat, Marwan; Zhu, Hai-Feng; Lambert, Andrew; Atchison, David A

    2016-07-01

    Retinal anatomical studies have used the Drasdo & Fowler three-refracting surface schematic eye to convert between retinal distances and object field angles. We compared its performance at this task with those of more sophisticated four-refracting surface schematic eyes. Raytracing was performed for Drasdo & Fowler, Lotmar, Navarro, Liou & Brennan, Kooijman and Atchison schematic eyes, and some of their variants. The Drasdo & Fowler eye gives a greater rate of change of object field angle with retinal distance at the retinal centre of about 5% than the other schematic eyes. This rate of change also increases much more quickly into the peripheral retina for the Drasdo & Fowler eye than for the other eyes. The reason for these differences is only that the Drasdo & Fowler eye is shorter than the other eyes. The relationship between retinal distance and visual field angle appears robust to changes in retinal radius of curvature when the retina is spherical. The retinal asphericity of Kooijman and Atchison eyes appears to play a role beyond 14 mm (~50°). Changing the length of the Drasdo & Fowler eye, to match those of the four-refracting surface schematic eyes, gives similar relationships between retinal distance and object field angle up to a retinal distance of approximately 14 mm (~50°). The relationship will change with refractive error as this is related to axial length and to retinal shape, and this should be taken into consideration for accurate conversions. For distances and angles beyond 14 mm and ~50°, retinal shape should be taken into account. © 2016 The Authors Ophthalmic & Physiological Optics © 2016 The College of Optometrists.

  11. Collie eye anomaly: a review

    Czech Academy of Sciences Publication Activity Database

    Palánová, Anna

    2015-01-01

    Roč. 60, č. 7 (2015), s. 345-350 ISSN 0375-8427 R&D Projects: GA MŠk ED2.1.00/03.0124 Institutional support: RVO:67985904 Keywords : hereditary * eye * disease * dog Subject RIV: GJ - Animal Vermins ; Diseases, Veterinary Medicine Impact factor: 0.560, year: 2015

  12. 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.

  13. Tomographic method for measurement of the gradient refractive index of the crystalline lens. I. The spherical fish lens.

    Science.gov (United States)

    Acosta, Eva; Vazquez, Daniel; Garner, Leon; Smith, George

    2005-03-01

    We present an iterative tomographic algorithm to reconstruct refractive-index profiles for meridional planes of the lens of the spherical fish eye from measurements of deflection angles of refracted rays. Numerical simulations show that the algorithm allows accuracy up to the fourth decimal place, provided that the refractive index can be regarded as an analytical function of the radial coordinate and the experimental errors are neglected. An experimental demonstration is given by applying the algorithm to retrieve the refractive-index profile of a spherical fish lens. The method is conceptually simple and does not require matching of the index of the surrounding medium to that of the surface of the lens, and the related iterative algorithm rapidly converges.

  14. Review on the refractive treatment methods of aphakia

    Directory of Open Access Journals (Sweden)

    Xiao-Yan Deng

    2015-06-01

    Full Text Available The refractive treatment methods of aphakia include corrective glasses, contact lens correction and intraocular lens(IOLimplantation. It magnifies images highly and limits vision field with corrective glasses. For infant aphakia corrective glasses are more likely to be chosen because their eyes are still unable to tolerate IOL implantation in the developmental stage. With low magnification of images, contact lens includes soft contact lens and rigid contact lens. The former is rarely used because it is prone to ocular lesions due to its poor oxygen permeability. The latter is widely used due to its good oxygen permeability especially suitable for the eyes of irregular astigmatism or iris missing due to trauma. At present, the most commonly used in clinical work is IOL implantation. The eye of IOL may avoid anisometropia, aberrations and so on because of more physiological anatomy. According to the IOL implantation site, it is divided into the anterior chamber IOL implantation and the posterior chamber IOL implantation. The anterior chamber IOL implantation is divided into angle fixed IOL implantation and iris fixed IOL implantation. The posterior chamber IOL implantation is divided into secondary in-the-bag IOL implantation, the ciliary sulcus IOL implantation and transscleral suture fixed IOL implantation.

  15. [Analysis of refractive status after cataract surgery in age-related cataract patients with shallow anterior chamber].

    Science.gov (United States)

    Yang, Fei; Hou, Xianru; Wu, Huijuan; Bao, Yongzhen

    2014-02-01

    To evaluate the characteristics of postoperative refractive status in age-related cataract patients with shallow anterior chamber and the correlation between pre-operative anterior chamber depth and postoperative refractive status. Prospective case-control study. Sixty-eight cases (90 eyes) with age-related cataract were recruited from October 2010 to January 2012 in People's Hospital Peking University including 28 cases (34 eyes) in control group and 40 cases (56 eyes) in shallow anterior chamber group according to anterior chamber depth (ACD) measured by Pentacam system. Axial length and keratometer were measured by IOL Master and intraocular lens power was calculated using SRK/T formula. Postoperative refraction, ACD and comprehensive eye examination were performed at 1 month and 3 months after cataract surgery. Using SPSS13.0 software to establish a database, the two groups were compared with independent samples t-test and correlation analysis were performed with binary logical regression. The postoperative refractive deviation at 1 month were (-0.39 ± 0.62) D in control group and (+0.73 ± 0.26) D in shallow anterior chamber group respectively which present statistical significance between the two groups (P = 0.00, t = 3.67); the postoperative refractive deviation in 3 month was (-0.37 ± 0.62) D in control group and (+0.79 ± 0.28) D in shallow anterior chamber group operatively which present statistical significance between the two groups (P = 0.00, t = 3.33). In shallow anterior chamber group, with the shallower of ACD, the greater of refractive deviation (P = 0.00, r1 month = -0.57, r3 months = -0.61). Hyperopic shift existed in age-related cataract patients with shallow anterior chamber and the shallower of ACD was, the greater of hyperopic shift happened.

  16. Clinical study of the clusters of diffuse lamellar keratitis after laser corneal refractive surgery

    Directory of Open Access Journals (Sweden)

    Qing-Hong Lin

    2017-06-01

    Full Text Available AIM: To investigate the potential causes and management of the clusters of diffuse lamellar keratitis(DLKafter laser corneal refractive surgery. METHODS: The study enrolled 98 eyes(53 patientscomplicated with DLK after receiving laser in situ keratomileusis(LASIK, FS-LASIK or small-incision lenticule extraction(SMILEin our center from February 10th,2016 to February 22th,2016. They were given clinical classification treatments according to corneal layer inflammatory extent and then followed up after 1, 3, 5, 7, 10d and 1mo. RESULTS: The clusters of DLK occurred 5 times in the study period. The incidence and degree of DLK significantly decreased after changed the sterilization, surgical equipments, temperature and humidity of the operating room. There were 80 eyes(82%had stage 1 DLK, 11 eyes(11%had stage 2, 4 eyes(4%had stage 3 and 3 eyes(3%had stage 4. The incidence of DLK after FS-LASIK was 40%(79 eyes in 42 patients, that after LASIK assistant by Hastome keratome was 45%(10 eyes in 5 patients, that after SMILE was 20%(9 eyes in 6 patients. After intensive treatment, as glucocorticoid treatment and flap lifting flushing, all cases recovered within 1mo. CONCLUSION: The outbreak of DLK may be associated with the disposable item, flushing liquor, temperature and humidity of the operating room. Early diagnosis, prevention and treatment are the key of decreasing the incidence of DLK.

  17. Detection of the early keratoconus based on corneal biomechanical properties in the refractive surgery candidates

    Directory of Open Access Journals (Sweden)

    Zofia Pniakowska

    2016-01-01

    Full Text Available Context: Subclinical keratoconus is contraindication to refractive surgery. The currently used methods of preoperative screening do not always allow differentiating between healthy eyes and those with subclinical keratoconus. Aim: To evaluate biomechanical parameters of the cornea, waveform score (WS, and intraocular pressure (IOP as potentially useful adjuncts to the diagnostic algorithm for precise detection of the early keratoconus stages and selection of refractive surgery candidates. Settings and Design: Department of Ophthalmology and prospective cross-sectional study. Patients and Methods: Patients enrolled in the study were diagnosed with refractive disorders. We assessed parameters of corneal biomechanics such as corneal hysteresis (CH, corneal resistance factor (CRF, Goldman-correlated IOP (IOPg, corneal compensated IOP, WS, and keratoconus match index (KMI. They were classified into one of three groups based on the predefined KMI range: Group 1 (from 0.352 to 0.757 – 45 eyes, Group 2 (from −0.08 to 0.313 – 52 eyes, and Group 0 - control group (from 0.761 to 1.642 – 80 eyes. Results: In both study groups, IOPg, CRF, and CH were decreased when compared to control (P < 0.0001. In control group, there was positive correlation between CH and KMI (P < 0.05, with no correlations in any of the two study groups. CRF correlated positively with KMI in control (P < 0.0001 and in Group 2 (P < 0.05. Conclusions: CH and CRF, together with WS and IOPg, consist a clinically useful adjunct to detect subclinical keratoconus in patients referred for refractive surgery when based on KMI staging.

  18. Comparison between refraction measured by Spot Vision ScreeningTM and subjective clinical refractometry

    OpenAIRE

    de Jesus, Daniela Lima; Villela, Fl?vio Fernandes; Orlandin, Luis Fernando; Eiji, Fernando Naves; Dantas, Daniel Oliveira; Alves, Milton Ruiz

    2016-01-01

    OBJECTIVE: The purpose of this study was to evaluate the accuracy of Spot Vision ScreeningTM as an autorefractor by comparing refraction measurements to subjective clinical refractometry results in children and adult patients. METHODS: One-hundred and thirty-four eyes of 134 patients were submitted to refractometry by Spot and clinical refractometry under cycloplegia. Patients, students, physicians, staff and children of staff from the Hospital das Clínicas (School of Medicine, University of...

  19. Eye diseases in children in jourdan

    International Nuclear Information System (INIS)

    Mousa, A.M.V.; Suha, A.E.M

    2014-01-01

    Objective: To investigate eye diseases in children in Jordan and to see whether it is necessary to conduct a visual screening programme. Methods: The study was conducted between July 2010 and July 2012 at four Royal Medical Service hospitals located in northern, eastern, middle and southern parts of Jordan. Children aged (6-14 years) attending paediatric clinics for various reasons were enrolled. Ophthalmologic assessment included visual acuity and anterior and posterior segment examination. Patients with visual acuity of less than 20/20 underwent refraction under cyclopegia. Results: Of the 3200 children in the study ocular abnormalities were found in 366 (11.4%); 312 (9.8%) had visual acuity less than 20/20 in one or both eyes. Refractive error was seen in 286 (8.9%); while vernal catarrh was the second most common ocular abnormality with 51 (1.6%) patients followed by squint 16(0.5%). Four (0.12%) patients had severe visual impairment and one (0.03%) patient was blind. Conclusion: The prevalence of refractive error was high in school children in the study area. It is important to conduct a visual screening programme in early school years in order to prevent amblyopia. (author)

  20. REFRACTIVE ERROR STATUS IN BAYELSA STATE, NIGERIA

    African Journals Online (AJOL)

    LIVINGSTON

    deepening poverty because of their inability to see well” . In 2002, the .... all the refractions) and other health workers. During the period .... To the best of our knowledge, there is no ... 2020 and eliminate uncorrected refractive error within the ...

  1. Microstructured optical fiber refractive index sensor

    DEFF Research Database (Denmark)

    Town, Graham E.; McCosker, Ravi; Yuan, Scott Wu

    2010-01-01

    We describe a dual-core microstructured optical fiber designed for refractive index sensing of fluids. We show that by using the exponential dependence of intercore coupling on analyte refractive index, both large range and high sensitivity can be achieved in the one device. We also show...

  2. Measurements of photoinduced refractive index changes in ...

    Indian Academy of Sciences (India)

    Abstract. We report the pump–probe measurements of nonlinear refractive index changes in photochromic bacteriorhodopsin films. The photoinduced absorption is caused by pump beam at 532 nm and the accompanying refractive index changes are studied using a probe beam at 633 nm. The proposed technique is ...

  3. 3D super-virtual refraction interferometry

    KAUST Repository

    Lu, Kai; AlTheyab, Abdullah; Schuster, Gerard T.

    2014-01-01

    Super-virtual refraction interferometry enhances the signal-to-noise ratio of far-offset refractions. However, when applied to 3D cases, traditional 2D SVI suffers because the stationary positions of the source-receiver pairs might be any place

  4. Light rays in gravitating, refractive media

    International Nuclear Information System (INIS)

    Noonan, T.W.

    1982-01-01

    The field-to-particle method of H. P. Robertson is applied to the general-relativistic Maxwell equations in order to obtain the general-relativistic equation of motion for a photon in a refractive medium. For the special case of an uncharged, refractive, spherically symmetric mass, the exact first-order differential equation for the light-ray path is given

  5. Refractive regression after laser in situ keratomileusis.

    Science.gov (United States)

    Yan, Mabel K; Chang, John Sm; Chan, Tommy Cy

    2018-04-26

    Uncorrected refractive errors are a leading cause of visual impairment across the world. In today's society, laser in situ keratomileusis (LASIK) has become the most commonly performed surgical procedure to correct refractive errors. However, regression of the initially achieved refractive correction has been a widely observed phenomenon following LASIK since its inception more than two decades ago. Despite technological advances in laser refractive surgery and various proposed management strategies, post-LASIK regression is still frequently observed and has significant implications for the long-term visual performance and quality of life of patients. This review explores the mechanism of refractive regression after both myopic and hyperopic LASIK, predisposing risk factors and its clinical course. In addition, current preventative strategies and therapies are also reviewed. © 2018 Royal Australian and New Zealand College of Ophthalmologists.

  6. Refractive Results: Safety and Efficacy of Secondary Piggyback Sensar™ AR40 Intraocular Lens Implantation to Correct Pseudophakic Refractive Error

    Directory of Open Access Journals (Sweden)

    Alahmady Hamad Alsmman Hassan

    2016-01-01

    Full Text Available In this study we evaluate the visual outcomes, safety, efficacy, and stability of implanting of second sulcus intraocular lens (IOL to correct unsatisfied ametropic patients after phacoemulsification. Methods. Retrospective study of 15 eyes (15 patients underwent secondary intraocular lens implanted into the ciliary sulcus. The IOL used was a Sensar IOL three-piece foldable hydrophobic acrylic IOL. The first IOL in all patients was acrylic intrabagal IOL implanted in uncomplicated phacoemulsification surgery. Results. Fifteen eyes (15 patients were involved in this study. Preoperatively, mean log⁡MAR UDVA and CDVA were 0.88 ± 0.22 and 0.19 ± 0.13, respectively, with a mean follow-up of 28 months (range: 24 to 36 months. At the end of the follow-up, all eyes achieved log⁡MAR UDVA of 0.20 ± 0.12 with postoperative refraction ranging from 0.00 to −0.50 D of attempted emmetropia. Conclusions. Implantation of the second sulcus SensarAR40 IOL was found to be safe, easy, and simple technique for management of ametropia following uncomplicated phacoemulsification.

  7. Amblyopia and refractive errors among school-aged children with low socioeconomic status in southeastern Turkey.

    Science.gov (United States)

    Caca, Ihsan; Cingu, Abdullah Kursat; Sahin, Alparslan; Ari, Seyhmus; Dursun, Mehmet Emin; Dag, Umut; Balsak, Selahattin; Alakus, Fuat; Yavuz, Abdullah; Palanci, Yilmaz

    2013-01-01

    To investigate the prevalence of refractive errors and other eye diseases, incidence and types of amblyopia in school-aged children, and their relation to gender, age, parental education, and socioeconomic factors. A total of 21,062 children 6 to 14 years old were screened. The examination included visual acuity measurements and ocular motility evaluation. Autorefraction under cycloplegia and examination of the external eye, anterior segment, media, and fundus were performed. There were 11,118 females and 9,944 males. The average age was 10.56 ± 3.59 years. When all of the children were evaluated, 3.2% had myopia and 5.9% had hyperopia. Astigmatism 0.50 D or greater was present in 14.3% of children. Myopia was associated with older age, female gender, and higher parental education. Hyperopia was inversely proportional with older age. Spectacles were needed in 4,476 (22.7%) children with refractive errors, and 10.6% of children were unaware of their spectacle needs. Amblyopia was detected in 2.6% of all children. The most common causes of amblyopia were anisometropia (1.2%) and strabismus (0.9%). Visual impairment is a common disorder in school-aged children. Eye health screening programs are beneficial in early detection and proper treatment of refractive errors. Copyright 2013, SLACK Incorporated.

  8. Modeling the influence of LASIK surgery on optical properties of the human eye

    Science.gov (United States)

    Szul-Pietrzak, Elżbieta; Hachoł, Andrzej; Cieślak, Krzysztof; Drożdż, Ryszard; Podbielska, Halina

    2011-11-01

    The aim was to model the influence of LASIK surgery on the optical parameters of the human eye and to ascertain which factors besides the central corneal radius of curvature and central thickness play the major role in postsurgical refractive change. Ten patients were included in the study. Pre- and postsurgical measurements included standard refraction, anterior corneal curvature and pachymetry. The optical model used in the analysis was based on the Le Grand and El Hage schematic eye, modified by the measured individual parameters of corneal geometry. A substantial difference between eye refractive error measured after LASIK and estimated from the eye model was observed. In three patients, full correction of the refractive error was achieved. However, analysis of the visual quality in terms of spot diagrams and optical transfer functions of the eye optical system revealed some differences in these measurements. This suggests that other factors besides corneal geometry may play a major role in postsurgical refraction. In this paper we investigated whether the biomechanical properties of the eyeball and changes in intraocular pressure could account for the observed discrepancies.

  9. What Is Dry Eye?

    Medline Plus

    Full Text Available ... Tips & Prevention News Ask an Ophthalmologist Patient Stories Español Eye Health / Eye Health A-Z Dry Eye ... Eye Treatment What Is Dry Eye? Leer en Español: ¿Qué es el ojo seco? Written By: Kierstan ...

  10. What Is Dry Eye?

    Medline Plus

    Full Text Available ... Eye Symptoms Causes of Dry Eye Dry Eye Treatment What Is Dry Eye? Leer en Español: ¿Qué ... Your Eyelid Nov 29, 2017 New Dry Eye Treatment is a Tear-Jerker Jul 21, 2017 Three ...

  11. Bags Under Eyes

    Science.gov (United States)

    Bags under eyes Overview Bags under eyes — mild swelling or puffiness under the eyes — are common as you age. With aging, the tissues around your ... space below your eyes, adding to the swelling. Bags under eyes are usually a cosmetic concern and ...

  12. About the Eye

    Medline Plus

    Full Text Available ... Ask a Scientist Video Series Glossary The Visual System Your Eyes’ Natural Defenses Eye Health and Safety First Aid Tips Healthy Vision Tips Protective Eyewear Sports and Your Eyes Fun Stuff Cool Eye Tricks Links to More Information Optical Illusions Printables About the Eye Your eyes ...

  13. Endothelial cell loss and refractive predictability in femtosecond laser-assisted cataract surgery compared with conventional cataract surgery

    DEFF Research Database (Denmark)

    Krarup, Therese; Holm, Lars Morten; la Cour, Morten

    2014-01-01

    and the contralateral eye operated by CPS (stop and chop technique). Both eyes had intraocular aspheric lenses implanted. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), central corneal endothelial cell count and hexagonality with a non-contact specular microscope were assessed......PURPOSE: To investigate the amount of endothelial cell loss (ECL) and refractive predictability by femtosecond laser-assisted cataract surgery (FLACS) compared to conventional phacoemulsification cataract surgery (CPS). METHODS: Forty-seven patients had one eye operated by FLACS...

  14. Fluid Mixing in the Eye Under Rapid Eye Movement

    Science.gov (United States)

    Huang, Jinglin; Gharib, Morteza

    2017-11-01

    Drug injection is an important technique in certain treatments of eye diseases. The efficacy of chemical mixing plays an important role in determining pharmacokinetics of injected drugs. In this study, we build a device to study the chemical mixing behavior in a spherical structure. The mixing process is visualized and analyzed qualitatively. We hope to understand the chemical convection and diffusion behaviors in correlation with controlled rapid mechanical movements. The results will have potential applications in treatment of eye diseases. Resnick Institute at Caltech.

  15. Refractive index depth profile in PMMA due to proton irradiation

    International Nuclear Information System (INIS)

    Szilasi, S.Z.; Rajta, I.; Budai, J.; Toth, Z.; Petrik, P.; Baradacs, E.

    2006-01-01

    for the determination of optical properties. All irradiations in this work have been performed on the 5 MV Van de Graaff accelerator of the Institute. The samples were Roehm GS233 type PMMA. The main irradiation parameters were: ∼2 MeV proton energy and 100 nC/mm 2 fluence, because these are typical values for P-beam Writing on PMMA. In this experiment, what we called 'PMMA foil method', the proton energy was varied in the range 1.7-2.1 MeV. A 50 μm thick PMMA foil was attached to the top of bulk PMMA samples in order to decelerate the protons. Depending on the used energy, different energy delivery levels were reached at the bulk PMMA surface (Fig. 1.). The ellipsometric analyses were performed on a Woollam M2000F rotating compensator ellipsometer in Szeged. The measurements were carried out at 476 different wavelengths in the range of 245-1000 nm. The angle of incidence (50 deg, 52 deg, 54 deg, 56 deg, 58 deg) was chosen to be near the Brewster-angle of PMMA. From the ellipsometric measurements the refractive index and the extinction coefficient as a function of the wavelength can be determined by a special modeling procedure. For full details of this work see the complete paper [2]. Here we present one particular visualisation of the results. In the investigated proton energy range the Bragg curves behave similarly, the protons slow down by many collisions of small energy transfer to the electrons of the sample. We calculated the energy loss ΔE/Δx for the 1.7-2.1 MeV protons after passing through 50 μm of PMMA, then we found the same energy loss value on the 2 MeV protons Bragg curve in bulk PMMA. Having the refractive index values at the 1.7-2.1 MeV protons at 50 μm depth, we plotted the refractive index values caused by 2 MeV protons at the calculated depths. Fig. 2. shows these results. In addition we also plotted the Bragg curve of 2 MeV protons on the same depth scale. Since the agreement between the measured refractive indices and the Bragg curve looks

  16. Reducing visual deficits caused by refractive errors in school and preschool children: results of a pilot school program in the Andean region of Apurimac, Peru

    Science.gov (United States)

    Latorre-Arteaga, Sergio; Gil-González, Diana; Enciso, Olga; Phelan, Aoife; García-Muñoz, Ángel; Kohler, Johannes

    2014-01-01

    Background Refractive error is defined as the inability of the eye to bring parallel rays of light into focus on the retina, resulting in nearsightedness (myopia), farsightedness (Hyperopia) or astigmatism. Uncorrected refractive error in children is associated with increased morbidity and reduced educational opportunities. Vision screening (VS) is a method for identifying children with visual impairment or eye conditions likely to lead to visual impairment. Objective To analyze the utility of vision screening conducted by teachers and to contribute to a better estimation of the prevalence of childhood refractive errors in Apurimac, Peru. Design A pilot vision screening program in preschool (Group I) and elementary school children (Group II) was conducted with the participation of 26 trained teachers. Children whose visual acuity was<6/9 [20/30] (Group I) and≤6/9 (Group II) in one or both eyes, measured with the Snellen Tumbling E chart at 6 m, were referred for a comprehensive eye exam. Specificity and positive predictive value to detect refractive error were calculated against clinical examination. Program assessment with participants was conducted to evaluate outcomes and procedures. Results A total sample of 364 children aged 3–11 were screened; 45 children were examined at Centro Oftalmológico Monseñor Enrique Pelach (COMEP) Eye Hospital. Prevalence of refractive error was 6.2% (Group I) and 6.9% (Group II); specificity of teacher vision screening was 95.8% and 93.0%, while positive predictive value was 59.1% and 47.8% for each group, respectively. Aspects highlighted to improve the program included extending training, increasing parental involvement, and helping referred children to attend the hospital. Conclusion Prevalence of refractive error in children is significant in the region. Vision screening performed by trained teachers is a valid intervention for early detection of refractive error, including screening of preschool children. Program

  17. Fully 3D refraction correction dosimetry system

    International Nuclear Information System (INIS)

    Manjappa, Rakesh; Makki, S Sharath; Kanhirodan, Rajan; Kumar, Rajesh; Vasu, Ram Mohan

    2016-01-01

    The irradiation of selective regions in a polymer gel dosimeter results in an increase in optical density and refractive index (RI) at those regions. An optical tomography-based dosimeter depends on rayline path through the dosimeter to estimate and reconstruct the dose distribution. The refraction of light passing through a dose region results in artefacts in the reconstructed images. These refraction errors are dependant on the scanning geometry and collection optics. We developed a fully 3D image reconstruction algorithm, algebraic reconstruction technique-refraction correction (ART-rc) that corrects for the refractive index mismatches present in a gel dosimeter scanner not only at the boundary, but also for any rayline refraction due to multiple dose regions inside the dosimeter. In this study, simulation and experimental studies have been carried out to reconstruct a 3D dose volume using 2D CCD measurements taken for various views. The study also focuses on the effectiveness of using different refractive-index matching media surrounding the gel dosimeter. Since the optical density is assumed to be low for a dosimeter, the filtered backprojection is routinely used for reconstruction. We carry out the reconstructions using conventional algebraic reconstruction (ART) and refractive index corrected ART (ART-rc) algorithms. The reconstructions based on FDK algorithm for cone-beam tomography has also been carried out for comparison. Line scanners and point detectors, are used to obtain reconstructions plane by plane. The rays passing through dose region with a RI mismatch does not reach the detector in the same plane depending on the angle of incidence and RI. In the fully 3D scanning setup using 2D array detectors, light rays that undergo refraction are still collected and hence can still be accounted for in the reconstruction algorithm. It is found that, for the central region of the dosimeter, the usable radius using ART-rc algorithm with water as RI matched

  18. Fully 3D refraction correction dosimetry system.

    Science.gov (United States)

    Manjappa, Rakesh; Makki, S Sharath; Kumar, Rajesh; Vasu, Ram Mohan; Kanhirodan, Rajan

    2016-02-21

    The irradiation of selective regions in a polymer gel dosimeter results in an increase in optical density and refractive index (RI) at those regions. An optical tomography-based dosimeter depends on rayline path through the dosimeter to estimate and reconstruct the dose distribution. The refraction of light passing through a dose region results in artefacts in the reconstructed images. These refraction errors are dependant on the scanning geometry and collection optics. We developed a fully 3D image reconstruction algorithm, algebraic reconstruction technique-refraction correction (ART-rc) that corrects for the refractive index mismatches present in a gel dosimeter scanner not only at the boundary, but also for any rayline refraction due to multiple dose regions inside the dosimeter. In this study, simulation and experimental studies have been carried out to reconstruct a 3D dose volume using 2D CCD measurements taken for various views. The study also focuses on the effectiveness of using different refractive-index matching media surrounding the gel dosimeter. Since the optical density is assumed to be low for a dosimeter, the filtered backprojection is routinely used for reconstruction. We carry out the reconstructions using conventional algebraic reconstruction (ART) and refractive index corrected ART (ART-rc) algorithms. The reconstructions based on FDK algorithm for cone-beam tomography has also been carried out for comparison. Line scanners and point detectors, are used to obtain reconstructions plane by plane. The rays passing through dose region with a RI mismatch does not reach the detector in the same plane depending on the angle of incidence and RI. In the fully 3D scanning setup using 2D array detectors, light rays that undergo refraction are still collected and hence can still be accounted for in the reconstruction algorithm. It is found that, for the central region of the dosimeter, the usable radius using ART-rc algorithm with water as RI matched

  19. Tutorial on Biostatistics: Linear Regression Analysis of Continuous Correlated Eye Data.

    Science.gov (United States)

    Ying, Gui-Shuang; Maguire, Maureen G; Glynn, Robert; Rosner, Bernard

    2017-04-01

    To describe and demonstrate appropriate linear regression methods for analyzing correlated continuous eye data. We describe several approaches to regression analysis involving both eyes, including mixed effects and marginal models under various covariance structures to account for inter-eye correlation. We demonstrate, with SAS statistical software, applications in a study comparing baseline refractive error between one eye with choroidal neovascularization (CNV) and the unaffected fellow eye, and in a study determining factors associated with visual field in the elderly. When refractive error from both eyes were analyzed with standard linear regression without accounting for inter-eye correlation (adjusting for demographic and ocular covariates), the difference between eyes with CNV and fellow eyes was 0.15 diopters (D; 95% confidence interval, CI -0.03 to 0.32D, p = 0.10). Using a mixed effects model or a marginal model, the estimated difference was the same but with narrower 95% CI (0.01 to 0.28D, p = 0.03). Standard regression for visual field data from both eyes provided biased estimates of standard error (generally underestimated) and smaller p-values, while analysis of the worse eye provided larger p-values than mixed effects models and marginal models. In research involving both eyes, ignoring inter-eye correlation can lead to invalid inferences. Analysis using only right or left eyes is valid, but decreases power. Worse-eye analysis can provide less power and biased estimates of effect. Mixed effects or marginal models using the eye as the unit of analysis should be used to appropriately account for inter-eye correlation and maximize power and precision.

  20. Comparison of the visual and intraocular optical performance of a refractive multifocal IOL with rotational asymmetry and an apodized diffractive multifocal IOL.

    Science.gov (United States)

    Alió, Jorge L; Plaza-Puche, Ana B; Javaloy, Jaime; Ayala, María José

    2012-02-01

    To compare the visual outcomes and intraocular optical quality observed postoperatively in patients implanted with a rotationally asymmetric multifocal intraocular lens (IOL) and an apodized diffractive multifocal IOL. Seventy-four consecutive eyes of 40 cataract patients (age range: 36 to 79 years) were divided into two groups: zonal refractive group, 39 eyes implanted with a rotationally asymmetric multifocal IOL (Lentis Mplus LS-312 IOL, Oculentis GmbH); and diffractive group, 35 eyes implanted with an apodized diffractive multifocal IOL (ReSTOR SN6AD3, Alcon Laboratories Inc). Distance and near visual acuity outcomes, contrast sensitivity, intraocular optical quality, and defocus curves were evaluated during 3-month follow-up. Calculation of the intraocular aberrations was performed by subtracting corneal aberrations from total ocular aberrations. Uncorrected near visual acuity and distance-corrected near visual acuity were better in the diffractive group than in the zonal refractive group (P=.01), whereas intermediate visual acuity (defocus +1.00 and +1.50 diopters) was better in the zonal refractive group. Photopic contrast sensitivity was significantly better in the zonal refractive group (P=.04). Wavefront aberrations (total, higher order, tilt, primary coma) were significantly higher in the zonal refractive group than in the diffractive group (P=.02). Both multifocal IOLs are able to successfully restore visual function after cataract surgery. The zonal refractive multifocal IOL provides better results in contrast sensitivity and intermediate vision, whereas the diffractive multifocal IOL provides better near vision at a closer distance. Copyright 2012, SLACK Incorporated.

  1. VISUAL ACUITY AND CLINICAL REFRACTION FOLLOWING IMPLANTATION OF VARIOUS MULTIFOCAL INTRAOCULAR LENSES

    Directory of Open Access Journals (Sweden)

    N. N. Temirov

    2015-01-01

    Full Text Available Aim. To analyze visual acuity, clinical refraction, and defocusing tolerance after the implantation of monofocal IOL with rotational asymmetric optic (Lentis Mplus 313 MF compared with Acrysof ReSTOR SN6AD1.Materials and methods. Phacoemulsification was performed in a total of 194 patients (288 eyes, i.e., 144 patients (188 eyes with cataract and 50 patients (100 eyes with presbyopia and high ametropia. The patients were divided into two groups. Study group included 132 patients (194 eyes implanted with Lentis Mplus while control group included 62 patients (94 eyes implanted with Acrysof ReSTOR. Uncorrected distance (5 m, intermediate (50‑70 cm, and near (20‑40 cm visual acuity under photopic (85 cd/m2 and mesopic (8 cd/m2 conditions were measured, objective and subjective refractometry were performed, and defocusing tolerance was evaluated.Results. Postoperatively, uncorrected distance and near visual acuity was high while intermediate visual acuity was moderately low. Lentis Mplus patients had better near and intermediate visual acuity under mesopic conditions as compared with Acrysof ReSTOR patients. Emmetropia (target refraction was achieved in 90.2% of study group patients and in 87.2% of control group patients. In patients implanted with Lentis Mplus, refraction was measured by subjective method. Optimal A-constant for Lentis Mplus and Acrysof ReSTOR was 118.0 and 118.6, respectively. Under defocusing, Lentis Mplus patients had better visual acuity than Acrysof ReSTOR patients. This indirectly confirms better intermediate vision.Conclusions. Lentis Mplus provides better vision at various distances that does not almost depend on light levels and induces minimal dysphotopsia. 

  2. Initial resident refractive surgical experience: outcomes of PRK and LASIK for myopia.

    Science.gov (United States)

    Wagoner, Michael D; Wickard, Joseph C; Wandling, George R; Milder, Lisa C; Rauen, Matthew P; Kitzmann, Anna S; Sutphin, John E; Goins, Kenneth M

    2011-03-01

    To evaluate and compare the outcome of initial resident surgical experience with photorefractive keratectomy (PRK) and LASIK. Retrospective review of all cases performed with the VISX Star S4 platform (Abbott Medical Optics) between July 1, 2003 and June 30, 2007. Inclusion criteria were spherical equivalent of -0.50 to -10.00 diopters (D), refractive astigmatic error of ≤3.00 D, intention to provide full distance correction, and minimum 3-month postoperative follow-up after initial ablation or retreatment (if performed). A total of 153 cases performed by 20 different residents met the inclusion criteria; 38 eyes underwent PRK and 115 eyes had LASIK. After initial treatment, mean Snellen uncorrected distance visual acuity (UDVA) after PRK was 20/17.3 and after LASIK was 20/19.5. Photorefractive keratectomy was associated with a significantly better approximation between preoperative corrected distance visual acuity (CDVA) and postoperative UDVA (ΔlogMAR 0.009 vs 0.091; P=.004) and a greater percentage of eyes that achieved UDVA of 20/20 or better (94.7% vs 78.3%; P=.02) or 20/30 or better (100% vs 87.8%; P=.02). There was a higher prevalence of retreatment in eyes that underwent LASIK (7.0% vs 0%; P=.20). One (0.9%) eye lost 2 lines of CDVA after LASIK. Supervised refractive surgery residents can achieve excellent visual outcomes in patients operated during their initial refractive experience. Photorefractive keratectomy was associated with better visual outcome than LASIK. Copyright 2011, SLACK Incorporated.

  3. About the Eye

    Medline Plus

    Full Text Available ... your eye. It helps your eye focus light so things look sharp and clear. Sclera (SKLEH-ruh) ... the different parts of your eye work together so you can see and make sense of the ...

  4. About the Eye

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    Full Text Available ... Glossary The Visual System Your Eyes’ Natural Defenses Eye Health and Safety First Aid Tips Healthy Vision ... to More Information Optical Illusions Printables About the Eye Your eyes are made up of many different ...

  5. Fluorescein eye stain

    Science.gov (United States)

    Abnormal results may point to: Abnormal tear production (dry eye) Blocked tear duct Corneal abrasion (a scratch on ... object in eye ) Infection Injury or trauma Severe dry eye associated with arthritis (keratoconjunctivitis sicca)

  6. What Is Dry Eye?

    Medline Plus

    Full Text Available ... Member Services Advocacy Foundation About Subspecialties & More Eye Health Home Annual Meeting Clinical Education Practice Management Member ... Center Redmond Ethics Center Global Ophthalmology Guide Eye Health Find an Ophthalmologist Academy Store Eye Health A- ...

  7. What Is Dry Eye?

    Medline Plus

    Full Text Available ... Dry Eye Symptoms Related Ask an Ophthalmologist Answers Can a six-month dissolvable punctal plug be removed ... my eyes dry after LASIK? Jun 19, 2016 Can I be tested whether I close my eyes ...

  8. EyeGENE

    Data.gov (United States)

    U.S. Department of Health & Human Services — The eyeGENE® Biorepository and corresponding Database contain family history and clinical eye exam data from subjects enrolled in eyeGENE® Program coupled to...

  9. Comparative characteristics of morphometric, biometric and biomechanical parameters of myopic eyes in children with different types of progressive myopia

    Directory of Open Access Journals (Sweden)

    T. E. Tsybulskaya

    2014-10-01

    Full Text Available Aim. With the progression of myopic process in children the changes of morphometric, biometric and biomechanical parameters of eyeball are observed. In order to study these parameters in the axial and refractive myopia 32 patients (64 eyes with axial and 26 patients (46 eyes with refractive myopia have been examined. Methods and results. It has been established that in patients with axial and refractive progressive myopia in 56.4% of cases there is a decrease of peripapillary zone thickness of nerve fiber and decrease of ganglion cells layer thickness, an increase of corneal-compensated intraocular pressure by 1.3 times, and also the reduce of corneal hysteresis by 1.2 times. Conclusion. These changes do not depend on the degree of refraction and are associated with an increase in axial length of the eye and decrease in the biomechanical properties of the root-scleral capsule regardless the type of myopia.

  10. Ray tracing for inhomogeneous media applied to the human eye

    Science.gov (United States)

    Diaz-Gonzalez, G.; Iturbe-Castillo, M. D.; Juarez-Salazar, R.

    2017-08-01

    Inhomogeneous or gradient index media exhibit a refractive index varying with the position. This kind of media are very interesting because they can be found in both synthetic as well as real life optical devices such as the human lens. In this work we present the development of a computational tool for ray tracing in refractive optical systems. Particularly, the human eye is used as the optical system under study. An inhomogeneous medium with similar characteristics to the human lens is introduced and modeled by the so-called slices method. The useful of our proposal is illustrated by several graphical results.

  11. Análise comparativa entre a refração clínica subjetiva e a automatizada obtida por sensor de frentes de onda Comparative analyses between clinical refraction and automatic refraction obtained through a wave front sensor

    Directory of Open Access Journals (Sweden)

    Wilson de Freitas

    2007-08-01

    Full Text Available OBJETIVO: Avaliar e comparar os resultados obtidos da refração estática clínica com a obtida por sensor de frentes de onda. MÉTODOS: Estudo prospectivo, não seqüencial, de 279 olhos de 147 pacientes. Todos os pacientes foram examinados sob cicloplegia. Primeiro realizamos a refração clínica e a seguir a automatizada por sensor de frentes de onda. Os dados refracionais obtidos foram decompostos para análise vetorial. Foram analisados separadamente os dados de um olho por paciente e dos dois olhos. RESULTADOS: A diferença entre a refração clínica e a automatizada foi de -0,19 DE combinada com -0,06 DC no eixo de 15º para os dados de um olho por paciente e -0,17 DE combinada com -0,05 DC no eixo de 3º para todos os olhos da amostra. CONCLUSÃO: Os dados da refração clínica são comparáveis com os da refração obtida por um sensor de frentes de onda.PURPOSE: To evaluate and compare refractive errors obtained through clinical subjective and automatized wavefront refraction analyses in eyes under cycloplegia. METHODS: Prospective study of 147 patients, 279 eyes, undergoing preoperative examination for refractive surgery. Clinical subjective refraction was performed first followed by wavefront refraction. Results on astigmatism obtained from refraction were decomposed in power vectors for statistical analyses. Data were first analyzed in one eye and then in both eyes. RESULTS: The mean difference between clinical subjective refraction and automatized wavefront refraction on cycloplegic eyes was of -0.19 SD combined with -0.06 CD in the 15º axis for data in one eye, and -0.17 SD combined with -0.05 CD in the 3º axis for data in both eyes of the same patient. CONCLUSION: In the present study clinical subjective refraction and automatized wavefront refraction under cycloplegia had similar numerical values.

  12. Refractive index inhomogeneity within an aerogel block

    International Nuclear Information System (INIS)

    Bellunato, T.; Calvi, M.; Da Silva Costa, C.F.; Matteuzzi, C.; Musy, M.; Perego, D.L.

    2006-01-01

    Evaluating local inhomogeneities of the refractive index inside aerogel blocks to be used as Cherenkov radiator is important for a high energy physics experiment where angular resolution is crucial. Two approaches are described and compared. The first one is based on the bending of a laser beam induced by refractive index gradients along directions normal to the unperturbed optical path. The second method exploits the Cherenkov effect itself by shooting an ultra-relativistic collimated electron beam through different points of the aerogel surface. Local refractive index variations result in sizable differences in the Cherenkov photons distribution

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

    Directory of Open Access Journals (Sweden)

    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.

  14. 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.

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

    Science.gov (United States)

    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.

  16. Understanding refraction contrast using a comparison of absorption and refraction computed tomographic techniques

    Science.gov (United States)

    Wiebe, S.; Rhoades, G.; Wei, Z.; Rosenberg, A.; Belev, G.; Chapman, D.

    2013-05-01

    Refraction x-ray contrast is an imaging modality used primarily in a research setting at synchrotron facilities, which have a biomedical imaging research program. The most common method for exploiting refraction contrast is by using a technique called Diffraction Enhanced Imaging (DEI). The DEI apparatus allows the detection of refraction between two materials and produces a unique ''edge enhanced'' contrast appearance, very different from the traditional absorption x-ray imaging used in clinical radiology. In this paper we aim to explain the features of x-ray refraction contrast as a typical clinical radiologist would understand. Then a discussion regarding what needs to be considered in the interpretation of the refraction image takes place. Finally we present a discussion about the limitations of planar refraction imaging and the potential of DEI Computed Tomography. This is an original work that has not been submitted to any other source for publication. The authors have no commercial interests or conflicts of interest to disclose.

  17. Childhood eye care services in South Darfur State of Sudan: Learner and parent perspectives

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    Saif H. Alrasheed

    2016-04-01

    Full Text Available Purpose: Most causes of childhood visual impairment are either treatable or preventable. Eye health education plays an important role in reducing avoidable causes of visual impairment as well as to help ensure a healthy and educated community. The main objective of this study was to assess the Knowledge, Attitudes and Practices of the students and their parents on childhood eye services and barriers for accessing child eye care. Methods: The study was conducted in South Darfur State of Sudan between January and February 2015. Both quantitative and qualitative methods were used to collect data from eight secondary schools. Four schools for boys and four schools for girls were randomly selected from a list of 21 districts of South Darfur State and the Knowledge, Attitudes and Practices surveys were conducted with the students to collect quantitative data. In addition, seven focus group discussions were conducted with the children’s parents to collect qualitative data. Results: The majority (57.5% of the students reported that they knew about refractive error; however, 33.07% reported never hearing about refractive error. About 70.3% of the respondents believed that uncorrected refractive error leads to visual impairment, 21% believed refractive error did not cause visual impairment and 30.5% reported that wearing spectacles was not effective in the treatment of refractive error. With regard to the information about eye healthcare, 88.1% of the participants reported they did not have enough information about eye care. The reported need for more information about prevention, treatment and symptoms was 34.0%, 31.4% and 17.5%, respectively. With regard to barriers, 80.6% of the students reported never having had their eyes tested. The most cited barriers were cost, fear of wearing spectacles and fear of an eye examination. In addition, 72.6% of students reported that their health insurance did not cover eye care services. Most (53.6% of the parents

  18. Distribution of Binocular Vision Anomalies and Refractive Errors in Iranian Children With Learning Disabilities

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    Yekta

    2015-11-01

    Full Text Available Background Visual problems in children contribute to learning disorders, which are one of the most influential factors in learning. Objectives The aim of the present study was to determine the prevalence of refractive and binocular vision errors in children with learning disorders. Patients and Methods In this cross-sectional study, 406 children with learning disorders with a mean age of 8.56 ± 2.4 years were evaluated. Examinations included the determination of refractive errors with an auto-refractometer and static retinoscopy, measurement of visual acuity with a Snellen chart, evaluation of ocular deviation, and measurement of stereopsis, amplitude of accommodation, and near point of convergence. Results Of the 406 participants, 319 (78.6% were emmetropic in the right eye, 14.5% had myopia, and 6.9% had hyperopia according to cycloplegic refraction. Astigmatism was detected in 75 (18.5% children. In our study, 89.9% of the children had no deviation, 1.0% had esophoria, and 6.4% had exophoria . In addition, 2.2% of the children had suppression. The near point of convergence ranged from 3 to 18 cm, with a mean of 10.12 ± 3.274 cm. Moreover, 98.5 and 98.0% of the participants achieved complete vision with the best correction in the right and left eye, respectively. The best corrected visual acuity in the right and left eye was achieved in 98.5 and 98.0% of the children, respectively. Conclusions The pattern of visual impairment in learning-impaired children is not much different from that in normal children; however, because these children may not be able to express themselves clearly, lack of correct diagnosis and appropriate treatment has resulted in a marked defect in recognizing visual disorders in these children. Therefore, gaining knowledge of the prevalence of refractive errors in children with learning disorders can be considered the first step in their treatment.

  19. Refractive error and visual impairment in school children in Northern Ireland.

    Science.gov (United States)

    O'Donoghue, L; McClelland, J F; Logan, N S; Rudnicka, A R; Owen, C G; Saunders, K J

    2010-09-01

    To describe the prevalence of refractive error (myopia and hyperopia) and visual impairment in a representative sample of white school children. The Northern Ireland Childhood Errors of Refraction study, a population-based cross-sectional study, examined 661 white 12-13-year-old and 392 white 6-7-year-old children between 2006 and 2008. Procedures included assessment of monocular logarithm of the minimum angle of resolution (logMAR), visual acuity (unaided and presenting) and binocular open-field cycloplegic (1% cyclopentolate) autorefraction. Myopia was defined as -0.50DS or more myopic spherical equivalent refraction (SER) in either eye, hyperopia as > or =+2.00DS SER in either eye if not previously classified as myopic. Visual impairment was defined as >0.30 logMAR units (equivalent to 6/12). Levels of myopia were 2.8% (95% CI 1.3% to 4.3%) in younger and 17.7% (95% CI 13.2% to 22.2%) in older children: corresponding levels of hyperopia were 26% (95% CI 20% to 33%) and 14.7% (95% CI 9.9% to 19.4%). The prevalence of presenting visual impairment in the better eye was 3.6% in 12-13-year-old children compared with 1.5% in 6-7-year-old children. Almost one in four children fails to bring their spectacles to school. This study is the first to provide robust population-based data on the prevalence of refractive error and visual impairment in Northern Irish school children. Strategies to improve compliance with spectacle wear are required.

  20. REFractions: The Representing Equivalent Fractions Game

    Science.gov (United States)

    Tucker, Stephen I.

    2014-01-01

    Stephen Tucker presents a fractions game that addresses a range of fraction concepts including equivalence and computation. The REFractions game also improves students' fluency with representing, comparing and adding fractions.

  1. Intelligent Planning for Laser Refractive Surgeries

    Science.gov (United States)

    Wang, Wei; Yue, Yong; Elsheikh, Ahmed; Bao, Fangjun

    2018-02-01

    Refractive error is one of leading ophthalmic diseases for both genders all over the world. Laser refractive correction surgery, e.g., laser in-situ keratomileusis (LASIK), has been commonly used worldwide. The prediction of surgical parameters, e.g., corneal ablation depth, depends on the doctor’s experience, theoretical formula and surgery reference manual in the preoperative diagnosis. The error of prediction may present a potential surgical risk and complication. Being aware of the surgery parameters is important because these can be used to estimate a patient’s post-operative visual quality and help the surgeon plan a suitable treatment. Therefore, in this paper we discuss data mining techniques that can be utilized for the prediction of laser refractive correction surgery parameters. It can provide the surgeon with a reference for possible surgical parameters and outcomes of the patient before the laser refractive correction surgery.

  2. Development of a subjective refraction simulator

    Science.gov (United States)

    Perches, S.; Ares, J.; Collados, M. V.

    2013-11-01

    We have developed simulation software by Matlab (MathworksInc.) with a graphical interface designed for non-expert users. This simulator allows you to complete the process of subjective refraction starting from the aberrometry of the patients and analyse the influence of different factors during the exam. In addition to explain the graphical interface and its working, we show two examples about a complete process of subjective refraction with the influence of high order aberrations and without them showing the retinal image obtained in each step of the refraction process. When the Jackson Cross-Cylinder technique is made with this software, it becomes clear the difficulty of chosen between two images when high order aberrations are present. Therefore, the variability of response during the refraction can be a problem when the examiner has to reach an adequate optical prescription.

  3. Isaac Newton and the astronomical refraction.

    Science.gov (United States)

    Lehn, Waldemar H

    2008-12-01

    In a short interval toward the end of 1694, Isaac Newton developed two mathematical models for the theory of the astronomical refraction and calculated two refraction tables, but did not publish his theory. Much effort has been expended, starting with Biot in 1836, in the attempt to identify the methods and equations that Newton used. In contrast to previous work, a closed form solution is identified for the refraction integral that reproduces the table for his first model (in which density decays linearly with elevation). The parameters of his second model, which includes the exponential variation of pressure in an isothermal atmosphere, have also been identified by reproducing his results. The implication is clear that in each case Newton had derived exactly the correct equations for the astronomical refraction; furthermore, he was the first to do so.

  4. The refractive index of relic gravitons

    CERN Document Server

    Giovannini, Massimo

    2016-01-01

    The dynamical evolution of the refractive index of the tensor modes of the geometry produces a specific class of power spectra characterized by a blue (i.e. slightly increasing) slope which is directly determined by the competition of the slow-roll parameter and of the rate of variation of the refractive index. Throughout the conventional stages of the inflationary and post-inflationary evolution, the microwave background anisotropies measurements, the pulsar timing limits and the big-bang nucleosythesis constraints set stringent bounds on the refractive index and on its rate of variation. Within the physically allowed region of the parameter space the cosmic background of relic gravitons leads to a potentially large signal for the ground based detectors (in their advanced version) and for the proposed space-borne interferometers. Conversely, the lack of direct detection of the signal will set a qualitatively new bound on the dynamical variation of the refractive index.

  5. Dispersion characteristics of negative refraction sonic crystals

    International Nuclear Information System (INIS)

    Wu, L.-Y.; Chen, L.-W.; Wang, R.C.-C.

    2008-01-01

    Dispersion characteristics of negative refraction sonic crystals are investigated. The plane wave expansion method is used to calculate the equifrequency surface; the dependences of refractive direction on frequencies and incident angles for triangular lattices are shown. There exist the positive and negative refractive waves which include k.V g ≥0 and k.V g ≤0 in the second band for the triangular system. We also use the finite element method to demonstrate that the relative intensity of the transmitted acoustic waves is dependent on incident frequencies and angles. The positions of the partial band gaps obtained by the plane wave expansion method are in good agreement with those obtained by the finite element method. The sonic crystals with negative effective index are shown to have higher transmission intensities. By using the negative refraction behavior, we can design a sonic crystal plane lens to focus a sonic wave

  6. Deviations of Lambert-Beer???s law affect corneal refractive parameters after refractive surgery

    OpenAIRE

    Jim??nez Cuesta, Jos?? Ram??n; Rodr??guez-Mar??n, Francisco; Gonz??lez Anera, Rosario; Jim??nez del Barco Jaldo, Luis Miguel

    2006-01-01

    We calculate whether deviations of Lambert-Beer???s law, which regulates depth ablation during corneal ablation, significantly influence corneal refractive parameters after refractive surgery and whether they influence visual performance. For this, we compute a point-to-point correction on the cornea while assuming a non-linear (including a quadratic term) fit for depth ablation. Post-surgical equations for refractive parameters using a non-linear fit show significant differences with respect...

  7. Contribution of spontaneous polarization and its fluctuations to refraction of light in ferroelectrics

    Czech Academy of Sciences Publication Activity Database

    Markovin, P.A.; Trepakov, Vladimír; Tagantsev, A. K.; Dejneka, Alexandr; Andreev, D. A.

    2016-01-01

    Roč. 58, č. 1 (2016), 134-139 ISSN 1063-7834 R&D Projects: GA ČR GA15-13778S Institutional support: RVO:68378271 Keywords : contribution * spontaneous polarization * fluctuations * refraction * light * ferroelectrics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.860, year: 2016

  8. Acoustic metasurface for refracted wave manipulation

    Science.gov (United States)

    Han, Li-Xiang; Yao, Yuan-Wei; Zhang, Xin; Wu, Fu-Gen; Dong, Hua-Feng; Mu, Zhong-Fei; Li, Jing-bo

    2018-02-01

    Here we present a design of a transmitted acoustic metasurface based on a single row of Helmholtz resonators with varying geometric parameters. The proposed metasurface can not only steer an acoustic beam as expected from the generalized Snell's law of refraction, but also exhibits various interesting properties and potential applications such as insulation of two quasi-intersecting transmitted sound waves, ultrasonic Bessel beam generator, frequency broadening effect of anomalous refraction and focusing.

  9. High-Density Near-Field Readout over 50 GB Capacity Using Solid Immersion Lens with High Refractive Index

    Science.gov (United States)

    Shinoda, Masataka; Saito, Kimihiro; Kondo, Takao; Ishimoto, Tsutomu; Nakaoki, Ariyoshi

    2003-02-01

    We have investigated high-density near-field readout using a solid immersion lens with a high refractive index. By using a glass material with a high refractive index of 2.08, we developed an optical pick-up with the effective numerical aperture of 1.8. We could observe a clear eye pattern for a 50 GB capacity disc in 120 mm diameter. We confirmed that the near-field readout system is promising method of realizing a high-density optical disc system.

  10. Refractive index contrast in porous silicon multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Nava, R.; Mora, M.B. de la; Tagueena-Martinez, J. [Centro de Investigacion en Energia, Universidad Nacional Autonoma de Mexico, Temixco, Morelos (Mexico); Rio, J.A. del [Centro de Investigacion en Energia, Universidad Nacional Autonoma de Mexico, Temixco, Morelos (Mexico); Centro Morelense de Innovacion y Transferencia Tecnologica, Consejo de Ciencia y Tecnologia del Estado de Morelos (Mexico)

    2009-07-15

    Two of the most important properties of a porous silicon multilayer for photonic applications are flat interfaces and a relative large refractive index contrast between layers in the optical wavelength range. In this work, we studied the effect of the current density and HF electrolyte concentration on the refractive index of porous silicon. With the purpose of increasing the refractive index contrast in a multilayer, the refractive index of porous silicon produced at low current was studied in detail. The current density applied to produce the low porosity layers was limited in order to keep the electrolyte flow through the multilayer structure and to avoid deformation of layer interfaces. We found that an electrolyte composed of hydrofluoric acid, ethanol and glycerin in a ratio of 3:7:1 gives a refractive index contrast around 1.3/2.8 at 600 nm. Several multilayer structures with this refractive index contrast were fabricated, such as dielectric Bragg mirrors and microcavities. Reflectance spectra of the structures show the photonic quality of porous silicon multilayers produced under these electrochemical conditions. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. On the effective refractive index of blood

    Science.gov (United States)

    Nahmad-Rohen, Alexander; Contreras-Tello, Humberto; Morales-Luna, Gesuri; García-Valenzuela, Augusto

    2016-01-01

    We calculated the real and imaginary parts of the effective refractive index {n}{eff} of blood as functions of wavelength from 400 to 800 nm; we employed van de Hulst’s theory, together with the anomalous diffraction approximation, for the calculation. We modelled blood as a mixture of plasma and erythrocytes. Our results indicate that erythrocyte orientation has a strong effect on {n}{eff}, making blood an optically anisotropic medium except when the erythrocytes are randomly oriented. In the case in which their symmetry axis is perpendicular to the wave vector, {n}{eff} equals the refractive index of plasma at certain wavelengths. Furthermore, the erythrocytes’ shape affects their contribution to {n}{eff} in an important way, implying that studies on the effective refractive index of blood should avoid approximating them as spheres or spheroids. Finally, the effective refractive index of blood predicted by van de Hulst’s theory is different from what would be obtained by averaging the refractive indices of its constituents weighted by volume; such a volume-weighted average is appropriate only for haemolysed blood. We then measured the real part of the refractive index of various blood solutions using two different experimental setups. One of the most important results of our expriment is that {n}{eff} is measurable to a good degree of precision even for undiluted blood, although not all measuring apparatuses are appropriate. The experimental data is self-consistent and in reasonable agreement with our theoretical calculations.

  12. Reflective and refractive objects for mixed reality.

    Science.gov (United States)

    Knecht, Martin; Traxler, Christoph; Winklhofer, Christoph; Wimmer, Michael

    2013-04-01

    In this paper, we present a novel rendering method which integrates reflective or refractive objects into a differential instant radiosity (DIR) framework usable for mixed-reality (MR) applications. This kind of objects are very special from the light interaction point of view, as they reflect and refract incident rays. Therefore they may cause high-frequency lighting effects known as caustics. Using instant-radiosity (IR) methods to approximate these high-frequency lighting effects would require a large amount of virtual point lights (VPLs) and is therefore not desirable due to real-time constraints. Instead, our approach combines differential instant radiosity with three other methods. One method handles more accurate reflections compared to simple cubemaps by using impostors. Another method is able to calculate two refractions in real-time, and the third method uses small quads to create caustic effects. Our proposed method replaces parts in light paths that belong to reflective or refractive objects using these three methods and thus tightly integrates into DIR. In contrast to previous methods which introduce reflective or refractive objects into MR scenarios, our method produces caustics that also emit additional indirect light. The method runs at real-time frame rates, and the results show that reflective and refractive objects with caustics improve the overall impression for MR scenarios.

  13. Influence of the corneal optical zone on the point-spread function of the human eye

    Science.gov (United States)

    Rol, Pascal O.; Parel, Jean-Marie A.

    1992-08-01

    In refractive surgery, a number of surgical techniques have been developed to correct ametropia (refractive defaults) of the eye by changing the exterior shape of the cornea. Because the air-cornea interface makes up for about two thirds of the refractive power of the eye, a refractive correction can be obtained by a suitable reshaping of the cornea. Postoperatively, it is usually observed that the corneal region consists of two or more zones which are characterized by different optical parameters exhibiting in particular different focal distances. Under normal circumstances, only the central area of the cornea is involved in the formation of the retinal image. However, if part of the light entering the eye through peripheral portions of the cornea with refractive properties different from the central area can pass the pupil, an out-of-focus `ghost' image may be overlaid on the retina causing a blur. In such a case the resolution, and the contrast performance of the eye which is expected from a successful operation, may be reduced. This study is an attempt to quantify the vision blur as a function of the diameter of the central zone, i.e., the optical zone which is of importance for vision.

  14. The relationship between the retinal image quality and the refractive index of defects arising in IOL: numerical analysis

    Science.gov (United States)

    Geniusz, Malwina

    2017-09-01

    The best treatment for cataract patients, which allows to restore clear vision is implanting an artificial intraocular lens (IOL). The image quality of the lens has a significant impact on the quality of patient's vision. After a long exposure the implant to aqueous environment some defects appear in the artificial lenses. The defects generated in the IOL have different refractive indices. For example, glistening phenomenon is based on light scattering on the oval microvacuoles filled with an aqueous humor which refractive index value is about 1.34. Calcium deposits are another example of lens defects and they can be characterized by the refractive index 1.63. In the presented studies it was calculated how the difference between the refractive indices of the defect and the refractive index of the lens material affects the quality of image. The OpticStudio Professional program (from Radiant Zemax, LLC) was used for the construction of the numerical model of the eye with IOL and to calculate the characteristics of the retinal image. Retinal image quality was described in such characteristics as Point Spread Function (PSF) and the Optical Transfer Function with amplitude and phase. The results show a strong correlation between the refractive indices difference and retinal image quality.

  15. Prevalence of refractive error and visual impairment among rural school-age children of Goro District, Gurage Zone, Ethiopia.

    Science.gov (United States)

    Kedir, Jafer; Girma, Abonesh

    2014-10-01

    Refractive error is one of the major causes of blindness and visual impairment in children; but community based studies are scarce especially in rural parts of Ethiopia. So, this study aims to assess the prevalence of refractive error and its magnitude as a cause of visual impairment among school-age children of rural community. This community-based cross-sectional descriptive study was conducted from March 1 to April 30, 2009 in rural villages of Goro district of Gurage Zone, found south west of Addis Ababa, the capital of Ethiopia. A multistage cluster sampling method was used with simple random selection of representative villages in the district. Chi-Square and t-tests were used in the data analysis. A total of 570 school-age children (age 7-15) were evaluated, 54% boys and 46% girls. The prevalence of refractive error was 3.5% (myopia 2.6% and hyperopia 0.9%). Refractive error was the major cause of visual impairment accounting for 54% of all causes in the study group. No child was found wearing corrective spectacles during the study period. Refractive error was the commonest cause of visual impairment in children of the district, but no measures were taken to reduce the burden in the community. So, large scale community level screening for refractive error should be conducted and integrated with regular school eye screening programs. Effective strategies need to be devised to provide low cost corrective spectacles in the rural community.

  16. Heritability and familial aggregation of refractive error in the Old Order Amish.

    Science.gov (United States)

    Peet, Jon A; Cotch, Mary-Frances; Wojciechowski, Robert; Bailey-Wilson, Joan E; Stambolian, Dwight

    2007-09-01

    To determine the heritability of refractive error and familial aggregation of myopia and hyperopia in an elderly Old Order Amish (OOA) population. Nine hundred sixty-seven siblings (mean age, 64.2 years) in 269 families were recruited for the Amish Eye Study in the Lancaster County area of Pennsylvania. Refractive error was determined by noncycloplegic manifest refraction. Heritability of refractive error was estimated with multivariate linear regression as twice the residual sibling-sibling correlation after adjustment for age and gender. Logistic regression models were used to estimate the sibling recurrence odds ratio (OR(s)). Myopia and hyperopia were defined with five different thresholds. The age- and gender-adjusted heritability of refractive error was 70% (95% CI: 48%-92%) in the OOA. Age and gender-adjusted OR(s) and sibling recurrence risk (lambda(s)), with different thresholds defining myopia ranged from 3.03 (95% CI: 1.58-5.80) to 7.02 (95% CI: 3.41-14.46) and from 2.36 (95% CI: 1.65-3.19) to 5.61 (95% CI: 3.06-9.34). Age and gender-adjusted OR(s) and lambda(s) for different thresholds of hyperopia ranged from 2.31 (95% CI: 1.56-3.42) to 2.94 (95% CI: 2.04-4.22) and from 1.33 (95% CI: 1.22-1.43) to 1.85 (95% CI: 1.18-2.78), respectively. Women were significantly more likely than men to have hyperopia. There was no significant gender difference in the risk of myopia. In the OOA, refractive error is highly heritable. Hyperopia and myopia aggregate strongly in OOA families.

  17. PREVALENCE OF REFRACTIVE ERRORS AMONG CHILDREN IN RURA L AREAS OF CHITTOOR DISTRICT, A . P

    Directory of Open Access Journals (Sweden)

    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.

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

    Directory of Open Access Journals (Sweden)

    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.

  19. Refractive error and visual impairment in private school children in Ghana.

    Science.gov (United States)

    Kumah, Ben D; Ebri, Anne; Abdul-Kabir, Mohammed; Ahmed, Abdul-Sadik; Koomson, Nana Ya; Aikins, Samual; Aikins, Amos; Amedo, Angela; Lartey, Seth; Naidoo, Kovin

    2013-12-01

    To assess the prevalence of refractive error and visual impairment in private school children in Ghana. A random selection of geographically defined classes in clusters was used to identify a sample of school children aged 12 to 15 years in the Ashanti Region. Children in 60 clusters were enumerated and examined in classrooms. The examination included visual acuity, retinoscopy, autorefraction under cycloplegia, and examination of anterior segment, media, and fundus. For quality assurance, a random sample of children with reduced and normal vision were selected and re-examined independently. A total of 2454 children attending 53 private schools were enumerated, and of these, 2435 (99.2%) were examined. Prevalence of uncorrected, presenting, and best visual acuity of 20/40 or worse in the better eye was 3.7, 3.5, and 0.4%, respectively. Refractive error was the cause of reduced vision in 71.7% of 152 eyes, amblyopia in 9.9%, retinal disorders in 5.9%, and corneal opacity in 4.6%. Exterior and anterior segment abnormalities occurred in 43 (1.8%) children. Myopia (at least -0.50 D) in one or both eyes was present in 3.2% of children when measured with retinoscopy and in 3.4% measured with autorefraction. Myopia was not significantly associated with gender (P = 0.82). Hyperopia (+2.00 D or more) in at least one eye was present in 0.3% of children with retinoscopy and autorefraction. The prevalence of reduced vision in Ghanaian private school children due to uncorrected refractive error was low. However, the prevalence of amblyopia, retinal disorders, and corneal opacities indicate the need for early interventions.

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

    Directory of Open Access Journals (Sweden)

    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

  1. Comparison between refraction measured by Spot Vision Screening™ and subjective clinical refractometry.

    Science.gov (United States)

    de Jesus, Daniela Lima; Villela, Flávio Fernandes; Orlandin, Luis Fernando; Eiji, Fernando Naves; Dantas, Daniel Oliveira; Alves, Milton Ruiz

    2016-02-01

    The purpose of this study was to evaluate the accuracy of Spot Vision Screening™ as an autorefractor by comparing refraction measurements to subjective clinical refractometry results in children and adult patients. One-hundred and thirty-four eyes of 134 patients were submitted to refractometry by Spot and clinical refractometry under cycloplegia. Patients, students, physicians, staff and children of staff from the Hospital das Clínicas (School of Medicine, University of São Paulo) aged 7-50 years without signs of ocular disease were examined. Only right-eye refraction data were analyzed. The findings were converted in magnitude vectors for analysis. The difference between Spot Vision Screening™ and subjective clinical refractometry expressed in spherical equivalents was +0.66±0.56 diopters (D), +0.16±0.27 D for the vector projected on the 90 axis and +0.02±0.15 D for the oblique vector. Despite the statistical significance of the difference between the two methods, we consider the difference non-relevant in a clinical setting, supporting the use of Spot Vision Screening™ as an ancillary method for estimating refraction.

  2. Comparison between refraction measured by Spot Vision ScreeningTM and subjective clinical refractometry

    Directory of Open Access Journals (Sweden)

    Daniela Lima de Jesus

    2016-02-01

    Full Text Available OBJECTIVE: The purpose of this study was to evaluate the accuracy of Spot Vision ScreeningTM as an autorefractor by comparing refraction measurements to subjective clinical refractometry results in children and adult patients. METHODS: One-hundred and thirty-four eyes of 134 patients were submitted to refractometry by Spot and clinical refractometry under cycloplegia. Patients, students, physicians, staff and children of staff from the Hospital das Clínicas (School of Medicine, University of São Paulo aged 7-50 years without signs of ocular disease were examined. Only right-eye refraction data were analyzed. The findings were converted in magnitude vectors for analysis. RESULTS: The difference between Spot Vision ScreeningTM and subjective clinical refractometry expressed in spherical equivalents was +0.66±0.56 diopters (D, +0.16±0.27 D for the vector projected on the 90 axis and +0.02±0.15 D for the oblique vector. CONCLUSIONS: Despite the statistical significance of the difference between the two methods, we consider the difference non-relevant in a clinical setting, supporting the use of Spot Vision ScreeningTM as an ancillary method for estimating refraction.

  3. Comparison between refraction measured by Spot Vision ScreeningTM and subjective clinical refractometry

    Science.gov (United States)

    de Jesus, Daniela Lima; Villela, Flávio Fernandes; Orlandin, Luis Fernando; Eiji, Fernando Naves; Dantas, Daniel Oliveira; Alves, Milton Ruiz

    2016-01-01

    OBJECTIVE: The purpose of this study was to evaluate the accuracy of Spot Vision ScreeningTM as an autorefractor by comparing refraction measurements to subjective clinical refractometry results in children and adult patients. METHODS: One-hundred and thirty-four eyes of 134 patients were submitted to refractometry by Spot and clinical refractometry under cycloplegia. Patients, students, physicians, staff and children of staff from the Hospital das Clínicas (School of Medicine, University of São Paulo) aged 7-50 years without signs of ocular disease were examined. Only right-eye refraction data were analyzed. The findings were converted in magnitude vectors for analysis. RESULTS: The difference between Spot Vision ScreeningTM and subjective clinical refractometry expressed in spherical equivalents was +0.66±0.56 diopters (D), +0.16±0.27 D for the vector projected on the 90 axis and +0.02±0.15 D for the oblique vector. CONCLUSIONS: Despite the statistical significance of the difference between the two methods, we consider the difference non-relevant in a clinical setting, supporting the use of Spot Vision ScreeningTM as an ancillary method for estimating refraction. PMID:26934234

  4. Reading ability with pseudophakic monovision and with refractive multifocal intraocular lenses: comparative study.

    Science.gov (United States)

    Ito, Misae; Shimizu, Kimiya

    2009-09-01

    To the compare the reading ability after bilateral cataract surgery in patients who had pseudophakic monovision achieved by monofocal intraocular lens (IOL) implantation and patients who had refractive multifocal IOL implantation. Department of Ophthalmology, Kitasato University Hospital, Kanagawa, Japan. This study evaluated patients who had bilateral cataract surgery using the monovision method with monofocal IOL implantation to correct presbyopia (monovision group) or who had bilateral cataract surgery with refractive multifocal IOL implantation (multifocal group). In the monovision group, the dominant eye was corrected for distance vision and the nondominant eye for near vision. The maximum reading speed, critical character size, and reading acuity were measured binocularly without refractive correction using MNREAD-J acuity charts. The monovision group comprised 38 patients and the multifocal group, 22 patients. The mean maximum reading speed was 350.5 characters per minute (cpm) +/- 62.3 (SD) in the monovision group and 355.0 +/- 53.3 cpm in the multifocal group; the difference was not statistically significant. The mean critical character size was 0.24 +/- 0.12 logMAR and 0.40 +/- 0.16 logMAR, respectively (P<.05). The mean reading acuity was 0.05 +/- 0.12 logMAR and 0.19 +/- 0.11 logMAR, respectively (P<.01). The monovision group had better critical character size and reading acuity results. The monovision method group had better reading ability; however, careful patient selection is essential.

  5. Physics of negative refractive index materials

    International Nuclear Information System (INIS)

    Ramakrishna, S Anantha

    2005-01-01

    In the past few years, new developments in structured electromagnetic materials have given rise to negative refractive index materials which have both negative dielectric permittivity and negative magnetic permeability in some frequency ranges. The idea of a negative refractive index opens up new conceptual frontiers in photonics. One much-debated example is the concept of a perfect lens that enables imaging with sub-wavelength image resolution. Here we review the fundamental concepts and ideas of negative refractive index materials. First we present the ideas of structured materials or meta-materials that enable the design of new materials with a negative dielectric permittivity, negative magnetic permeability and negative refractive index. We discuss how a variety of resonance phenomena can be utilized to obtain these materials in various frequency ranges over the electromagnetic spectrum. The choice of the wave-vector in negative refractive index materials and the issues of dispersion, causality and energy transport are analysed. Various issues of wave propagation including nonlinear effects and surface modes in negative refractive materials (NRMs) are discussed. In the latter part of the review, we discuss the concept of a perfect lens consisting of a slab of a NRM. This perfect lens can image the far-field radiative components as well as the near-field evanescent components, and is not subject to the traditional diffraction limit. Different aspects of this lens such as the surface modes acting as the mechanism for the imaging of the evanescent waves, the limitations imposed by dissipation and dispersion in the negative refractive media, the generalization of this lens to optically complementary media and the possibility of magnification of the near-field images are discussed. Recent experimental developments verifying these ideas are briefly covered

  6. Impact of First Eye versus Second Eye Cataract Surgery on Visual Function and Quality of Life.

    Science.gov (United States)

    Shekhawat, Nakul S; Stock, Michael V; Baze, Elizabeth F; Daly, Mary K; Vollman, David E; Lawrence, Mary G; Chomsky, Amy S

    2017-10-01

    To compare the impact of first eye versus second eye cataract surgery on visual function and quality of life. Cohort study. A total of 328 patients undergoing separate first eye and second eye phacoemulsification cataract surgeries at 5 veterans affairs centers in the United States. Patients with previous ocular surgery, postoperative endophthalmitis, postoperative retinal detachment, reoperation within 30 days, dementia, anxiety disorder, hearing difficulty, or history of drug abuse were excluded. Patients received complete preoperative and postoperative ophthalmic examinations for first eye and second eye cataract surgeries. Best-corrected visual acuity (BCVA) was measured 30 to 90 days preoperatively and postoperatively. Patients completed the National Eye Institute Visual Functioning Questionnaire (NEI-VFQ) 30 to 90 days preoperatively and postoperatively. The NEI-VFQ scores were calculated using a traditional subscale scoring algorithm and a Rasch-refined approach producing visual function and socioemotional subscale scores. Postoperative NEI-VFQ scores and improvement in NEI-VFQ scores comparing first eye versus second eye cataract surgery. Mean age was 70.4 years (±9.6 standard deviation [SD]). Compared with second eyes, first eyes had worse mean preoperative BCVA (0.55 vs. 0.36 logarithm of the minimum angle of resolution (logMAR), P < 0.001), greater mean BCVA improvement after surgery (-0.50 vs. -0.32 logMAR, P < 0.001), and slightly worse postoperative BCVA (0.06 vs. 0.03 logMAR, P = 0.039). Compared with first eye surgery, second eye surgery resulted in higher postoperative NEI-VFQ scores for nearly all traditional subscales (P < 0.001), visual function subscale (-3.85 vs. -2.91 logits, P < 0.001), and socioemotional subscale (-2.63 vs. -2.10 logits, P < 0.001). First eye surgery improved visual function scores more than second eye surgery (-2.99 vs. -2.67 logits, P = 0.021), but both first and second eye surgeries resulted in similar

  7. Correction of refractive errors in rhesus macaques (Macaca mulatta) involved in visual research.

    Science.gov (United States)

    Mitchell, Jude F; Boisvert, Chantal J; Reuter, Jon D; Reynolds, John H; Leblanc, Mathias

    2014-08-01

    Macaques are the most common animal model for studies in vision research, and due to their high value as research subjects, often continue to participate in studies well into old age. As is true in humans, visual acuity in macaques is susceptible to refractive errors. Here we report a case study in which an aged macaque demonstrated clear impairment in visual acuity according to performance on a demanding behavioral task. Refraction demonstrated bilateral myopia that significantly affected behavioral and visual tasks. Using corrective lenses, we were able to restore visual acuity. After correction of myopia, the macaque's performance on behavioral tasks was comparable to that of a healthy control. We screened 20 other male macaques to assess the incidence of refractive errors and ocular pathologies in a larger population. Hyperopia was the most frequent ametropia but was mild in all cases. A second macaque had mild myopia and astigmatism in one eye. There were no other pathologies observed on ocular examination. We developed a simple behavioral task that visual research laboratories could use to test visual acuity in macaques. The test was reliable and easily learned by the animals in 1 d. This case study stresses the importance of screening macaques involved in visual science for refractive errors and ocular pathologies to ensure the quality of research; we also provide simple methodology for screening visual acuity in these animals.

  8. Comparison of the ratio of keratometric change to refractive change induced by myopic ablation.

    Science.gov (United States)

    Moshirfar, Majid; Christiansen, Steven M; Kim, Gene

    2012-10-01

    To compare the ratio of keratometric change (ΔK) to refractive change (ΔSE) induced by refractive laser ablation. The charts of 3337 eyes that underwent LASIK or photorefractive keratectomy (PRK) from 2002 to 2011 were retrospectively reviewed, and the ratio ΔK/ΔSE measured at 3 months postoperatively was compared between eyes with low ΔSE (0.00 to 2.99 diopters [D]), moderate ΔSE (3.00 to 5.99 D), and high ΔSE (6.00 to 8.99 D). Eyes were further stratified by LASIK vs PRK; custom vs conventional treatments; microkeratome vs IntraLase (Abbott Medical Optics Inc) femtosecond laser-created flaps; and flat (38.00 to 41.99 D) vs moderate (42.00 to 45.99 D) vs steep (46.00 to 49.99 D) preoperative keratometry, and the ratio ΔK/ΔSE was similarly compared. Significant differences were found in the ratio ΔK/ΔSE among eyes with low ΔSE (1.00±0.50 D), moderate ΔSE (0.83±0.19 D), and steep ΔSE (0.80±0.15 D) (PLASIK vs PRK, custom vs conventional treatments, and microkeratome vs IntraLase flaps. Significant differences in the ratio ΔK/ΔSE were also found in eyes with low, moderate, and high ΔSE regardless of preoperative keratometry. The ratio ΔK/ΔSE compared with ΔSE follows a nonlinear pattern and tended to be higher and more variable at lower amounts of correction. The change in simulated keratometry required to achieve 1.00 D of myopic refractive correction decreased as the amount of refractive change increased, was more variable with lower amounts of correction, and followed a nonlinear relationship. Many variables, such as LASIK vs PRK, custom vs conventional, and microkeratome vs IntraLase flaps, affected the ratio of ΔK/ΔSE for moderate and high myopic corrections. Copyright 2012, SLACK Incorporated.

  9. Retinal images in the human eye with implanted intraocular lens

    Science.gov (United States)

    Zając, Marek; Siedlecki, Damian; Nowak, Jerzy

    2007-04-01

    A typical proceeding in cataract is based on the removal of opaque crystalline lens and inserting in its place the artificial intraocular lens (IOL). The quality of retinal image after such procedure depends, among others, on the parameters of the IOL, so the design of the implanted lens is of great importance. An appropriate choice of the IOL material, especially in relation to its biocompatibility, is often considered. However the parameter, which is often omitted during the IOL design is its chromatic aberration. In particular lack of its adequacy to the chromatic aberration of a crystalline lens may cause problems. In order to fit better chromatic aberration of the eye with implanted IOL to that of the healthy eye we propose a hybrid - refractive-diffractive IOL. It can be designed in such way that the total longitudinal chromatic aberration of an eye with implanted IOL equals the total longitudinal chromatic aberration of a healthy eye. In this study we compare the retinal image quality calculated numerically on the basis of the well known Liou-Brennan eye model with typical IOL implanted with that obtained if the IOL is done as hybrid (refractive-diffractive) design.

  10. Cryogenic refractive index of Heraeus homosil glass

    Science.gov (United States)

    Miller, Kevin H.; Quijada, Manuel A.; Leviton, Douglas B.

    2017-08-01

    This paper reports measurements of the refractive index of Homosil (Heraeus) over the wavelength range of 0.34—3.16 μm and temperature range of 120—335 K. These measurements were performed by using the Cryogenic High Accuracy Refraction Measuring System (CHARMS) facility at the NASA's Goddard Space Flight Center. These measurements were in support of an integrated Structural-Thermal-Optical-Performance (STOP) model that was developed for a fieldwidened Michelson interferometer that is being built and tested for the High Spectral Resolution Lidar (HSRL) project at the NASA Langley Research Center (LaRC). The cryogenic refractive index measurements were required in order to account for the highly sensitive performance of the HSRL instrument to changes in refractive index with temperature, temperature gradients, thermal expansion, and deformation due to mounting stresses. A dense coverage of the absolute refractive index over the aforementioned wavelength and temperature ranges was used to determine the thermo-optic coefficient (dn/dT) and dispersion relation (dn/dλ) as a function of wavelength and temperature. Our measurements of Homosil will be compared with measurements of other glasses from the fused silica family studied in CHARMS as well as measurements reported elsewhere in the literature.

  11. Corneal thickness in dry eyes in an Iraqi population

    OpenAIRE

    Ali,Noora Mauwafak; Hamied,Furkaan M; Farhood,Qasim K

    2017-01-01

    Noora Mauwafak Ali,1 Furkaan M Hamied,1 Qasim K Farhood2 1Department of Surgery, College of Medicine, Al-Qadisiya University, Diwaniyah, 2Department of Surgery, College of Medicine, University of Babylon, Hillah, Iraq Background: Dry eye disorder is a multifactorial disease of the tears and ocular surface that results in discomfort and visual disturbance. Corneal pachymetry becomes increasingly important in refractive surgery, for the accurate assessment of intraocular pressure, and in the ...

  12. Public Awareness regarding Common Eye Diseases among Saudi Adults in Riyadh City: A Quantitative Study

    Directory of Open Access Journals (Sweden)

    Waleed A. Al Rashed

    2017-01-01

    Full Text Available Aim. The current study aimed to evaluate the knowledge of eye disease and awareness of eye care among the Saudi adults and to explore existing eye-related misconceptions in the community. Methods. A cross-sectional study was conducted in Riyadh city during May and June 2016. A self-administered anonymous online questionnaire was used to explore the most common misconceptions related to eye diseases and eye care. Results. Out of 1000 individuals, only 711 (71.1% participant responses were received. The participants’ acceptable knowledge (score ≥50% was high about the eye problem in diabetes (88.6%, ocular trauma (81.2%, and other general eye diseases (91.3%, whereas low about refractive errors (63%, pediatric eye problems (51.5%, and glaucoma (14.8%. The variation in knowledge about specific ocular morbidities was significant (p<0.001. The majority of participants reported sources of information about the common eye diseases and eye care encountered from the community, internet-based resources, and social media. Conclusions. The majority of the participants had awareness about the common eye diseases, whereas low percentage of participant’s awareness about specific condition of eye diseases. Public eye health awareness should be more focused on social media and the internet to be able to cover the younger individuals of the community.

  13. Nature versus nurture: A systematic approach to elucidate gene-environment interactions in the development of myopic refractive errors.

    Science.gov (United States)

    Miraldi Utz, Virginia

    2017-01-01

    Myopia is the most common eye disorder and major cause of visual impairment worldwide. As the incidence of myopia continues to rise, the need to further understand the complex roles of molecular and environmental factors controlling variation in refractive error is of increasing importance. Tkatchenko and colleagues applied a systematic approach using a combination of gene set enrichment analysis, genome-wide association studies, and functional analysis of a murine model to identify a myopia susceptibility gene, APLP2. Differential expression of refractive error was associated with time spent reading for those with low frequency variants in this gene. This provides support for the longstanding hypothesis of gene-environment interactions in refractive error development.

  14. Eye structure and amphibious foraging in albatrosses

    Science.gov (United States)

    Martin, G. R.

    1998-01-01

    Anterior eye structure and retinal visual fields were determined in grey-headed and black-browed albatrosses, Diomedea melanophris and D. chrysostoma (Procellariiformes, Diomedeidae), using keratometry and an ophthalmoscopic reflex technique. Results for the two species were very similar and indicate that the eyes are of an amphibious optical design suggesting that albatross vision is well suited to the visual pursuit of active prey both on and below the ocean surface. The corneas are relatively flat (radius ca. 14.5 mm) and hence of low absolute refractive power (ca. 23 dioptres). In air the binocular fields are relatively long (vertical extent ca. 70 degrees) and narrow (maximum width in the plane of the optic axes 26–32 degrees), a topography found in a range of bird species that employ visual guidance of bill position when foraging. The cyclopean fields measure approximately 270 degrees in the horizontal plane, but there is a 60 degrees blind sector above the head owing to the positioning of the eyes below the protruding supraorbital ridges. Upon immersion the monocular fields decrease in width such that the binocular fields are abolished. Anterior eye structure, and visual field topography in both air and water, show marked similarity with those of the Humboldt penguin.

  15. Eye aberration analysis with Zernike polynomials

    Science.gov (United States)

    Molebny, Vasyl V.; Chyzh, Igor H.; Sokurenko, Vyacheslav M.; Pallikaris, Ioannis G.; Naoumidis, Leonidas P.

    1998-06-01

    New horizons for accurate photorefractive sight correction, afforded by novel flying spot technologies, require adequate measurements of photorefractive properties of an eye. Proposed techniques of eye refraction mapping present results of measurements for finite number of points of eye aperture, requiring to approximate these data by 3D surface. A technique of wave front approximation with Zernike polynomials is described, using optimization of the number of polynomial coefficients. Criterion of optimization is the nearest proximity of the resulted continuous surface to the values calculated for given discrete points. Methodology includes statistical evaluation of minimal root mean square deviation (RMSD) of transverse aberrations, in particular, varying consecutively the values of maximal coefficient indices of Zernike polynomials, recalculating the coefficients, and computing the value of RMSD. Optimization is finished at minimal value of RMSD. Formulas are given for computing ametropia, size of the spot of light on retina, caused by spherical aberration, coma, and astigmatism. Results are illustrated by experimental data, that could be of interest for other applications, where detailed evaluation of eye parameters is needed.

  16. Negative refraction angular characterization in one-dimensional photonic crystals.

    Directory of Open Access Journals (Sweden)

    Jesus Eduardo Lugo

    2011-04-01

    Full Text Available Photonic crystals are artificial structures that have periodic dielectric components with different refractive indices. Under certain conditions, they abnormally refract the light, a phenomenon called negative refraction. Here we experimentally characterize negative refraction in a one dimensional photonic crystal structure; near the low frequency edge of the fourth photonic bandgap. We compare the experimental results with current theory and a theory based on the group velocity developed here. We also analytically derived the negative refraction correctness condition that gives the angular region where negative refraction occurs.By using standard photonic techniques we experimentally determined the relationship between incidence and negative refraction angles and found the negative refraction range by applying the correctness condition. In order to compare both theories with experimental results an output refraction correction was utilized. The correction uses Snell's law and an effective refractive index based on two effective dielectric constants. We found good agreement between experiment and both theories in the negative refraction zone.Since both theories and the experimental observations agreed well in the negative refraction region, we can use both negative refraction theories plus the output correction to predict negative refraction angles. This can be very useful from a practical point of view for space filtering applications such as a photonic demultiplexer or for sensing applications.

  17. Negative refraction angular characterization in one-dimensional photonic crystals.

    Science.gov (United States)

    Lugo, Jesus Eduardo; Doti, Rafael; Faubert, Jocelyn

    2011-04-06

    Photonic crystals are artificial structures that have periodic dielectric components with different refractive indices. Under certain conditions, they abnormally refract the light, a phenomenon called negative refraction. Here we experimentally characterize negative refraction in a one dimensional photonic crystal structure; near the low frequency edge of the fourth photonic bandgap. We compare the experimental results with current theory and a theory based on the group velocity developed here. We also analytically derived the negative refraction correctness condition that gives the angular region where negative refraction occurs. By using standard photonic techniques we experimentally determined the relationship between incidence and negative refraction angles and found the negative refraction range by applying the correctness condition. In order to compare both theories with experimental results an output refraction correction was utilized. The correction uses Snell's law and an effective refractive index based on two effective dielectric constants. We found good agreement between experiment and both theories in the negative refraction zone. Since both theories and the experimental observations agreed well in the negative refraction region, we can use both negative refraction theories plus the output correction to predict negative refraction angles. This can be very useful from a practical point of view for space filtering applications such as a photonic demultiplexer or for sensing applications.

  18. Refractive errors in students from Middle Eastern backgrounds living and undertaking schooling in Australia.

    Science.gov (United States)

    Azizoglu, Serap; Junghans, Barbara M; Barutchu, Ayla; Crewther, Sheila G

    2011-01-01

      Environmental factors associated with schooling systems in various countries have been implicated in the rising prevalence of myopia, making the comparison of prevalence of refractive errors in migrant populations of interest. This study aims to determine the prevalence of refractive errors in children of Middle Eastern descent, raised and living in urban Australia but actively maintaining strong ties to their ethnic culture, and to compare them with those in the Middle East where myopia prevalence is generally low.   A total of 354 out of a possible 384 late primary/early secondary schoolchildren attending a private school attracting children of Middle Eastern background in Melbourne were assessed for refractive error and visual acuity. A Shin Nippon open-field NVision-K5001 autorefractor was used to carry out non-cycloplegic autorefraction while viewing a distant target. For statistical analyses students were divided into three age groups: 10-11 years (n = 93); 12-13 years (n = 158); and 14-15 years (n = 102).   All children were bilingual and classified as of Middle Eastern (96.3 per cent) or Egyptian (3.7 per cent) origin. Ages ranged from 10 to 15 years, with a mean of 13.17 ± 0.8 (SEM) years. Mean spherical equivalent refraction (SER) for the right eye was +0.09 ± 0.07 D (SEM) with a range from -7.77 D to +5.85 D. The prevalence of myopia, defined as a spherical equivalent refraction 0.50 D or more of myopia, was 14.7 per cent. The prevalence of hyperopia, defined as a spherical equivalent refraction of +0.75 D or greater, was 16.4 per cent, while hyperopia of +1.50 D or greater was 5.4 per cent. A significant difference in SER was seen as a function of age; however, no significant gender difference was seen.   This is the first study to report the prevalence of refractive errors for second-generation Australian schoolchildren coming from a predominantly Lebanese Middle Eastern Arabic background, who endeavour to maintain their ethnic ties. The

  19. Retinal vessel caliber and myopic retinopathy: the blue mountains eye study.

    Science.gov (United States)

    Li, Haitao; Mitchell, Paul; Rochtchina, Elena; Burlutsky, George; Wong, Tien Y; Wang, Jie Jin

    2011-12-01

    To evaluate changes in the retinal vasculature in eyes with myopic retinopathy. Population-based, cross-sectional study. Emmetropic and myopic participants from the Blue Mountains Eye Study baseline survey were included in this study. Myopia was defined as a refractive error of less than -1.00 diopter. Myopic retinopathy was defined if either staphyloma, lacquer crack, Fuchs' spot or chorioretinal atrophy were present in myopic eyes. Retinal vascular caliber was measured from fundus photographs using standardized methods. The association of retinal vascular caliber with myopic retinopathy was assessed using generalized estimating equation models. A total of 2598 eyes of 1409 subjects were selected from 3654 baseline participants, with 2076 emmetropic eyes (normal controls), 486 myopic eyes without myopic retinopathy (myopic controls) and 36 myopic eyes with myopic retinopathy (cases). After adjusting for age, gender, height, body mass index and blood pressure, eyes with myopic retinopathy had significantly narrower mean arteriolar (166.6μm) and venular caliber (213.3μm), compared to normal (188.1μm and 226.9μm, respectively) or myopic control eyes (190.4μm and 227.0μm, respectively) (all P retinopathy and the two control groups remained significant after additional adjustment for refraction (all P retinopathy is associated with attenuation of retinal vessels.

  20. Eyes Wide Open

    Directory of Open Access Journals (Sweden)

    Zoi Manesi

    2016-04-01

    Full Text Available Research from evolutionary psychology suggests that the mere presence of eye images can promote prosocial behavior. However, the “eye images effect” is a source of considerable debate, and findings across studies have yielded somewhat inconsistent support. We suggest that one critical factor may be whether the eyes really need to be watching to effectively enhance prosocial behavior. In three experiments, we investigated the impact of eye images on prosocial behavior, assessed in a laboratory setting. Participants were randomly assigned to view an image of watching eyes (eyes with direct gaze, an image of nonwatching eyes (i.e., eyes closed for Study 1 and averted eyes for Studies 2 and 3, or an image of flowers (control condition. Upon exposure to the stimuli, participants decided whether or not to help another participant by completing a dull cognitive task. Three independent studies produced somewhat mixed results. However, combined analysis of all three studies, with a total of 612 participants, showed that the watching component of the eyes is important for decision-making in this context. Images of watching eyes led to significantly greater inclination to offer help as compared to images of nonwatching eyes (i.e., eyes closed and averted eyes or images of flowers. These findings suggest that eyes gazing at an individual, rather than any proxy to social presence (e.g., just the eyes, serve as a reminder of reputation. Taken together, we conclude that it is “eyes that pay attention” that can lift the veil of anonymity and potentially facilitate prosocial behavior.

  1. Dry eyes : a commonly missed eye condition

    OpenAIRE

    Vella, Mario;

    2014-01-01

    Tears are an important component in providing moisture and lubrication for the eyes, thereby maintaining vision and comfort. Dry eyes (keratoconjunctivitis sicca) result when there is either decreased production of tears or by poor tear quality which in turn lead to more rapid evaporation.

  2. Visual impairment attributable to uncorrected refractive error and other causes in the Ghanaian youth: The University of Cape Coast Survey.

    Science.gov (United States)

    Abokyi, Samuel; Ilechie, Alex; Nsiah, Peter; Darko-Takyi, Charles; Abu, Emmanuel Kwasi; Osei-Akoto, Yaw Jnr; Youfegan-Baanam, Mathurin

    2016-01-01

    To determine the prevalence of visual impairment attributable to refractive error and other causes in a youthful Ghanaian population. A prospective survey of all consecutive visits by first-year tertiary students to the Optometry clinic between August, 2013 and April, 2014. Of the 4378 first-year students aged 16-39 years enumerated, 3437 (78.5%) underwent the eye examination. The examination protocol included presenting visual acuity (PVA), ocular motility, and slit-lamp examination of the external eye, anterior segment and media, and non-dilated fundus examination. Pinhole acuity and fundus examination were performed when the PVA≤6/12 in one or both eyes to determine the principal cause of the vision loss. The mean age of participants was 21.86 years (95% CI: 21.72-21.99). The prevalence of bilateral visual impairment (BVI; PVA in the better eye ≤6/12) and unilateral visual impairment UVI; PVA in the worse eye ≤6/12) were 3.08% (95% CI: 2.56-3.72) and 0.79% (95% CI: 0.54-1.14), respectively. Among 106 participants with BVI, refractive error (96.2%) and corneal opacity (3.8%) were the causes. Of the 27 participants with UVI, refractive error (44.4%), maculopathy (18.5%) and retinal disease (14.8%) were the major causes. There was unequal distribution of BVI in the different age groups, with those above 20 years having a lesser burden. Eye screening and provision of affordable spectacle correction to the youth could be timely to eliminate visual impairment. Copyright © 2014 Spanish General Council of Optometry. Published by Elsevier Espana. All rights reserved.

  3. Coping with dry eyes: a qualitative approach.

    Science.gov (United States)

    Yeo, Sharon; Tong, Louis

    2018-01-16

    Dry eye is a common problem that affects many people worldwide, reducing quality of life and impacting daily activities. A qualitative approach often used in medicine and other disciplines is used to evaluate how people with dry eye cope with this impact. Six focus group sessions were conducted at the Singapore National Eye Centre (SNEC), premises of an eye research institute. These focus groups consist of a spectrum of dry eye sufferers (30 women, 8 men, aged 61 ± 11.8 years). Standard methods of coding followed by determination of themes were adhered to. Where classification was difficult, consensus was made between 3 assessors. Audio-recorded transcripts were coded in 10 themes by 3 assessors independently. Four of the themes involved traditional measures such as lid warming, cleansing, lubrication and oral dietary supplements. The other themes discovered were Traditional Chinese Medicine, modification of eye-care habits (e.g. wearing sunglasses), environmental humidity, lifestyle (e.g. sleeping habits), psychological attitude, and lastly sharing and communication. Holistic coping strategies were found to be prominent in dry eye sufferers from these focus groups, and people tend to find personalised ways of coping with the impact of dry eye on daily living.

  4. What Is Dry Eye?

    Medline Plus

    Full Text Available Subspecialties Cataract/Anterior Segment Comprehensive Ophthalmology Cornea/External Disease Glaucoma Neuro-Ophthalmology/Orbit Pediatric Ophthalmology/Strabismus Ocular Pathology/Oncology Oculoplastics/Orbit Refractive Management/Intervention Retina/ ...

  5. Childhood Eye Diseases in Bayelsa State, Nigeria: A Tertiary Eye ...

    African Journals Online (AJOL)

    -Streit) and a posterior segement examination using a direct and indirect ophthalmoscopes (KeelerR) as necessary. Those requiring refraction was sent to the optometrist. Objective refraction was done using a Carl Zeiss 599 autorefractometer ...

  6. Retrospective Analysis of the Post-Operative Changes in Higher-Order Aberrations: A Comparison of the WaveLight EX500 to the VISX S4 Laser in Refractive Surgery.

    Science.gov (United States)

    Reed, Donovan S; Apsey, Douglas; Steigleman, Walter; Townley, James; Caldwell, Matthew

    2017-11-01

    In an attempt to maximize treatment outcomes, refractive surgery techniques are being directed toward customized ablations to correct not only lower-order aberrations but also higher-order aberrations specific to the individual eye. Measurement of the entirety of ocular aberrations is the most definitive means to establish the true effect of refractive surgery on image quality and visual performance. Whether or not there is a statistically significant difference in induced higher-order corneal aberrations between the VISX Star S4 (Abbott Medical Optics, Santa Ana, California) and the WaveLight EX500 (Alcon, Fort Worth, Texas) lasers was examined. A retrospective analysis was performed to investigate the difference in root-mean-square (RMS) value of the higher-order corneal aberrations postoperatively between two currently available laser platforms, the VISX Star S4 and the WaveLight EX500 lasers. The RMS is a compilation of higher-order corneal aberrations. Data from 240 total eyes of active duty military or Department of Defense beneficiaries who completed photorefractive keratectomy (PRK) or laser in situ keratomileusis (LASIK) refractive surgery at the Wilford Hall Ambulatory Surgical Center Joint Warfighter Refractive Surgery Center were examined. Using SPSS statistics software (IBM Corp., Armonk, New York), the mean changes in RMS values between the two lasers and refractive surgery procedures were determined. A Student t test was performed to compare the RMS of the higher-order aberrations of the subjects' corneas from the lasers being studied. A regression analysis was performed to adjust for preoperative spherical equivalent. The study and a waiver of informed consent have been approved by the Clinical Research Division of the 59th Medical Wing Institutional Review Board (Protocol Number: 20150093H). The mean change in RMS value for PRK using the VISX laser was 0.00122, with a standard deviation of 0.02583. The mean change in RMS value for PRK using the

  7. Wave-vector and polarization dependence of conical refraction.

    Science.gov (United States)

    Turpin, A; Loiko, Yu V; Kalkandjiev, T K; Tomizawa, H; Mompart, J

    2013-02-25

    We experimentally address the wave-vector and polarization dependence of the internal conical refraction phenomenon by demonstrating that an input light beam of elliptical transverse profile refracts into two beams after passing along one of the optic axes of a biaxial crystal, i.e. it exhibits double refraction instead of refracting conically. Such double refraction is investigated by the independent rotation of a linear polarizer and a cylindrical lens. Expressions to describe the position and the intensity pattern of the refracted beams are presented and applied to predict the intensity pattern for an axicon beam propagating along the optic axis of a biaxial crystal.

  8. Negative refraction using Raman transitions and chirality

    Energy Technology Data Exchange (ETDEWEB)

    Sikes, D. E.; Yavuz, D. D. [Department of Physics, 1150 University Avenue, University of Wisconsin at Madison, Madison, Wisconsin 53706 (United States)

    2011-11-15

    We present a scheme that achieves negative refraction with low absorption in far-off resonant atomic systems. The scheme utilizes Raman resonances and does not require the simultaneous presence of an electric-dipole transition and a magnetic-dipole transition near the same wavelength. We show that two interfering Raman tran-sitions coupled to a magnetic-dipole transition can achieve a negative index of refraction with low absorption through magnetoelectric cross-coupling. We confirm the validity of the analytical results with exact numerical simulations of the density matrix. We also discuss possible experimental implementations of the scheme in rare-earth metal atomic systems.

  9. Plasma rich in growth factors eye drops to treat secondary ocular surface disorders in patients with glaucoma

    Directory of Open Access Journals (Sweden)

    Sánchez-Avila RM

    2018-05-01

    Full Text Available Ronald M Sánchez-Avila,1 Jesus Merayo-Lloves,1 Maria Laura Fernández,1,2 Luis Alberto Rodríguez-Gutiérrez,1 Pedro Pablo Rodríguez-Calvo,1 Andres Fernández-Vega Cueto,1 Francisco Muruzabal,3,4 Gorka Orive,3–6 Eduardo Anitua3,4 1University Institute Fernández-Vega, Ophthalmological Research Foundation, University of Oviedo, Oviedo, Spain; 2Quilmes Eye Center, Buenos Aires, Argentina; 3University Institute for Regenerative Medicine and Oral Implantology (UIRMI, University of the Basque Country, Eduardo Anitua Foundation, Vitoria, Spain; 4Biotechnology Institute (BTI, Vitoria, Spain; 5Laboratory of Pharmacy and Pharmaceutical Technology, Faculty of Pharmacy, University of the Basque Country, Vitoria, Spain; 6Networking Biomedical Research Center on Bioengineering, Biomaterials and Nanomedicine, CIBER-BBN, Vitoria, Spain Purpose: To evaluate the efficacy and safety of plasma rich in growth factors (PRGF eye drops in patients with glaucoma with secondary ocular surface disorders (OSDs due to surgeries and topical hypotensive drugs use. Materials and methods: A retrospective case-series study design was used including six patients (eight eyes diagnosed with glaucoma who received surgical (nonpenetrating deep sclerectomy and/or trabeculectomy and medical treatments (hypotensive eye drops to control intraocular pressure (IOP and who developed secondary OSDs, unresponsive to conventional treatments. Patients were treated with PRGF eye drops (four times a day. Outcome measures were ocular surface disease index (OSDI, best-corrected visual acuity (BCVA, in logarithm of the minimum angle of resolution, visual analog scale (VAS, frequency and severity of symptoms, and IOP. The safety of the treatment was also evaluated. Results: Six patients (seven eyes with open-angle glaucoma and one eye with uveitic glaucoma treated with PRGF eye drops were evaluated. Mean age was 71 years (SD=7.2, range 58–79 years. Five were female and one was male. The mean

  10. What Is Dry Eye?

    Medline Plus

    Full Text Available ... Kierstan Boyd Reviewed By: Brenda Pagan-Duran MD Sep. 01, 2017 Our eyes need tears to stay ... tear duct to insert a permanent punctal plug? Sep 12, 2017 Why are my eyes bloodshot when ...

  11. What Is Dry Eye?

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  13. Pink Eye (Conjunctivitis)

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  14. About the Eye

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  16. Preventing Eye Injuries

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    ... Your Eyes Sep 20, 2017 Eye Injuries from Laundry Packets On the Rise Jun 30, 2017 ... Medical Disclaimer Privacy Policy Terms of Service For Advertisers For Media Ophthalmology Job Center © American ...

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  1. About the Eye

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  6. Eye Involvement in TSC

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    ... eye involvement. Nonretinal and Retinal Eye Findings Facial angiofibromas may involve the eyelids of individuals with TSC, ... the hamartomas have many blood vessels (as are angiofibromas of the skin). Less than half of the ...

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  12. The prevalence of refractive error in three communities of Cape Town, South Africa

    Directory of Open Access Journals (Sweden)

    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

  13. [Visual outcomes 5 years after small incision lenticule extraction (SMILE), surgery on spherocylindrical myopia eyes, from 616 eyes].

    Science.gov (United States)

    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.

  14. Immunology of the eye

    OpenAIRE

    Weronika Ratajczak; Beata Tokarz-Deptuła; Wiesław Deptuła

    2018-01-01

    The eye is an organ of sight characterized by unusual immunological properties, resulting from its anatomical structure and physiology, as well as the presence of specific elements that, through the mechanisms of innate and adaptive immunity, provide homeostasis of the eyeball. This article reviews the defensive elements of individual eye structures: conjunctiva, cornea, lacrimal gland, anterior chamber of the eye, uvea, retina and eye-associated lymphoid tissue (EALT), where we distinguish a...

  15. [Peripheral refraction and retinal contour in children with myopia by results of refractometry and partial coherence interferometry].

    Science.gov (United States)

    Tarutta, E P; Milash, S V; Tarasova, N A; Romanova, L I; Markosian, G A; Epishina, M V

    2014-01-01

    To determine the posterior pole contour of the eye based on the relative peripheral refractive error and relative eye length. A parallel study was performed, which enrolled 38 children (76 eyes) with myopia from -1.25 to -10.82 diopters. The patients underwent peripheral refraction assessment with WR-5100K Binocular Auto Refractometer ("Grand Seiko", Japan) and partial coherence tomography with IOLMaster ("Carl Zeiss", Germany) for the relative eye length in areas located 15 and 30 degrees nasal and temporal from the central fovea along the horizontal meridian. In general, refractometry and interferometry showed high coincidence of defocus signs and values for the areas located 15 and 30 degrees nasal as well as 15 degrees temporal from the fovea. However, in 41% of patients defocus signs determined by the two methods mismatched in one or more areas. Most of the mismatch cases were mild myopia. We suppose that such a mismatch is caused by optical peculiarities of the anterior eye segment that have an impact on refractometry results.

  16. Application of Suresight handheld auto-refractometer in refraction screening for infants in Community Health Service Center

    Directory of Open Access Journals (Sweden)

    Li-Hua Guo

    2014-08-01

    Full Text Available AIM: To observe the application of Suresight handheld auto-refractometer in measuring diopter of infants in Community Health Service Center. METHODS:Totally 836 cases(1 672 eyesfrom June 2013 to December 2013 were examined diopter of infants by Suresight handheld auto-refractometer in Community Health Service Center. RESULTS: Within 1 672 eyes of 836 infants were examined, 202 eyes were diagnosed ametropia, 38 eyes were suspicious, 240 eyes were transferred to the department of ophthalmology, the referral rate was 14.35%; 172 eyes were diagnosed ametropia, and the diagnosis rate of the referral patients was 71.67%. Among 172 eyes, 46 eyes were provided with corrected glasses, accounting for 2.75% of the number of screening, and 126 eyes were given intensive monitoring, accounting for 7.54% of the number of screening.CONCLUSION: Application of Suresight handheld auto-refractometer in refraction screening for infants in Community Health Service Center is convenient and effective. With two-way referral between community health service center and department of ophthalmology can monitor and intervene vision development of infants much earlier.

  17. Potassium channel and NKCC cotransporter involvement in ocular refractive control mechanisms.

    Directory of Open Access Journals (Sweden)

    Sheila G Crewther

    Full Text Available Myopia affects well over 30% of adult humans globally. However, the underlying physiological mechanism is little understood. This study tested the hypothesis that ocular growth and refractive compensation to optical defocus can be controlled by manipulation of potassium and chloride ion-driven transretinal fluid movements to the choroid. Chicks were raised with +/-10D or zero power optical defocus rendering the focal plane of the eye in front of, behind, or at the level of the retinal photoreceptors respectively. Intravitreal injections of barium chloride, a non-specific inhibitor of potassium channels in the retina and RPE or bumetanide, a selective inhibitor of the sodium-potassium-chloride cotransporter were made, targeting fluid control mechanisms. Comparison of refractive compensation to 5 mM Ba(2+ and 10(-5 M bumetanide compared with control saline injected eyes shows significant change for both positive and negative lens defocus for Ba(2+ but significant change only for negative lens defocus with bumetanide (Rx(SAL(-10D = -8.6 +/- .9 D; Rx(Ba2+(-10D = -2.9 +/- .9 D; Rx(Bum(-10D = -2.9 +/- .9 D; Rx(SAL(+10D = +8.2 +/- .9 D; Rx(Ba2+(+10D = +2.8 +/- 1.3 D; Rx(Bum(+10D = +8.0 +/- .7 D. Vitreous chamber depths showed a main effect for drug conditions with less depth change in response to defocus shown for Ba(2+ relative to Saline, while bumetanide injected eyes showed a trend to increased depth without a significant interaction with applied defocus. The results indicate that both K channels and the NKCC cotransporter play a role in refractive compensation with NKCC blockade showing far more specificity for negative, compared with positive, lens defocus. Probable sites of action relevant to refractive control include the apical retinal pigment epithelium membrane and the photoreceptor/ON bipolar synapse. The similarities between the biometric effects of NKCC inhibition and biometric reports of the blockade of the retinal ON response, suggest a

  18. The effect of humidity and temperature on visual outcomes after myopic corneal laser refractive surgery

    Directory of Open Access Journals (Sweden)

    Hood CT

    2016-11-01

    Full Text Available Christopher T Hood,1 Roni M Shtein,1 Daniel Veldheer,1,2 Munira Hussain,1 Leslie M Niziol,1 David C Musch,1,3 Shahzad I Mian1 1Department of Ophthalmology and Visual Sciences, University of Michigan W.K. Kellogg Eye Center, Ann Arbor, MI, 2Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, 3Department of Epidemiology, University of Michigan, Ann Arbor, MI, USA Objective: To determine whether procedure room environmental conditions are associated with outcomes after myopic laser in situ keratomileusis (LASIK or laser-assisted keratomileusis (LASEK. Design: Retrospective chart review. Participants: Eight hundred sixty-three eyes of 458 consecutive patients at a university-based academic practice. Methods: We reviewed the medical records of consecutive patients who underwent LASIK or LASEK over a 3-year period. Linear mixed regression models were used to investigate the association of laser room temperature and humidity with the outcomes of visual acuity and postoperative manifest spherical equivalent refraction. Repeated measures logistic regression models were used for the outcomes of diffuse lamellar keratitis (DLK and need for enhancement surgery. Results: Subjects were on an average 38.6 years old at the time of surgery (standard deviation [SD] =10.3 and the average spherical equivalent refraction of eyes was 3.8 diopters (SD =2.03. Regression models did not reveal a significant association between temperature and uncorrected distance visual acuity (UDVA or corrected distance visual acuity (CDVA, or between humidity and UDVA (P>0.05 for all. However, increased humidity was associated with a small but statistically significant improvement in CDVA after LASIK at 1 day, 1 month, 3 months, and 1 year postoperatively (P<0.05 for all. There was no significant association between temperature and humidity and the need for enhancement, the incidence of DLK, or postoperative manifest refraction. Conclusion: While increased laser

  19. The all seeing eye?

    NARCIS (Netherlands)

    Koenderink, Jan J.

    2014-01-01

    The All Seeing Eye? Did you know that you are probably a believer in the All Seeing Eye? The odds are that I’m right—why? Well, the bulk of mainstream vision literature blindly relies on the All Seeing Eye. It is written all over papers, albeit between the lines. Understandably so, for scientists

  20. About the Eye

    Medline Plus

    Full Text Available ... other programs with respect to blinding eye diseases, visual disorders, mechanisms of visual function, preservation of sight, and the special health ... Eye Ask a Scientist Video Series Glossary The Visual System Your Eyes’ Natural Defenses Eye Health and ...

  1. Eye and orbital cavity

    International Nuclear Information System (INIS)

    Panfilova, G.V.; Koval', G.Yu.

    1984-01-01

    Radioanatomy of eyes and orbit is described. Diseases of the orbit (developmental anomalies, inflammatory diseases, lacrimal apparatus deseases, toxoplasmosis, tumors and cysts et al.), methods of foreign body localization in the eye are considered. Roentgenograms of the orbit and calculation table for foreign body localization in spherical eyes of dissimilar diameter are presented

  2. Investigating the relationship between foveal morphology and refractive error in a population with infantile nystagmus syndrome.

    Science.gov (United States)

    Healey, Natasha; McLoone, Eibhlin; Mahon, Gerald; Jackson, A Jonathan; Saunders, Kathryn J; McClelland, Julie F

    2013-04-26

    We explored associations between refractive error and foveal hypoplasia in infantile nystagmus syndrome (INS). We recruited 50 participants with INS (albinism n = 33, nonalbinism infantile nystagmus [NAIN] n = 17) aged 4 to 48 years. Cycloplegic refractive error and logMAR acuity were obtained. Spherical equivalent (SER), most ametropic meridian (MAM) refractive error, and better eye acuity (VA) were used for analyses. High resolution spectral-domain optical coherence tomography (SD-OCT) was used to obtain foveal scans, which were graded using the Foveal Hypoplasia Grading Scale. Associations between grades of severity of foveal hypoplasia, and refractive error and VA were explored. Participants with more severe foveal hypoplasia had significantly higher MAMs and SERs (Kruskal-Wallis H test P = 0.005 and P = 0.008, respectively). There were no statistically significant associations between foveal hypoplasia and cylindrical refractive error (Kruskal-Wallis H test P = 0.144). Analyses demonstrated significant differences between participants with albinism or NAIN in terms of SER and MAM (Mann-Whitney U test P = 0.001). There were no statistically significant differences between astigmatic errors between participants with albinism and NAIN. Controlling for the effects of albinism, results demonstrated no significant associations between SER, and MAM and foveal hypoplasia (partial correlation P > 0.05). Poorer visual acuity was associated statistically significantly with more severe foveal hypoplasia (Kruskal-Wallis H test P = 0.001) and with a diagnosis of albinism (Mann-Whitney U test P = 0.001). Increasing severity of foveal hypoplasia is associated with poorer VA, reflecting reduced cone density in INS. Individuals with INS also demonstrate a significant association between more severe foveal hypoplasia and increasing hyperopia. However, in the absence of albinism, there is no significant relation between refractive outcome and degree of foveal hypoplasia

  3. Optics of the human cornea influence the accuracy of stereo eye-tracking methods: a simulation study.

    Science.gov (United States)

    Barsingerhorn, A D; Boonstra, F N; Goossens, H H L M

    2017-02-01

    Current stereo eye-tracking methods model the cornea as a sphere with one refractive surface. However, the human cornea is slightly aspheric and has two refractive surfaces. Here we used ray-tracing and the Navarro eye-model to study how these optical properties affect the accuracy of different stereo eye-tracking methods. We found that pupil size, gaze direction and head position all influence the reconstruction of gaze. Resulting errors range between ± 1.0 degrees at best. This shows that stereo eye-tracking may be an option if reliable calibration is not possible, but the applied eye-model should account for the actual optics of the cornea.

  4. MANAGEMENT OF RESIDUAL REFRACTIVE ERROR AFTER CATARACT PHACOEMULSIFICATION. PART 2. INTRAOCULAR APPROACHES

    Directory of Open Access Journals (Sweden)

    K. B. Pershin

    2017-01-01

    Full Text Available The review presents an  analysis  of the  literature  data  on  the  methods of surgical  correction of residual  refractive  error after cataract phacoemulsification. Keratorefractive and intraocular approaches are  considered in details.  A comparison of the  efficacy and  safet y  of different groups   of methods on  the  example  of comparative studies is given.  Historically earlier  keratorefractive methods (laser  vision correction with LASIK and  PRK techniques on intact  eyes,  LASIK after  implantation  of multifocal  IOLs and arcuate keratotomy  after  phaco  are  indicated  for  the  correction of astigmatic refractive  error and  a small  spherical refractive error. Intraocular methods, including the  replacement of the  IOL  and  «piggyback» IOLs implantation  are  used  to  correct a large spherical refractive error. The introduction  of new  technology, the  implantation  of light-adjustable  IOLs, will  expand  the  existing evidence  and provide greater predictabilit y and efficiency of the  method  of correction of residual  refractive error.

  5. Postural stability in the elderly during sensory perturbations and dual tasking: the influence of refractive blur.

    Science.gov (United States)

    Anand, Vijay; Buckley, John G; Scally, Andy; Elliott, David B

    2003-07-01

    To determine the influence of refractive blur on postural stability during somatosensory and vestibular system perturbation and dual tasking. Fifteen healthy, elderly subjects (mean age, 71 +/- 5 years), who had no history of falls and had normal vision, were recruited. Postural stability during standing was assessed using a force platform, and was determined as the root mean square (RMS) of the center of pressure (COP) signal in the anterior-posterior (A-P) and medial-lateral directions collected over a 30-second period. Data were collected under normal standing conditions and with somatosensory and vestibular system perturbations. Measurements were repeated with an additional physical and/or cognitive task. Postural stability was measured under conditions of binocular refractive blur of 0, 1, 2, 4, and 8 D and with eyes closed. The data were analyzed with a population-averaged linear model. The greatest increases in postural instability were due to disruptions of the somatosensory and vestibular systems. Increasing refractive blur caused increasing postural instability, and its effect was greater when the input from the other sensory systems was disrupted. Performing an additional cognitive and physical task increased A-P RMS COP further. All these detrimental effects on postural stability were cumulative. The findings highlight the multifactorial nature of postural stability and indicate why the elderly, many of whom have poor vision and musculoskeletal and central nervous system degeneration, are at greater risk of falling. The findings also highlight that standing instability in both normal and perturbed conditions was significantly increased with refractive blur. Correcting visual impairment caused by uncorrected refractive error could be a useful intervention strategy to help prevent falls and fall-related injuries in the elderly.

  6. MULTIDISCIPLINARY APPROACH TO THE CORRECTION OF ACCOMMODATION REFRACTION DISORDERS IN VISUALLY INTENSIVE LABOR PERSONS

    Directory of Open Access Journals (Sweden)

    I. G. Ovechkin

    2015-01-01

    Full Text Available Increased load on the visual analyzer of an operator, increase in everyday visual performance, universal introduction of information displaying on cathode-ray tubes result in temporary and stable visual disturbances. Accommodative refractive apparatus of an eye is one of the key points of application of visually intensive labor. Work associated with permanent eyestrain overloads oculomotor and accommodative apparatus thus provoking myopic shift, increase in dynamic refraction, exophoric or esophoric shift of initial visual equilibrium. Accommodation disorders are accompanied by changes in ciliary muscle blood supply, abnormalities of vegetative segment regulation, parasympathetic brain vascular dystonia due to the decreased tonus of sympathetic nervous system. Evaluation of certain kind of activity in terms of ergonomics includes examination of visual status and visual working capacity, development of visual professiograms and vision standards for certain professions, justification of methods and tools of visual work optimization. Visual disturbances in operators developing in the course of visually intensive occupational work should be considered from the viewpoint of traditional accommodation and refraction disorders as well as functional manifestations of general fatigue or thoracic cervical spine dysfunction. Symptoms of accommodative asthenopia can be regarded as a functional manifestation of general fatigue syndrome or functional neurosis. Development of multidisciplinary approach to the correction of accommodation refraction disorders in visually intensive labor persons is of scientific urgency and practical reasonability. There is a long-felt need in additional attraction of different specialists who use in their work physical factors for accommodative asthenopia correction. Development of multidisciplinary approach to accommodation refraction disorder correction in visually intensive labor persons is based on syndromic pathogenic

  7. Recognizing and Treating Eye Injuries

    Science.gov (United States)

    ... Eye Injuries First Aid for Eye Scratches Protective Eyewear Children’s Eye Injuries: Prevention and Care Eye Injuries ... Academy Jobs at the Academy Financial Relationships with Industry Medical Disclaimer Privacy Policy Terms of Service For ...

  8. Characterising refractive index dispersion in chalcogenide glasses

    DEFF Research Database (Denmark)

    Fang, Y.; Sojka, L.; Jayasuriya, D.

    2016-01-01

    Much effort has been devoted to the study of glasses that contain the chalcogen elements (sulfur, selenium and tellurium) for photonics' applications out to MIR wavelengths. In this paper we describe some techniques for determining the refractive index dispersion characteristics of these glasses...

  9. Refractive index dispersion law of silica aerogel

    International Nuclear Information System (INIS)

    Bellunato, T.; Calvi, M.; Matteuzzi, C.; Musy, M.; Perego, D.L.; Storaci, B.

    2007-01-01

    This paper presents measurements of the refractive index of a hygroscopic silica aerogel block at several wavelengths. The measurements, performed with a monochromator, have been compared with different parameterisations for n(λ), in order to determine the best chromaticity law for the aerogel. This is an important input for design and operation of RICH detectors with silica aerogel radiator. (orig.)

  10. Compound refractive X-ray lens

    International Nuclear Information System (INIS)

    Nygren, D.R.; Cahn, R.; Cederstrom, B.; Danielsson, M.; Vestlund, J.

    2000-01-01

    An apparatus and method are disclosed for focusing X-rays. In one embodiment, his invention is a commercial-grade compound refractive X-ray lens. The commercial-grade compound refractive X-ray lens includes a volume of low-Z material. The volume of low-Z material has a first surface which is adapted to receive X-rays of commercially-applicable power emitted from a commercial-grade X-ray source. The volume of low-Z material also has a second surface from which emerge the X-rays of commercially-applicable power which were received at the first surface. Additionally, the commercial-grade compound refractive X-ray lens includes a plurality of openings which are disposed between the first surface and the second surface. The plurality of openings are oriented such that the X-rays of commercially-applicable power which are received at the first surface, pass through the volume of low-Z material and through the plurality openings. In so doing, the X-rays which emerge from the second surface are refracted to a focal point

  11. Real time refractive index measurement by ESPI

    International Nuclear Information System (INIS)

    Torroba, R.; Joenathan, C.

    1991-01-01

    In this paper a method to measure refractive index variations in real time is reported. A technique to introduce reference fringes in real time is discussed. Both the theoretical and experimental results are presented and an example with phase shifting is given. (author). 8 refs, 5 figs

  12. Compound refractive X-ray lens

    Science.gov (United States)

    Nygren, David R.; Cahn, Robert; Cederstrom, Bjorn; Danielsson, Mats; Vestlund, Jonas

    2000-01-01

    An apparatus and method for focusing X-rays. In one embodiment, his invention is a commercial-grade compound refractive X-ray lens. The commercial-grade compound refractive X-ray lens includes a volume of low-Z material. The volume of low-Z material has a first surface which is adapted to receive X-rays of commercially-applicable power emitted from a commercial-grade X-ray source. The volume of low-Z material also has a second surface from which emerge the X-rays of commercially-applicable power which were received at the first surface. Additionally, the commercial-grade compound refractive X-ray lens includes a plurality of openings which are disposed between the first surface and the second surface. The plurality of openings are oriented such that the X-rays of commercially-applicable power which are received at the first surface, pass through the volume of low-Z material and through the plurality openings. In so doing, the X-rays which emerge from the second surface are refracted to a focal point.

  13. seismic refraction investigation of the subsurface structure

    African Journals Online (AJOL)

    DR. AMINU

    employed for exploration include magnetic, electrical and gravitational methods, which depends on the earth's natural fields. Others are seismic and electromagnetic methods, which depends on the introduction of artificial energy in thereof. The seismic refraction method uses the seismic energy that returns to the surface of ...

  14. Wave refraction studies off Agonda beach (Goa)

    Digital Repository Service at National Institute of Oceanography (India)

    Krishnakumar, V.; Pathak, M.C.; Kotnala, K.L.

    Analysis of wave refraction and longshore current has been carried out for a narrow strip off the shores of Agonda (Goa, India). Zones with high wave energy and rip currents have been demarcated. It is found from the analysis that the southern part...

  15. Is LASIK for Me? A Patient's Guide to Refractive Surgery

    Science.gov (United States)

    Is LASIK for Me? A Patient’s Guide to Refractive Surgery October 2008 Is LASIK for Me? A Patient’s Guide to Refractive Surgery Table of Contents LASIK: A COMPREHENSIVE GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 What Is ...

  16. Prevalence of Refractive errors among Primary School Pupils in ...

    African Journals Online (AJOL)

    Administrator

    Effective management of blindness due to refractive errors is readily available in developed countries. 1 ... Key words: Refractive errors, Children, Prevalence, Kenya. 165 .... financial support towards the funding of this study. REFERENCES. 1.

  17. refractive errors among secondary school students in Isuikwuato

    African Journals Online (AJOL)

    Eyamba

    STUDENTS IN ISUIKWUATO LOCAL GOVERNMENT AREA OF ... the prevalence and types of refractive errors among secondary school students ... KEYWORDS: Refractive error, Secondary School students, ametropia, .... interviews of the teachers as regards the general performance of those students with obvious visual.

  18. Marangoni Flowers and the Evil Eye: Overhead Presentations of Marangoni Flow

    Science.gov (United States)

    Mundell, Donald W.

    2009-01-01

    Intermolecular forces and surface tension gradients in solutions lead to remarkable flows, known as Marangoni flows, where liquid flows from a region of low surface tension towards higher surface tension. Details of these flows, not visible to the naked eye, are made visible on an overhead projector owing to variation in the index of refraction.…

  19. Negative Refraction Angular Characterization in One-Dimensional Photonic Crystals

    OpenAIRE

    Lugo, Jesus Eduardo; Doti, Rafael; Faubert, Jocelyn

    2011-01-01

    Background Photonic crystals are artificial structures that have periodic dielectric components with different refractive indices. Under certain conditions, they abnormally refract the light, a phenomenon called negative refraction. Here we experimentally characterize negative refraction in a one dimensional photonic crystal structure; near the low frequency edge of the fourth photonic bandgap. We compare the experimental results with current theory and a theory based on the group velocity de...

  20. EYE GAZE TRACKING

    DEFF Research Database (Denmark)

    2017-01-01

    This invention relates to a method of performing eye gaze tracking of at least one eye of a user, by determining the position of the center of the eye, said method comprising the steps of: detecting the position of at least three reflections on said eye, transforming said positions to spanning...... a normalized coordinate system spanning a frame of reference, wherein said transformation is performed based on a bilinear transformation or a non linear transformation e.g. a möbius transformation or a homographic transformation, detecting the position of said center of the eye relative to the position...... of said reflections and transforming this position to said normalized coordinate system, tracking the eye gaze by tracking the movement of said eye in said normalized coordinate system. Thereby calibration of a camera, such as knowledge of the exact position and zoom level of the camera, is avoided...