WorldWideScience

Sample records for astigmatism

  1. Astigmatism

    Science.gov (United States)

    ... a type of refractive error of the eye. Refractive errors cause blurred vision and are the most common reason ... causes vision to be out of focus. The cause of astigmatism is unknown. It is usually present from birth. ...

  2. Facts about Astigmatism

    Science.gov (United States)

    ... Information > Refractive Errors > Facts About Astigmatism Facts About Astigmatism This information was developed by the National Eye ... is the best person to answer specific questions. Astigmatism Defined What is astigmatism? Astigmatism is a common ...

  3. Astigmatism in reflector antennas.

    Science.gov (United States)

    Cogdell, J. R.; Davis, J. H.

    1973-01-01

    Astigmatic phase error in large parabolic reflector antennas is discussed. A procedure for focusing an antenna and diagnosing the presence and degree of astigmatism is described. Theoretical analysis is conducted to determine the nature of this error in such antennas.

  4. Effects of Induced Astigmatism.

    Science.gov (United States)

    Schubert, Delwyn G.; Walton, Howard N.

    1968-01-01

    The relationship of astigmatism to reading and the possible detrimental effects it might have on reading were investigated. The greatest incidence of astigmatism was for the with-the-rule type ranging from .50 to 1.00 diopter. This type of astigmatism was induced in 35 seniors from the Los Angeles College of Optometry by placing cylindrical lenses…

  5. Control of postoperative astigmatism.

    OpenAIRE

    Atkins, A D; Roper-Hall, M. J.

    1985-01-01

    Thirty-six eyes with excessive astigmatism following cataract extraction via a corneal section were subjected to suture adjustment. This was performed six to eight weeks postoperatively under topical anaesthesia. The cases were selected from a large volume of corneal section cases because they had over 3.0 dioptres astigmatism. We reduced astigmatism significantly in the majority. There were no serious complications.

  6. Astigmatism following cataract surgery.

    OpenAIRE

    Reading, V M

    1984-01-01

    The changes in corneal curvature were determined at regular intervals over a one-year period following intracapsular cataract extraction by microsurgical techniques. During the first postoperative month photokeratometric measurements showed rapid changes in astigmatism associated with large changes in the direction of the axis. Thereafter astigmatism against-the-rule predominated. Data from the small group of patients who underwent surgery in which the technique of phacoemulsification was use...

  7. Astigmatism following retinal detachment surgery.

    OpenAIRE

    Goel, R.; Crewdson, J; Chignell, A H

    1983-01-01

    Eighty-three patients on whom successful retinal detachment had been performed were studied to note astigmatic changes following surgery. In the majority of cases the errors following such surgery are of no great clinical importance. However, in some situations a high degree of astigmatism may be produced. This study showed that these sequelae are particularly likely after radial buckling procedures, and surgeons favouring these techniques should be aware that astigmatic errors can be induced...

  8. Optics of astigmatism and retinal image quality

    OpenAIRE

    Vilaseca, M.; Díaz-Doutón, F.; Luque, S. O.; Aldaba, M.; Arjona, M.; Pujol, J.

    2012-01-01

    In the first part of this chapter, the optical condition of astigmatism is defined. The main causes and available classifications of ocular astigmatism are briefly described. The most relevant optical properties of image formation in an astigmatic eye are analysed and compared to that of an emmetropic eye and an eye with spherical ametropia. The spectacle prescription and axis notation for astigmatism are introduced, and the correction of astigmatism by means of lenses is briefly described. ...

  9. Control of astigmatism in cataract surgery.

    OpenAIRE

    Brown, N. A.; Sparrow, J M

    1988-01-01

    A study is reported on cataract surgery, with intraocular lens implant, with measurement of the preoperative astigmatism and of the postoperative astigmatism over 28 weeks. Nine interrupted 10/0 nylon sutures are used to close a limbal section. Preoperative astigmatism is compensated for in the method of suturing by the placement of additional sutures. Postoperatively sutures are cut in line with the plus cylinder axis in eyes showing excessive astigmatism with the rule. Final postoperative a...

  10. Surgical correction of postoperative astigmatism

    OpenAIRE

    Lindstrom Richard

    1990-01-01

    The photokeratoscope has increased the understanding of the aspheric nature of the cornea as well as a better understanding of normal corneal topography. This has significantly affected the development of newer and more predictable models of surgical astigmatic correction. Relaxing incisions effectively flatten the steeper meridian an equivalent amount as they steepen the flatter meridian. The net change in spherical equivalent is, therefore, negligible. Poor predictability is the major limit...

  11. Anterior and Posterior Corneal Astigmatism after Refractive Lenticule Extraction for Myopic Astigmatism

    OpenAIRE

    2015-01-01

    Purpose. To assess the amount and the axis orientation of anterior and posterior corneal astigmatism after refractive lenticule extraction (ReLEx) for myopic astigmatism. Methods. We retrospectively examined 53 eyes of 53 consecutive patients (mean age ± standard deviation, 33.2 ± 6.5 years) undergoing ReLEx to correct myopic astigmatism (manifest cylinder = 0.5 diopters (D)). Power vector analysis was performed with anterior and posterior corneal astigmatism measured with a rotating Scheimpf...

  12. Comparison of Astigmatic Correction after Femtosecond Lenticule Extraction and Small-Incision Lenticule Extraction for Myopic Astigmatism

    OpenAIRE

    Kobashi, Hidenaga; Kamiya, Kazutaka; Ali, Mohamed A.; Igarashi, Akihito; Elewa, Mohamed Ehab M.; Shimizu, Kimiya

    2015-01-01

    Purpose To compare postoperative astigmatic correction between femtosecond lenticule extraction (FLEx) and small-incision lenticule extraction (SMILE) in eyes with myopic astigmatism. Methods We examined 26 eyes of 26 patients undergoing FLEx and 26 eyes of 26 patients undergoing SMILE to correct myopic astigmatism (manifest astigmatism of 1 diopter (D) or more). Visual acuity, cylindrical refraction, the predictability of the astigmatic correction, and the astigmatic vector components using ...

  13. Orbital angular momentum of general astigmatic modes

    International Nuclear Information System (INIS)

    We present an operator method to obtain complete sets of astigmatic Gaussian solutions of the paraxial wave equation. In case of general astigmatism, the astigmatic intensity and phase distribution of the fundamental mode differ in orientation. As a consequence, the fundamental mode has a nonzero orbital angular momentum, which is not due to phase singularities. Analogous to the operator method for the quantum harmonic oscillator, the corresponding astigmatic higher-order modes are obtained by repeated application of raising operators on the fundamental mode. The nature of the higher-order modes is characterized by a point on a sphere, in analogy with the representation of polarization on the Poincare sphere. The north and south poles represent astigmatic Laguerre-Gaussian modes, similar to circular polarization on the Poincare sphere, while astigmatic Hermite-Gaussian modes are associated with points on the equator, analogous to linear polarization. We discuss the propagation properties of the modes and their orbital angular momentum, which depends on the degree of astigmatism and on the location of the point on the sphere

  14. Some results concerning the constant astigmatism equation

    CERN Document Server

    Hlaváč, Adam

    2012-01-01

    In this paper we continue investigation of the constant astigmatism equation z_{yy} + (1/z)_{xx} + 2 = 0. We newly interpret its solutions as describing spherical orthogonal equiareal patterns, with relevance to two-dimensional plasticity. We show how the classical Bianchi superposition principle for the sine-Gordon equation can be extended to generate an arbitrary number of solutions of the constant astigmatism equation by algebraic manipulations. As a by-product, we show that sine-Gordon solutions give slip line fields on the sphere. Finally, we compute the solutions corresponding to classical Lipschitz surfaces of constant astigmatism via the corresponding equiareal patterns.

  15. Individual electrostatic astigmatic tubular lenses

    International Nuclear Information System (INIS)

    Electron-optical properties of three-electrode individual astigmatic tubular lenses with similar electrode diameters are investigated. It has been assumed while calculations that gaps between the el ctrodes are infinitely small and lines separating them are presented as part of line of intersection of two cylinders with equal radius. Parameters characterizing paraxial properties of lenses and coefficients of their spherical aberration for subject position on the infinity at different ratios of electrode potential and distances between gaps are determined. The three-electrode individual lens focuses charged particle beams in one plain and it scatters them in another one in the whole chosen range of potential ratios. It is revealed that coefficients of spherical aberration in individual lenses have different signs and one of the coefficients passes through zero

  16. Surgical management of astigmatism with toric intraocular lenses

    OpenAIRE

    Ventura, Bruna V.; Li Wang; Weikert, Mitchell P.; Shaun B. Robinson; Koch, Douglas D.

    2014-01-01

    Correction of corneal astigmatism is a key element of cataract surgery, since post-surgical residual astigmatism can compromise the patient's uncorrected visual acuity. Toric intraocular lenses (IOLs) compensate for corneal astigmatism at the time of surgery, correcting ocular astigmatism. They are a predictable treatment. However, accurate measurement of corneal astigmatism is mandatory for choosing the correct toric IOL power and for planning optimal alignment. When calculating the power of...

  17. Perioperative Modulating Factors on Astigmatism in Sutured Cataract Surgery

    OpenAIRE

    Cho, Yang Kyeung; Kim, Man Soo

    2009-01-01

    Purpose To evaluate the factors that affect postoperative astigmatism and post-suture removal astigmatism, and to evaluate the risk factors associated with astigmatism axis shift. Methods We performed a retrospective chart review of 130 eyes that had undergone uneventful phacoemulsification cataract surgery. Preoperative astigmatism was divided into four groups (Groups I, II, III, and IV) according to the differences between the axis of preoperative astigmatism (flattest axis) and the incisio...

  18. Distribution of Posterior Corneal Astigmatism According to Axis Orientation of Anterior Corneal Astigmatism

    OpenAIRE

    Miyake,Toshiyuki; Shimizu, Kimiya; Kamiya, Kazutaka

    2015-01-01

    Purpose To investigate the distribution of posterior corneal astigmatism in eyes with with-the-rule (WTR) and against-the-rule (ATR) anterior corneal astigmatism. Methods We retrospectively examined six hundred eight eyes of 608 healthy subjects (275 men and 333 women; mean age ± standard deviation, 55.3 ± 20.2 years). The magnitude and axis orientation of anterior and posterior corneal astigmatism were determined with a rotating Scheimpflug system (Pentacam HR, Oculus) when we divided the su...

  19. A design of PAL with astigmatism

    Science.gov (United States)

    Wei, Yefei; Xiang, Huazhong; Zhu, Tianfeng; Chen, Jiabi

    2015-08-01

    Progressive addition lens (PAL) is designed for those who suffer from myopia and presbyopia to have a clear vision from a far distance to a nearby distance. Additionally there are many people that also suffer from astigmatism and need to be corrected. The cylinder power can't be simply added to the diopter of the PAL directly, because the diopter of the PAL needs to be changed smoothly. A methods has been proposed in this article to solve the problem, the freeform surface height of a PAL without astigmatism and the cylindrical lens surface height for the correction of astigmatism are calculated separately. The both two surface heights were added together, then the final surface is produced and shown with the both properties of PALs and cylindrical lenses used to correct the astigmatism.

  20. Tubular astigmatism-tunable fluidic lens.

    Science.gov (United States)

    Kopp, Daniel; Zappe, Hans

    2016-06-15

    We demonstrate a new means to fabricate three-dimensional liquid lenses which may be tuned in focal length and astigmatism. Using actuation by electrowetting-on-dielectrics, astigmatism in arbitrary directions may be tuned independently, with almost no cross talk between orthogonal orientations. The lens is based on electrodes structured on planar polyimide foils and subsequently rolled, enabling high-resolution patterning of complex electrodes along the azimuthal and radial directions of the lens. Based on a design established through fluidic and optical simulations, the astigmatism tuning is experimentally verified by a change of the corresponding Zernike coefficients measured using a Shack-Hartmann wavefront sensor. It was seen that the back focal length can be tuned by 5 mm and 0° and 45° astigmatism by 3 μm through application of voltages in the range of 50  Vrms. It was observed that the cross talk with other aberrations is very low, suggesting a novel means for astigmatism control in imaging systems. PMID:27304276

  1. Improved astigmatic focus error detection method

    Science.gov (United States)

    Bernacki, Bruce E.

    1992-01-01

    All easy-to-implement focus- and track-error detection methods presently used in magneto-optical (MO) disk drives using pre-grooved media suffer from a side effect known as feedthrough. Feedthrough is the unwanted focus error signal (FES) produced when the optical head is seeking a new track, and light refracted from the pre-grooved disk produces an erroneous FES. Some focus and track-error detection methods are more resistant to feedthrough, but tend to be complicated and/or difficult to keep in alignment as a result of environmental insults. The astigmatic focus/push-pull tracking method is an elegant, easy-to-align focus- and track-error detection method. Unfortunately, it is also highly susceptible to feedthrough when astigmatism is present, with the worst effects caused by astigmatism oriented such that the tangential and sagittal foci are at 45 deg to the track direction. This disclosure outlines a method to nearly completely eliminate the worst-case form of feedthrough due to astigmatism oriented 45 deg to the track direction. Feedthrough due to other primary aberrations is not improved, but performance is identical to the unimproved astigmatic method.

  2. Optic nerve hypoplasia and astigmatism: a new association.

    OpenAIRE

    Zeki, S. M.

    1990-01-01

    Thirty-one patients with optic nerve hypoplasia (ONH) or septo-optic dysplasia and two patients with segmental ONH underwent retinoscopy. The results were compared with those of 20 normal subjects. There was a higher prevalence of astigmatism in the patients than in the controls. Two patients with segmental ONH had no evidence of astigmatism. The association of astigmatism with ONH has not hitherto been reported. The close association of ONH with astigmatism highlights the importance of perfo...

  3. Threshold to predict astigmatism reduction after pterygium excision

    OpenAIRE

    Julio Morán, Gemma; de Carvalho Mendes Castanheira, Amélia Maria; Kostov, Belchin Adriyanov; Pujol Vives, Pere

    2014-01-01

    Purpose. To compare corneal astigmatism after pterygium excision, using limbal-conjunctival autograft (LCA) with and without mitomycin C (MMC) and to establish a threshold for postoperative astigmatism reduction.; Methods. Sixty-eight eyes with primary pterygium were consecutively sampled and assigned to LCA with MMC (MMC+) or LCA without MMC (MMC-). Corneal lesion length, corneal lesion area, preoperative corneal astigmatism (PRCA), and postoperative corneal astigmatism (POCA) at 1, 3, and 6...

  4. Rectangular Laser Resonators with Astigmatic Compensation

    DEFF Research Database (Denmark)

    Skettrup, Torben

    2005-01-01

    An investigation of rectangular resonators with a view to the compensation of astigmatism has been performed. In order to have beam waists placed at the same positions in the tangential and sagittal planes, pairs of equal mirrors were considered. It was found that at least two concave mirrors are...... necessary to obtain compensation. Four-concave-mirror systems are most stable close to the quadratic geometry, although the symmetric quadratic resonator itself cannot be compensated for astigmatism. Using four equal concave mirrors, compensation of astigmatism can be obtained in two arms at the same time....... Usually several stability ranges are found for four-mirror resonators with pair-wise equal mirrors, and it is possible with these systems to obtain small compensated beam waist radii suitable for frequency conversion. Relevant formulae are given and several relevant examples are shown using simulation...

  5. Astigmatism in relation to length and site of corneal lacerations

    Directory of Open Access Journals (Sweden)

    Srihari Atti

    2016-01-01

    Conclusions: The corneal astigmatism depends upon the length and site of corneal laceration. Severity of astigmatism was directly proportion to the length of corneal laceration. The wound was nearer to the centre of the cornea, the greater was the astigmatism. [Int J Res Med Sci 2016; 4(1.000: 165-168

  6. Astigmatism induced by conventional spherical ablation after PRK and LASIK in myopia with astigmatism < 1.00 D

    OpenAIRE

    Christiansen, Steven M.; Mifflin, Mark D.; Edmonds, Jason N; Simpson, Rachel G; Moshirfar, Majid

    2012-01-01

    Background The purpose of this study was to evaluate surgically-induced astigmatism after spherical ablation in photorefractive keratectomy (PRK) and laser-assisted in situ keratomileusis (LASIK) for myopia with astigmatism < 1.00 D. Methods The charts of patients undergoing spherical PRK or LASIK for the correction of myopia with minimal astigmatism of

  7. Comparison of astigmatic correction after femtosecond lenticule extraction and small-incision lenticule extraction for myopic astigmatism.

    Directory of Open Access Journals (Sweden)

    Hidenaga Kobashi

    Full Text Available To compare postoperative astigmatic correction between femtosecond lenticule extraction (FLEx and small-incision lenticule extraction (SMILE in eyes with myopic astigmatism.We examined 26 eyes of 26 patients undergoing FLEx and 26 eyes of 26 patients undergoing SMILE to correct myopic astigmatism (manifest astigmatism of 1 diopter (D or more. Visual acuity, cylindrical refraction, the predictability of the astigmatic correction, and the astigmatic vector components using Alpin's method, were compared between the two groups 3 months postoperatively.We found no statistically significant difference in manifest cylindrical refraction (p=0.74 or in the percentage of eyes within ± 0.50 D of their refraction (p=0.47 after the two surgical procedures. Moreover, no statistically significant difference was detected between the groups in astigmatic vector components, namely, surgically induced astigmatism (0.80, target induced astigmatism (p=0.87, astigmatic correction index (p=0.77, angle of error (p=0.24, difference vector (p=0.76, index of success (p=0.91, flattening effect (p=0.79, and flattening index (p=0.84.Both FLEx and SMILE procedures are essentially equivalent in correcting myopic astigmatism using vector analysis, suggesting that the lifting or non-lifting of the flap does not significantly affect astigmatic outcomes after these surgical procedures.

  8. LASIK for Spherical Refractive Myopia: Effect of Topographic Astigmatism (Ocular Residual Astigmatism, ORA) on Refractive Outcome

    OpenAIRE

    Frings, Andreas; Richard, Gisbert; Steinberg, Johannes; Skevas, Christos; Druchkiv, Vasyl; Katz, Toam; Linke, Stephan J.

    2015-01-01

    Purpose In eyes with a preoperative plano refractive cylinder, it would appear that there is no rationale for astigmatic treatment. The aim of this retrospective, cross-sectional data analysis was to determine the amount of topographic astigmatism in refractive plano eyes that results in reduced efficacy after myopic laser in situ keratomileusis (LASIK). Methods This study included 267 eyes from 267 consecutive myopic patients with a refractive plano cylinder. Receiver operating characteristi...

  9. Tunable astigmatic π/2 mode converter

    International Nuclear Information System (INIS)

    The scheme of a tunable astigmatic π/2 mode converter is described. The converter provides the use of input beams with the twofold variable Rayleigh length, while variations in the optical length of the converter itself do not exceed 1/6. (laser beams)

  10. Optical advantages of astigmatic aberration corrected heliostats

    Science.gov (United States)

    van Rooyen, De Wet; Schöttl, Peter; Bern, Gregor; Heimsath, Anna; Nitz, Peter

    2016-05-01

    Astigmatic aberration corrected heliostats adapt their shape in dependence of the incidence angle of the sun on the heliostat. Simulations show that this optical correction leads to a higher concentration ratio at the target and thus in a decrease in required receiver aperture in particular for smaller heliostat fields.

  11. Relationship between age, corneal astigmatism, and ocular dimensions with reference to astigmatism in eyes undergoing routine cataract surgery.

    Science.gov (United States)

    Collier Wakefield, O; Annoh, R; Nanavaty, M A

    2016-04-01

    PurposeTo assess the relationship between age, corneal astigmatism, and ocular dimensions with reference to astigmatism correction during cataract surgery.MethodsIn this cross-sectional study of right eyes of 2247 consecutive patients attending cataract surgery preassessment, data on patient demographics, axial length (AL), anterior chamber depth (ACD), and keratometric astigmatism were collected. Astigmatism was further analyzed as against-the-rule (ATR: steepest meridian 180±30°), with-the-rule (WTR: 90±30°), and oblique (OB: 30-60°or 120-150°).ResultsMean age, AL, and ACD were 72.28±13.84 years, 23.99±1.85 mm and 3.08 ±0.52 mm, respectively. In all, 20.4% eyes had ≤0.50 diopters (D), 55.2% had 0.51-1.50 D, 7.9% had 2.01-3.00 D, and 3.7% eyes had >3.00 D of astigmatism. Overall, 44.2% of eyes had corneal astigmatism >1.00 D. Average astigmatism in age ranges 40-49, 50-59, 60-69, 70-79, 80-89, and 90+ years were 0.82, 1.04, 1.04, 1.02, 1.15 and 2.01 D, respectively. The magnitude of preoperative astigmatism positively correlated with age (Pastigmatism, respectively, with advancing age. The magnitude of ATR astigmatism inversely correlates to AL (Pastigmatism is more prevalent with increasing magnitude of astigmatism (Pastigmatism between 0.51 and 1.5 D. ATR astigmatism increases, whereas WTR decreases with age. ATR astigmatism inversely correlates to AL. With increasing age, the magnitude of astigmatism increases and ATR astigmatism becomes increasingly prevalent. The likelihood of a patient requiring astigmatic correction increases with age. PMID:26795412

  12. Surgical management of astigmatism with toric intraocular lenses

    Directory of Open Access Journals (Sweden)

    Bruna V. Ventura

    2014-04-01

    Full Text Available Correction of corneal astigmatism is a key element of cataract surgery, since post-surgical residual astigmatism can compromise the patient's uncorrected visual acuity. Toric intraocular lenses (IOLs compensate for corneal astigmatism at the time of surgery, correcting ocular astigmatism. They are a predictable treatment. However, accurate measurement of corneal astigmatism is mandatory for choosing the correct toric IOL power and for planning optimal alignment. When calculating the power of toric IOLs, it is important to consider anterior and posterior corneal astigmatism, along with the surgically induced astigmatism. Accurate toric lens alignment along the calculated meridian is also crucial to achieve effective astigmatism correction. There are several techniques to guide IOL alignment, including the traditional manual marking technique and automated systems based on anatomic and topographic landmarks. The aim of this review is to provide an overview on astigmatism management with toric IOLs, including relevant patient selection criteria, corneal astigmatism measurement, toric IOL power calculation, toric IOL alignment, clinical outcomes and complications.

  13. The astigmatism factor for semiconductor injection lasers

    International Nuclear Information System (INIS)

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

  14. Current Approaches for Management of Postpenetrating Keratoplasty Astigmatism

    OpenAIRE

    Mohammad Zare; Sepehr Feizi

    2011-01-01

    A successful corneal graft requires both clarity and an acceptable refraction. A clear corneal graft may be an optical failure if high astigmatism limits visual acuity. Intraoperative measures to reduce postkeratoplasty astigmatism include round and central trephination of cornea with an adequate size, appropriate sutures with evenly distributed tension, and perfect graft-host apposition. Suture manipulation has been described for minimising early postoperative astigmatism. If significant ast...

  15. On multisoliton solutions of the constant astigmatism equation

    Science.gov (United States)

    Hlaváč, Adam

    2015-09-01

    We introduce an algebraic formula producing infinitely many exact solutions of the constant astigmatism equation {z}{yy}+{(1/z)}{xx}+2=0 from a given seed. A construction of corresponding surfaces of constant astigmatism is then a matter of routine. As a special case, we consider multisoliton solutions of the constant astigmatism equation defined as counterparts of famous multisoliton solutions of the sine-Gordon equation. A few particular examples are surveyed as well.

  16. On multisoliton solutions of the constant astigmatism equation

    OpenAIRE

    Hlaváč, Adam

    2015-01-01

    We introduce an algebraic formula producing infinitely many exact solutions of the constant astigmatism equation $ z_{yy} + ({1}/{z})_{xx} + 2 = 0 $ from a given seed. A construction of corresponding surfaces of constant astigmatism is then a matter of routine. As a special case, we consider multisoliton solutions of the constant astigmatism equation defined as counterparts of famous multisoliton solutions of the sine-Gordon equation. A few particular examples are surveyed as well.

  17. Perceptual Adaptation to the Correction of Natural Astigmatism

    OpenAIRE

    Vinas, Maria; Sawides, Lucie; de Gracia, Pablo; Marcos, Susana

    2012-01-01

    Background: The visual system adjusts to changes in the environment, as well as to changes within the observer, adapting continuously to maintain a match between visual coding and visual environment. We evaluated whether the perception of oriented blur is biased by the native astigmatism, and studied the time course of the after-effects following spectacle correction of astigmatism in habitually non-corrected astigmats. Methods and Findings: We tested potential shifts of the perceptual judgme...

  18. Propagation of Lissajous singularities through an astigmatic lens

    International Nuclear Information System (INIS)

    The analytical expression for the propagation of Lissajous singularities through an astigmatic lens is derived and used to study the dynamic evolution of Lissajous singularities after passing through the astigmatic lens and the dependence of Lissajous singularities on the control parameters where the effect of astigmatism of the lens is stressed. It is shown that motion, pair creation and annihilation, handedness reversal and change in the degree of polarization of Lissajous singularities may take place. In particular, a single Lissajous singularity may appear and vanish due to the presence of the astigmatic lens

  19. Selective suture cutting for control of astigmatism following cataract surgery

    OpenAIRE

    Bansal R; Gupta Amod; Grewal SPS

    1992-01-01

    Use of 10-0 monofilament nylon in ECCE cataract surgery leads to high with the rule astigmatism. Many intraoperative and post operative methods have been used to minimise post operative astigmatism. We did selective suture cutting in 38 consecutive patients. Mean keratometric astigmatism at three and six weeks post operative was 5.76 and 5.42 dioptres (D) respectively. 77.5% of eyes had astigmatism above 2 D. Selective suture cutting along the axis of the plus high cylinder was done af...

  20. Effect of pterygium excision on pterygium induced astigmatism.

    OpenAIRE

    Maheshwari Sejal

    2003-01-01

    Pterygium is known to affect refractive astigmatism, which can have a significant impact on vision. This study was undertaken to evaluate the effect of pterygium excision on refractive astigmatism. Thirty-six eyes with primary pterygium with astigmatism of 2D or more were analysed before and after pterygium excision. Astigmatism increased with the increase in the grade of pterygium (P = 0.000001). The preoperative refractive cylinder decreased from 4.60±2D to 2.20±2.04D (P = 0.0...

  1. The Impact of Pterygium Excision on Corneal Astigmatism

    International Nuclear Information System (INIS)

    Objective: To compare the corneal astigmatism before and after the excision of pterygium and also to determine the correlation of pterygium size with the postoperative corneal astigmatism. Study Design: Cross-sectional interventional study. Place and Duration of Study: Eye Department, Combined Military Hospital, Abbottabad, from May 2011 to March 2012. Methodology: Thirty patients underwent pterygium excision. Pre-operatively Snellen visual acuity, manifest refraction and slit lamp examination was done. The size of the pterygium was recorded in mm by projecting a horizontal slit lamp beam from the limbus to the apex. All the pterygium were equal to or greater than 2.5 mm. Keratometry was performed with an automated keratometer. Keratometric data was recorded pre-operatively and at 28 days postoperatively. Wilcoxon signed rank test was used for comparing the pre-operative and the postoperative corneal astigmatism. Spearman's rank order was calculated to observe correlation of pterygium size with the postoperative astigmatism. Results: The median (mean rank) pre-operative astigmatism of 2.25 (15.50) reduced to a median (mean rank) postoperative astigmatism of 1.30 (14.96). This decrease in the postoperative astigmatism was statistically significant (p < 0.001). There was a statistically non-significant correlation between the postoperative astigmatism and the pterygium size (rs = -0.29, p = 0.12). Conclusion: Pterygium excision caused significant reduction in corneal astigmatism. (author)

  2. Kerr-lens Mode Locking Without Nonlinear Astigmatism

    CERN Document Server

    Yefet, Shi; Pe'er, Avi

    2013-01-01

    We demonstrate a Kerr-lens mode locked folded cavity using a planar (non-Brewster) Ti:sapphire crystal as a gain and Kerr medium, thus cancelling the nonlinear astigmatism caused by a Brewster cut Kerr medium. Our method uses a novel cavity folding in which the intra-cavity laser beam propagates in two perpendicular planes such that the astigmatism of one mirror is compensated by the other mirror, enabling the introduction of an astigmatic free, planar-cut gain medium. We demonstrate that this configuration is inherently free of nonlinear astigmatism, which in standard cavity folding needs a special power specific compensation.

  3. Effect of pterygium excision on pterygium induced astigmatism.

    Directory of Open Access Journals (Sweden)

    Maheshwari Sejal

    2003-01-01

    Full Text Available Pterygium is known to affect refractive astigmatism, which can have a significant impact on vision. This study was undertaken to evaluate the effect of pterygium excision on refractive astigmatism. Thirty-six eyes with primary pterygium with astigmatism of 2D or more were analysed before and after pterygium excision. Astigmatism increased with the increase in the grade of pterygium (P = 0.000001. The preoperative refractive cylinder decreased from 4.60±2D to 2.20±2.04D (P = 0.00001 after pterygium excision.

  4. Polarization-based compensation of astigmatism

    Science.gov (United States)

    Chowdhury, Dola Roy; Bhattacharya, Kallol; Chakraborty, Ajay K.; Ghosh, Raja

    2004-02-01

    One approach to aberration compensation of an imaging system is to introduce a suitable phase mask at the aperture plane of an imaging system. We utilize this principle for the compensation of astigmatism. A suitable polarization mask used on the aperture plane together with a polarizer-retarder combination at the input of the imaging system provides the compensating polarization-induced phase steps at different quadrants of the apertures masked by different polarizers. The aberrant phase can be considerably compensated by the proper choice of a polarization mask and suitable selection of the polarization parameters involved. The results presented here bear out our theoretical expectation.

  5. Longitudinal Change and Stability of Refractive, Keratometric, and Internal Astigmatism in Childhood

    OpenAIRE

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

    2015-01-01

    Native American children from a tribe with a high prevalence of astigmatism show little change in astigmatism with age. Longitudinal data suggest that internal compensation for keratometric astigmatism may contribute to the stability of astigmatism in Tohono O'odham children.

  6. Treatment of corneal astigmatism with the new small-incision lenticule extraction (SMILE) laser technique: Is treatment of high degree astigmatism equally accurate, stable and safe as treatment of low degree astigmatism?

    OpenAIRE

    Hansen, Rasmus Søgaard; Grauslund, Jakob; Lyhne, Niels; Vestergaard, Anders Højslet

    2014-01-01

    Field: Ophthalmology Introduction: SMILE has proven effective in treatment of myopia and low degrees of astigmatism (less than 2 dioptres (D)), but there are no studies on treatment of high degrees of astigmatism (2 or more D). The aim of this study was to compare results after SMILE treatment for low or high degrees of astigmatism concerning accuracy, stability, and safety. Methods: Retrospective study of 1017 eyes treated with SMILE for myopia with low astigmatism or myopia with high astigm...

  7. Computation of power and astigmatism of rectangular pupil wavefront

    International Nuclear Information System (INIS)

    Least square method is used to fit power and astigmatism of rectangular pupil wavefront data, which avoids data interpolation of the blank area in circular domain. In the experiments, the maximal difference of power and astigmatism of circular domain data between commercial software and our method is less than 0.005 wavelength, which proves the proposed method's feasibility. For rectangular pupil wavefront data, the differences of astigmatism increase as the rectangle element's length-width ratio increases, Therefore the proposed method is more applicable for rectangular pupil wavefront calculation. (authors)

  8. Nonlocal conservation laws of the constant astigmatism equation

    OpenAIRE

    Hlaváč, Adam; Marvan, Michal

    2016-01-01

    For the constant astigmatism equation, we construct a system of nonlocal conservation laws (an abelian covering) closed under the reciprocal transformations. We give functionally independent potentials modulo a Wronskian type relation.

  9. The effects of lateral head tilt on ocular astigmatic axis

    Directory of Open Access Journals (Sweden)

    Hamid Fesharaki

    2014-01-01

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

  10. PRE OPERATIVE CORNEAL ASTIGMATISM IN PATIENTS WITH CATARACT

    OpenAIRE

    Venkateswara Rao; Hanumantha Rao; Sivacharan; Anitha Devi

    2015-01-01

    AIM: To determine corneal astigmatism in patients with cataract posted for surgery. To achieve good visual outcome, significant corneal astigmatism has to be taken care of at the time of surgery either by corneal or limba l relaxing incisions or by implantation of toric intraocular lens. MATERIALS AND METHODS: This is a prospective observational case series conducted on 200 patients with cataract who attended the out - patient department of ophthalmology and c...

  11. CORNEAL ASTIGMATISM AFTER MANUAL SMALL INCISION CATARACT SURGERY

    OpenAIRE

    Rajni; Mohd Ayaz; Pallvi; Syed Tariq

    2014-01-01

    INTRODUCTION: Cataract is the leading cause of preventable blindness in India. Manual Small Incision Cataract Surgery is still the preferred method of cataract surgery because of its low cost and non-dependence on costly equipments. Postoperatively astigmatism is an important cause of poor uncorrected visual acuity after cataract surgery. Purpose: The purpose of this study was to assess corneal astigmatism in manual small incision cataract surgery in superior versus temporal ...

  12. Decoupling of coherent gaussian beams with general astigmatism

    OpenAIRE

    Serna Galán, Julio; Nemes, George

    1993-01-01

    We show how to decouple a coherent Gaussian beam having general astigmatism (to transform it into a beam having only simple astigmatism, or orthogonal symmetry) by using a single rotated thin cylindrical lens. The resulting coherent orthogonal Gaussian beam may be further transformed into a stigmatic (rotationally symmetric) Gaussian beam by an orthogonal telescopic magnifier. The initial beam parameters must be known; we suggest a procedure for their measurement.

  13. Corneal irregular astigmatism after laser in situ keratomileusis for myopia

    OpenAIRE

    Baek, T. M.; K. H. Lee; Tomidokoro, A; Oshika, T

    2001-01-01

    AIMS—To quantitatively evaluate the changes in corneal irregular astigmatism after laser in situ keratomileusis (LASIK) in relation to the amount of laser ablation.
METHODS—In 189 eyes of 116 patients undergoing LASIK for myopia, corneal topography was obtained before and 1 month after surgery. Using Fourier harmonic analysis of the topography data, corneal irregular astigmatism (asymmetry and higher order irregularity) was calculated.
RESULTS—By surgery, asymmetry component significantly inc...

  14. Development and Treatment of Astigmatism-Related Amblyopia

    OpenAIRE

    Harvey, Erin M.

    2009-01-01

    Blur induced by uncorrected astigmatism during early development can result in amblyopia, as evidenced by reduced best-corrected vision relative to normal, in measures of grating acuity, vernier acuity, contrast sensitivity across a range of spatial frequencies, recognition acuity, and stereoacuity. In addition, uncorrected astigmatism during early development can result in meridional amblyopia (MA), or best-corrected visual deficits that are greater for, or are present only for, specific sti...

  15. Suturing technique for control of postkeratoplasty astigmatism and myopia.

    OpenAIRE

    Dursun, Dilek; Forster, Richard K.; Feuer, William J.

    2002-01-01

    PURPOSE: We previously demonstrated that selective suture removal reduces keratoplasty astigmatism; however, a myopic shift was induced with increasing number of interrupted sutures removed. This study is an attempt to determine the effects of a modified surgical technique on postkeratoplasty myopia, astigmatism, and anisometropia. METHODS: Optical penetrating keratoplasties were performed on 92 eyes of 84 patients. The study group consisted of 92 consecutive penetrating keratoplasties perfor...

  16. Laser intrastromal keratomileusis for high myopia and myopic astigmatism

    OpenAIRE

    Condon, P; Mulhern, M; Fulcher, T.; Foley-Nolan, A; O'Keefe, M.

    1997-01-01

    BACKGROUND—Laser intrastromal keratomileusis (LASIK) is an evolving technique which enables high degrees of myopia (>8.0 dioptres) and myopic astigmatism to be corrected. This paper describes initial experience with this procedure. It also details the methodology, the results, the problems encountered, and discusses retreatment procedures.
METHODS—51 eyes (48 primary cases and three retreatments) underwent LASIK for simple myopia or compound myopic astigmatism. After the keratotomy was fashio...

  17. Comparative study of surgically induced astigmatism in superior versus temporal incision in small incision cataract surgery case

    Directory of Open Access Journals (Sweden)

    Kuruva Nandyala Sree Kavitha

    2015-11-01

    Conclusions: Placement of incision on steep axis reduces pre-existing astigmatism. Thus in ATR astigmatism it is placed temporally and in WTR astigmatism it is placed superiorly. Thus a simple modification in incision placement can minimize surgically induced astigmatism and reduce pre-existing astigmatism [Int J Res Med Sci 2015; 3(11.000: 3027-3031

  18. CORNEAL ASTIGMATISM AFTER MANUAL SMALL INCISION CATARACT SURGERY

    Directory of Open Access Journals (Sweden)

    Rajni

    2014-11-01

    Full Text Available INTRODUCTION: Cataract is the leading cause of preventable blindness in India. Manual Small Incision Cataract Surgery is still the preferred method of cataract surgery because of its low cost and non-dependence on costly equipments. Postoperatively astigmatism is an important cause of poor uncorrected visual acuity after cataract surgery. Purpose: The purpose of this study was to assess corneal astigmatism in manual small incision cataract surgery in superior versus temporal incision. MATERIALS AND METHODS: A total of 100 patients were included in our study. 50 patients received superior incision and 50 patients received temporal incision. Surgically induced astigmatism was calculated in these patients postoperatively. RESULTS: We observed mean 1.16 D of surgically induced astigmatism in patients with superior incision and mean 0.62 D of astigmatism in patients with temporal incision at the end of 12th postoperative week. CONCLUSION: The results of the present study showed a favourable influence of temporal incision over superior incision in manual incision cataract surgery in terms of surgically induced astigmatism.

  19. Treatment of corneal astigmatism with the new small-incision lenticule extraction (SMILE) laser technique: Is treatment of high degree astigmatism equally accurate, stable and safe as treatment of low degree astigmatism?

    DEFF Research Database (Denmark)

    Hansen, Rasmus Søgaard; Grauslund, Jakob; Lyhne, Niels; Vestergaard, Anders Højslet

    Field: Ophthalmology Introduction: SMILE has proven effective in treatment of myopia and low degrees of astigmatism (less than 2 dioptres (D)), but there are no studies on treatment of high degrees of astigmatism (2 or more D). The aim of this study was to compare results after SMILE treatment for...... low or high degrees of astigmatism concerning accuracy, stability, and safety. Methods: Retrospective study of 1017 eyes treated with SMILE for myopia with low astigmatism or myopia with high astigmatism from 2011-2013 at the Department of Ophthalmology, Odense University Hospital, Denmark. Inclusion...... criteria were: Best spectacle-corrected visual acuity (BSCVA) of 20/25 or better on Snellen chart, and no other ocular condition than myopia with or without astigmatism. Results: In total 660 eyes completed the 3 months follow-up examination, in which 536 eyes had pre-operatively low astigmatism (mean...

  20. Astigmatism induced by conventional spherical ablation after PRK and LASIK in myopia with astigmatism < 1.00 D

    OpenAIRE

    Christiansen, Steven

    2012-01-01

    Steven M Christiansen,1 Mark D Mifflin,1 Jason N Edmonds,1 Rachel G Simpson,2 Majid Moshirfar11John A Moran Eye Center, University of Utah, Salt Lake City, UT, 2The University of Arizona College of Medicine, Phoenix, AZ, USABackground: The purpose of this study was to evaluate surgically-induced astigmatism after spherical ablation in photorefractive keratectomy (PRK) and laser-assisted in situ keratomileusis (LASIK) for myopia with astigmatism < 1.00 D.Methods: The charts of patients ...

  1. Astigmatism induced by conventional spherical ablation after PRK and LASIK in myopia with astigmatism < 1.00 D

    Directory of Open Access Journals (Sweden)

    Christiansen SM

    2012-12-01

    Full Text Available Steven M Christiansen,1 Mark D Mifflin,1 Jason N Edmonds,1 Rachel G Simpson,2 Majid Moshirfar11John A Moran Eye Center, University of Utah, Salt Lake City, UT, 2The University of Arizona College of Medicine, Phoenix, AZ, USABackground: The purpose of this study was to evaluate surgically-induced astigmatism after spherical ablation in photorefractive keratectomy (PRK and laser-assisted in situ keratomileusis (LASIK for myopia with astigmatism < 1.00 D.Methods: The charts of patients undergoing spherical PRK or LASIK for the correction of myopia with minimal astigmatism of <1.00 D from 2002 to 2012 at the John A Moran Eye Center in Salt Lake City, UT, were retrospectively reviewed. Astigmatism was measured by manifest refraction. The final astigmatic refractive outcome at 6 months postoperatively was compared with the initial refraction by Alpins vector analysis.Results: For PRK, average cylinder increased from 0.39 ± 0.25 (0.00–0.75 preoperatively to 0.55 ± 0.48 (0.00–1.75 postoperatively (P = 0.014, compared with an increase in LASIK eyes from 0.40 ± 0.27 (0.00–0.75 preoperatively to 0.52 ± 0.45 (0.00–2.00 postoperatively (P = 0.041. PRK eyes experienced an absolute value change in cylinder of 0.41 ± 0.32 (0.00–1.50 and LASIK eyes experienced a change of 0.41 ± 0.31 (0.00–1.50, P = 0.955. Mean surgically-induced astigmatism was 0.59 ± 0.35 (0.00–1.70 in PRK eyes, with an increase in surgically-induced astigmatism of 0.44 D for each additional 1.00 D of preoperative cylinder; in LASIK eyes, mean surgically-induced astigmatism was 0.55 ± 0.32 (0.00–1.80, P = 0.482, with an increase in surgically-induced astigmatism of 0.29 D for each 1.00 D of preoperative cylinder.Conclusion: Spherical ablation can induce substantial astigmatism even in eyes with less than one diopter of preoperative astigmatism in both PRK and LASIK. No significant difference in the magnitude of surgically-induced astigmatism was found between eyes

  2. Goos-H\\"anchen and Imbert-Fedorov shifts for astigmatic Gaussian beams

    CERN Document Server

    Ornigotti, Marco

    2015-01-01

    In this work we investigate the role of the beam astigmatism in the Goos-H\\"anchen and Imbert-Fedorov shift. As a case study, we consider a Gaussian beam focused by an astigmatic lens and we calculate explicitly the corrections to the standard formulas for beam shifts due to the astigmatism induced by the lens. Our results show that astigmatism may enhance the angular part of the shift.

  3. Goos-Hänchen and Imbert-Fedorov shifts for astigmatic Gaussian beams

    Science.gov (United States)

    Ornigotti, Marco; Aiello, Andrea

    2015-06-01

    In this work we investigate the role of the beam astigmatism in the Goos-Hänchen and Imbert-Fedorov shift. As a case study, we consider a Gaussian beam focused by an astigmatic lens and we calculate explicitly the corrections to the standard formulas for beam shifts due to the astigmatism induced by the lens. Our results show that the different focusing in the longitudinal and transverse direction introduced by an astigmatic lens may enhance the angular part of the shift.

  4. STUDY OF ASTIGMATISM IN SMALL INCISSION CATARACT SURGERY BETWEEN TEMPORAL AND SUPERIOR INCISSIONS

    Directory of Open Access Journals (Sweden)

    Sivacharan

    2014-10-01

    Full Text Available Surgically induced astigmatism is a part of cataract surgery. Surgically induced astigmatism varies with distance the incision is made from limbus and site of incision. Small incision cataract surgery a suturless technique of cataract surgery can be done through both temporal and superior sclerocorneal incisions. Since majority of patients undergoing cataract surgery have an against the rule astigmatism, a temporal sclerocorneal incision is better than superior sclera incisions in respect to astigmatism.

  5. Astigmatism and visual recovery after 'large incision' extracapsular cataract surgery and 'small' incisions for phakoemulsification.

    OpenAIRE

    Zheng, L; Merriam, J C; Zaider, M

    1997-01-01

    PURPOSE: This study compares the change over time of the astigmatism caused by "large" incision extracapsular cataract extraction (ECCE) and three smaller incisions for phakoemulsification. Based on this data, a mathematical model that predicts the course of astigmatism after a superior incision of length 3 to 12 mm has been developed. The relationship of axial length and preoperative astigmatism to induced post-operative astigmatism, the recovery of visual acuity, and the rate of YAG laser c...

  6. Astigmatic intensity equation for electron microscopy based phase retrieval

    International Nuclear Information System (INIS)

    Phase retrieval, in principle, can be performed in a transmission electron microscope (TEM) using arbitrary aberrations of electron waves; provided that the aberrations are well-characterised and known. For example, the transport of intensity equation (TIE) can be used to infer the phase from a through-focus series of images. In this work an 'astigmatic intensity equation' (AIE) is considered, which relates phase gradients to intensity variations caused by TEM objective lens focus and astigmatism variations. Within the paraxial approximation, it is shown that an exact solution of the AIE for the phase can be obtained using efficient Fourier transform methods. Experimental requirements for using the AIE are the measurement of a through-focus derivative and another intensity derivative, which is taken with respect to objective lens astigmatism variation. Two quasi-experimental investigations are conducted to test the validity of the solution

  7. Optical vortex trajectories in an astigmatic and elliptical Gaussian beam

    CERN Document Server

    Roux, F S

    2006-01-01

    An optical vortex, produced at one point in an optical beam, would propagate through an optical system to another point where the vortex can be used for some purpose. However, asymmetrical optical elements in such a system can cause astigmatism or at least distroy the rotational symmetry of the beam, which may affect the propagation of the vortex in an undesirable way. While an optical vortex in a rotationally symmetric, stigmatic Gaussian beam retains its initial morphology for as far as it propagates, the morphology of an optical vortex in an asymmetric or astigmatic Gaussian beam changes. The vortex can even be replaced by another with the opposite topological charge. We consider the behavior of single noncanonical vortices propagating in Gaussian beams that are asymmetric and/or astigmatic. General expressions for the vortex trajectories are provided. The locations of the flip planes and the evolution of the anisotropy of the vortex are considered for different non-ideal situations.

  8. Quasi-Bessel beams from asymmetric and astigmatic illumination sources.

    Science.gov (United States)

    Müller, Angelina; Wapler, Matthias C; Schwarz, Ulrich T; Reisacher, Markus; Holc, Katarzyna; Ambacher, Oliver; Wallrabe, Ulrike

    2016-07-25

    We study the spatial intensity distribution and the self-reconstruction of quasi-Bessel beams produced from refractive axicon lenses with edge emitting laser diodes as asymmetric and astigmatic illumination sources. Comparing these to a symmetric mono-mode fiber source, we find that the asymmetry results in a transition of a quasi-Bessel beam into a bow-tie shaped pattern and eventually to a line shaped profile at a larger distance along the optical axis. Furthermore, we analytically estimate and discuss the effects of astigmatism, substrate modes and non-perfect axicons. We find a good agreement between experiment, simulation and analytic considerations. Results include the derivation of a maximal axicon angle related to astigmatism of the illuminating beam, impact of laser diode beam profile imperfections like substrate modes and a longitudinal oscillation of the core intensity and radius caused by a rounded axicon tip. PMID:27464190

  9. Solutions for stability and astigmatism in high power laser resonators

    Science.gov (United States)

    Narro, R.; Arronte, M.; de Posada, E.; Ponce, L.; Rodríguez, E.

    2009-09-01

    A method is proposed for the design of fundamental mode high power resonators, with joined stability zones. A parameter is created which gives the minimum length a laser resonator should have while having at the same time the broadest stabilities zones. For multimode and large mode volume resonators, a configuration is introduced for maximizing the laser overall efficiency due to the compensation of the astigmatism induced by the flash lamp pumping heating. The later configuration proposes a dual-active medium resonator, with 90 degree rotation around the optical axis between the astigmatic thermal lenses of the mediums. The reliability of this configuration is corroborated experimentally using a Nd:YAG dual-active medium resonator. It is found that in the pumping power range where the astigmatism compensation is possible, the overall efficiency is constant, even when increasing the excitation power with the consequent increase of the thermal lens dioptric power.

  10. Impact of astigmatism and high-order aberrations on subjective best focus.

    Science.gov (United States)

    Marcos, Susana; Velasco-Ocana, Miriam; Dorronsoro, Carlos; Sawides, Lucie; Hernandez, Martha; Marin, Gildas

    2015-08-01

    We studied the role of native astigmatism and ocular aberrations on best-focus setting and its shift upon induction of astigmatism in 42 subjects (emmetropes, myopes, hyperopes, with-the-rule [WTR] and against-the-rule [ATR] myopic astigmats). Stimuli were presented in a custom-developed adaptive optics simulator, allowing correction for native aberrations and astigmatism induction (+1 D; 6-mm pupil). Best-focus search consisted on randomized-step interleaved staircase method. Each subject searched best focus for four different images, and four different conditions (with/without aberration correction, with/without astigmatism induction). The presence of aberrations induced a significant shift in subjective best focus (0.4 D; p astigmatism produced a statistically significant shift of the best-focus setting in all groups under natural aberrations (p = 0.001), and in emmetropes and in WTR astigmats under corrected aberrations (p induced astigmatism was significantly different across groups, both for natural aberrations and AO-correction (p astigmats upon induction of astigmatism, symmetrically with respect to the best-focus shift in nonastigmatic myopes. The shifts are consistent with a bias towards vertical and horizontal retinal blur in WTR and ATR astigmats, respectively, indicating adaptation to native astigmatism. PMID:26237300

  11. Astigmatism correction in cataract surgery with Rayner toric intraocular lenses

    OpenAIRE

    Painter, Sally

    2010-01-01

    Sally L Painter, Kikkeri S Arun, Jonathan K Kam, CK PatelOxford Eye Hospital, John Radcliffe Hospital, Headley Way, Headington, Oxford, United KingdomBackground: Cataract surgery is increasingly regarded as a refractive procedure. Corneal astigmatism can be reduced by the insertion of a toric intraocular lens (T-IOL). Rayner T-flex T-IOLs are licensed for the correction of astigmatism.Methods: In this retrospective study, 46 eyes from 34 patients, in whom T-IOLs were inserted, have been exami...

  12. Higher Order Aberration and Astigmatism in Children with Hyperopic Amblyopia

    OpenAIRE

    Choi, Seung Kwon; Chang, Ji Woong

    2016-01-01

    Purpose To investigate the changes in corneal higher-order aberration (HOA) during amblyopia treatment and the correlation between HOA and astigmatism in hyperopic amblyopia children. Methods In this retrospective study, a total of 72 eyes from 72 patients ranging in age from 38 to 161 months were included. Patients were divided into two groups based on the degree of astigmatism. Corneal HOA was measured using a KR-1W aberrometer at the initial visit and at 3-, 6-, and 12-month follow-ups. Co...

  13. LASIK for post penetrating keratoplasty astigmatism and myopia

    OpenAIRE

    Webber, S.; Lawless, M; Sutton, G; Rogers, C.

    1999-01-01

    AIMS—To report the results of a series of patients who were treated with LASIK to correct post penetrating keratoplasty ametropia.
METHODS—26 eyes of 24 patients underwent LASIK to correct astigmatism and myopia after corneal transplantation; 14 eyes also received arcuate cuts in the stromal bed at the time of surgery. The mean preoperative spherical equivalent was −5.20D and the mean preoperative astigmatism was 8.67D.
RESULTS—The results of 25 eyes are reported. The mean 1 month values for ...

  14. An Astigmatic Detection System for Polymeric Cantilever-based Sensors

    DEFF Research Database (Denmark)

    Hwu, En-Te; Liao, Hsien-Shun; Bosco, Filippo; Chen, Ching-Hsiu; Keller, Stephan Sylvest; Boisen, Anja; Huang, Kuang-Yuh

    2012-01-01

    We demonstrate the use of an astigmatic detection system (ADS) for resonance frequency identification of polymer microcantilever sensors. The ADS technology is based on a DVD optical head combined with an optical microscope (OM). The optical head has a signal bandwidth of 80 MHz, allowing thermal...

  15. Defocus and twofold astigmatism correction in HAADF-STEM

    Energy Technology Data Exchange (ETDEWEB)

    Rudnaya, M.E., E-mail: m.rudnaya@tue.nl [CASA, Department of Mathematics and Computer Science, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven (Netherlands); Van den Broek, W. [EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp (Belgium); Doornbos, R.M.P. [Embedded Systems Institute, PO Box 513, 5600 MB Eindhoven (Netherlands); Mattheij, R.M.M.; Maubach, J.M.L. [CASA, Department of Mathematics and Computer Science, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven (Netherlands)

    2011-07-15

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

  16. Astigmatism and coma-free prism dye ring laser

    International Nuclear Information System (INIS)

    The characteristics of two prism ring lasers for cw operation have been experimentally studied. With improved compensation for aberrations due to astigmatism and coma, cw ring lasers operated in the traveling-wave mode provide high output efficiency, stable narrow bandwidth in multimode and single-mode operation, and a broad tuning range

  17. Corneal shape and astigmatism: with a note on myopia.

    OpenAIRE

    Weale, R A

    1988-01-01

    The elliptical shape and the physiological astigmatism of the normal neonatal human cornea are attributed to the ellipsoidal shape of the eyeball. This in turn is a feature of ocular development. The analysis is used to examine earlier observations on myopia.

  18. Defocus and twofold astigmatism correction in HAADF-STEM

    International Nuclear Information System (INIS)

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

  19. ASTIGMATISM IN PRIMARY PTERYGIUM AND ITS EFFECT ON VISUAL ACUITY

    Directory of Open Access Journals (Sweden)

    Devika

    2015-09-01

    Full Text Available BACKGROUND: Pterygium is a fairly common condition in a tropical country like India with average incidence being 5.2%. Surgery being offered as a treatment for pterygium does not, at present, have a universally accepted indication based on the size. This study was done to make an attempt to define the indication for surgical exicision of pterygium. AIMS: To find out an association between increasing size of pterygium and degree of induced corneal astigmatism and to assess if corneal astigmatism induced by pterygium affects best corrected visual acuity (BCVA and thus making it an indication for pterygium excision surgery. SETTINGS AND DESIGN: Hospital Out Patient Departmen t (OPD based prospective clinical cross sectional study on patients with unilateral pterygium. METHODS AND MATERIAL : 33 patients were included in this study who had unilateral pterygium of varying sizes. Evaluation was done using slit - lamp beam for size o f pterygium in millimetre from the limbus, ketatometry using Bausch and Lomb keratometer, autorefractometer objective refraction readings, visual acuity and BCVA using Snellens chart. STATISTICAL ANALYSIS USED: Chi - square - test, Karl - Pearson correlation coe fficient, Kruskal - Wallis - co - efficient using SPSS statistics 22.0 . RESULTS: 33 people having unilateral pterygium were divided into three groups on the basis of size of the pterygium - ≤2mm, 2.1 - 3mm, >3mm. The co - relation coefficient between the astigmatism induced to BCVA was maximum for the 3rd group with pterygium size >3mm and was statistically significant. CONCLUSION: Pterygium induces ‘with the rule’ astigmatism. Surgery is indicated in patients of pterygium size >3mm as the astigmatism induced affects the BCVA

  20. Success rates in the correction of astigmatism with toric and spherical soft contact lens fittings

    Directory of Open Access Journals (Sweden)

    Sevda Aydin Kurna

    2010-08-01

    Full Text Available Sevda Aydin Kurna, Tomris Şengör, Murat Ün, Suat AkiFatih Sultan Mehmet Education and Research Hospital, Ophthalmology Clinics, lstanbul, TurkeyObjectives: To evaluate success rates in the correction of astigmatism with toric and spherical soft contact lens fitting.Methods: 30 patients with soft toric lenses having more than 1.25 D of corneal astigmatism (25 eyes; Group A or having 0.75–1.25 D of corneal astigmatism (22 eyes; Group B and 30 patients with soft spheric lenses having 0.75–1.25 D of corneal astigmatism (28 eyes; Group C or less than 0.75 D of corneal astigmatism (23 eyes; Group D were included in the study. Corrected and uncorrected monocular visual acuity measurement with logMAR, biomicroscopic properties, autorefractometry and corneal topography were performed for all patients immediately before and at least 20 minutes after the application of contact lenses. ­Success of contact lens fitting was evaluated by three parameters: astigmatic neutralization, visual success, and retinal deviation.Results: After soft toric lens application, spheric dioptres, cylindric and keratometric astigmatism, and retinal deviation decreased significantly in Groups A and B (P < 0.05. In Group C, spheric dioptres and retinal deviation decreased (P < 0.05, while cylindric and keratometric astigmatism did not change significantly (P > 0.05. In Group D, spheric dioptres, retinal deviation, and cylindric astigmatism decreased (P < 0.05. Keratometric astigmatism did not change significantly (P > 0.05 and astigmatic neutralization even increased.Conclusions: Visual acuity and residual spherical equivalent refraction remained between tolerable limits with the use of toric and spheric contact lenses. Spherical lenses failed to mask corneal toricity during topography, while toric lenses caused central neutralization and decrease in corneal cylinder in low and moderate astigmatic eyes.Keywords: astigmatism, soft toric lenses, soft spheric lenses

  1. Simple scheme for the astigmatic transformation of laser modes

    International Nuclear Information System (INIS)

    A simple astigmatic scheme for obtaining focused Laguerre-Gaussian beams upon the π/2 conversion of Hermite-Gaussian radiation modes is described. A zone in the vicinity of the focal region of a lens is estimated where the beam satisfies the conditions for the capture and confinement of microparticles. It is shown that this optical scheme uses the fractional Fourier transform, whose application in the π/2 converter is demonstrated for the first time. (control of laser radiation parameters)

  2. Lagrangian and Hamiltonian structures for the constant astigmatism equation

    International Nuclear Information System (INIS)

    In this paper we found a Lagrangian representation and corresponding Hamiltonian structure for the constant astigmatism equation. Utilizing this Hamiltonian structure and extra conservation law densities we construct a first evolution commuting flow of the third order. We also apply the recursion operator and present a second Hamiltonian structure. This bi-Hamiltonian structure allows us to replicate infinitely many local commuting flows and corresponding local conservation law densities. (paper)

  3. Astigmatic Changes after Horizontal Rectus Muscle Surgery in Intermittent Exotropia

    OpenAIRE

    Hong, Seung Woo; Kang, Nam Yeo

    2012-01-01

    Purpose To evaluate the changes of refractive astigmatism after horizontal rectus muscle surgery in intermittent exotropic children. Methods Sixty-nine exotropic patients were retrospectively reviewed. Of those, 35 patients received unilateral lateral rectus recession (BLR group, 35 eyes) and 34 patients received unilateral lateral rectus recession and medial rectus resection (R&R group, 34 eyes). Non-cycloplegic refractions were measured until 6 months postoperatively. Spherical equivalent (...

  4. Stability properties of a rotating astigmatic optical cavity

    Science.gov (United States)

    Habraken, Steven J. M.; Nienhuis, Gerard

    2009-02-01

    We study the effects of rotation on the stability properties of an astigmatic two-mirror cavity. We show that rotation can both stabilize and destabilize a cavity and investigate the effects of such a rotationally-induced transition on the spatial structure and the orbital angular momentum of the cavity modes. Our method relies on the connection between ray and wave optics and is exact within the time-dependent paraxial approximation.

  5. Surgically Induced Corneal Astigmatism Following Intravitreal Ranibizumab Injection

    OpenAIRE

    Kocatürk, Tolga; Erkan, Erol; Eğrilmez, Sait; Çakmak, Harun; Dündar, Sema O.; Dayanir, Volkan

    2015-01-01

    Purpose : To evaluate surgically induced astigmatism (SIA) after an intravitreal ranibizumab (IVR) injection. Methods : Fifty eight eyes of 58 patients who underwent IVR injection due to age-related macular degeneration (wet form) or macular edema were included in this study. Patients’ pre- and postoperative detailed ophthalmologic examinations were done and topographic keratometric values (K1, K2) were noted. Pre- and postoperative measurements were compared. Results : The mean preoperative ...

  6. Development of the fast astigmatic auto-focus microscope system

    International Nuclear Information System (INIS)

    In this paper, a fast auto-focus microscope system was developed based on the astigmatic method. A collimated infrared laser beam was employed in the infinite-corrected microscope optical axis by the beam splitter and reflected by the sample surface. By embedding an astigmatic lens in the system, the reflected laser beam has different focal lengths in the sagittal and tangential planes. As the microscope's relative distance varies, the reflected laser beam shape also varies and can be detected by an embedded four-quadrant photodiode, i.e., the focus error signal (FES) can be found. Then, a fast auto-focus system can be realized by converting the FES to the microscope's defocus distance. We designed an astigmatic auto-focus system for a 20× objective lens with a ±50 µm working range, and this system could also be used for 10× and 5× objectives with ±200 µm and ±800 µm working ranges, respectively

  7. Alignment of two mirror astronomical telescopes (the astigmatic component)

    Science.gov (United States)

    Schmid, Tobias; Thompson, Kevin; Rolland, Jannick

    2008-07-01

    The effects of alignment perturbations on the aberration fields of two mirror astronomical telescopes are discussed. It is demonstrated that expressions describing alignment induced field-linear astigmatism, published by McLeod based on the work of Schroeder, can be obtained using nodal aberration theory. Rather than merely providing a different derivation for alignment induced astigmatism, it is shown that nodal theory can provide several insights that are significant for the development of effective alignment techniques. In the example of a specific telescope sited on Mt. Hopkins (Ritchey- Chretien), two approaches to identify misalignments of the secondary mirror are demonstrated. One approach utilizes the eccentricity of defocused star images and their orientation angles to calculate the misalignment of the secondary mirror after axial coma is removed. A second approach based on the location of the two zeros of the astigmatic aberration field is then shown to give equivalent results, but at the same time ensuring a complete model of all possible effects of misalignment on the performance of the telescope.

  8. A COMPARISON OF SURGICAL INDUCED ASTIGMATISM FOLLOWING PHACOEMULSIFICATION WITH CLEAR CORNEAL VERSUS SCLERAL INCISION

    Directory of Open Access Journals (Sweden)

    Satyavardhana Rao

    2015-11-01

    Full Text Available The present study included 50 Cases, Group-1- 25 Cases, underwent Temporal Sclera incision phacoemulsification, Group-2: 25 Cases underwent temporal clear corneal incision phacoemulsification. Out of this majority of the cases with scleral incision Group showed an surgically induced astigmatism of 0.5 D(56%, in clear corneal group 40% showed 0.5 D and 32% showed 0.75 D of Surgically induced astigmatism. The mean surgically induced astigmatism in scleral incision Group was 0.550.28 and in clear corneal group 0.690.25. In both the cases there is decrease in pre-operative against the rule astigmatism to Post–Operative against the rule astigmatism and an increase in with the rule astigmatism from Pre-Operative to Post–Operative period, but this is seen more with clear corneal incision group compared to scleral incision group.

  9. Minimizing Surgically Induced Astigmatism at the Time of Cataract Surgery Using a Square Posterior Limbal Incision

    OpenAIRE

    Richard Potvin; Paul Ernest; Warren Hill

    2011-01-01

    Purpose. To compare the surgically induced astigmatism from clear corneal and square posterior limbal incisions at the time of cataract surgery. Methods. Surgically induced astigmatism was calculated for a set of eyes after cataract surgery using a temporal 2.2 mm square posterior limbal incision. Results were compared to similar available data from surgeons using clear corneal incisions of similar size. Results. Preoperative corneal astigmatism averaged 1.0 D and was not significantly differ...

  10. The Effect of Different Suturing Techniques on Astigmatism after Penetrating Keratoplasty

    OpenAIRE

    Kim, Sang Jin; Wee, Won Ryang; Lee, Jin Hak; Kim, Mee Kum

    2008-01-01

    The purpose of this study was to compare the effects on astigmatism after penetrating keratoplasty with three different suture techniques. In this prospective study, 38 eyes of 38 patients underwent penetrating keratoplasty with three suturing techniques: interrupted, single running, and double running. Topographic astigmatism was measured at 2, 6, 12, and 18 months after keratoplasty. During 18 months after surgery, the interrupted suture group had higher astigmatism than the double running ...

  11. STUDY OF ASTIGMATISM IN SMALL INCISSION CATARACT SURGERY BETWEEN TEMPORAL AND SUPERIOR INCISSIONS

    OpenAIRE

    Sivacharan; Hanumantharao

    2014-01-01

    Surgically induced astigmatism is a part of cataract surgery. Surgically induced astigmatism varies with distance the incision is made from limbus and site of incision. Small incision cataract surgery a suturless technique of cataract surgery can be done through both temporal and superior sclerocorneal incisions. Since majority of patients undergoing cataract surgery have an against the rule astigmatism, a temporal sclerocorneal incision is better than superior sclera incision...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-12-31

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

  13. Correction of high amounts of astigmatism through orthokeratology. A case report

    OpenAIRE

    Baertschi, Michael; Wyss, Michael

    2010-01-01

    The purpose of this case report is to introduce a method for a successful treatment of high astigmatism with a new orthokeratology design, called FOKX (Falco Kontaktlinsen, Switzerland). This novel toric orthokeratology contact lens design, the fitting approach and the performance of FOKX lenses will be illustrated in the form of a case report. Correcting astigmatism with orthokeratology offers a new perspective for all patients suffering astigmatism.

  14. A COMPARISON OF SURGICAL INDUCED ASTIGMATISM FOLLOWING PHACOEMULSIFICATION WITH CLEAR CORNEAL VERSUS SCLERAL INCISION

    OpenAIRE

    Satyavardhana Rao

    2015-01-01

    The present study included 50 Cases, Group-1- 25 Cases, underwent Temporal Sclera incision phacoemulsification, Group-2: 25 Cases underwent temporal clear corneal incision phacoemulsification. Out of this majority of the cases with scleral incision Group showed an surgically induced astigmatism of 0.5 D(56%), in clear corneal group 40% showed 0.5 D and 32% showed 0.75 D of Surgically induced astigmatism. The mean surgically induced astigmatism in scleral incision Group was 0.5...

  15. Astigmatism-corrected Czerny-Turner imaging spectrometer for broadband spectral simultaneity

    International Nuclear Information System (INIS)

    A low-cost, broadband, astigmatism-corrected Czerny-Turner arrangement with a fixed plane grating is proposed. A wedge cylindrical lens is used to correct astigmatism over a broadband spectral range. The principle and method of astigmatism correction are described in detail. We compare the performance of this modified Czerny-Turner arrangement with that of the traditional Czerny-Turner arrangement by using a practical Czerny-Turner imaging spectrometer example.

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

    International Nuclear Information System (INIS)

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

  17. Astigmatism-corrected Czerny-Turner imaging spectrometer for broadband spectral simultaneity

    Energy Technology Data Exchange (ETDEWEB)

    Xue Qingsheng

    2011-04-01

    A low-cost, broadband, astigmatism-corrected Czerny-Turner arrangement with a fixed plane grating is proposed. A wedge cylindrical lens is used to correct astigmatism over a broadband spectral range. The principle and method of astigmatism correction are described in detail. We compare the performance of this modified Czerny-Turner arrangement with that of the traditional Czerny-Turner arrangement by using a practical Czerny-Turner imaging spectrometer example.

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

    Science.gov (United States)

    Dergachev, A. A.; Ionin, A. A.; Kandidov, V. P.; Mokrousova, D. V.; Seleznev, L. V.; Sinitsyn, D. V.; Sunchugasheva, E. S.; Shlenov, S. A.; Shustikova, A. P.

    2014-12-01

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

  19. Properties of elementary astigmatic pencils of rays in a decentered optical system

    International Nuclear Information System (INIS)

    Properties of elementary astigmatic pencils of rays of an optical system with small decentering are formulated using the technique based on translating astigmatism from the intermediate space of the optical system to the space of images. The results obtained are not limited by the approximations based on expansions in series and are valid for decentering-caused astigmatism of an arbitrary order. The necessity of calculating at least two elementary pencils of rays when analyzing the effect of decenterings on the astigmatism is proved. 5 refs., 3 figs

  20. Reduction in astigmatism in manual small incision cataract surgery through change of incision site

    OpenAIRE

    Gokhale Nikhil; Sawhney Saurabh

    2005-01-01

    To compare the astigmatism induced by a superior, supero-temporal and temporal incision in manual small incision cataract surgery. Induced astigmatism was analysed by Cartesian coordinates based analysis, using Holladay′s system. Mean astigmatism induced by surgery was 1.28 D x 2.9 degrees for superior incision, 0.20 D x 23.7 degrees for supero-temporal incision and 0.37 D x 90 degrees for temporal incision. The study found that induced astigmatism was lower in the temporal and super...

  1. Postoperative Astigmatic Outcomes Based on the Haptic Axis of Intraocular Lenses Inserted in Cataract Surgery

    OpenAIRE

    Kim, In-Tae; Park, Hae-Young Lopilly; Kim, Hyun-Seung

    2011-01-01

    Purpose This study was conducted to compare post-operative astigmatic outcomes of two groups, with-the-rule (WTR) and against-the-rule (ATR) astigmatism patients, according to the haptic axis of intraocular lenses (IOLs) inserted in cataract surgery. Methods Seventy-two eyes with WTR astigmatism and 79 eyes with ATR astigmatism had cataract surgery through a clear corneal temporal incision. These two groups of eyes were then each divided into 2 groups based on whether the haptic axis of the i...

  2. Reduction in astigmatism in manual small incision cataract surgery through change of incision site

    Directory of Open Access Journals (Sweden)

    Gokhale Nikhil

    2005-01-01

    Full Text Available To compare the astigmatism induced by a superior, supero-temporal and temporal incision in manual small incision cataract surgery. Induced astigmatism was analysed by Cartesian coordinates based analysis, using Holladay′s system. Mean astigmatism induced by surgery was 1.28 D x 2.9 degrees for superior incision, 0.20 D x 23.7 degrees for supero-temporal incision and 0.37 D x 90 degrees for temporal incision. The study found that induced astigmatism was lower in the temporal and superotemporal groups compared to that in the superior group.

  3. Propagation properties of partially polarized Gaussian Schell-model beams through an astigmatic lens

    Science.gov (United States)

    Pan, Liuzhan; Wang, Beizhan; Lu, Baida

    2005-09-01

    Based on the beam coherent-polarization (BCP) matrix approach and propagation law of partially coherent beams, analytical propagation equations of partially polarized Gaussian Schell-model (PGSM) beams through an astigmatic lens are derived, which enables us to study the propagation-induced polarization changes and irradiance distributions at any propagation distance of PGSM beams through an astigmatic lens within the framework of the paraxial approximation. Detailed numerical results for a PGSM beam passing through an astigmatic lens are presented. A comparison with the aberration-free case is made, and shows that the astigmatism affects the propagation properties of PGSM beams.

  4. Astigmatic Outcomes of Temporal versus Nasal Clear Corneal Phacoemulsification

    Directory of Open Access Journals (Sweden)

    Mohammad Pakravan

    2009-04-01

    Full Text Available

    PURPOSE: To compare the astigmatic outcomes of phacoemulsification cataract surgery using temporal versus nasal clear corneal incisions. METHODS: In a clinical trial, consecutive patients with senile cataracts underwent phacoemulsification and implantation of a hydrophobic acrylic foldable intraocular lens through a horizontal clear corneal incision (temporal in right and nasal in left eyes. Outcome measures included keratometric astigmatism and surgically induced astigmatism (SIA calculated by the vector analysis method using the Holladay-Cravy-Koch formula. RESULTS: The nasal and temporal groups consisted of 20 eyes each. Mean preoperative keratometric astigmatism was 0.63±0.48 D and 0.38±0.39 D in the temporal and nasal incision groups respectively (P=0.09. Data on 10 eyes in each study group was available for the six-month analysis. Mean keratometric astigmatism was as follows in the temporal and nasal groups respectively: 0.85±0.47 D versus 1.95±0.45 D at 1 week (P < 0.001, 0.73±0.46 D versus 1.79±0.55 D at 4 weeks (P < 0.001, and 0.63±0.30 D versus 1.05±0.56 D at 6 months (P=0.053 after surgery. SIA at the same follow-up intervals was 0.71±0.20 D versus 1.80±0.22 D (P < 0.001, 0.63±0.20 D versus 1.65±0.31 D (P < 0.001 and 0.26±0.46 D versus 0.92±0.36 D (P=0.002 in the temporal versus nasal incision groups

  5. Vector beam synthesis by means of astigmatic conversion

    International Nuclear Information System (INIS)

    We propose a new scheme based on a modified Mach–Zehnder interferometer for generating vector beams. The beams are formed with the help of a special diffractive optical element, which performs the astigmatic transformation of an input Hermite–Gaussian beam into two complexly conjugated Laguerre–Gaussian beams. The scheme allows us to obtain radially and azimuthally polarized beams and beams with a more complex polarization structure. A theoretical estimation for the transformation of beams both of radial and azimuthal polarization has been fulfilled. (paper)

  6. Properties of an astigmatic π/2-mode converter

    International Nuclear Information System (INIS)

    The properties of the astigmatic π/2 converter are analysed upon the transformation of eigen- and non-eigenmodes, and beams of arbitrary type. It is shown that the action of the converter can be reduced to even and odd numbers of Fourier transforms performed independently in two orthogonal planes containing the optical axis of the converter. The operation of two arbitrary oriented π/2 converters in tandem is described. This scheme permits obtaining at the same plane alternatively either the object image or its Fourier transform. Examples of the numerical simulation of the radiation propagation through the examined optical schemes are presented. (laser beams)

  7. Digital refraction distortion correction with an astigmatic coherence sensor

    Science.gov (United States)

    Marks, Daniel L.; Stack, Ronald A.; Brady, David J.

    2002-10-01

    We demonstrate the sensing and correction of an isoplanatic refractive distortion (not lens aberrations), using the complete measurement of the partially coherent field in an aperture that the previously described astigmatic coherence sensor provides. Isoplanatic distortions, and in general distortions that do not cause energy loss, maintain the orthogonality of the coherent modes. We use the fact that a common distortion will occur to all coherent modes to separate the distortion from the source behind it, rather than requiring a reference source at a different wavelength. Digital deconvolution was performed on the full four-dimensional partially coherent field for simultaneously computing the distortion and the source intensity distribution.

  8. How to Convert the Obliquely Crossed to Non-Crossed Astigmatism? A Simple Method Using Vector Analysis

    OpenAIRE

    Vojniković, Božo; Gabrić, Nikica; Dekaris, Iva

    2013-01-01

    The authors discussed about the problem of special form in astigmatism classification. This special type of astigmatism is the form of obliquely crossed astigmatism. In which the meridians, major and minor, are not right angles. In this astigmatism is not possible to prescribing for cylindrical (toric) spectacle lens. Authors describe the Thompson formula for oblique crossed cylinder and observe that this formula is to complicate for calculation new cylinder power. In this reason, the authors...

  9. COMPARISON OF SURGICALLY INDUCED ASTIGMATISM WITH SMALL INCISION CATARACT SURGERY AND PHACOEMULSIFICATION

    OpenAIRE

    Umesh; Shivanand; Smitha; Arvind L.; Kshama; Anju; Kathyayini; Abhinav,

    2015-01-01

    BACKGROUND: Surgically induced astigmatism is the cause of poor postoperative vision even after uneventful cataract surgery. AIM: The aim of the study was to compare the effect of surgically induced astigmatism in SICS and Phacoemulsification after taking the incision in the steepest meridian. SETTING: KLE Hospital, Belagavi, Karnataka. DESIGN: Lon...

  10. COMPARISON OF SURGICALLY INDUCED ASTIGMATISM WITH SMALL INCISION CATARACT SURGERY AND PHACOEMULSIFICATION

    Directory of Open Access Journals (Sweden)

    Umesh

    2015-09-01

    Full Text Available BACKGROUND: Surgically induced astigmatism is the cause of poor postoperative vision even after uneventful cataract surgery. AIM: The aim of the study was to compare the effect of surgically induced astigmatism in SICS and Phacoemulsification after taking the incision in the steepest meridian. SETTING: KLE Hospital, Belagavi, Karnataka. DESIGN: Longitudinal study. MATERIAL AND METHODS: A total of 100 eyes of 100 patients with mean age of 62 years were included in the study. Consecutive patients with cataract were randomly assigned to undergo phacoemulsification or manual SICS by a single surgeon experienced in both techniques. Group A underwent SICS (Small Incision Cataract Surgery and group B had phacoemulsification. Surgically induced astigmatism was analyzed by SIA software. STATISTICAL ANALYSIS : Non - parametric method (Mann whitney U test . RESULTS: The measurement of induced astigmatism was taken: dK, the net keratometric change in corneal toricity. Average dK for Group A (SICS was +0.05 D and for Group B (Phacoemulsification was - 0.53 D. There was a difference of - 0.49 D between the two groups in terms of induced keratometric astigmatism. The SICS group actually demonstrated on the average a greater iatrogenic astigmatism than the phacoemulsification group keratometrically. This is clinically or statistically significant (P<0.001. CONCLUSIONS: Phacoemulsification induces less astigmatism than SICS. Iatrogenic astigmatism is more with SICS.

  11. Toric Intraocular Lenses in the Correction of Astigmatism During Cataract Surgery

    DEFF Research Database (Denmark)

    Kessel, Line; Andresen, Jens; Tendal, Britta; Erngaard, Ditte; Flesner, Per; Hjortdal, Jesper

    2016-01-01

    evaluated as surgical complications and residual astigmatism. CLINICAL RELEVANCE: Postoperative astigmatism is an important cause of suboptimal UCDVA and need for distance spectacles. Toric IOLs may correct for preexisting corneal astigmatism at the time of surgery. METHODS: We performed a systematic...... literature search in the Embase, PubMed, and CENTRAL databases within the Cochrane Library. We included randomized clinical trials (RCTs) if they compared toric with non-toric IOL implantation (± relaxing incision) in patients with regular corneal astigmatism and age-related cataracts. We assessed the risk.......36-0.71) and moderate quality evidence that toric IOL implantation was not associated with an increased risk of complications (RR, 1.73; 95% CI, 0.60-5.04). Residual astigmatism was lower in the toric IOL group than in the non-toric IOL plus relaxing incision group (mean difference, 0.37 diopter [D]; 95% CI...

  12. Irregular Astigmatism after Corneal Refractive Surgery-An overview of the State of the Art

    International Nuclear Information System (INIS)

    Irregular astigmatism is a challenging problem for the refractive surgeon. The aim of this paper is to describe the author's experience and a literature review of the latest advances in the diagnosis and management of this difficult complication. We present a compilation of the different alternatives to treat irregular astigmatism secondary to corneal/ refractive surgery, as well as an innovative method to quantify the degree of irregular astigmatism, taking into account the clinical symptoms and the corneal aberrometric data. The outcome of the different choices to treat irregular astigmatism is presented, from contact lens fitting to the most recent ablative techniques based on corneal wavefront. Although irregular astigmatism is still one of the worst of refractive surgery, the better knowledge of the causes, the enhanced diagnostic devices and the improvement of the refractive surgical techniques have given the refractive surgeon a wide set of the alternatives to improve the patients visual performance, and to avoid unwanted litigations. (author)

  13. Astigmatism error modification for absolute shape reconstruction using Fourier transform method

    Science.gov (United States)

    He, Yuhang; Li, Qiang; Gao, Bo; Liu, Ang; Xu, Kaiyuan; Wei, Xiaohong; Chai, Liqun

    2014-12-01

    A method is proposed to modify astigmatism errors in absolute shape reconstruction of optical plane using Fourier transform method. If a transmission and reflection flat are used in an absolute test, two translation measurements lead to obtain the absolute shapes by making use of the characteristic relationship between the differential and original shapes in spatial frequency domain. However, because the translation device cannot guarantee the test and reference flats rigidly parallel to each other after the translations, a tilt error exists in the obtained differential data, which caused power and astigmatism errors in the reconstructed shapes. In order to modify the astigmatism errors, a rotation measurement is added. Based on the rotation invariability of the form of Zernike polynomial in circular domain, the astigmatism terms are calculated by solving polynomial coefficient equations related to the rotation differential data, and subsequently the astigmatism terms including error are modified. Computer simulation proves the validity of the proposed method.

  14. Opposite Clear Corneal Incisions versus Steep Meridian Incision Phacoemulsification for Correction of Pre-existing Astigmatism

    Directory of Open Access Journals (Sweden)

    Mohammad Naim Aminifard

    2015-01-01

    Full Text Available Background: To compare the efficacy of adding an opposite clear corneal incision (OCCI on the steep meridian versus performing surgery on the steep meridian alone during phacoemulsification in reducing pre-existing corneal astigmatism in Alzahra ophthalmology center. Materials and Methods: This randomized clinical trial was performed on 40 eyes with corneal astigmatism undergoing phacoemulsification and divided randomly to two groups. In the first group 3.2 mm phacoemulsification incision was made on steep meridian and in the other group after the procedure was completed the surgeon made 3.2 mm incision opposite to the main incision. Patients were followed with refraction, keratometry at 1, 4, 12 weeks. Results: Mean corrected astigmatism was greater in opposite clear corneal incision group than steep meridian incision phacoemulsification group. No significant change occurred in amount of astigmatism in two groups. Conclusion: Opposite clear corneal incisions achieve an enhanced effect over single clear corneal incisions in treating preexisting astigmatism in cataract patients.

  15. Quasi two-dimensional astigmatic solitons in soft chiral metastructures.

    Science.gov (United States)

    Laudyn, Urszula A; Jung, Paweł S; Karpierz, Mirosław A; Assanto, Gaetano

    2016-01-01

    We investigate a non-homogeneous layered structure encompassing dual spatial dispersion: continuous diffraction in one transverse dimension and discrete diffraction in the orthogonal one. Such dual diffraction can be balanced out by one and the same nonlinear response, giving rise to light self-confinement into astigmatic spatial solitons: self-focusing can compensate for the spreading of a bell-shaped beam, leading to quasi-2D solitary wavepackets which result from 1D transverse self-localization combined with a discrete soliton. We demonstrate such intensity-dependent beam trapping in chiral soft matter, exhibiting one-dimensional discrete diffraction along the helical axis and one-dimensional continuous diffraction in the orthogonal plane. In nematic liquid crystals with suitable birefringence and chiral arrangement, the reorientational nonlinearity is shown to support bell-shaped solitary waves with simple astigmatism dependent on the medium birefringence as well as on the dual diffraction of the input wavepacket. The observations are in agreement with a nonlinear nonlocal model for the all-optical response. PMID:26975651

  16. SPECT reconstruction algorithms for converging hole and astigmatic collimators

    International Nuclear Information System (INIS)

    One of the problems posed by the astigmatic collimator is an accurate and effective description of its imaging properties. Since the image of an object can change drastically with its position relative to the collimator, the traditional method of describing a collimator in terms of its resolution and sensitivity is inadequate and must be extended to include the effects of source position. The authors have developed the generalized collimator transfer function (GCTF) to describe the non-stationary effects of collimator hole pattern on imaging. This concept is ideally suited to deal with the non-stationary effects of convergent and astigmatic collimation. The performance of a stationary imaging system can be described mathematically in terms of its point source response function (PSRF). The PSRF describes the image resulting from a point source located anywhere in front of the camera. the underlying assumption is that if the image of a point source is known, then the image of any extended source distribution can be reconstructed by convolution of the point source response function with the extended source distribution. For stationary systems the imaging processes is assumed to be shift-invariant. However, the authors goal is to analyze systems that are not necessarily shift-invariant. In order to accommodate such systems, they introduce the generalized point source response function (GPSRF). During the past year they have applied the GPSRF to generate SPECT images of analytical phantoms constructed as a collection of Gaussian source distributions

  17. Quasi two-dimensional astigmatic solitons in soft chiral metastructures

    Science.gov (United States)

    Laudyn, Urszula A.; Jung, Paweł S.; Karpierz, Mirosław A.; Assanto, Gaetano

    2016-03-01

    We investigate a non-homogeneous layered structure encompassing dual spatial dispersion: continuous diffraction in one transverse dimension and discrete diffraction in the orthogonal one. Such dual diffraction can be balanced out by one and the same nonlinear response, giving rise to light self-confinement into astigmatic spatial solitons: self-focusing can compensate for the spreading of a bell-shaped beam, leading to quasi-2D solitary wavepackets which result from 1D transverse self-localization combined with a discrete soliton. We demonstrate such intensity-dependent beam trapping in chiral soft matter, exhibiting one-dimensional discrete diffraction along the helical axis and one-dimensional continuous diffraction in the orthogonal plane. In nematic liquid crystals with suitable birefringence and chiral arrangement, the reorientational nonlinearity is shown to support bell-shaped solitary waves with simple astigmatism dependent on the medium birefringence as well as on the dual diffraction of the input wavepacket. The observations are in agreement with a nonlinear nonlocal model for the all-optical response.

  18. Polarization-induced astigmatism caused by topographic masks

    Science.gov (United States)

    Ruoff, Johannes; Neumann, Jens Timo; Schmitt-Weaver, Emil; van Setten, Eelco; le Masson, Nicolas; Progler, Chris; Geh, Bernd

    2007-10-01

    With the continuous shrink of feature sizes the pitch of the mask comes closer to the wave length of light. It has been recognized that in this case polarization effects of the mask become much more pronounced and deviations in the diffraction efficiencies from the well-known Kirchhoff approach can no longer be neglected. It is not only the diffraction efficiencies that become polarization-dependent, also the phases of the diffracted orders tend to deviate from Kirchhoff theory when calculated rigorously. This also happens for large structures, where these phase deviations can mimic polarization dependent wave front aberrations, which in the case of polarized illumination can lead to non-negligible focus shifts that depend on the orientation and the features size themselves. This orientation dependence results in a polarization induced astigmatism offset, which can be of the same order of magnitude or even larger as polarization effects stemming from the lens itself. Hence, for correctly predicting polarization induced astigmatism offsets, one has to both consider lens and mask effects at the same time. In this paper we present a comprehensive study of polarized induced phase effects of topographic masks and develop a simple theoretical model that accurately describes the observed effects.

  19. An astigmatic corrected target-aligned solar concentrator

    Science.gov (United States)

    Lando, Mordechai; Kagan, Jacob; Linyekin, Boris; Sverdalov, Ludmila; Pecheny, Grigory; Achiam, Yaakov

    2000-06-01

    Highly concentrated solar energy is required for solar pumping of solid state lasers, and for other applications. High concentration may be obtained by a combination of a primary concentrator with f/ D>2 in addition to a non-imaging concentrator. We have designed and constructed a novel tower primary concentrator. A 3.4 m diameter primary mirror, composed of 61 segments, was mounted on a commercial two-axis positioner. Unlike the common zenith mounting, the positioner fixed axis is directed southwards, pointing at 32° above the horizon. With this novel mounting, the concentrator is the first implementation of the astigmatic corrected target aligned (ACTA) design which flattens the irradiation density variation during the day. The primary mirror segments are each mounted on a separate two-axis mount, and aligned to compensate for astigmatism. The segments are spherically curved with R=17 m radius of curvature, while their vertexes are placed on an R/2=8.5 m radius spherical cap. A four-segment plane mirror reflects the light towards a horizontal focal plane. We have measured the absorbed solar power into a 89×91 mm 2 rectangular aperture and found good agreement with optical design calculations. Peak solar concentration in the focal plane exceeded 400 suns.

  20. Single application on iris localization technology in excimer laser for astigmatism

    Directory of Open Access Journals (Sweden)

    Jun-Hua Hao

    2014-06-01

    Full Text Available AIM:To discuss the single application on iris localization technology in excimer laser for the treatment of astigmatism. METHODS:Totally 203 cases(406 eyesof laser in situ keratomileusis(LASIKin the treatment of compound myopic astigmatism patients were operated from November 2011 to November 2012 in our hospital. They were divided into two groups. One was observation group using iris localization and the other was control group using routine operation. Patients in the observation group of 100 cases(200 eyes, aged 18-43 years old, spherical diopter was -1.25 to -8.75D, astigmatism was -1.0 to -3.25D. In control group, 103 patients(206 eyes, aged 19-44 years old, spherical diopter was -1.75-9.50D, astigmatism was -1.0 to -3.25D. The patients in the observation group before the application of WaveScan aberrometer check for iris image, spherical lens, cylindrical lens and astigmatism axis data operation, only single application of iris location, without using wavefront aberration guided technology, laser cutting patterns for conventional LASIK model, spherical, cylindrical mirror and astigmatism axis data source to preoperative wavefront aberration results. The control group received routine LASIK. It was applicated comprehensive optometry optometry respectively to examine astigmatism and axial, based on the computer analysis during the preoperative, 1wk after the operation, and 6mo. Analysis of using SPSS 17 statistical software, it was independent-sample t test between the two groups of residual astigmatism and astigmatism axis. RESULTS:Postoperative residual astigmatism, the observation group was significantly better than the control group. Astigmatism axial measurement after operation, the observation group was significantly less than that of the control group. Postoperative visual acuity at 6mo, the observation group was better than that of the control group. The difference was statistically significant. CONCLUSION: For patients who cannot

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

    Directory of Open Access Journals (Sweden)

    Giuliano de Oliveira Freitas

    2013-10-01

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

  2. Effect of the chosen incision on corneal astigmatism after implantable collamer lens surgery

    Directory of Open Access Journals (Sweden)

    Xia Jiang

    2014-06-01

    Full Text Available AIM: To evaluate the effect of the chosen incision on corneal astigmatism after implantable collamer lens(ICLsurgery.METHODS: The study included 195 eyes of 102 patients, and all eyes were randomly divided into two groups: the chosen incision group(Group A, 97 eyesand temporal corneal incision(Group B, 98 eyes. Before the operation, and 1wk,1mo and 3mo after the operation, each patient was examined with corneal topography to observe the changes of corneal astigmatism. RESULTS: Preoperative corneal astigmatisms were(1.26±0.35D in group A and(1.28±0.38D in group B, thus there was no statistically significant difference(P>0.05. One week postoperatively, the astigmatism were(0.93±0.29D in group A and(1.32±0.33D in group B. One month postoperatively, the astigmatism were(0.85±0.16D in group A and(1.27±0.18D in group B. Three months postoperatively, the astigmatism were(0.80±0.13D in group A and(1.25±0.20D in group B. The differences between the two groups were statistically significant(PCONCLUSION: The chosen incision can reduce postoperative astigmatism to a certain extent after ICL surgery.

  3. Effect of the against the rule myopic astigmatism on the near vision of the elderly.

    OpenAIRE

    Kordić, Rajko; Kalauz, Miro; Kuzman, Tomislav; Masnec, Sanja; Škegro, Ivan; Vidović, Tomislav; Suić-Popović, Smiljka; Cerovski, Branimir; Rezaković, Saida; Barišić Kutija, Marija

    2014-01-01

    In the two groups of patients with myopic astigmatism the uncorrected near vision was tested after cataract surgery. Each group with 20 patients ages 60–80. All patients enrolled in study have uncorrected far vision 0.5 or better on Snellen tables. In the fi rst group patients were with the rule after surgery myopic astigmatism (1–1.50 Diopter), and in the second group were patients with against the rule after surgery myopic astigmatism (1–1.50 Diopter). Patients in the second gro...

  4. Success rates in the correction of astigmatism with toric and spherical soft contact lens fittings

    OpenAIRE

    Sevda Aydin Kurna; Tomris Şengör; Murat Ün; et al, ...

    2010-01-01

    Sevda Aydin Kurna, Tomris Şengör, Murat Ün, Suat AkiFatih Sultan Mehmet Education and Research Hospital, Ophthalmology Clinics, lstanbul, TurkeyObjectives: To evaluate success rates in the correction of astigmatism with toric and spherical soft contact lens fitting.Methods: 30 patients with soft toric lenses having more than 1.25 D of corneal astigmatism (25 eyes; Group A) or having 0.75–1.25 D of corneal astigmatism (22 eyes; Group B ) and 30 patients with soft sp...

  5. Success rates in the correction of astigmatism with toric and spherical soft contact lens fittings

    OpenAIRE

    Aydin Kurna, Sevda

    2010-01-01

    Sevda Aydin Kurna, Tomris Şengör, Murat Ün, Suat AkiFatih Sultan Mehmet Education and Research Hospital, Ophthalmology Clinics, lstanbul, TurkeyObjectives: To evaluate success rates in the correction of astigmatism with toric and spherical soft contact lens fitting.Methods: 30 patients with soft toric lenses having more than 1.25 D of corneal astigmatism (25 eyes; Group A) or having 0.75–1.25 D of corneal astigmatism (22 eyes; Group B ) and 30 patients with soft s...

  6. Changes in astigmatism between the ages of 1 and 4 years: a longitudinal study.

    OpenAIRE

    Abrahamsson, M; Fabian, G.; Sjöstrand, J

    1988-01-01

    Changes in astigmatism during development were studied in 299 infants with astigmatism as they grew from 1 to 4 years of age. All consecutive cases of 1-year-old infants with an astigmatism of 1.0 D or more in at least one eye found at an ophthalmic screening survey were selected for follow-up. The cycloplegic refraction was longitudinally followed at yearly intervals. During development there was no decrease in the degree of hypermetropia, but there was a significant decrease in the incidenc...

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

    OpenAIRE

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

    2015-01-01

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

  8. Can opposite clear corneal incisions have a role with post-laser in situ keratomileusis astigmatism?

    OpenAIRE

    Hatem El-Awady; Asaad A Ghanem

    2012-01-01

    Purpose: To evaluate the astigmatic correcting effect of paired opposite clear corneal incisions (OCCIs) on the steep axis in patients with residual astigmatism after laser in situ keratomileusis (LASIK) Materials and Methods: Thirty-one eyes of 24 patients with a mean age of 28.4 years ±2.46 (range, 19-36 years) were recruited for the study. Inclusion criteria included residual astigmatism of ≥1.5 diopter (D) after LASIK with inadequate residual stromal bed thickness that precluded ablat...

  9. Astigmatism in candidates of Cataract surgery and its relationship with corneal optical power, axial length, sex and patient age

    Directory of Open Access Journals (Sweden)

    Siatiri H

    2000-08-01

    Full Text Available This study was conducted to define the prevalence and types of corneal astigmatism in relation with corneal optical power, axial length, sex and patient age. 641 cataract patients were included in a descriptive study. Complete eye examinations were included in a descriptive study. Complete eye examinations were performed. The data were analysed by standard procedures including analysis of variance, chi square test and multiple linear regression models. With the rule, astigmatism was 55.6% in younger cases and against the rule astigmatism was 55.6% in younger cases and against the rule astigmatism was 43.7% in older cases (P<0.0001. Against the rule astigmatism was 55.8% in older males and 34.6% in older females (P<0.0001.There was 0.023d decrease in kpol for each year increase in age 1 (P<0.0001. Axial length in males was 23.35±1.79 mm (P<0.05 for second degree model to show relationship between astigmatism and axial length R2 was 0.019 and 0.03 by increasing axial length up to 26 mm corneal power decreased, but further increase in axial length led to corneal power increase. For each diopter increase in corneal power there was 0.1 diopetr increase in net astigmatism (P<0.0001. In corneal powers less than 45.5 diopter there was no difference between direction of astigmatism, but in corneal powers more than 45.5 diopter with the rule astigmatism was dominated (P=0.01. younger cases had more with the rule astigmatism andolder cases had more against the rule astigmatism. Against the rule astigmatism was more common in older males than in older females. With the rule astigmatism ratio shifted to ATR astigmastism ratio with age but there was no change in against the rule astigmatism ratio with age. Males had 0.22 mm axial length more than females. There was significant relationship between axial length and net astigmatism. Abnormal size eyes had more astigmatism.Emmetropization mechanism of cornea did not work for eyes longer than 26 mm. Myopia was

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

    DEFF Research Database (Denmark)

    Augustsson, P.; Barnkob, Rune; Bruus, Henrik; Kähler, C. J.; Laurell, T.; Marín, Á. G.; Rossi, M.

    We introduce full three-dimensional tracking of particles in an acoustophoresis microchannel using Astigmatism Particle Tracking Velocimetry (APTV) [1]. For the first time the interaction between acoustic streaming and the primary acoustic radiation force in microchannel acoustophoresis are exami...

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

    DEFF Research Database (Denmark)

    Augustsson, P.; Barnkob, Rune; Bruus, Henrik; Kähler, C. J.; Laurell, T.; Marín, Á. G.; Rossi, M.

    We introduce full three-dimensional tracking of particles in an acoustophoresis microchannel using Astigmatism Particle Tracking Velocimetry (APTV) [1]. For the first time the interaction between acoustic streaming and the primary acoustic radiation force in microchannel acoustophoresis are...

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2006-03-02

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

  14. SURGICALLY INDUCED ASTIGMATISM AFTER 20G VS 23G PARS PLANA VITRECTOMY

    Directory of Open Access Journals (Sweden)

    Lokabhi Reddy

    2015-05-01

    Full Text Available Pars Plana Vitrectomy is done to clear the Vitreous cavity of the Eye. Trans conjunctival Sutureless Vitrectomy with 23G & 25G has become more popular over the Conventional 20G Vitrectomy in recent times. It has many advantages. Less amount of Surgically Induc ed Astigmatism is one of the Advantages with Sutureless Vitrectomy, which will have the Advantage of Early Visual rehabilitation with better Vision. An interventional comparative study was done between 20G & 23 G Pars Plana Vitrectomy in 2 Groups of 30 pat ients each to assess the amount of Post - Operative Astigmatism. The cases were followed up for 6 months to assess the long term effects. There was a significant difference in immediate Post - Operative Astigmatism. But after some time the difference is much l ess showing that the main advantage on Astigmatism with Trans conjunctival Sutureless Vitrectomy is noted mainly during the first few weeks after the Surgery.

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

    Science.gov (United States)

    Barriga, P.; Zhao, Chunnong; Ju, Li; Blair, David G.

    2006-03-01

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

  16. Profile of astigmatism in school going children at state level hospital in Uttarakhand

    OpenAIRE

    Manisha Gupta; Vatsala Vats; Rupali Tyagi

    2016-01-01

    Background: Astigmatism is a clinically important condition and accounts for about 13% of the refractive errors of the eye. Its prevalence has been reported to vary with ethnicity, age, and sex. The aim of this study was to evaluate the profile of astigmatism in school going children and compared with similar studies in India and Asian countries. Methods: This was prospective cross and ndash; sectional hospital based study. The children aged between 5-13 years of age attending the eye OPD...

  17. Characteristics of Astigmatism in a Population of Tunisian School-Children

    OpenAIRE

    Ahmed Chebil; Lina Jedidi; Nibrass Chaker; Fedra Kort; Rym Limaiem; Fatma Mghaieth; Leila El Matri

    2015-01-01

    Purpose: To evaluate the characteristics of astigmatism in a cross-sectional study of schoolchildren in Tunisia. Materials and Methods: A random cluster design was used to recruit children from primary schools across urban and rural settings in Tunisia, from 2008 to 2010. A total of 6192 students aged 6-14-years old were enrolled. All students whose uncorrected visual acuity was worse than 20/20 underwent a complete ophthalmic examination. Astigmatism was defined as the cylinder power of ...

  18. The efficacy of a single continuous nylon suture for control of post keratoplasty astigmatism.

    OpenAIRE

    Van Meter, W

    1996-01-01

    PURPOSE: Post operative adjustment of a single continuous suture is an effective means of reducing post keratoplasty astigmatism. This study evaluates post keratoplasty keratometry following suture adjustment with an adjusted suture in place and after the suture is removed. METHODS: Average keratometric astigmatism was measured over 24 months time in 26 patients with an adjusted continuous suture and 24 patients with a continuous suture that was not adjusted. Average keratometry in 43 patient...

  19. Preoperative corneal astigmatism among adult patients with cataract in Northern Nigeria

    OpenAIRE

    Mohammed Isyaku; Ali, Syed A.; Sadiq Hassan

    2014-01-01

    The prevalence and nature of corneal astigmatism among patients with cataract has not been well-documented in the resident African population. This retrospective study was undertaken to investigate preexisting corneal astigmatism in adult patients with cataract. We analyzed keratometric readings acquired by manual Javal-Schiotz keratometry before surgery between January 1, 2011 and December 31, 2011. There were 3,169 patients (3286 eyes) aged between 16 and 110 years involved with a Male to f...

  20. A rapid method to correct objective lens astigmatism in a TEM

    International Nuclear Information System (INIS)

    This work describes a rapid method to correct the two-fold astigmatism of transmission electron microscope (TEM) objective lens employing caustic curve when no objective aperture is inserted. The method makes use of rounding the caustic curve via the objective lens stigmators after the condenser lens astigmatism has been corrected. It has many advantages over other methods, it is fast, straightforward, and does not need holes or an amorphous material.

  1. PAIRED OPPOSITE CLEAR CORNEAL INCISIONS TO REDUCE PREEXISTING CORNEAL ASTIGMATISM IN PHACOEMULSIFICATION

    OpenAIRE

    Chandrakant; Narayan; Srinivasulu; Prabhu; Inchara; Sushma; Padmini

    2015-01-01

    BACKGROUND: To study the effect of paired opposite clear corneal incisions on the steep axis on preexisting corneal astigmatism in phacoemulsification. MATERIALS AND METHODS : This study was performed on 30 eyes of 30 patients who had keratometric astigmatism of more than 1 diopter. All patients underwent clear corneal phacoemulsification with a 3.2mm clear corneal incision on the stee p axis. An additional similar incision was placed on the steep axis opposit...

  2. Meridional lenticular astigmatism associated with bilateral concurrent uveal metastases in renal cell carcinoma

    OpenAIRE

    Priluck JC; Grover S; Chalam KV

    2012-01-01

    Joshua C Priluck, Sandeep Grover, KV ChalamDepartment of Ophthalmology, University of Florida College of Medicine, Jacksonville, FL, USAPurpose: To demonstrate a case illustrating meridional lenticular astigmatism as a result of renal cell carcinoma uveal metastases.Methods: Case report with images.Results: Clinical findings and diagnostic testing of a patient with acquired meridional lenticular astigmatism are described. The refraction revealed best-corrected visual acuity of 20/20&ndash...

  3. The Changes in Corneal Astigmatism after Botulinum Toxin-A Injection in Patients with Blepharospasm

    OpenAIRE

    Moon, Nam Ju; Lee, Hyeon IL; Kim, Jae Chan

    2006-01-01

    To determine if the involuntary contractions of eyelids may have any effects on the development of corneal astigmatism, we performed this prospective study which includes 19 patients with either essential blepharospasm or hemifacial spasm. In hemifacial spasm, the degree of corneal astigmatism was evaluated between two eyes. Then the topographic changes were checked using vector analysis technique before and after passively opening the eyelids. They were also measured before and at 1 and 6 mo...

  4. The correction of corneal astigmatism of toric intraocular lenses in patients who underwent cataract surgery. Review

    OpenAIRE

    G. A. Fedyashev

    2014-01-01

    The paper presents an overview of the methods of surgical correction of corneal astigmatism in patients who underwent cataract surgery with IOL implantation, gives an idea of toric IOL, their advantages over other methods of the astigmatism correction, the criteria for patient selection, calculation features, preoperative marking. Besides the concept of rotational instability is sanctified position the IOL within the eye, its causes, methods of detecting the position of the IOL, as well as su...

  5. Thermal Correction of Astigmatism in the Gravitational Wave Observatory GEO 600

    OpenAIRE

    Wittel, H.; Lück, H; Affeldt, C.; Dooley, K; Grote, H.; Leong, J; Prijatelj, M.; Schreiber, E.; Slutsky, J.; Strain, K.; Was, M.; Willke, B.; Danzmann, K.

    2013-01-01

    The output port of GEO 600 is dominated by unwanted high order modes (HOMs). The current thermal actuation system, a ring heater behind one of the folding mirrors, causes a significant amount of astigmatism, which produces HOMs. We have built and installed an astigmatism correction system, based on heating this folding mirror at the sides (laterally). With these side heaters and the ring heater behind the mirror, it is possible to tune its radius of curvature in the horizontal and the vertica...

  6. CORNEAL ASTIGMATISM AFTER ECCE: A COMPARATIVE STUDY BETWEEN SILK VERSUS NYLON SUTURE

    OpenAIRE

    Sunita; jai; Sanjeev Kumar; Dilip; Manish Kumar; Ishan

    2013-01-01

    ABSTRAC T: INTRODUCTION: Cataract as a potent cause of loss of vision in old age persons is probably known since the dawn of human civilization. Post operative astigmatism after cataract extraction remains a big problem for cataract surgeons since Jacques Daviel e ra. Astigmatism is that type of refractive anomaly in which no point focus is formed owing to the unequal refraction of the incident light by the diopteric system of the eye in different meridians. The goal of m...

  7. Evaluation of Refractive Results of LASIK and LASEK in Patients with Myopia and Myopic Astigmatism

    OpenAIRE

    Okan Taşkın; Zeynep Özbek

    2014-01-01

    Objectives: To compare the mean visual acuity, spherical equivalent (SE), cylindrical refractive error, and central corneal thickness (CCT) results of LASIK and LASEK in patients with myopia and myopic astigmatism. Materials and Methods: A retrospective review of the patients who underwent LASIK or LASEK for myopia or myopic astigmatism between 2008 and 2011 was performed in the Department of Ophthalmology at Dokuz Eylül University School of Medicine. Preoperative data collected were...

  8. Effects of induced astigmatism on foot placement strategies when stepping onto a raised surface.

    Directory of Open Access Journals (Sweden)

    Louise Johnson

    Full Text Available PURPOSE: Large changes in spectacle prescription can increase falls risk in older people. We investigated the effect of induced astigmatism (a common cause of distorted or blurred vision in older people on locomotor stepping patterns to determine whether the orientation of astigmatic changes could have differential effects on gait safety when negotiating steps and stairs. METHODS: 10 older adults (mean age 76.0±6.4 years walked up to and stepped onto a raised block whilst wearing their spectacle prescription and when blurred with ±3.00D cylinders at axes 45°, 90°, 135° and 180°. Gait measurements included foot placement before the block, toe clearance over the block edge and foot placement on the block. RESULTS: Induced astigmatism with axes at 90°, providing magnification in the horizontal meridian only, caused no change in stepping pattern. Induced astigmatism with axes at 180° caused foot placement changes in the anterior or posterior direction according to whether magnification was positive or negative in the vertical meridian (block perceived higher or lower respectively. Induced astigmatism with axes oblique at 45° and 135° (causing the block to be perceived as a parallelogram sloping downwards either to the right or left caused gait changes in the anterior and posterior, vertical and lateral directions. Changes in lateral foot placement appeared to be an attempt to maintain constant foot clearance levels over the block edge by stepping over the perceived 'lower' side of the 'sloping' block. CONCLUSIONS: Astigmatic changes with oblique axes had the greatest effect on gait. Clinicians, including optometrists, physiotherapists, occupational therapists and nurses should counsel older patients about the effects of astigmatism on gait safety. Furthermore, partial prescribing of astigmatic corrections should be considered to reduce the risk of falling.

  9. Analysis of Postoperative Corneal Astigmatism after Phacoemulsification Through a Clear Corneal Incision

    OpenAIRE

    Sušić, Nikola; Brajković, Jasenka; Kalauz-Surać, Ivana

    2007-01-01

    The aim of the study was to analyze postoperative corneal astigmatism after phacoemulsification with intraocular lens implantation through a clear corneal incision. This prospective study included 22 eyes (10 right and 12 left eyes) having had phacoemulsification with implantation of a foldable intraocular lens through a clear corneal incision. A superotemporal incision was used in all right eyes, and superonasal incision in all left eyes. Astigmatism was measured by autorefractometer-keratom...

  10. Effects of Induced Astigmatism on Foot Placement Strategies when Stepping onto a Raised Surface

    OpenAIRE

    Johnson, Louise; Supuk, Elvira; Buckley, John G.; Elliott, David B.

    2013-01-01

    Purpose Large changes in spectacle prescription can increase falls risk in older people. We investigated the effect of induced astigmatism (a common cause of distorted or blurred vision in older people) on locomotor stepping patterns to determine whether the orientation of astigmatic changes could have differential effects on gait safety when negotiating steps and stairs. Methods 10 older adults (mean age 76.0±6.4 years) walked up to and stepped onto a raised block whilst wearing their specta...

  11. Toric implantable collamer lens for moderate to high myopic astigmatism: 3-year follow-up

    OpenAIRE

    Sari, Esin Sogutlu; Piñero Llorens, David Pablo; Kubaloglu, Anil; Evcili, Pinar Sorgun; Koytak, Arif; Kutlutürk, Isil; ÖZERTÜRK, Yusuf

    2013-01-01

    Background To evaluate the 3-year clinical outcomes after toric implantable collamer lens (ICL) implantation for the management of moderate to high myopic astigmatism. Methods Thirty-four eyes of 20 patients who underwent toric ICL implantation were reviewed. All eyes completed 3-year follow-up. Uncorrected (UDVA) and corrected (CDVA) distance LogMAR visual acuities, refraction, endothelial cell density (ECD), and surgical complications were evaluated. Vectorial analysis of astigmatic correct...

  12. Comparison of surgically induced astigmatism in corneo-scleral and clear corneal incision in phacoemulsification

    Directory of Open Access Journals (Sweden)

    Latha N.V

    2015-12-01

    Full Text Available Background: The objective of the study was to determine and compare the surgically induced astigmatism in patients who have undergone phacoemulsification with clear corneal and corneoscleral incisions made superiorly and temporally. Methods: Study was conducted in 100 patients who underwent cataract surgery from a period of November 2012 to July 2014. They were evaluated pre and post-operatively. Pre-op and Post-op Vision, retinoscopy and keratometry were analysed and surgically induced astigmatism was calculated using Vector method. Results: Surgically induced astigmatism calculated with SIA Calculator using Holladay's method was as follows ; Superior corneoscleral 0.79 D, Temporal corneoscleral 0.52 D , Superior clear corneal 0.60 D ,Temporal clear corneal 0.73 D . A higher incidence of against the rule astigmatism was seen pre-operatively (45% and post-operatively (42%. Conclusions: From our study, we have concluded that no significant difference was seen in the surgically induced astigmatism following phacoemulsification in all four incisions though the least SIA value was obtained with Temporal corneo-scleral. To conclude, Temporal corneo-scleral incisions being farther away from the visual axis has minimal effect on the corneal curvature with near astigmatic neutrality. [Int J Res Med Sci 2015; 3(12.000: 3812-3818

  13. MAGNITUDE OF POST OPERATIVE CORNEAL ASTIGMATISM AFTER PHACOEMULSIFICATION THROUGH 3.2MM TEMPORAL CLEAR CORNEAL INCISION

    Directory of Open Access Journals (Sweden)

    Neeraj

    2014-04-01

    Full Text Available Surgically induced astigmatism (SIA is a common obstacle for achieving excellent uncorrected visual acuity after Phacoemulsification with implantation of foldable IOL. The aim of the study was to determine the magnitude of surgically induced post-operative astigmatism after phacoemulsification with intraocular lens implantation through a temporal clear corneal incision. This study included 16 eyes with senile cataract which were operated using phacoemulsification with implantation of a foldable intraocular lens through a temporal clear corneal incision. Temporal incision at 180 degree was used for all cases. Astigmatism was measured by autorefracto keratometer preoperatively and at 6 weeks postoperatively. The mean surgically induced astigmatism was 0.53 D (Diopter with the Rule. The vertical component of astigmatism increased postoperatively than preoperatively. Horizontal component of astigmatism decreased in majority of cases postoperatively

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

    OpenAIRE

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

    2016-01-01

    Background 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. Methods Eleven eyes with coma-like-aberrations-dominant corneal optics and with low lenticular astigmatism (LA) were selected for astigmatism analysis and f...

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

    OpenAIRE

    Yongqi He; Siquan Zhu; Ming Chen; Dejiao Li

    2009-01-01

    Objective. This is prospective randomized control trial to compare the mean keratometric corneal astigmatism diopter power (not surgical induced astigmatism) among preop and one-month and three-month postop phacoemulcification of either a clear temporal corneal incision or a superior scleral tunnel Incision, using only keratometric astigmatic power reading to evaluate the difference between the two cataract surgery incisions. Methods. 120 patients (134 eyes) underwent phacoemulcification were...

  16. On-axis spectral shifts and spectral switches of Gaussian Schell-model beams focused by an astigmatic aperture lens

    Science.gov (United States)

    Yuan, Xiao; Pan, Liuzhan; Ding, Chaoliang; Lü, Baida

    2008-10-01

    Starting from the propagation law of partially coherent light, the on-axis spectral shifts and spectral switches of Gaussian Schell-model (GSM) beams focused by an astigmatic aperture lens are studied. It is shown that, as compared with an aberration-free case whose spectral shifts and spectral switches are induced by spatial correlation and aperture diffraction, the spectral shifts and spectral switches of GSM beams also depend upon the astigmatism of the lens for an astigmatism case. Detailed numerical calculations are made to illustrate the behavior of spectral shifts and spectral switches of GSM beams focused by an astigmatic aperture lens.

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

    Science.gov (United States)

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

    2015-06-01

    [Purpose] To assess the changes in falling risk depending on the induced axis direction of astigmatism using cylindrical lenses in a static posture. [Subjects and Methods] Twenty subjects (10 males, 10 females; mean age, 23.4 ± 2.70 years) fully corrected by subjective refraction participated. To induce myopic simple astigmatism conditions, cylindrical lenses of +0.50, +1.00, +1.50, +2.00, +3.00, +4.00, and +5.00 D were used. The direction of astigmatic axes were induced under five conditions with increased cylindrical powers:, 180°, 90°, and 45° on both eyes; 180°/90° right/left eye, and 45°/135° right/left eye. Changes in the fall risk index were analyzed using the TETRAX biofeedback system. Measurements were performed for 32 seconds for each condition. [Results] The fall risk index increased significantly from C+4.00 D in 180°/90° right/left eye, C+3.00 D in 45°/135° right/left eye, and C+3.00 D in 45° on both eyes versus corrected emmetropia. Among the five axis conditions with the same cylindrical power lenses, the increase in the fall risk index was highest at 45° in both eyes. [Conclusion] Uncorrected oblique astigmatism may increase falling risk compared to with-the-rule and against-the-rule astigmatism. Clinical specialists should consider appropriate correction of astigmatism for preventing falls, especially for uncorrected oblique astigmatism. PMID:26180360

  18. CORNEAL ASTIGMATISM AFTER ECCE: A COMPARATIVE STUDY BETWEEN SILK VERSUS NYLON SUTURE

    Directory of Open Access Journals (Sweden)

    Sunita

    2013-11-01

    Full Text Available ABSTRAC T: INTRODUCTION: Cataract as a potent cause of loss of vision in old age persons is probably known since the dawn of human civilization. Post operative astigmatism after cataract extraction remains a big problem for cataract surgeons since Jacques Daviel e ra. Astigmatism is that type of refractive anomaly in which no point focus is formed owing to the unequal refraction of the incident light by the diopteric system of the eye in different meridians. The goal of modern cataract surgery is to produce a pseudo phakic with the quality of vision of a normal phakic eye. Various studies to find out any effect of IOL on post operative astigmatism were carried out but results are controversial. MATERIAL AND METHODS: 60 patients suffering from cataract and fit for extr action were enlisted during the month of August 2008 to February 2009. The general, physical and local examination including preoperative Keratometry, vision and tension were recorded. RESULTS: In the present study, male patients were 38 (63% and female p atients were 22 (37%. Out of the total 60 cases studied, corneo - scleral section of 28 cases (47% were sutured with 10 - 0 nylon suture (Group A while sections of 32 cases were sutured with 8 - 0 black virgin silk suture (Group B.Out of 28 cases of Group A, interrupted sutures were applied in 14 cases (50% (Group A 1 . Cross interrupted sutures were applied in 9 cases (32% Group A 2 , while bootlace continuous sutures were applied in 5 cases (18% (Group A 3 . Out of 32 cases of Group B, interrupted sutures we re applied in 26 cases (80% (Group B 1 , cross interrupted were applied in 3 cases (10% (Group B 2 , while bootlace continuous suture were applied in 3 cases (Group B 3 . In the present series, 19 cases (31% showed with the rule astigmatism, 21 cases (36% showed astigmatism against the rule and 20 cases (33% showed no astigmatism preoperatively, 16 cases were in the range of 0.50D to 1.0D and 12 cases were in the range of 1

  19. Effects of optically imposed astigmatism on early eye growth in chicks.

    Directory of Open Access Journals (Sweden)

    Chin Hung Geoffrey Chu

    Full Text Available To determine the effects of optically imposed astigmatism on early eye growth in chicks.5-day-old (P5 White Leghorn chicks were randomly assigned to either wear, monocularly, a "high magnitude" (H: +4.00DS/-8.00DC crossed-cylindrical lens oriented at one of four axes (45, 90, 135, and 180; n = 20 in each group, or were left untreated (controls; n = 8. Two additional groups wore a "low magnitude" (L: +2.00DS/-4.00DC cylindrical lens orientated at either axis 90 or 180 (n = 20 and n = 18, respectively. Refractions were measured at P5 and after 7 days of treatment for all chicks (P12, whereas videokeratography and ex-vivo eyeshape analysis were performed at P12 for a subset of chicks in each group (n = 8.Compared to controls, chicks in the treatment groups developed significant amounts of refractive astigmatism (controls: 0.03 ± 0.22DC; treatment groups: 1.34 ± 0.22DC to 5.51 ± 0.26DC, one-way ANOVAs, p ≤ 0.05 with axes compensatory to those imposed by the cylindrical lenses. H cylindrical lenses induced more refractive astigmatism than L lenses (H90 vs. L90: 5.51 ± 0.26D vs. 4.10 ± 0.16D; H180 vs. L180: 2.84 ± 0.44D vs. 1.34 ± 0.22D, unpaired two-sample t-tests, both p ≤ 0.01; and imposing with-the-rule (H90 and L90 and against-the-rule astigmatisms (H180 and L180 resulted in, respectively, steeper and flatter corneal shape. Both corneal and internal astigmatisms were moderately to strongly correlated with refractive astigmatisms (Pearson's r: +0.61 to +0.94, all p ≤ 0.001. In addition, the characteristics of astigmatism were significantly correlated with multiple eyeshape parameters at the posterior segments (Pearson's r: -0.27 to +0.45, all p ≤ 0.05.Chicks showed compensatory ocular changes in response to the astigmatic magnitudes imposed in this study. The correlations of changes in refractive, corneal, and posterior eyeshape indicate the involvement of anterior and posterior ocular segments during the development of astigmatism.

  20. Application of the astigmatic method to the thickness measurement of glass substrates

    Science.gov (United States)

    Zhang, Jingchao; Ding, Rui; Yan, Xi; Li, Li; Han, Zhiping

    2011-06-01

    We developed a high accuracy thickness measurement system for glass substrates based on the optical design of the astigmatic method. Reflective optical measurement systems are the most widely used glass thickness measurement methods in current industrial production practice. The incline of glass in reflective optical measurement system is the main factor of inaccuracy of thickness data. Compared with reflective optical measurement system, we found our design could effectively eliminate errors of glass thickness caused by slightly shifts of glass tilt. The astigmatic optical system includes a laser diode, a cylindrical lens, and a quadrant detector. This method measures the astigmatic focusing error signal induced form the measured glass placed in the astigmatic optical system. The astigmatic focusing error signal is converted into the thickness of the glass substrate. The proposed glass thickness measurement system is verified by using a coordinate measuring machine (CMM). On the validation of our system using tri-ordinate measuring machine, the accuracy of the proposed system is 0.2 μm, with a standard deviation of 0.7μm within the thickness measuring range of 1.2mm.

  1. Non-toric extended depth of focus contact lenses for astigmatism and presbyopia correction

    Science.gov (United States)

    Ben Yaish, Shai; Zlotnik, Alex; Yehezkel, Oren; Lahav-Yacouel, Karen; Belkin, Michael; Zalevsky, Zeev

    2010-02-01

    Purpose: Testing whether the extended depth of focus technology embedded on non-toric contact lenses is a suitable treatment for both astigmatism and presbyopia. Methods: The extended depth of focus pattern consisting of microndepth concentric grooves was engraved on a surface of a mono-focal soft contact lens. These grooves create an interference pattern extending the focus from a point to a length of about 1mm providing a 3.00D extension in the depth of focus. The extension in the depth of focus provides high quality focused imaging capabilities from near through intermediate and up to far ranges. Due to the angular symmetry of the engraved pattern the extension in the depth of focus can also resolve regular as well as irregular astigmatism aberrations. Results: The contact lens was tested on a group of 8 astigmatic and 13 subjects with presbyopia. Average correction of 0.70D for astigmatism and 1.50D for presbyopia was demonstrated. Conclusions: The extended depth of focus technology in a non-toric contact lens corrects simultaneously astigmatism and presbyopia. The proposed solution is based upon interference rather than diffraction effects and thus it is characterized by high energetic efficiency to the retina plane as well as reduced chromatic aberrations.

  2. Preoperative corneal astigmatism among adult patients with cataract in Northern Nigeria

    Directory of Open Access Journals (Sweden)

    Mohammed Isyaku

    2014-01-01

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

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

    Science.gov (United States)

    Twelker, J. Daniel; Miller, Joseph M.; Campus, Irene

    2016-01-01

    Purpose. To determine rate of convergence insufficiency (CI) and accommodative insufficiency (AI) and assess the relation between CI, AI, visual symptoms, and astigmatism in school-age children. Methods. 3rd–8th-grade students completed the Convergence Insufficiency Symptom Survey (CISS) and binocular vision testing with correction if prescribed. Students were categorized by astigmatism magnitude (no/low: AI, and presence of symptoms. Analyses determine rate of clinical CI and AI and symptomatic CI and AI and assessed the relation between CI, AI, visual symptoms, and astigmatism. Results. In the sample of 484 students (11.67 ± 1.81 years of age), rate of symptomatic CI was 6.2% and symptomatic AI 18.2%. AI was more common in students with CI than without CI. Students with AI only (p = 0.02) and with CI and AI (p = 0.001) had higher symptom scores than students with neither CI nor AI. Moderate and high astigmats were not at increased risk for CI or AI. Conclusions. With-the-rule astigmats are not at increased risk for CI or AI. High comorbidity rates of CI and AI and higher symptoms scores with AI suggest that research is needed to determine symptomatology specific to CI. PMID:27525112

  4. Toric intraocular lenses for correction of astigmatism in keratoconus and after corneal surgery

    Science.gov (United States)

    Mol, Ilse EMA; Van Dooren, Bart TH

    2016-01-01

    Purpose To describe the results of cataract extraction with toric intraocular lens (IOL) implantation in patients with preexisting astigmatism from three corneal conditions (keratoconus, postkeratoplasty, and postpterygium surgery). Methods Cataract patients with topographically stable, fairly regular (although sometimes very high) corneal astigmatism underwent phacoemulsification with implantation of a toric IOL (Zeiss AT TORBI 709, Alcon Acrysof IQ toric SN6AT, AMO Tecnis ZCT). Postoperative astigmatism and refractive outcomes, as well as visual acuities, vector reduction, and complications were recorded for all eyes. Results This study evaluated 17 eyes of 16 patients with a mean age of 60 years at the time of surgery. Mean follow-up in this study was 12 months. The corrected distance Snellen visual acuity (with spectacles or contact lenses) 12 months postoperatively was 20/32 or better in 82% of eyes. The mean corneal astigmatism was 6.7 diopters (D) preoperatively, and 1.5 D of refractive cylinder at 1-year follow-up. No vision-compromising intra- or postoperative complications occurred and decentration or off-axis alignment of toric IOLs were not observed. Conclusion Phacoemulsification with toric IOL implantation was a safe and effective procedure in the three mentioned corneal conditions. Patient selection, counseling, and IOL placement with optimal astigmatism correction are crucial. PMID:27382249

  5. Keratometric astigmatism after ECCE in eastern Nepal. Continuous versus interrupted sutures.

    Directory of Open Access Journals (Sweden)

    Sood Archana

    2003-01-01

    Full Text Available Purpose: The study aimed to compute and compare the keratometric astigmatism induced by wound closure with continuous and interrupted sutures in conventional extracapsular cataract extraction with intraocular lens implantation at a single centre in eastern Nepal. Methods: Sixty eyes of 60 patients were included in the study. All patients received conventional extracapsular cataract extraction and single piece modified C-loop posterior chamber intraocular lens. Thirty eyes were sutured with continuous (Group 1 and 30 eyes with interrupted sutures (Group 2. The results were analysed by the unpaired student′s t-test. Results: At the end of 6 weeks, Group 1 patients had significantly higher astigmatism (3.53 ± 2.19D compared to Group 2 patients (1.7 ± 1.35. A majority of patients in both groups had with-the-rule astigmatism throughout the postoperative period. Conclusion: Interrupted sutures cause less astigmatism than continuous suture. The factors responsible for high astigmatism in continuous sutures call for further analysis.

  6. On the calibration of astigmatism particle tracking velocimetry for microflows

    International Nuclear Information System (INIS)

    Astigmatism particle tracking velocimetry (APTV) is a method to determine three components (3C) of the velocity field in a volume (3D) using a single camera. The depth position of the particles is coded by optical distortions caused by a cylindrical lens in the optical setup. This technique is particularly suited for microfluidic applications as measurement errors due to spatial averaging and depth of correlation, typically encountered with μPIV approaches, are eliminated so that the measurement precision is enhanced. Unfortunately, the current state of the technique is limited by the small measurement region achievable with the current calibration procedures as well as by higher order image aberrations (Cierpka et al 2010 Meas. Sci. Technol. 21 045401). In order to extend the size of the measurement volume and to account for all image aberrations, a new intrinsic calibration procedure, based on the imaging function of the particles, is proposed in the paper at hand. It provides an extended measurement depth, taking into account all image aberrations. In this work, the calibration procedure was applied to a μPIV arrangement but could also be implemented on macroscopic experimental setups. The calibration procedure is qualified with synthetic data as well as Poiseuille flow in a straight rectangular micro-channel with a cross-sectional area of 200 ×  500 µm2. The three-dimensional velocity distribution of the whole channel was resolved via APTV with uncertainties of 0.9% and 3.7% of the centerline velocity, uc, for the in-plane and out-of-plane components, respectively. Further investigations using different cylindrical-lens focal lengths, magnifications and particle sizes provide information about achievable measurement depths and help to design and adapt the optimal system for the desired experiment

  7. On the calibration of astigmatism particle tracking velocimetry for microflows

    Science.gov (United States)

    Cierpka, C.; Rossi, M.; Segura, R.; Kähler, C. J.

    2011-01-01

    Astigmatism particle tracking velocimetry (APTV) is a method to determine three components (3C) of the velocity field in a volume (3D) using a single camera. The depth position of the particles is coded by optical distortions caused by a cylindrical lens in the optical setup. This technique is particularly suited for microfluidic applications as measurement errors due to spatial averaging and depth of correlation, typically encountered with μPIV approaches, are eliminated so that the measurement precision is enhanced. Unfortunately, the current state of the technique is limited by the small measurement region achievable with the current calibration procedures as well as by higher order image aberrations (Cierpka et al 2010 Meas. Sci. Technol. 21 045401). In order to extend the size of the measurement volume and to account for all image aberrations, a new intrinsic calibration procedure, based on the imaging function of the particles, is proposed in the paper at hand. It provides an extended measurement depth, taking into account all image aberrations. In this work, the calibration procedure was applied to a μPIV arrangement but could also be implemented on macroscopic experimental setups. The calibration procedure is qualified with synthetic data as well as Poiseuille flow in a straight rectangular micro-channel with a cross-sectional area of 200 × 500 µm2. The three-dimensional velocity distribution of the whole channel was resolved via APTV with uncertainties of 0.9% and 3.7% of the centerline velocity, uc, for the in-plane and out-of-plane components, respectively. Further investigations using different cylindrical-lens focal lengths, magnifications and particle sizes provide information about achievable measurement depths and help to design and adapt the optimal system for the desired experiment.

  8. Broadband astigmatism-free Czerny-Turner imaging spectrometer using spherical mirrors

    International Nuclear Information System (INIS)

    We describe the elimination of the astigmatism of a Czerny-Turner imaging spectrometer, built using spherical optics and a plane grating, over a broad spectral region. Starting with the principle of divergent illumination of the grating, which removes astigmatism at one chosen wavelength, we obtain design equations for the distance from the grating to the focusing mirror and the detector angle that remove the astigmatism to first order in wavelength. Experimentally, we demonstrate near diffraction-limited performance from 740 to 860 nm and over a 5 mm transverse spatial extent, while ray-tracing calculations show that barring finite-aperture and detector size limitations, this range extends from 640 to 900 nm and over 10 mm transversely. Our technique requires no additional optics and uses standard off-the-shelf components.

  9. Prevalence of Corneal Astigmatism in Tohono O'odham Native American Children 6 Months to 8 Years of Age

    OpenAIRE

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

    2011-01-01

    The prevalence of corneal astigmatism in infants and young children who are members of a Native American tribe indicates that the mean amount of corneal astigmatism is higher than reported for non–Native American populations and increases from 1.43 D in 1-year-olds to nearly 2.00 D by school age.

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

    Directory of Open Access Journals (Sweden)

    Yang An

    2016-03-01

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

  11. Analyses of surgically induced astigmatism and axis deviation in microcoaxial phacoemulsification.

    Science.gov (United States)

    Özyol, Erhan; Özyol, Pelin

    2014-06-01

    To evaluate surgically induced astigmatism (SIA) and axis deviation after coaxial microincision superotemporal clear corneal phacoemulsification incision in eyes with differently located steep axis. This prospective, comparative study included four groups of 45 eyes with age-related cataracts; each group underwent 2.2-mm superotemporal clear corneal incision (CCI) cataract surgery. The four groups of patients were divided by location of the steep axis. Groups were matched according to symmetry of the steep axis for both right and left eyes as follows--0°-45° of steep axis for right eyes, and 136°-180° for left eyes (group 1); 46°-90° for right eyes and 91°-135° for left eyes (group 2); 91°-135° for right eyes and 46°-90° for left eyes (group 3); and 136°-180° for right eyes and 0°-45° for left eyes (group 4). Outcome measures included changes in mean total astigmatism, SIA, and axis deviation. Astigmatism was measured by manual keratometry readings before surgery and week 1, week 4, week 8, and week 12 postoperatively. SIA was calculated by the vector analysis (Holladay-Cravy-Koch method). The magnitude of mean total astigmatism was lowest in group 3 and highest in group 1 at week 12. SIA was 0.39 diopters (D), 0.22 D, 0.17 D, and 0.28 D in group 1, group 2, group 3, and group 4, respectively. The change in astigmatic axis deviation was highest in group 3 (23.6 ± 16.6) (P < 0.05). Axis deviation and SIA were stable after week 4. Planning of CCI on or near the steep axis can help decrease corneal astigmatism. PMID:24081915

  12. Toric intraocular lenses for correction of astigmatism in keratoconus and after corneal surgery

    Directory of Open Access Journals (Sweden)

    Mol IEMA

    2016-06-01

    Full Text Available Ilse EMA Mol,1,2 Bart TH Van Dooren1,2 1Department of Ophthalmology, Amphia Hospital, Breda, 2Department of Ophthalmology, Erasmus Medical Center, Rotterdam, the Netherlands Purpose: To describe the results of cataract extraction with toric intraocular lens (IOL implantation in patients with preexisting astigmatism from three corneal conditions (keratoconus, postkeratoplasty, and postpterygium surgery.Methods: Cataract patients with topographically stable, fairly regular (although sometimes very high corneal astigmatism underwent phacoemulsification with implantation of a toric IOL (Zeiss AT TORBI 709, Alcon Acrysof IQ toric SN6AT, AMO Tecnis ZCT. Postoperative astigmatism and refractive outcomes, as well as visual acuities, vector reduction, and complications were recorded for all eyes.Results: This study evaluated 17 eyes of 16 patients with a mean age of 60 years at the time of surgery. Mean follow-up in this study was 12 months. The corrected distance Snellen visual acuity (with spectacles or contact lenses 12 months postoperatively was 20/32 or better in 82% of eyes. The mean corneal astigmatism was 6.7 diopters (D preoperatively, and 1.5 D of refractive cylinder at 1-year follow-up. No vision-compromising intra- or postoperative complications occurred and decentration or off-axis alignment of toric IOLs were not observed.Conclusion: Phacoemulsification with toric IOL implantation was a safe and effective procedure in the three mentioned corneal conditions. Patient selection, counseling, and IOL placement with optimal astigmatism correction are crucial. Keywords: toric intraocular lens, phacoemulsification, corneal astigmatism, keratoconus, postkeratoplasty, postpterygium surgery

  13. Properties of high-order transverse modes in astigmatic laser cavities

    International Nuclear Information System (INIS)

    A theory of the modes in a resonator bounded by the surface of a triaxial ellipsoid was given previously by Weinstein. We have applied this theory to characterize the modes observed in a large-aperture Brewster-window laser. Recognizing that Brewster windows impart astigmatism to the laser cavity, we can find an equivalent ellipsoidal cavity with which to associate the modes. The theory predicts various forms of mode structure, depending on the total astigmatism present. We have verified the theory experimentally and show that high-order modes having rectangular symmetry may be obtained even though a circular aperture is used in the cavity. (auth)

  14. Optical enhancement cavity with astigmatism correction for laser compton light source

    International Nuclear Information System (INIS)

    Energetic photon beam produced via Laser-Compton scattering is expected to have variety of applications. An optical enhancement cavity with a small spot size at the collision point is a key to realize a high average flux. It is known that astigmatism arising from finite incident angle on the concave mirror limits the smallest spot size in the case of conventional 4-mirror ring cavity. We discuss a design of an optical cavity with astigmatism compensation utilizing additional convex mirrors. It improves the ellipticity of beam profile at the focus point and can realize a smaller spot size. (author)

  15. Symmetry of the spatial structure of radiation upon transverse mode locking in an astigmatic resonator laser

    International Nuclear Information System (INIS)

    The influence of the astigmatic resonator parameters on the symmetry of the spatial structure of the radiation intensity is analysed upon transverse mode locking in a nonuniformly pumped laser. Conditions for the transition from the circular symmetry to its violation are found. At a fixed astigmatism of the resonator, the symmetry is determined, first of all, by the resonator length and losses. The theoretical conclusions are confirmed by the experiments with diode end-pumped Nd:YAG and Nd:YLF lasers. (resonators)

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-06-06

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

  18. The correction of corneal astigmatism of toric intraocular lenses in patients who underwent cataract surgery. Review

    Directory of Open Access Journals (Sweden)

    G. A. Fedyashev

    2014-07-01

    Full Text Available The paper presents an overview of the methods of surgical correction of corneal astigmatism in patients who underwent cataract surgery with IOL implantation, gives an idea of toric IOL, their advantages over other methods of the astigmatism correction, the criteria for patient selection, calculation features, preoperative marking. Besides the concept of rotational instability is sanctified position the IOL within the eye, its causes, methods of detecting the position of the IOL, as well as surgical ways to improve its rotational stability.

  19. Off-Axis Astigmatic Gaussian Beam Combination Beyond the Paraxial Approximation

    Institute of Scientific and Technical Information of China (English)

    GAO Zeng-Hui; L(U) Bai-Da

    2007-01-01

    Taking the off-axis astigmatic Gaussian beam combination as an example, the beam-combination concept is extended to the nonparaxial regime. The closed-form propagation expressions for coherent and incoherent combinations of nonparaxial off-axis astigmatic Gaussian beams with rectangular geometry are derived and illustrated with numerical examples. It is shown that the intensity distributions of the resulting beam depend on the combination scheme and beam parameters in general, and in the paraxial approximation (i.e., for the small f-parameter)our results reduce to the paraxial ones.

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

    OpenAIRE

    Giuliano de Oliveira Freitas; Joel Edmur Boteon; Mario José Carvalho; Rogerio Melo Costa Pinto

    2013-01-01

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

  1. Meridional lenticular astigmatism associated with bilateral concurrent uveal metastases in renal cell carcinoma

    Directory of Open Access Journals (Sweden)

    Priluck JC

    2012-11-01

    Full Text Available Joshua C Priluck, Sandeep Grover, KV ChalamDepartment of Ophthalmology, University of Florida College of Medicine, Jacksonville, FL, USAPurpose: To demonstrate a case illustrating meridional lenticular astigmatism as a result of renal cell carcinoma uveal metastases.Methods: Case report with images.Results: Clinical findings and diagnostic testing of a patient with acquired meridional lenticular astigmatism are described. The refraction revealed best-corrected visual acuity of 20/20–1 OD (−2.50 + 0.25 × 090 and 20/50 OS (−8.25 + 3.25 × 075. Bilateral concurrent renal cell carcinoma metastases to the choroid and ciliary body are demonstrated by utilizing ultrasonography, ultrawidefield fluorescein angiography, and unique spectral-domain optical coherence tomography.Conclusions: Metastatic disease should be included in the differential of acquired astigmatism. Spectral-domain optical coherence tomography, ultrawidefield fluorescein angiography, and ultrasonography have roles in delineating choroidal metastases.Keywords: astigmatism, metastasis, optical coherence tomography, renal cell carcinoma

  2. Digital in-line holography with an elliptical, astigmatic Gaussian beam : wide-angle reconstruction

    CERN Document Server

    Verrier, Nicolas; Brunel, Marc; Lebrun, Denis; Janssen, Augustus J E M; 10.1364/JOSAA.25.001459

    2012-01-01

    We demonstrate in this paper that the effect of object shift in an elliptical, astigmatic Gaussian beam does not affect the optimal fractional orders used to reconstruct the holographic image of a particle or another opaque object in the field. Simulations and experimental results are presented.

  3. Optical-vortex pair creation and annihilation and helical astigmatism of a nonplanar ring resonator

    International Nuclear Information System (INIS)

    The creation and annihilation of pairs of optical vortices have been studied in transitions between patterns produced in a photorefractive oscillator. Smooth metamorphosis between stable patterns occurs through pair creation or annihilation but can be modeled using superposition of modes taking into account lifting of degeneracy of helical modes by helical astigmatism of the resonator. copyright 1996 The American Physical Society

  4. Unexpected periodicities in HRTEM images of orthorhombic zirconia due to astigmatism

    International Nuclear Information System (INIS)

    It is known that kinematically forbidden reflections caused by glide or screw symmetry elements remain forbidden dynamically under certain illumination conditions (The Gjonnes-Moodie extinction rules). These forbidden reflections can appear and contribute to images under conditions where crystal and/or beam tilt alignments are non-axial. Images with unexpected lattice periodicities due to beam tilt and/or crystal tilt have been refereed to as anomalous images and such images have been observed in various crystal structures. The situation in regard to thin crystals of rutile-like structures has been clarified where, by using CBED combined with HRTEM images at a range of crystal thicknesses, it was shown that rutile does exhibit the accepted space group (P42/mnm). In this paper we show that residual astigmatism can also lead to anomalous images similar to those caused by beam tilt and/or crystal tilt, but where the images are not due to the occurrence of forbidden reflections. Astigmatism has a severe effect on the high-resolution images of o-ZrO2 and for even a small amount of residual astigmatism, the images show marked changes in comparison to images calculated for perfect conditions. In fact, it was found that in most cases it was not possible to match simulated images with experimental images without considering the effect of astigmatism

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

    Directory of Open Access Journals (Sweden)

    Giuliano de Oliveira Freitas

    2013-12-01

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

  6. SURGICALLY INDUCED ASTIGMATISM AFTER 20G VS 23G PARS PLANA VITRECTOMY

    OpenAIRE

    Lokabhi Reddy; Suneetha

    2015-01-01

    Pars Plana Vitrectomy is done to clear the Vitreous cavity of the Eye. Trans conjunctival Sutureless Vitrectomy with 23G & 25G has become more popular over the Conventional 20G Vitrectomy in recent times. It has many advantages. Less amount of Surgically Induc ed Astigmatism is one of the Advantages with Sutureless Vitrectomy, which wil...

  7. Observation of lasing modes with exotic localized wave patterns from astigmatic large-Fresnel-number cavities.

    Science.gov (United States)

    Lu, T H; Lin, Y C; Liang, H C; Huang, Y J; Chen, Y F; Huang, K F

    2010-02-01

    We investigate the lasing modes in large-Fresnel-number laser systems with astigmatism effects. Experimental results reveal that numerous lasing modes are concentrated on exotic patterns corresponding to intriguing geometries. We theoretically use the quantum operator algebra to construct the wave representation for manifesting the origin of the localized wave patterns. PMID:20125716

  8. Precise and unbiased estimation of astigmatism and defocus in transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Vulovic, Milos, E-mail: milos.vulovic@gmail.com [Quantitative Imaging Group, Faculty of Applied Sciences, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft (Netherlands); Electron Microscopy Section, Molecular Cell Biology, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden (Netherlands); Franken, Erik [FEI Company, Achtseweg Noord 5, 5651 GG Eindhoven (Netherlands); Ravelli, Raimond B.G. [Electron Microscopy Section, Molecular Cell Biology, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden (Netherlands); Vliet, Lucas J. van [Quantitative Imaging Group, Faculty of Applied Sciences, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft (Netherlands); Rieger, Bernd, E-mail: b.rieger@tudelft.nl [Quantitative Imaging Group, Faculty of Applied Sciences, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft (Netherlands)

    2012-05-15

    Defocus and twofold astigmatism are the key parameters governing the contrast transfer function (CTF) in transmission electron microscopy (TEM) of weak phase objects. We present a new algorithm to estimate these aberrations and the associated uncertainties. Tests show very good agreement between simulated and estimated defocus and astigmatism. We evaluate the reproducibility of the algorithm on experimental data by repeating measurements of an amorphous sample under identical imaging conditions and by analyzing the linearity of the stigmator response. By using a new Thon ring averaging method, the modulation depth of the rings in a 1D averaged power spectrum density (PSD) can be enhanced compared to elliptical averaging. This facilitates a better contrast transfer assessment in the presence of spherical aberration. Our algorithm for defocus and astigmatism estimation inverts the contrast of the Thon rings and suppresses the background in the PSD using an adaptive filtering strategy. Template matching with kernels of various ellipticities is applied to the filtered PSD after transformation into polar coordinates. Maxima in the resulting 3D parameter space provide multiple estimates of the long axis orientation, frequencies and apparent ellipticities of the rings. The frequencies of the detected rings, together with outlier rejection and assignment of an order to the CTF zeros, are used to estimate the defocus and its uncertainty. From estimations of defocus and ellipticity, we derive astigmatism and its uncertainty. A two-pass approach refines the astigmatism and defocus estimate by taking into account the influence of the known spherical aberration on the shape and frequencies of the rings. The implementation of the presented algorithm is freely available for non-commercial use. -- Highlights: Black-Right-Pointing-Pointer Unbiased and precise defocus and astigmatism estimation with related uncertainties. Black-Right-Pointing-Pointer The background in the PSD is

  9. Precise and unbiased estimation of astigmatism and defocus in transmission electron microscopy

    International Nuclear Information System (INIS)

    Defocus and twofold astigmatism are the key parameters governing the contrast transfer function (CTF) in transmission electron microscopy (TEM) of weak phase objects. We present a new algorithm to estimate these aberrations and the associated uncertainties. Tests show very good agreement between simulated and estimated defocus and astigmatism. We evaluate the reproducibility of the algorithm on experimental data by repeating measurements of an amorphous sample under identical imaging conditions and by analyzing the linearity of the stigmator response. By using a new Thon ring averaging method, the modulation depth of the rings in a 1D averaged power spectrum density (PSD) can be enhanced compared to elliptical averaging. This facilitates a better contrast transfer assessment in the presence of spherical aberration. Our algorithm for defocus and astigmatism estimation inverts the contrast of the Thon rings and suppresses the background in the PSD using an adaptive filtering strategy. Template matching with kernels of various ellipticities is applied to the filtered PSD after transformation into polar coordinates. Maxima in the resulting 3D parameter space provide multiple estimates of the long axis orientation, frequencies and apparent ellipticities of the rings. The frequencies of the detected rings, together with outlier rejection and assignment of an order to the CTF zeros, are used to estimate the defocus and its uncertainty. From estimations of defocus and ellipticity, we derive astigmatism and its uncertainty. A two-pass approach refines the astigmatism and defocus estimate by taking into account the influence of the known spherical aberration on the shape and frequencies of the rings. The implementation of the presented algorithm is freely available for non-commercial use. -- Highlights: ► Unbiased and precise defocus and astigmatism estimation with related uncertainties. ► The background in the PSD is suppressed by adaptive filtering. ► Robust template

  10. Optimum form of posterior chamber intraocular lenses to minimize aberrational astigmatism.

    Science.gov (United States)

    Takei, K; Hommura, S; Okajima, H

    1995-01-01

    To optically determine the optimum form for a posterior chamber intraocular lens (PC IOL), we calculated the aberrational astigmatism induced by tilt and decentration of the PCIOL using an exact raytracing. First, the position and the radii of curvatures of the IOL were determined to make an emmetropic eye model using a paraxial raytracing. Next, the chief rays originating from the fovea centralis were traced backward through the tilted and/or decentrated PC IOL, the center of the pupil and the cornea, using trigonometric raytracing. Finally, the maximum and minimum aberrational astigmatism were calculated based on the Coddington's Equations for the sagittal and the tangential foci of the ray. All the refractive parameters in Gullstrand's No. 1 schematic eye were adopted. The effect of varying anterior corneal asphericity on the results was also examined. Four forms of polymethylmethacrylate PC IOLs (refractive index: 1.491) were analyzed; a plano-convex IOL with the curved surface facing the cornea, and three bi-convex forms with the ratio of anterior-to-posterior radii of curvatures of 1:4, 1:2 and 1:1, respectively. The 1:4 bi-convex form showed the lowest values for the maximum aberrational astigmatism calculated at every combination of tilt and decentration except 0 degrees tilt and/or 0 mm decentration. The aberrational astigmatism with the 1:4 bi-convex form of PC IOL did not exceed 1.0 D at the maximum tilt and decentration. The variation of anterior corneal asphericity did not influence the results. We conclude that the 1:4 bi-convex form of PC IOL minimizes the postoperative astigmatism induced by tilt and/or decentration of the lens. PMID:8926647

  11. Extended depth of focus intra-ocular lens: a solution for presbyopia and astigmatism

    Science.gov (United States)

    Zlotnik, Alex; Raveh, Ido; Ben Yaish, Shai; Yehezkel, Oren; Belkin, Michael; Zalevsky, Zeev

    2010-02-01

    Purpose: Subjects after cataract removal and intra-ocular lens (IOL) implantation lose their accommodation capability and are left with a monofocal visual system. The IOL refraction and the precision of the surgery determine the focal distance and amount of astigmatic aberrations. We present a design, simulations and experimental bench testing of a novel, non-diffractive, non-multifocal, extended depth of focus (EDOF) technology incorporated into an IOL that allows the subject to have astigmatic and chromatic aberrations-free continuous focusing ability from 35cm to infinity as well as increased tolerance to IOL decentration. Methods: The EDOF element was engraved on a surface of a monofocal rigid IOL as a series of shallow (less than one micron deep) concentric grooves around the optical axis. These grooves create an interference pattern extending the focus from a point to a length of about one mm providing a depth of focus of 3.00D (D stands for Diopters) with negligible loss of energy at any point of the focus while significantly reducing the astigmatic aberration of the eye and that generated during the IOL implantation. The EDOF IOL was tested on an optical bench simulating the eye model. In the experimental testing we have explored the characteristics of the obtained EDOF capability, the tolerance to astigmatic aberrations and decentration. Results: The performance of the proposed IOL was tested for pupil diameters of 2 to 5mm and for various spectral illuminations. The MTF charts demonstrate uniform performance of the lens for up to 3.00D at various illumination wavelengths and pupil diameters while preserving a continuous contrast of above 25% for spatial frequencies of up to 25 cycles/mm. Capability of correcting astigmatism of up to 1.00D was measured. Conclusions: The proposed EDOF IOL technology was tested by numerical simulations as well as experimentally characterized on an optical bench. The new lens is capable of solving presbyopia and astigmatism

  12. Influence of age, corneal astigmatism and some characteristics of intraocular lens on glare in pseudophakic persons

    Directory of Open Access Journals (Sweden)

    Avramović Siniša

    2007-01-01

    Full Text Available Background/Aim. Although an extraordinary visual acuity is achieved following the extracapsular cataract extraction with the implantation of intraocular lens, all the problems of vision are not solved in so doing and many of them should be considered. The aim of this study was to establish the influence of age, dioptric power of intraocular lens, corneal astigmatism and optic diameter of intraocular lens on glare in pseudophakic subjects. Methods. We examined 152 patients who underwent final correction at least two weeks after the suture removing what was performed if the astigmatism more than 2.0 D was measured by the use of a Javal keratometer. Examination was performed by a Rodenstock Adaptometer Nyctomat. According to the recommendation of the manufacturer, healthy persons should notice 50% of contrast under the constant glare and in the given time. Statistical data processing was performed by χ2 test. Results. In the group of patients with the findings lower than normal at constant glare there were 112 of eyes (73.68% as follows: 22 eyes (14.47% at the age from 50-55 years; 15 eyes (9.87% were at the age from 56-60 years; 18 eyes (11.84% were at the age from 61-65 years, and 57 eyes (37.50% were at the age from 66-70 years. Dioptric power of lenses up to 20.0 D had 37 eyes (24.3%, from 20.5-22.0 D 85 eyes (56.9% and more than 22.5 D, 27 eyes (17.8%. Regarding the results of discomfort caused by glare and corneal astigmatism, measured by a Javal keratometer, in the observed group normal results were found in 112 eyes (73.68%, and out of that number 95 (62.50% were with corneal astigmatism less than 20.0 D, and 17 (11.18% had astigmatism of 20.0 D and more. Out of 112 eyes there were 58 of them (38.16% with findings lower than normal in relation to the constant glare and with the lens diameter of 5.5 mm, 48 (31.58% with the lens diameter of 6.0mm, and 6 of them (3.95% with lens diameter of 6.5mm. Conclusion. The study determined a

  13. Induced astigmatism after cataract surgery - a retrospective analysis of cases from the University of Port Harcourt Teaching Hospital, Nigeria

    Directory of Open Access Journals (Sweden)

    A. O. Adio

    2011-12-01

    Full Text Available Visual rehabilitation after cataract surgery may often be disappointing due to induction of corneal astigmatism following issues in realigning, point to point, the corneal wound margin in the process of surgery despite biometry and use of the appropriateintraocular lens. The purpose of this study is to determine the amount of surgically induced astigmatism after sutured cataract extraction-extracapsular cataract extraction (ECCE and intracapsular cataract extraction (ICCE and intraocular lens (IOLimplantation in the University of Port Harcourt Teaching Hospital, Port Harcourt, Nigeria. Folders of all cataract patients operated on in the eye theatre of the aforenamed tertiary facility between2002 and 2006 were considered.  Relevant patient details and intraoperative and postoperative management were examined and reported upon. One hundred and fourteen eyes (114 of one hundred patients who had cataract surgeries done within the five-year period of this study were examined. ECCE + IOL implantation were examined in the period under review. The post-operative refraction objectively and subjectively was retrieved from the records of each patient. The post-operative cylinderpower (total astigmatism was recorded.Of 114 eyes, only 83 eyes (72.8% had refraction results postoperatively due to loss of fol-low-up. The total number with astigmatism was 57(68.7%. Forty-two had against-the-rule (73.7%, twelve (21.1% with-the-rule, while five (0.09% were oblique. The mean post-operative astigmatism was 1.85 D. The surgically induced corneal astigmatism was highest with ECCE with PCIOL. Astigmatism less than 2 D was highest in this group (ECCE with IOL while ICCE with ACIOL had the highest number with astigmatism in the range between 2 D and 4 D. The total astigmatism which was mainly with-the-rule (vertical plus cylinder did not seem to impair severely the post-operative visual acuity of the patients.In conclusion, surgically induced astigmatism affected almost

  14. Invariance of mode transformation by an astigmatic π/2 converter upon the input-beam displacement and tilt

    International Nuclear Information System (INIS)

    It is shown theoretically and experimentally that the transformation of modes by an astigmatic π/2 converter is invariant with respect to the input-beam displacement and tilt. The possibility is considered of using this property for manipulating microobjects and simultaneous generation of Laguerre-Gaussian modes of different orders with the help of the same astigmatic π/2 converter. (laser modes and beams)

  15. MAGNITUDE OF POST OPERATIVE CORNEAL ASTIGMATISM AFTER PHACOEMULSIFICATION THROUGH 3.2MM TEMPORAL CLEAR CORNEAL INCISION

    OpenAIRE

    Neeraj

    2014-01-01

    Surgically induced astigmatism (SIA) is a common obstacle for achieving excellent uncorrected visual acuity after Phacoemulsification with implantation of foldable IOL. The aim of the study was to determine the magnitude of surgically induced post-operative astigmatism after phacoemulsification with intraocular lens implantation through a temporal clear corneal incision. This study included 16 eyes with senile cataract which were operated using phacoemulsification with imp...

  16. Induced astigmatism after cataract surgery - a retrospective analysis of cases from the University of Port Harcourt Teaching Hospital, Nigeria

    OpenAIRE

    A. O. Adio; N. Aruoto

    2011-01-01

    Visual rehabilitation after cataract surgery may often be disappointing due to induction of corneal astigmatism following issues in realigning, point to point, the corneal wound margin in the process of surgery despite biometry and use of the appropriateintraocular lens. The purpose of this study is to determine the amount of surgically induced astigmatism after sutured cataract extraction-extracapsular cataract extraction (ECCE) and intracapsular cataract extraction (ICCE) and intraocular le...

  17. Distribution and Repeatability of Corneal Astigmatism Measurements (Magnitude and Axis) Evaluated With Color Light Emitting Diode Reflection Topography

    OpenAIRE

    Kanellopoulos, Anastasios John; Asimellis, George

    2015-01-01

    Purpose: To evaluate and investigate the distribution and repeatability of anterior corneal surface astigmatism measurements (axis and magnitude) using a novel corneal topographer. Methods: Anterior corneal surface astigmatism was investigated in a total of 195 eyes using a novel multicolored spot reflection topographer (Cassini; i-Optics). Two patient groups were studied, a younger-age group A and an older-age group B. Three consecutive acquisitions were obtained from each eye. The repeatabi...

  18. Comparative study of surgically induced astigmatism in superior versus temporal incision in small incision cataract surgery case

    OpenAIRE

    Kuruva Nandyala Sree Kavitha; Arikeri Krishna Kishore; Ganta Sudhakar Reddy; Khaiser Jehan

    2015-01-01

    Background: Location of incision has a significant impact on surgical outcome. It has been reported that temporal incisions induce less astigmatism than superior incisions indicating the importance of incision location. The objective of the present study was to study the effect of surgical induced astigmatism in superior versus temporal incision in small incision cataract surgery cases. Methods: 100 patients of cataract attending to Sarojini Devi eye hospital with the rule and against the ...

  19. Tunable astigmatic π/2 converter of laser modes with a fixed distance between input and output planes

    International Nuclear Information System (INIS)

    The scheme of a tunable astigmatic π/2 mode converter is proposed in which the distance between input and output planes is fixed. The converter is tuned only by rotating the cylindrical components of optical quadrupoles used in the converter around its optical axis. The Gouy phase difference in the orthogonal planes of the astigmatic π/2 converter required for mode conversion was achieved for the first time by using the scaled fractional Fourier transforms of the appropriate orders. (laser modes and beams)

  20. Astigmatism in candidates of Cataract surgery and its relationship with corneal optical power, axial length, sex and patient age

    OpenAIRE

    Siatiri H

    2000-01-01

    This study was conducted to define the prevalence and types of corneal astigmatism in relation with corneal optical power, axial length, sex and patient age. 641 cataract patients were included in a descriptive study. Complete eye examinations were included in a descriptive study. Complete eye examinations were performed. The data were analysed by standard procedures including analysis of variance, chi square test and multiple linear regression models. With the rule, astigmatism was 55.6% in ...

  1. Comparison of Wavelight Allegretto Eye-Q and Schwind Amaris 750S excimer laser in treatment of high astigmatism

    OpenAIRE

    Bohac, Maja; Biscevic, Alma; Koncarevic, Mateja; Anticic, Marija; Gabric, Nikica; Patel, Sudi

    2014-01-01

    Purpose To compare functional outcomes of Wavelight Allegretto Eye-Q 400Hz and Schwind Amaris 750S excimer laser for astigmatism between 2 and 7 diopters(D). Methods Prospective comparative non-randomized case series of 480 eyes assigned in two laser groups and further divided into myopic and mixed astigmatism subgroups. All treatments were centered on corneal vertex. One-year results were compared between the groups. Statistical analysis was performed using z-test. Results Both Allegretto an...

  2. Comparison of Mean Contrast Sensitivity Results of LASIK and LASEK in Patients with Myopia and Myopic Astigmatism

    OpenAIRE

    Okan Taşkın; Zeynep Özbek

    2014-01-01

    Objectives: To compare LASIK and LASEK for the correction of myopia and myopic astigmatism in terms of contrast sensitivity. Materials and Methods: Sixty eyes of 30 patients who underwent LASIK and 60 eyes of 30 patients who underwent LASEK for myopia and myopic astigmatism at the Excimer Laser Center of Dokuz Eylül University, Faculty of Medicine, were included in this study. Mean best-corrected contrast sensitivity values were noted before surgery. Mean uncorrected contrast sensiti...

  3. Corneal astigmatism change and wavefront aberration evaluation after cataract surgery: "Single" versus "paired opposite" clear corneal incisions

    OpenAIRE

    Hasan Razmjoo; Nima Koosha; Mohammad Hadi Vaezi; Behrooz Rahimi; Alireza Peyman

    2014-01-01

    Background: Correcting the pre-existing astigmatism is an optimal goal in cataract surgery. The aim of this study is to compare the astigmatic correcting effect of a single regular 3.2 mm clear corneal incision (CCI) with paired opposite CCI in cataract patients and effect of these incisions on optical aberrations using the wavefront quantitative analysis. Materials and Methods: This was a randomized controlled trial study undertaken in an ophthalmology referral center on 50 patients plan...

  4. CLINICAL STUDY OF VARIOUS TYPES OF INCISIONS IN SMALL INCISION CATARACT SURGERY IN RELATION TO THEIR ASTIGMATISM OUT COME

    OpenAIRE

    Sindhura; Venkateswarlu; Sudhakar Rao; Balla Vidya

    2015-01-01

    AIM: To evaluate the surgically induced astigmatism ¹with different types of incisions in manual small incision cataract surgery over a period of one week, two weeks, four weeks and six weeks post - operative period. As the incision is the major cause for surgically induced astigmatism and this effect is directly related to the length, shape, location and depth of the incision. METHODS: Pr ospective analysis of the medical records of a total of 100 patients...

  5. Modeling of astigmatic-elliptical beam shaping during fs-laser waveguide writing including beam truncation and diffraction effects

    Science.gov (United States)

    Ruiz De la Cruz, A.; Ferrer, A.; del Hoyo, J.; Siegel, J.; Solis, J.

    2011-08-01

    In this work, we report a model for accurately calculating the focal volumes corresponding to astigmatic elliptical beams used in fs-laser waveguide writing. The model is based on the use of the ABCD matrix formalism for the propagation of a Gaussian beam. The code includes the effects of propagation on the astigmatic elliptical beam, and the effects of beam truncation and diffraction at the entrance pupil of the focusing objective due to beam clipping when overfilling the pupil. The results predict that for a given astigmatism value and propagation distance it is possible to efficiently suppress the astigmatic focus closer to the surface. This explains previous experimental results where single structure waveguides with controllable aspect-ratio were fabricated using astigmatic-elliptical beams. Furthermore, we investigate the respective roles of astigmatism and beam propagation, as well as the strong impact of truncation and diffraction effects caused by clipping the beam at the pupil of the focusing optics. Finally, based on the results from our model, we present some practical considerations in terms of beam propagation and phase wrapping constraints.

  6. Thermal correction of astigmatism in the gravitational wave observatory GEO 600

    International Nuclear Information System (INIS)

    The output port of GEO 600 is dominated by unwanted higher order modes (HOMs). The current thermal actuation system, a ring heater behind one of the folding mirrors, causes a significant amount of astigmatism, which produces HOMs. We have built and installed an astigmatism correction system, based on heating this folding mirror at the sides (laterally). With these side heaters and the ring heater behind the mirror, it is possible to tune its radius of curvature in the horizontal and the vertical degree of freedom. We use this system to match the mirrors in the two arms of GEO 600 to each other, thereby reducing the contrast defect. The use of the side heaters reduces the power of the HOMs at the output of GEO 600 by approximately 37%. (paper)

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

    International Nuclear Information System (INIS)

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

  8. Thermal Correction of Astigmatism in the Gravitational Wave Observatory GEO 600

    CERN Document Server

    Wittel, Holger; Affeldt, Christoph; Dooley, Katherine L; Grote, Hartmut; Leong, Jonathan R; Prijatelj, Mirko; Schreiber, Emil; Slutsky, Jacob; Strain, Kenneth A; Was, Michal; Willke, Benno; Danzmann, Karsten

    2013-01-01

    The output port of GEO 600 is dominated by unwanted high order modes (HOMs). The current thermal actuation system, a ring heater behind one of the folding mirrors, causes a significant amount of astigmatism, which produces HOMs. We have built and installed an astigmatism correction system, based on heating this folding mirror at the sides (laterally). With these side heaters and the ring heater behind the mirror, it is possible to tune its radius of curvature in the horizontal and the vertical degree of freedom. We use this system to match the mirrors in the two arms of GEO 600 to each other, thereby reducing the contrast defect. The use of the side heaters reduces the power of the HOMs at the output of GEO 600 by approximately 37%.

  9. Abnormal periodicities due to astigmatism in HRTEM images of orthorhombic zirconia

    International Nuclear Information System (INIS)

    Full text: Apparently 'anomalous' images associated with diffracted beams that are both kinematically and dynamically forbidden are well known at close to zone-axis oriented crystals. These images have been explained as being due to the effects of small beam tilts and/or crystal tilts away from the zone axis, or possibly arising from changes in alignment on switching between image and SAD modes. Here we show using both experimental and simulated images that residual astigmatism can lead to abnormal periodicities in HRTEM images of orthorhombic ZrO2. In this case, the appearance of the 'anomalous' lattice fringe spacings is due to changes in diffracted beam amplitudes or phases of non-forbidden reflections due to small amounts of astigmatism resulting from specimen charging effects. Copyright (2002) Australian Society for Electron Microscopy Inc

  10. Effects of astigmatic aberration in holographic generation of Laguerre-Gaussian beam

    Science.gov (United States)

    Wada, Atsushi; Miyamoto, Yoko; Ohtani, Takumi; Nishihara, Noboru; Takeda, Mitsuo

    2001-05-01

    The Laguerre-Gaussian (LG) beam is an optical beam with a phase singularity that propagates along its axis. We have previously reported the fabrication of blazed transmission phase holograms to generate beams with phase singularities. A common problem encountered in the generation of a phase singularity with high charge is that the singularity tends to split into m individual charge 1 singularities, where m is the charge of the original singularity. We have found through numerical simulation that astigmatic aberration can cause a higher-charge phase singularity to split. We have also found that strong astigmatic aberrations make the resulting beam close to a Hermite-Gaussian beam rather than an LG beam. Experimental investigation of these phenomena agree with the numerical simulation.

  11. Thermal correction of astigmatism in the gravitational wave observatory GEO 600

    Science.gov (United States)

    Wittel, H.; Lück, H.; Affeldt, C.; Dooley, K. L.; Grote, H.; Leong, J. R.; Prijatelj, M.; Schreiber, E.; Slutsky, J.; Strain, K.; Was, M.; Willke, B.; Danzmann, K.

    2014-03-01

    The output port of GEO 600 is dominated by unwanted higher order modes (HOMs). The current thermal actuation system, a ring heater behind one of the folding mirrors, causes a significant amount of astigmatism, which produces HOMs. We have built and installed an astigmatism correction system, based on heating this folding mirror at the sides (laterally). With these side heaters and the ring heater behind the mirror, it is possible to tune its radius of curvature in the horizontal and the vertical degree of freedom. We use this system to match the mirrors in the two arms of GEO 600 to each other, thereby reducing the contrast defect. The use of the side heaters reduces the power of the HOMs at the output of GEO 600 by approximately 37%.

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

    Energy Technology Data Exchange (ETDEWEB)

    Patino, A [Universidad Technologica de Bolivar, Cartagena de Indias (Colombia); Durand, P-E; Fogret, E; Pellat-Finet, P, E-mail: alberto.patino-vanegas@univ-ubs.fr [Laboratoire de mathematiques et applications des mathematiques, Universite de Bretagne Sud, B P 92116, 56321 Lorient cedex (France)

    2011-01-01

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

  13. Change in Astigmatism After Temporal Clear Corneal Cataract Extraction in the Pediatric Population

    OpenAIRE

    Lam, Helene Y; Yen, Kimberly G

    2008-01-01

    Purpose: To evaluate the early postoperative change in astigmatism in pediatric patients having cataract extraction with intraocular lens implantation using sutured temporal clear corneal incision. Methods: A retrospective chart review was performed on all pediatric patients who underwent clear corneal cataract surgery with intraocular lens implantation between 12/01/2005 and 11/30/2006. Results: A total of 31 eyes of 22 patients who underwent temporal clear corneal cataract surgery and intra...

  14. Beam characteristics including general astigmatism effects in the Remote Steering ITER ECRH Upper Launcher

    International Nuclear Information System (INIS)

    Full text: General astigmatism treatment has been included in the description of the resulting beams for the latest design concepts proposed for the Remote Steering (RS) Launcher. The inclusion of general astigmatism is intended to provide the key parameters of the resulting beams and perform realistic beam tracing calculations in the plasma. It is in fact well known that the many requirements foreseen for the ITER ECRH Upper launcher force the beams to be injected in the plasma with a sufficient steering capability aiming at the stabilization of neoclassical tearing modes (NTM) through localized deposition of EC waves. To do this, double curvature mirrors are used in the latest RS quasi-optical systems. The mirrors are oriented at an angle with respect to each other and with respect to the directions of astigmatism of the incoming launched beam. The resulting beams are found to be generally astigmatic beams. The correct description of the beam parameters resulting from this kind of complex launching system can in principle be used to optimize the RS quasi-optical system (in terms of localized heating and current drive efficiency), acting for example on the curvatures of the last mirror. The curvature in the direction determined by the steering plane should not be considered a free parameter, since the necessary output steering range has to be granted, but the curvature in the direction orthogonal to the steering plane could be modified to improve the performances of the launcher. Starting from the design proposed, the analysis presented here includes beam optics calculations. This approach was agreed within affiliate institutes to optimise the efficiency of the RS Upper launcher design. The work was carried out under EFDA Task TW6-TPHE-ECHULB. (author)

  15. Conditioning optics for astigmatic Gaussian beams at 140 GHz, 0.5 MW

    International Nuclear Information System (INIS)

    A quasi-optical system has been designed to couple the power coming from a gyrotron with astigmatic gaussian beam output, into an oversized corrugated waveguide (HE11 mode). The fraction of the power injected in the transmission line can be controlled by means of a wire grid beam splitter. Polarization control is provided by two rotating corrugated mirrors of electrical depth λ/4 and λ/8 respectively

  16. Beam width evolution of astigmatic hollow Gaussian beams in highly nonlocal nonlinear media

    Science.gov (United States)

    Yang, Zhen-Feng; Jiang, Xue-Song; Yang, Zhen-Jun; Li, Jian-Xing; Zhang, Shu-Min

    We investigate the beam width evolution of astigmatic hollow Gaussian beams propagating in highly nonlocal nonlinear media. The input-power-induced different evolutions of the beam width are illustrated: (i) the beam widths in two transverse directions are compressed or broadened at the same time; (ii) the beam width in one transverse direction keeps invariant, and the other is compressed or broadened; (iii) furthermore, the beam width in one transverse direction is compressed, whereas it in the other transverse direction is broadened.

  17. Toric intraocular lenses for correction of astigmatism in keratoconus and after corneal surgery

    OpenAIRE

    Mol, Ilse

    2016-01-01

    Ilse EMA Mol,1,2 Bart TH Van Dooren1,2 1Department of Ophthalmology, Amphia Hospital, Breda, 2Department of Ophthalmology, Erasmus Medical Center, Rotterdam, the Netherlands Purpose: To describe the results of cataract extraction with toric intraocular lens (IOL) implantation in patients with preexisting astigmatism from three corneal conditions (keratoconus, postkeratoplasty, and postpterygium surgery).Methods: Cataract patients with topographically stable, fairly regular (although sometim...

  18. Femtosecond micromachining of symmetric waveguides at 1.5 microm by astigmatic beam focusing.

    Science.gov (United States)

    Cerullo, G; Osellame, R; Taccheo, S; Marangoni, M; Polli, D; Ramponi, R; Laporta, P; De Silvestri, S

    2002-11-01

    We report on a new spatial beam-shaping approach for fabrication of waveguides with a circular transverse profile by femtosecond laser pulses, using an astigmatic beam and controlling both beam waist and focal position in the tangential and sagittal planes. We apply this technique to write single-mode active waveguides at 1.5microm in Er:Yb-doped glass substrates. The experimental results are well described by a simple nonlinear absorption model. PMID:18033408

  19. Comparison of surgically induced astigmatism in corneo-scleral and clear corneal incision in phacoemulsification

    OpenAIRE

    Latha N.V; Risha Ravindran; Asha A.V; Twinkle Ann George

    2015-01-01

    Background: The objective of the study was to determine and compare the surgically induced astigmatism in patients who have undergone phacoemulsification with clear corneal and corneoscleral incisions made superiorly and temporally. Methods: Study was conducted in 100 patients who underwent cataract surgery from a period of November 2012 to July 2014. They were evaluated pre and post-operatively. Pre-op and Post-op Vision, retinoscopy and keratometry were analysed and surgically induced a...

  20. Pterygium surgery with conjunctival autograft and induced astigmatism in young men

    OpenAIRE

    Hüseyin Mayalı

    2012-01-01

    Objectives: To evaluate the results obtained from malesubjects who underwent pterygium surgery with conjunctivalautograft and to calculate the induced astigmatism.Materials and methods: Pterygium surgery with conjunctivalautograft was performed on 22 eyes of 20 subjectsdiagnosed with primary pterygium. If pterygium caused avision problem or approached the pupil level, and if surgerywas requested from the individuals for cosmetic reasons,the decision to operate was made. Patients who underwent...

  1. The role of sideport incision in astigmatism change after cataract surgery

    OpenAIRE

    Theodoulidou, Sofia

    2015-01-01

    Sofia Theodoulidou,1 Ioannis Asproudis,1 Christos Kalogeropoulos,1 Aristidis Athanasiadis,2 Miltiadis Aspiotis1 1Department of Ophthalmology, Medical School, University of Ioannina, Ioannina, Greece; 2Ophthalmology Clinic, General Hospital of Piraeus “Tzaneio”, Attiki, Greece Purpose: To study the changes in corneal astigmatism after cataract surgery when the sideport incision is performed at a predetermined location away from the tunnel incision. Setting: General Hospit...

  2. Comparison of Surgically Induced Astigmatisms after Clear Corneal Incisions of Different Sizes

    OpenAIRE

    Moon, Sung Chur; Mohamed, Tarek; Fine, I. Howard

    2007-01-01

    Purpose This study was performed to assess efficiency and stability of astigmatic change by incision size after cataract surgery. Methods This work was designed as a retrospective, comparative, nonrandomized interventional study. A total of 121 cases of cataract surgery were reviewed in 98 patients performed by one surgeon at the Oregon Eye Institute in Eugene, OR, USA with 3-year follow-ups. All procedures were performed with the temporal approach of self-sealing incisions. The serial change...

  3. Comparison of surgically induced astigmatism between one-handed and two-handed cataract surgery techniques

    OpenAIRE

    Kawahara A; Kurosaka D; Yoshida A

    2013-01-01

    Atsushi Kawahara,1 Daijiro Kurosaka,2 Akitoshi Yoshida31Department of Ophthalmology, Sapporo Tokushukai Hospital, Sapporo, 2Department of Ophthalmology, Iwate Medical University, Morioka, 3Department of Ophthalmology, Asahikawa Medical University, Asahikawa, JapanBackground: The purpose of this study was to compare surgically induced astigmatism (SIA) between one-handed and two-handed cataract surgery techniques.Methods: Eighty-eight eyes of 44 patients with no ocular disease other than catar...

  4. Keratometric astigmatism after ECCE in eastern Nepal. Continuous versus interrupted sutures.

    OpenAIRE

    Sood Archana; Thakur Sanjay Kumar; Kumar Sandeep; Badhu Badri

    2003-01-01

    Purpose: The study aimed to compute and compare the keratometric astigmatism induced by wound closure with continuous and interrupted sutures in conventional extracapsular cataract extraction with intraocular lens implantation at a single centre in eastern Nepal. Methods: Sixty eyes of 60 patients were included in the study. All patients received conventional extracapsular cataract extraction and single piece modified C-loop posterior chamber intraocular lens. Thirty eyes were sutured with...

  5. Pterygium surgery with conjunctival autograft and induced astigmatism in young men

    Directory of Open Access Journals (Sweden)

    Hüseyin Mayalı

    2012-09-01

    Full Text Available Objectives: To evaluate the results obtained from malesubjects who underwent pterygium surgery with conjunctivalautograft and to calculate the induced astigmatism.Materials and methods: Pterygium surgery with conjunctivalautograft was performed on 22 eyes of 20 subjectsdiagnosed with primary pterygium. If pterygium caused avision problem or approached the pupil level, and if surgerywas requested from the individuals for cosmetic reasons,the decision to operate was made. Patients who underwentany ocular surgery, have ocular surface disease,eyelid problems or systemic disease were not includedin the study. A complete ophthalmologic examination wasperformed before surgery, at one month following the surgery,and during the final controls. Induced astigmatismwas calculated by using refractive parameters and VectorialAnalysis Program.Results: Twenty-two eyes of 20 subjects were included inthe study. Mean age was 22.50 ± 4.15 (20-39 years. Allsubjects included in the study were male patients. Of the22 eyes, 14 were right and 8 were left eyes. In the evaluationsof visual acuity and intraocular pressure values preandpost- surgery, no statistical significance was detected(p=0.142, p=0.831. During the surgery, relapse was detectedin 4 eyes (18% and conjunctival granuloma (9%was detected in 2 eyes. Following the surgery, arithmeticaverage of the induced astigmatisms at 1st month was0.91±1.19 D; against-the-rule astigmatism was detectedin nearly 60% of the eyes. The subjects were followed upfor 93.59±36.47 days after the surgery.Conclusions: In primary pterygium subjects of youngage, surgery with conjunctival autograft was consideredas a preferable method due to its low number of relapseand complications, as well as absence of any adverse effecton visual acuity.Key words: Astigmatism, pterygium, young adult

  6. The role of sideport incision in astigmatism change after cataract surgery

    OpenAIRE

    Theodoulidou S; Asproudis I; Kalogeropoulos C; Athanasiadis A; Aspiotis M

    2015-01-01

    Sofia Theodoulidou,1 Ioannis Asproudis,1 Christos Kalogeropoulos,1 Aristidis Athanasiadis,2 Miltiadis Aspiotis1 1Department of Ophthalmology, Medical School, University of Ioannina, Ioannina, Greece; 2Ophthalmology Clinic, General Hospital of Piraeus “Tzaneio”, Attiki, Greece Purpose: To study the changes in corneal astigmatism after cataract surgery when the sideport incision is performed at a predetermined location away from the tunnel incision. Setting: General Hospital of Pi...

  7. Opto-Mechanical Model of Arcuates for Astigmatism Correction. Low and High Order Aberrations

    OpenAIRE

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

    2011-01-01

    To develop a realistic model of the opto-mechanical behaviour of the cornea after curved relaxing incisions, and compare the astigmatism correction predicted by the model with that of the Lindstrom's nomogram. Methods: A three-dimensional finite element model of the anterior hemisphere of the ocular surface was generated, considering three parts: cornea, limbus and sclera. The corneal tissue was modeled as a quasiincompressible, anisotropic hyperelastic constitutive behaviour s...

  8. Clinical Efficacy of Toric Orthokeratology in Myopic Ado-lescent with Moderate to High Astigmatism

    Institute of Scientific and Technical Information of China (English)

    Ming Luo; Shengsheng Ma; Na Liang

    2014-01-01

    Purpose:.To observe the efficacy of toric design orthokera-tology.(ortho-k).for correcting myopia and astigmatism in my-opic adolescents with moderate to high astigmatism. Methods:.This was a self-controlled clinical study..Twenty-four subjects(42 eyes).aged 9 to 16 years with myopia of 2.50-6.00 D complicated with rule astigmatism of 1.50-3.50 D were fitted with Lucid Night Toric Ortho-k Lenses (LUCID,KO-REA)..The changes in uncorrected visual acuity (UCVA), spherical degree, refraction, axial length (AL),.and corneal status were assessed at baseline, 1 night, 1 week, 1 month, 3 months, 6 months, and 1 year after the commencement of or-tho-k lens wear. Results: The success rate of the first lens fit was 92.8%. The UCVA after ortho-k wearing was improved significantly com-pared to the baseline during each visit (all P0.05)..Grade 1 corneal staining was observed at 1 week (23.8%),.1 month (21.4%), and 1 year (16.7%) fol-lowing lens wear, and was improved by lens cleaning,.discon-tinuing lens wear, and moistening the cornea with eye drops. No severe adverse events were reported. Conclusion: The toric ortho-k lens was effective and safe for correction of low to moderate myopia in children with moder-ate to high astigmatism..The lens also effectively controlled axial length elongation during 1 year of observation..However, the long-term efficacy remains to be elucidated.

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

    International Nuclear Information System (INIS)

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

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

    Directory of Open Access Journals (Sweden)

    R Bassily

    2010-03-01

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

  11. Use of a Toric Intraocular Lens and a Limbal-Relaxing Incision for the Management of Astigmatism in Combined Glaucoma and Cataract Surgery

    Science.gov (United States)

    Gibbons, Allister

    2016-01-01

    Purpose We report the surgical management of a patient with glaucoma undergoing cataract surgery with high preexisting astigmatism. A combination of techniques was employed for her astigmatism management. Methods A 76-year-old female with 5.5 dpt of corneal astigmatism underwent surgery in her left eye consisting of one-site trabeculectomy, phacoemulsification, toric intraocular lens implantation and a single inferior limbal-relaxing incision. Results Intraocular pressure control was achieved with no medication at 11 mm Hg; before the filtering procedure, the pressure was 16 mm Hg on two topical drugs. Astigmatism was reduced to 0.75 dpt, and both corrected and uncorrected visual acuity improved. Conclusions Astigmatism management can have a good outcome in combined procedures. We encourage surgeons to address astigmatism in the preoperative planning of patients undergoing glaucoma surgery associated with phacoemulsification.

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

    OpenAIRE

    Al-Zeraid, Ferial M.; Osuagwu, Uchechukwu L.

    2016-01-01

    Background Wavefront-guided Laser-assisted in situ keratomileusis (LASIK) is a widespread and effective surgical treatment for myopia and astigmatic correction but whether it induces higher-order aberrations remains controversial. The study was designed to evaluate the changes in higher-order aberrations after wavefront-guided ablation with IntraLase femtosecond laser in moderate to high astigmatism. Methods Twenty-three eyes of 15 patients with moderate to high astigmatism (mean cylinder, −3...

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

    OpenAIRE

    Zhang, Jiamei; Wang, Yan; Wu, Wenjing; XU, LULU; Li, Xiaojing; Dou, Rui

    2015-01-01

    Background To evaluate the refractive outcomes for the correction of low to moderate astigmatism up to 1 year following small incision lenticule extraction (SMILE) surgery. Methods This retrospective study enrolled 98 eyes from 98 patients who underwent SMILE surgery for the correction of myopia and astigmatism. Only right eyes were included in this study to avoid the bias of orientation errors. The vector method was used to analyze the outcomes of astigmatism at 1 month, 6 months and 12 mont...

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

    Directory of Open Access Journals (Sweden)

    Amedo AO

    2016-04-01

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

  15. Corneal astigmatism change and wavefront aberration evaluation after cataract surgery: "Single" versus "paired opposite" clear corneal incisions

    Directory of Open Access Journals (Sweden)

    Hasan Razmjoo

    2014-01-01

    Full Text Available Background: Correcting the pre-existing astigmatism is an optimal goal in cataract surgery. The aim of this study is to compare the astigmatic correcting effect of a single regular 3.2 mm clear corneal incision (CCI with paired opposite CCI in cataract patients and effect of these incisions on optical aberrations using the wavefront quantitative analysis. Materials and Methods: This was a randomized controlled trial study undertaken in an ophthalmology referral center on 50 patients planned for cataract surgery who were randomized to either single 3.2 mm CCI or paired opposite CCI group. Post-operative evaluation was performed at 12 weeks and included refraction, keratometery, corneal topography and wavefront analysis. Corneal astigmatism and post-operative values were compared in two groups. Results: The mean pre-operative corneal astigmatism was 2.58 ± 1.03 D in the single incision group and 2.70 ± 0.94 D in the paired opposite incisions group. After 12 weeks of surgery, the corneal astigmatism was reached to 2.15 ± 0.82 D in single incision group and 1.63 ± 1.21 in the paired opposite incisions group. There was a statistically significant difference in two arms of treatment regarding to surgically induced astigmatism after 3 months. The mean post-operative total and higher order aberrations and values were not significantly different in two groups. Conclusion: The results of our study showed that paired opposite incisions is an effective procedure for reducing pre-existing corneal astigmatism in cataract surgery. Paired incisions did not show any beneficial effect regarding wavefront aberrations compared with conventional single incision method.

  16. ROLE OF INCISION SITE IN REDUCING SURGICALLY INDUCE D ASTIGMATISM IN MANUAL SMALL INCISION CATARACT SURGE RY

    Directory of Open Access Journals (Sweden)

    Sathish

    2013-04-01

    Full Text Available INTRODUCTION: Phacoemulsification and foldable IOLs allow modern day surgeon to aim at minimal induction of any astigmatic error as well a s correct any pre-operative refractive errors thus making patients’ life, spectacle free i.e. una ided emmetropia. But its high price and maintenance with a long learning curve for the surg eon make it unsuitable for the Indian camp scenario. Manual SICS in comparison needs a larger incision f or both nucleus removal and a rigid IOL insertion, but still provides for a sutureless and c onvenient alternative to phaco. Manual SICS does induce some amount of astigmatism by altering corneal curvatures (i.e., by coupling effect, while phaco surgery with 3 mm incision is astigmatic ally neutral. Manifold of studies have been done to compare Surgically Induced Astigmatism of ma nual SICS to phaco surgery but not much has been done to compare various techniques in manua l SICS itself. In this study an attempt has been made to analyze t he role of incision site depending on the pre operative keratometry readings in reducing su rgically induced astigmatism in manual small incision cataract surgery.

  17. Comparison of surgically induced astigmatism between one-handed and two-handed cataract surgery techniques

    Directory of Open Access Journals (Sweden)

    Kawahara A

    2013-10-01

    Full Text Available Atsushi Kawahara,1 Daijiro Kurosaka,2 Akitoshi Yoshida31Department of Ophthalmology, Sapporo Tokushukai Hospital, Sapporo, 2Department of Ophthalmology, Iwate Medical University, Morioka, 3Department of Ophthalmology, Asahikawa Medical University, Asahikawa, JapanBackground: The purpose of this study was to compare surgically induced astigmatism (SIA between one-handed and two-handed cataract surgery techniques.Methods: Eighty-eight eyes of 44 patients with no ocular disease other than cataract, who underwent cataract surgery by a single surgeon, were selected for this study. Cataract surgery was performed by coaxial phacoemulsification and intraocular lens implantation via a 2.4 mm transconjunctival single-plane sclerocorneal incision at the 12 o'clock position. In each patient, one eye was subjected to coaxial phacoemulsification using a one-handed technique while the fellow eye was subjected to coaxial phacoemulsification using a two-handed technique. For the two-handed technique, a corneal side port was created at the 2 o'clock position. The appropriate incision meridian was identified by a preoperative axis mark. SIA was calculated using the Alpins method.Results: Mean SIA was 0.40 ± 0.28 diopters (D in the one-handed technique group and 0.39 ± 0.25 D in the two-handed technique group. No statistically significant difference was found in the mean SIA score. The mean torque value was −0.05 ± 0.26 D in the one-handed technique group and 0.11 ± 0.37 D in the two-handed technique group. Mean torque was significantly lower (P<0.05 in the one-handed technique group than in the two-handed technique group.Conclusion: The results indicate that the corneal side port in two-handed cataract surgery has a rotating effect on the axis of astigmatism.Keywords: cataract surgery, corneal side port, surgically induced astigmatism

  18. SURGICALLY INDUCED ASTIGMATISM AFTER IMPLANTATION OF FOLDABLE AND NON - FOLDABLE LENSES IN CATARACT SURGERY BY PHACOEMULSIFICATION

    Directory of Open Access Journals (Sweden)

    Vikas

    2015-01-01

    Full Text Available This prospective comparative study included 300 matched patients of different grades of senile cataract. All of them willfully underwent phacoemulsification at the hands of a single experienced surgeon, performing with a single and individual technique {Woodcutter’s technique 1 }; half of them were implanted with a foldable intraocular lens and the other half with a non - foldable PMMA intraocular lens. All the patients undergoing phacoemulsification had an improvement in vision. There was no statistically significant difference in the surgically induced astigmatism after implanting foldable or non - foldable IOL

  19. A Michelson controlled-not gate with a single-lens astigmatic mode converter.

    Science.gov (United States)

    Souza, C E R; Khoury, A Z

    2010-04-26

    We propose and demonstrate experimentally a single lens design for an astigmatic mode converter that transforms the transverse mode of paraxial optical beams. As an application, we implement a controlled-not gate based on a Michelson interferometer in which the photon polarization is the control bit and the first order transverse mode is the target. As a further application, we also build a transverse mode parity sorter which can be useful for quantum information processing as a measurement device for the transverse mode qubit. PMID:20588767

  20. Wide measurement range scanning heterodyne interferometer utilizing astigmatic position sensing scheme

    Science.gov (United States)

    Park, Youngkyu; Kim, Kyoung-Eop; Kim, Seong-Jin; Park, June-Gyu; Joo, Young-Hun; Shin, Bu Hyun; Lee, Seung-Yop; Cho, Kyuman

    2011-08-01

    A scanning heterodyne I/Q-interferometer scheme is proposed to overcome phase ambiguity caused by the periodic nature of its phase-dependent signal. A position sensing scheme using an astigmatic method in the confocal arrangement has been interfaced to the interferometer to retrieve the real phase value during a scanning process. The experimental results show that the vertical measurement range can be expanded up to 16μm. The potential of this interferometer on the scanning microscopy of a rough surface is discussed.

  1. Clinical studies of fully automatic computer optometry to test children astigmatism and the change of axial

    OpenAIRE

    Xiao-Zhen Huang

    2015-01-01

    AIM: To observe and analyze the detection results of child astigmatism before and after cycloplegia and axial changes by using computer automatic refractometer. METHODS:Sixty cases(120 eyes)with anisometropia founded by subjective optometry were selected as the research object. According to age, they were divided into 3~6 years groups(14 cases, 28 eyes), 7~9 years group(29 cases, 58 eyes)and 10~12 years group(17 cases, 34 eyes). Three groups of patients were given compound tropicamide eye dro...

  2. Effects of Optically Imposed Astigmatism on Early Eye Growth in Chicks

    OpenAIRE

    Chu, Chin Hung Geoffrey; Kee, Chea Su

    2015-01-01

    Purpose To determine the effects of optically imposed astigmatism on early eye growth in chicks. Methods 5-day-old (P5) White Leghorn chicks were randomly assigned to either wear, monocularly, a “high magnitude” (H: +4.00DS/-8.00DC) crossed-cylindrical lens oriented at one of four axes (45, 90, 135, and 180; n = 20 in each group), or were left untreated (controls; n = 8). Two additional groups wore a “low magnitude” (L: +2.00DS/−4.00DC) cylindrical lens orientated at either axis 90 or 180 (n ...

  3. Topographic and keratometric astigmatism up to 1 year following small flap trabeculectomy (microtrabeculectomy)

    OpenAIRE

    VERNON, S; Zambarakji, H; Potgieter, F; Evans, J.; Chell, P

    1999-01-01

    AIM—To determine the induced corneal astigmatism by measuring the changes in manual keratometry and computerised corneal videokeratoscopy up to 1 year following small flap trabeculectomy (microtrabeculectomy).
METHOD—A prospective study of a case series of small flap trabeculectomy procedures performed at the 90 degree meridian on 16 eyes of 16 patients, all followed to 1 year postoperatively. Changes in manual keratometry and computerised videokeratoscopy (Eyesys) readings were analysed by v...

  4. Influence of astigmatism on the fabrication of diffractive structures by use of focused ion-beam milling

    Science.gov (United States)

    Fu, Yongqi; Bryan, Ngoi Kok Ann

    2004-08-01

    Astigmatism exists in a focused-ion-beam (FIB) system and causes the shape of a beam spot to change from a normal circle to an ellipse. This variation influences the fabrication of diffractive structures by use of programmable controlled milling of a FIB. It is analyzed combined with the fabrication of blazed gratings and Fresnel diffractive lenses. Fabrication errors caused by a beam spot with astigmatism is discussed in detail for four cases of the long axis of an ellipse (a) in accordance with the X axis, (b) in accordance with the Y axis, (c) at 45° with the X axis, and (d) at -45° with the X axis. Finally, a method is given for correction of the astigmatism and how to determine the circularity of the beam spot qualitatively.

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

    Directory of Open Access Journals (Sweden)

    Giuliano de Oliveira Freitas

    2014-01-01

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

  6. Measurement of acceleration and orbital angular momentum of Airy beam and Airy-vortex beam by astigmatic transformation.

    Science.gov (United States)

    Singh, Brijesh Kumar; Remez, Roei; Tsur, Yuval; Arie, Ady

    2015-11-15

    Special beams, including the Airy beam and the vortex-embedded Airy beam, draw much attention due to their unique features and promising applications. Therefore, it is necessary to devise a straightforward method for measuring these peculiar features of the beams with ease. Hence we present the astigmatic transformation of Airy and Airy-vortex beam. The "acceleration" coefficient of the Airy beam is directly determined from a single image by fitting the astigmatically transformed beam to an analytic expression. In addition, the orbital angular momentum of optical vortex in Airy-vortex beam is measured directly using a single image. PMID:26565887

  7. CLINICAL STUDY OF VARIOUS TYPES OF INCISIONS IN SMALL INCISION CATARACT SURGERY IN RELATION TO THEIR ASTIGMATISM OUT COME

    Directory of Open Access Journals (Sweden)

    Sindhura

    2015-06-01

    Full Text Available AIM: To evaluate the surgically induced astigmatism ¹with different types of incisions in manual small incision cataract surgery over a period of one week, two weeks, four weeks and six weeks post - operative period. As the incision is the major cause for surgically induced astigmatism and this effect is directly related to the length, shape, location and depth of the incision. METHODS: Pr ospective analysis of the medical records of a total of 100 patients who underwent manual small incision cataract surgery with various types of incisions with SIA.

  8. Clinical outcomes of wavefront-guided laser in situ keratomileusis to treat moderate-to-high astigmatism

    OpenAIRE

    Schallhorn, Steven

    2015-01-01

    Steven C Schallhorn,1,2 Jan A Venter,2 Stephen J Hannan,2 Keith A Hettinger2 1University of California, San Francisco, CA, USA; 2Optical Express, Glasgow, UK Purpose: The purpose of this study was to evaluate the refractive and visual outcomes of wavefront-guided laser in situ keratomileusis (LASIK) in eyes with myopic astigmatism and cylindrical component ≥2.0 diopter (D).Methods: In this retrospective study, 611 eyes that underwent LASIK for simple or compound myopic astigmatism we...

  9. Clinical outcomes of wavefront-guided laser in situ keratomileusis to treat moderate-to-high astigmatism

    OpenAIRE

    Schallhorn SC; Venter JA; Hannan SJ; Hettinger KA

    2015-01-01

    Steven C Schallhorn,1,2 Jan A Venter,2 Stephen J Hannan,2 Keith A Hettinger2 1University of California, San Francisco, CA, USA; 2Optical Express, Glasgow, UK Purpose: The purpose of this study was to evaluate the refractive and visual outcomes of wavefront-guided laser in situ keratomileusis (LASIK) in eyes with myopic astigmatism and cylindrical component ≥2.0 diopter (D).Methods: In this retrospective study, 611 eyes that underwent LASIK for simple or compound myopic astigmatism were a...

  10. Characterization of a tunable astigmatic fluidic lens with adaptive optics correction for compact phoropter application

    Science.gov (United States)

    Fuh, Yiin-Kuen; Huang, Chieh-Tse

    2014-07-01

    Fluidically controlled lenses which adaptively correct prescribed refractive error without mechanically moving parts are extensively applied in the ophthalmic applications. Capable of variable-focusing properties, however, the associated aberrations due to curvature change and refractive index mismatch can inherently degrade image quality severely. Here we present the experimental study of the aberrations in tunable astigmatic lens and use of adaptive optics to compensate for the wavefront errors. Characterization of the optical properties of the individual lenses is carried out by Shack-Hartmann measurements. An adaptive optics (AO) based scheme is demonstrated for three injected fluidic volumes, resulting in a substantial reduction of the wavefront errors from -0.12, -0.25, -0.32 to 0.01, -0.01, -0.20 μm, respectively, corresponding to the optical power tenability of 0.83 to 1.84 D. Furthermore, an integrated optical phoroptor consisting of adjustable astigmatic lenses and AO correction is demonstrated such that an induced refraction error of -1 D cylinder at 180° of a model eye vision is experimentally corrected.

  11. A COMPARATIVE STUDY OF POST OPERATIVE ASTIGMATISM IN SUPERIOR VERSUS TEMPORAL APPROACH OF MANUAL SMALL INCISION CATARACT SURGERY

    Directory of Open Access Journals (Sweden)

    Jawed

    2014-06-01

    Full Text Available BACKGROUND: Manual small incision cataract surgery is a simple and less expensive technique of cataract surgery but gives visual result almost equivalent to Phacoemulsification. PURPOSE: To compare surgery induced astigmatism in manual small incision cataract surgery through superior and temporal approaches. METHODOLOGY: One hundred and thirty eyes were included in this study. Eyes with steeper vertical keratometric reading were subjected to superior small incision cataract surgery (SICS and those with a steeper horizontal keratometric reading were subjected to temporal small incision cataract surgery (SICS. Eyes with no astigmatism were randomly subjected to either type of surgery. Each group had 65 eyes. All the patients were followed up on 1st , 7th, 30th and 90th postoperative days. During each follow up, UCVA and BCVA were recorded, slit lamp examination was performed; autorefractometry and keratometric examinations were also performed. RESULTS: Out of 65 in the temporal incision group only 55 completed follow up till 90th day. The mean surgery induced astigmatism was found to be 1.45 ± 0.4 D in superior and 0.70 ± 0.3 D in the temporal incision group. Amount of surgery induced astigmatism was found to be significantly lower among the temporal incision group (t = 11.444, p = 0.000. CONCLUSION: SICS through temporal approach provides a better stabilization of refraction with significantly lesser amount of SIA than superior approach.

  12. Evaluation of Refractive Results of LASIK and LASEK in Patients with Myopia and Myopic Astigmatism

    Directory of Open Access Journals (Sweden)

    Okan Taşkın

    2014-10-01

    Full Text Available Objectives: To compare the mean visual acuity, spherical equivalent (SE, cylindrical refractive error, and central corneal thickness (CCT results of LASIK and LASEK in patients with myopia and myopic astigmatism. Materials and Methods: A retrospective review of the patients who underwent LASIK or LASEK for myopia or myopic astigmatism between 2008 and 2011 was performed in the Department of Ophthalmology at Dokuz Eylül University School of Medicine. Preoperative data collected were as follows: Mean SE, mean cylindrical refractive error, best-corrected visual acuity (BCVA, and mean CCT. Postoperative data included mean SE, uncorrected visual acuity (UCVA, mean CCT, and complications at 1, 3, and 6 months, as well as at the last control. The results in the LASIK group were compared to those in the LASEK group. Results: The both (LASIK and LASEK groups consisted of 60 eyes of 30 patients. All exams and surgeries were performed by one surgeon (ZO. The two groups were similar in terms of age and gender. Mean preoperative SE and BCVA values of the two groups were similar. The mean preoperative cylindrical refractive error values were significantly higher in the LASEK group (p=0.02. The mean preoperative CCT values were significantly lower in the LASEK group (p=0.0. At one month after the surgery, the mean SE and cylindrical refractive error values were not significantly different, but the mean UCVA values were significantly higher in the LASIK group (p=0.015. At six months, the mean SE, cylindrical refractive error, and UCVA values were not significantly different. The mean follow-up period was 13.4 (9-36 months months. Mean UCVA values at the last exam were higher than the preoperative mean BCVA values in both LASIK and LASEK groups. Conclusion: Both LASIK and LASEK are effective and safe procedures for correction of myopia and myopic astigmatism. The patients with normal corneal thickness and epithelium, normal lid aperture, and low trauma risk are

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

    Directory of Open Access Journals (Sweden)

    Lehmann RP

    2012-03-01

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

  14. Clinical outcomes of wavefront-guided laser in situ keratomileusis to treat moderate-to-high astigmatism

    Directory of Open Access Journals (Sweden)

    Schallhorn SC

    2015-07-01

    Full Text Available Steven C Schallhorn,1,2 Jan A Venter,2 Stephen J Hannan,2 Keith A Hettinger2 1University of California, San Francisco, CA, USA; 2Optical Express, Glasgow, UK Purpose: The purpose of this study was to evaluate the refractive and visual outcomes of wavefront-guided laser in situ keratomileusis (LASIK in eyes with myopic astigmatism and cylindrical component ≥2.0 diopter (D.Methods: In this retrospective study, 611 eyes that underwent LASIK for simple or compound myopic astigmatism were analyzed. Preoperative refractive cylinder ranged from -2.00 D to -6.00 D (mean -2.76±0.81 D, and the sphere was between 0.00 D and -9.75 D (mean -2.79±2.32 D. Predictability, visual outcomes, and vector analysis of changes in refractive astigmatism were evaluated.Results: At 3 months after LASIK, 83.8% of eyes had uncorrected distance visual acuity of 20/20 or better, 90.3% had manifest spherical equivalent within ±0.50 D, and 79.1% had residual refractive cylinder within ±0.50 D of intended correction. The mean correction ratio for refractive cylinder was 0.92±0.14, the mean error of angle was -0.45°±2.99°, and the mean error vector was 0.37±0.38 D. A statistically significant correlation was found between the error of magnitude (arithmetic difference in the magnitudes between surgically induced refractive correction and intended refractive correction and the intended refractive correction (r=0.26, P<0.01.Conclusion: Wavefront-guided LASIK for the correction of myopic astigmatism is safe, effective, and predictable. Keywords: myopic astigmatism, wavefront-guided LASIK, Hartmann–Shack aberrometer

  15. Analysis of familial aggregation in total, against-the-rule, with-the-rule, and oblique astigmatism by conditional and marginal models in the Tehran eye study

    Directory of Open Access Journals (Sweden)

    Mohammad H Rakhshani

    2012-01-01

    Full Text Available Purpose: The purpose was to determine the familial aggregation of the total, against-the-rule (ATR, with-the-rule (WTR, and oblique astigmatism by conditional and marginal models in the Tehran Eye Study. Materials and Methods: Total, ATR, WTR, and oblique astigmatism were studied in 3806 participants older than 5 years from August 2002 to December 2002 in the Tehran Eye Study. Astigmatism was defined as a cylinder worse than or equal to −0.5 D. WTR astigmatism was defined as 0 ± 19°, ATR astigmatism was defined as 90 ± 19°, and oblique when the axes were 20-70° and 110-160°. The familial aggregation was investigated with a conditional model (quadratic exponential and marginal model (alternating logistic regression after controlling for confounders. Results: Using the conditional model, the conditional familial aggregation odds ratios (OR (95% confidence interval for the total, WTR, ATRs, and oblique astigmatism were 1.49 (1.43-1.72, 1.91 (1.65-2.20, 2.00 (1.70-2.30, and 1.86 (1.37-2.54, respectively. In the marginal model, the marginal OR of the parent-offspring and sib-sib in the total astigmatism were 1.35 (1.13-1.63 and 1.54 (1.13-2.11, respectively; WTR 1.53 (1.06-2.20 and 1.94 (1.21-3.13 and; ATR 2.13 (1.01-4.50 and 2.23 (1.52-3.30. The model was statistically significant in sib-sib relationship only for oblique astigmatism with OR of 3.00 (1.25-7.20. Conclusion: The results indicate familial aggregation of astigmatism in the population in Tehran adjusted for age, gender, cataract, duration of education, and body mass index, so that the addition of a new family member affected with astigmatism, as well as having a sibling or parents with astigmatism, significantly increases the odds of exposure to the disease for all four phenotypes. This aggregation can be due to genetic and/or environmental factors. Dividing astigmatism into three phenotypes increased the odds ratios.

  16. Electron-optical parameters of an immersion astigmatic lense made of two coaxial cylinders with cuttings

    International Nuclear Information System (INIS)

    The analytical numerical method is used to calculate cardinal elements of the immersion axisymmetric-quadrupole (AQ) lense formed by two coaxial cylinders with two symmetric cuttings in the internal cylinder. Potential distribution on the axis of such a lense is obtained in the form of a simple empyrical formula which approximates the results of measurements on the electrolitic bath with good accuracy. The calculation of electron-optical properties of the first AQ order of the lense is computerized by numerical integration of paraxial motion equations. The dependences of focal distances and focal positions in a wide region of potential changes on electrodes with different cutting lengths and widths in the internal electrode are studied. The AQ lense of simple design considered can form astigmatic beams and can be used in different electron and ion devices, whose tracts have elements with a noncircular aperture

  17. The origin of the Gouy phase anomaly and its generalization to astigmatic wavefields

    Science.gov (United States)

    Visser, T. D.; Wolf, E.

    2010-09-01

    One of the most poorly understood subjects in physical optics is the origin of the Gouy phase (sometimes called "the phase anomaly near focus"). This is evident from the large number of publications on the subject, many of which attribute it to quite different causes. In this paper we show that the Gouy phase anomaly can be clearly understood from elementary properties of normal congruences of light rays and from the relationship between geometrical optics and physical optics. We also show that the Gouy phase anomaly may be regarded as a degenerate case of a rapid π/2 phase change that is found to occur at each focal line of an astigmatic pencil of rays. The intensity distribution in the region of the phase changes is also presented. Furthermore, symmetry relations for both the phase anomaly and the intensity distribution are derived.

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

    KAUST Repository

    Oba, Tatsuya

    2012-06-19

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

  19. Evaluation of the orientation of the steepest meridian of regular astigmatism among highly myopic Egyptian patients seeking non-ablative surgical correction of the refractive error

    OpenAIRE

    Refai, Tamer Adel

    2015-01-01

    Introduction: LASIK surgery is currently the preferred procedure to correct low to moderate myopia. The aim of this study was to determine the orientation of the steepest meridian of regular astigmatism in order to determine the relative incidence of vertical, horizontal, and oblique regular astigmatism among highly myopic Egyptian patients seeking non-ablative surgical correction of the refractive error. Methods: One hundred and one eyes of 68 highly myopic patients who were seeking refracti...

  20. Successful toric intraocular lens implantation in a patient with induced cataract and astigmatism after posterior chamber toric phakic intraocular lens implantation: a case report

    OpenAIRE

    Kamiya Kazutaka; Nakamura Akio; Miyake Hideyuki; Nishimoto Hiroyuki; Shimizu Kimiya

    2012-01-01

    Abstract Introduction We report the case of a patient in whom simultaneous toric phakic intraocular lens removal and phacoemulsification with toric intraocular lens implantation were beneficial for reducing pre-existing astigmatism and acquiring good visual outcomes in eyes with implantable collamer lens-induced cataract and astigmatism. Case presentation A 53-year-old woman had undergone toric implantable collamer lens implantation three years earlier. After informed consent was obtained, we...

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

    OpenAIRE

    Appenteng Osae, Eugene

    2016-01-01

    Angela Ofeibea Amedo, Kwadwo Amoah, Nana Yaa Koomson, David Ben Kumah, Eugene Appenteng Osae Department of Optometry and Visual Science, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana Abstract: To investigate which of two tunnel incision forms (frown versus straight) in sutureless manual small incision cataract surgery creates more corneal astigmatism. Sixty eyes of 60 patients who had consented to undergo cataract surgery and to partake in this study were followed from ba...

  2. A Comparative Study of Surgically Induced Astigmatism in Superior and Temporal Scleral Incision in Manual Small Incision Cataract Surgery

    OpenAIRE

    Renu M Magdum; Abha Gahlot; Rupali D.Maheshgauri; Khevna Patel

    2012-01-01

    Aim: To evaluate the amount and type of surgically induced astigmatism in superior and temporal scleral incision in Manual Small Incision Cataract Surgery (MSICS). Material and Methods: A prospective randomized comparative study was carried out in 100 cases of senile or pre-senile cataract. All the patients underwent MSICS under peribulbar anaesthesia. The patients with very hard cataract were excluded so as to keep the incision size uniformity (6-6.5mm). 50 cases received superior scleral in...

  3. A COMPARATIVE STUDY OF SURGICALLY INDUCED ASTIGMATISM IN FROWN VERSUS CHEVRON INCISION IN MANUAL SMALL INCISION CATARACT SURGERY

    OpenAIRE

    Prakash; Satish; Savita; Meghana; Madhumita; Ambika A.; Amar; Mohan

    2013-01-01

    ABSTRACT: PUR POSE : To compare the surgically induced astigmatism following chevron incision versus frown incision in MSICS. METHOD: The study was conducted from January 2012 to December 2012. 200 patients were selected of which 100 patients above the age of 50yrs, with soft cataracts, up to grade 2 nuclear sc lerosis underwent MSICS with chevron incision and t he remaining matched group underwent MSICS with frown incision. For all the pa...

  4. A COMPARATIVE STUDY OF SURGICALLY INDUCED ASTIGMATISM IN STRAIGHT, FROWN AND MODIFIED CHEVRON INCISIONS IN MANUAL SMALL INCISION CATARACT SURGERY

    Directory of Open Access Journals (Sweden)

    Deepshikha

    2015-04-01

    Full Text Available PURPOSE : To compare the surgically induced astigmatism following straight, frown and modified chevron incisions in MSICS. METHOD: This is a Prospective interventional study conducted in RIO Bhopal during academic session of April 2009 to October 2010 in which 145 eyes of 137 patients were evaluated. Patients with relatively soft nuclei and healthy cornea, adequate anterior chamber an d those who could be called up for regular follow up were chosen for the study. Preoperative keratometry was done to determine K - reading in both horizontal and vertical meridians. Astigmatism was graded and classified according to Holmström’s gradation 1 37 .9% cases we re given straight incision, 18. 6% cases were given Frown incision. While in the remaining 43 . 4% cases Modified chevron was made. In majority of cases 71%, 6 . 5 mm incision was made while larger incision 7mm and 7 . 5mm were made in 23 . 4% and 5 . 5% cases respectively. Post - operative keratometry readings were taken at first post - operative day and at the end of 6 th week following surgery and surgically induced astigmatism was calculated. RESULTS: Post operatively frown incision group’s average SIA was 0 . 68 D . Modified chevron incision group had 1 . 02 D SIA, Straight incision group had the maximum SIA of 1 . 15D. However the mean surgically induced astigmatism in all incision types in our study was found to have SIA=1 . 01 D . CONCLUSION: In our study we obs erved that Frown incision was the best of all incision types with regards to SIA.

  5. ROLE OF INCISION SITE IN REDUCING SURGICALLY INDUCE D ASTIGMATISM IN MANUAL SMALL INCISION CATARACT SURGE RY

    OpenAIRE

    Sathish; Prakash; Gunderao; Kaup; Kanchana; Ambika A.; Amar; Uma

    2013-01-01

    INTRODUCTION: Phacoemulsification and foldable IOLs allow modern day surgeon to aim at minimal induction of any astigmatic error as well a s correct any pre-operative refractive errors thus making patients’ life, spectacle free i.e. una ided emmetropia. But its high price and maintenance with a long learning curve for the surg eon make it unsuitable for the Indian camp scenario. Manual SICS in comparison needs a larger incision f or both nucleus removal and a ...

  6. A COMPARATIVE STUDY OF SURGICALLY INDUCED ASTIGMATISM IN STRAIGHT, FROWN AND MODIFIED CHEVRON INCISIONS IN MANUAL SMALL INCISION CATARACT SURGERY

    OpenAIRE

    Deepshikha; Anand

    2015-01-01

    PURPOSE : To compare the surgically induced astigmatism following straight, frown and modified chevron incisions in MSICS. METHOD: This is a Prospective interventional study conducted in RIO Bhopal during academic session of April 2009 to October 2010 in which 145 eyes of 137 patients were evaluated. Patients with relatively soft nuclei and healthy cornea, adequate anterior chamber an d those who could be called up for regular follow up were chosen for the study. Pr...

  7. A COMPARATIVE STUDY OF POST OPERATIVE ASTIGMATISM IN SUPERIOR VERSUS TEMPORAL APPROACH OF MANUAL SMALL INCISION CATARACT SURGERY

    OpenAIRE

    Jawed; Himadri; De, Abhijit; Rathindra; Surabhi; Uttam; Deepak; Madhusudan,

    2014-01-01

    BACKGROUND: Manual small incision cataract surgery is a simple and less expensive technique of cataract surgery but gives visual result almost equivalent to Phacoemulsification. PURPOSE: To compare surgery induced astigmatism in manual small incision cataract surgery through superior and temporal approaches. METHODOLOGY: One hundred and thirty eyes were included in this study. Eyes with steeper vertical keratometric reading were subjected to superior small incision catarac...

  8. Electron-optical properties of an astigmatic flat-electrode lense and a system of two-such lenses

    International Nuclear Information System (INIS)

    Astigmatic three-flat-electrode lense with holes is studied, holes in edge electrodes of the lense being round and a hole in the medium electrode being rectangular. Penta-electrode doublet made of these lenses is also investigated. Lense electrodes are made of brass with thickness of 1 mm. The diameter of holes in edge electrodes is equal to the width of a rectangular hole. The rectangular hole width was equal to 15 and 30 mm, the length - 60 mm. Distance between electrodes was equal to 15 mm. In lense doublet the distance between lenses was 30 mm. Electron-optical characteristics of the first and third order has been obtained. It is shown that considered lense has negative spherical aberration and the doublet of these lenses - reduced sphercal aberration. The lense, considered, can be used both as an independent focusing element and as a corrector of astigmatism and spherical aberration. Such a lense can be successfully used in different electron-optical devices both as an independent electron-optical element and as a corrector of astigmatism and spherical aberration

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

    Directory of Open Access Journals (Sweden)

    Je Hwan Yoon

    2013-01-01

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

  10. 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

    Purpose 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. Patients and methods 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. Results 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. Conclusion 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. PMID:27099463

  11. Use of astigmatic re-focusing at HP-XPS end-station

    International Nuclear Information System (INIS)

    In this paper we present the refocusing optics for the new high pressure photoelectron spectroscopy (HP-XPS) branch line at MAX-lab, based on a plane grating monochromator with vertically collimated beam. For the HP-XPS instrument, the required spot size is dictated by the small geometric acceptance of the HP-XPS electron energy analyzer. Whereas a pair of bendable mirrors in a KB configuration has some advantages as refocusing elements, we have studied whether similar performance can be achieved with a single non-bendable mirror. In this solution, however, the need for strong horizontal magnification results in a strong vertical magnification and into a very asymmetric image, the height being just a fraction of the width. We have studied through an analytical geometrical model and ray tracing simulations the use of astigmatism to increase the vertical beam size up to the geometric acceptance of the detector. As a result the vertical beam size at sample plane is mostly determined by the photon angular distribution and is not dependent on the exit slit aperture size. In addition the vertical beam size can be controlled by the grating cff parameter, making possible to adjust the photon density and minimize sample damage by the radiation.

  12. Inspection focus technology of space tridimensional mapping camera based on astigmatic method

    Science.gov (United States)

    Wang, Zhi; Zhang, Liping

    2010-10-01

    The CCD plane of the space tridimensional mapping camera will be deviated from the focal plane(including the CCD plane deviated due to camera focal length changed), under the condition of space environment and vibration, impact when satellite is launching, image resolution ratio will be descended because defocusing. For tridimensional mapping camera, principal point position and focal length variation of the camera affect positioning accuracy of ground target, conventional solution is under the condition of vacuum and focusing range, calibrate the position of CCD plane with code of photoelectric encoder, when the camera defocusing in orbit, the magnitude and direction of defocusing amount are obtained by photoelectric encoder, then the focusing mechanism driven by step motor to compensate defocusing amount of the CCD plane. For tridimensional mapping camera, under the condition of space environment and vibration, impact when satellite is launching, if the camera focal length changes, above focusing method has been meaningless. Thus, the measuring and focusing method was put forward based on astigmation, a quadrant detector was adopted to measure the astigmation caused by the deviation of the CCD plane, refer to calibrated relation between the CCD plane poison and the asrigmation, the deviation vector of the CCD plane can be obtained. This method includes all factors caused deviation of the CCD plane, experimental results show that the focusing resolution of mapping camera focusing mechanism based on astigmatic method can reach 0.25 μm.

  13. Correção do astigmatismo na cirurgia da catarata Surgical correction of astigmatism during cataract surgery

    Directory of Open Access Journals (Sweden)

    Edison Ferreira e Silva

    2007-08-01

    Full Text Available OBJETIVOS: Avaliar a eficácia das incisões periféricas relaxantes limbares (IPRL na redução do astigmatismo pré-operatório durante a cirurgia de catarata. MÉTODOS: Foram estudados prospectivamente 103 olhos de 103 pacientes submetidos as IPRL, utilizando o nomograna de Nichamin durante a cirurgia de catarata pela facoemulsificação. Após o 1º e 6º mês foram avaliadas as mudanças no astigmatismo topográfico, na indução do astigmatismo e no índice de sucesso. Os pacientes foram separados em dois grupos segundo o tipo de astigmatismo no pré-operatório (a favor da regra e contra a regra e estudados separadamente. RESULTADOS: Ocorreram diferenças estatisticamente significativas entre os valores dos astigmatismos topográficos no pré e pós-operatório nos dois grupos. Verificou-se indução de 1,10 ± 0,9 dioptrias e 37% de índice de sucesso no grupo de astigmatismo a favor da regra e 1,70 ± 0,80 dioptrias e 51% de índice de sucesso no grupo de astigmatismo contra a regra após o 6º mês de seguimento. CONCLUSÃO: A incisão periférica relaxante limbar é efetiva na redução do astigmatismo pré-existente durante a cirurgia da catarata. O procedimento mostrou ser seguro e de fácil realização. O nomograma de Nichamim na nossa experiência hipocorrige o astigmatismo planejado em ambos os grupos estudados.PURPOSE: To evaluate the effect of peripheral limbar relaxing incisions (PLRI in the reduction of the astigmatism during cataract surgery. METHODS: We studied prospectively 103 eyes of 103 patients submitted to PLRI, using the Nichamim nomogram during cataract surgery by phacoemulsification. After the first and sixth month we analized the changes in astigmatism topography, induction of astigmatism and sucess rate. The patients were divided into two groups according to the astigmatism (with-the-rule and against-the-rule, and studied separately. RESULTS: There was a statistically significant change in the mean astigmatism

  14. Transmissive liquid-crystal device correcting primary coma aberration and astigmatism in laser scanning microscopy

    Science.gov (United States)

    Tanabe, Ayano; Hibi, Terumasa; Ipponjima, Sari; Matsumoto, Kenji; Yokoyama, Masafumi; Kurihara, Makoto; Hashimoto, Nobuyuki; Nemoto, Tomomi

    2016-03-01

    Laser scanning microscopy allows 3D cross-sectional imaging inside biospecimens. However, certain aberrations produced can degrade the quality of the resulting images. We previously reported a transmissive liquid-crystal device that could compensate for the predominant spherical aberrations during the observations, particularly in deep regions of the samples. The device, inserted between the objective lens and the microscope revolver, improved the image quality of fixed-mouse-brain slices that were observed using two-photon excitation laser scanning microscopy, which was originally degraded by spherical aberration. In this study, we developed a transmissive device that corrects primary coma aberration and astigmatism, motivated by the fact that these asymmetric aberrations can also often considerably deteriorate image quality, even near the sample surface. The device's performance was evaluated by observing fluorescent beads using single-photon excitation laser scanning microscopy. The fluorescence intensity in the image of the bead under a cover slip tilted in the y-direction was increased by 1.5 times after correction by the device. Furthermore, the y- and z-widths of the imaged bead were reduced to 66% and 65%, respectively. On the other hand, for the imaged bead sucked into a glass capillary in the longitudinal x-direction, correction with the device increased the fluorescence intensity by 2.2 times compared to that of the aberrated image. In addition, the x-, y-, and z-widths of the bead image were reduced to 75%, 53%, and 40%, respectively. Our device successfully corrected several asymmetric aberrations to improve the fluorescent signal and spatial resolution, and might be useful for observing various biospecimens.

  15. 3D multifocus astigmatism and compressed sensing (3D MACS) based superresolution reconstruction.

    Science.gov (United States)

    Huang, Jiaqing; Sun, Mingzhai; Gumpper, Kristyn; Chi, Yuejie; Ma, Jianjie

    2015-03-01

    Single molecule based superresolution techniques (STORM/PALM) achieve nanometer spatial resolution by integrating the temporal information of the switching dynamics of fluorophores (emitters). When emitter density is low for each frame, they are located to the nanometer resolution. However, when the emitter density rises, causing significant overlapping, it becomes increasingly difficult to accurately locate individual emitters. This is particularly apparent in three dimensional (3D) localization because of the large effective volume of the 3D point spread function (PSF). The inability to precisely locate the emitters at a high density causes poor temporal resolution of localization-based superresolution technique and significantly limits its application in 3D live cell imaging. To address this problem, we developed a 3D high-density superresolution imaging platform that allows us to precisely locate the positions of emitters, even when they are significantly overlapped in three dimensional space. Our platform involves a multi-focus system in combination with astigmatic optics and an ℓ 1-Homotopy optimization procedure. To reduce the intrinsic bias introduced by the discrete formulation of compressed sensing, we introduced a debiasing step followed by a 3D weighted centroid procedure, which not only increases the localization accuracy, but also increases the computation speed of image reconstruction. We implemented our algorithms on a graphic processing unit (GPU), which speeds up processing 10 times compared with central processing unit (CPU) implementation. We tested our method with both simulated data and experimental data of fluorescently labeled microtubules and were able to reconstruct a 3D microtubule image with 1000 frames (512×512) acquired within 20 seconds. PMID:25798314

  16. Effect of Corneal Incision Enlargement on Surgically Induced Astigmatism in Biaxial Microincision Cataract Surgery

    Directory of Open Access Journals (Sweden)

    Mehmet Tetikoğlu

    2016-06-01

    Full Text Available Objectives: To evaluate surgically induced astigmatism (SIA in biaxial microincision cataract surgery with enlargement of one corneal incision during intraocular lens implantation (IOL. Materials and Methods: Data from 683 eyes with cataract that underwent biaxial microincision cataract surgery and IOL were retrospectively analyzed. The operated eyes were divided into 4 groups defined by final corneal incision length after IOL implantation. There were 83 eyes with 1.6 mm corneal incisions (group 1 and 200 eyes in each of the 2, 2.4, and 2.8 mm corneal incision groups (groups 2, 3 and 4, respectively. SIA was assessed using preoperative and postoperative keratometric values at one month. Results: The mean magnitude of SIA was 0.83±0.4 D in group 1, 0.93±0.5 D in group 2, 1.03±0.6 D in group 3 and 1.04±0.7 D in group 4. The SIA showed statistically significant differences between the four groups (p=0.05. Pairwise group comparisons revealed significant differences between groups 1 and 3 and groups 1 and 4 (p=0.005. Conclusion: Biaxial microincision cataract surgery with an incision size of 1.6 mm resulted in the least SIA. Enlargement of the corneal incision beyond 2.0 mm during IOL implantation led to significant increases in SIA. We believe that with the development and dissemination of IOLs which can be inserted through small corneal incisions, biaxial microincision cataract surgery will be the best choice to prevent SIA and increase visual acuity

  17. Comparison of Mean Contrast Sensitivity Results of LASIK and LASEK in Patients with Myopia and Myopic Astigmatism

    Directory of Open Access Journals (Sweden)

    Okan Taşkın

    2014-12-01

    Full Text Available Objectives: To compare LASIK and LASEK for the correction of myopia and myopic astigmatism in terms of contrast sensitivity. Materials and Methods: Sixty eyes of 30 patients who underwent LASIK and 60 eyes of 30 patients who underwent LASEK for myopia and myopic astigmatism at the Excimer Laser Center of Dokuz Eylül University, Faculty of Medicine, were included in this study. Mean best-corrected contrast sensitivity values were noted before surgery. Mean uncorrected contrast sensitivity values were evaluated 1 month and 6 months after surgery as well as at the last exam. Complications were noted. The results of LASIK and LASEK groups were compared. Results: The two groups were similar in terms of age and gender. No significant difference was noted between the mean preoperative best-corrected contrast sensitivity values of the two groups. Mean uncorrected contrast sensitivity values were not significantly different at the first and sixth months. Mean last exam time was 13.4 (9-36 months. Also at the last exam, mean uncorrected contrast sensitivity values were not significantly different. Mean uncorrected contrast sensitivity values at the last exam were higher than the preoperative mean best-corrected contrast sensitivity values in both LASIK and LASEK groups. Conclusion: Both LASIK and LASEK for the correction of myopia and myopic astigmatism seem to be safe procedures in terms of contrast sensitivity when performed to appropriate patients. Neither technique demonstrated significantly different contrast sensitivity results in this study. (Turk J Ophthalmol 2014; 44: 436-9

  18. Functional outcome and patient satisfaction after laser in situ keratomileusis for correction of myopia and myopic astigmatism

    Directory of Open Access Journals (Sweden)

    Mahfouth A Bamashmus

    2015-01-01

    Full Text Available Purpose: The purpose was to evaluate subjective quality of vision and patient satisfaction after laser in situ keratomileusis (LASIK for myopia and myopic astigmatism. Patients and Methods: A self-administered patient questionnaire consisting 29 items was prospectively administered to LASIK patients at the Yemen Magrabi Hospital. Seven scales covering specific aspects of the quality of vision were formulated including; global satisfaction; quality of uncorrected and corrected vision; quality of night vision; glare; daytime driving and; night driving. Main outcome measures were responses to individual questions and scale scores and correlations with clinical parameters. The scoring scale ranged from 1 (dissatisfied to 3 (very satisfied and was stratified in the following manner: 1-1.65 = dissatisfied; 1.66-2.33 = satisfied and; 2.33-3 = very satisfied. Data at 6 months postoperatively are reported. Results: This study sample was comprised of 200 patients (122 females: 78 males ranging in age from 18 to 46 years old. The preoperative myopic sphere was − 3.50 ± 1.70 D and myopic astigmatism was 0.90 ± 0.82 D. There were 96% of eyes within ± 1.00 D of the targeted correction. Postoperatively, the uncorrected visual acuity was 20/40 or better in 99% of eyes. The mean score for the overall satisfaction was 2.64 ± 0.8. A total of 98.5% of patients was satisfied or very satisfied with their surgery, 98.5% considered their main goal for surgery was achieved. Satisfaction with uncorrected vision was 2.5 ± 0.50. The main score for glare was 1.98 ± 0.7 at night. Night driving was rated more difficult preoperatively by 6.2%, whereas 79% had less difficulty driving at night. Conclusion: Patient satisfaction with uncorrected vision after LASIK for myopia and myopic astigmatism appears to be excellent and is related to the residual refractive error postoperatively.

  19. Propagation of an arbitrary vortex pair through an astigmatic optical system and determination of its net topological charge

    CERN Document Server

    Reddy, Salla Gangi; Aadhi, A; Banerji, J; Singh, R P

    2013-01-01

    We embed a pair of vortices with different topological charges in a Gaussian beam and study its evolution through an astigmatic optical system, a tilted lens. The propagation dynamics is explained by a closed-form analytical expression. Furthermore, we show that a careful examination of the intensity distribution at a predicted position past the lens can provide us with the net charge present in the beam. To the best of our knowledge, our method is the first non-interferometric technique to measure the net charge of an arbitrary vortex pair. Our experimental results are in close agreement with the theoretical predictions.

  20. Artisan iris-fixated toric phakic intraocular lens for the correction of high astigmatism after deep anterior lamellar keratoplasty

    OpenAIRE

    Al-Dreihi, Madonna G.; Louka, Bachar I.; Anas A Anbari

    2013-01-01

    We report the refractive correction of high astigmatism in one eye of a 23-year-old woman following deep anterior lamellar keratoplasty (DALK) using an Artisan iris-fixated, toric, phakic intraocular lens (IOL). One year after implantation, uncorrected and corrected distance visual acuities were both 20/25, refraction was −1.00 D cylinder, and the endothelial cell count was 1827 cells/mm2. Iris-fixated phakic IOLs are not recommended for every postkeratoplasty patient with high refractive err...

  1. A comparative analysis of the uncertainty of astigmatism-{mu}PTV, stereo-{mu}PIV, and {mu}PIV

    Energy Technology Data Exchange (ETDEWEB)

    Cierpka, C.; Rossi, M.; Segura, R.; Kaehler, C.J. [Universitaet der Bundeswehr Muenchen, Institute of Fluid Mechanics and Aerodynamics, Neubiberg (Germany); Mastrangelo, F. [Department of Mechanics, Torino (Italy)

    2012-03-15

    Astigmatism or wavefront deformation, microscopic particle tracking velocimetry (A-{mu}PTV) (Chen et al. in Exp Fluids 47:849-863, 2009; Cierpka et al. in Meas Sci Technol 21:045401, 2010b) is a method to determine the complete 3D3C velocity field in micro-fluidic devices with a single camera. By using an intrinsic calibration procedure that enables a robust and precise calibration on the basis of the measured data itself (Cierpka et al. in Meas Sci Technol 22:015401, doi:10.1088/0957-0233/22/1/015401, 2011), accurate results without errors due to spatial averaging or bias due to the depth of correlation can be obtained. This method takes all image aberrations into account, allows for the use of the whole CCD sensor, and is easy to apply without expert knowledge. In this paper, a comparative study is presented to assess the uncertainties of two state-of-the-art methods for 3C3D velocity field measurements in microscopic flows: stereoscopic micro-particle image velocimetry (S-{mu}PIV) and astigmatism micro-particle tracking velocimetry (A-{mu}PTV). First, the main parameters affecting all methods' measurement uncertainty are identified, described, and quantified. Second, the test case of the flow over a backward-facing step is analyzed using all methods. For comparison, standard 2D2C {mu}PIV measurements and numerical flow simulations are shown as well. Advantages and disadvantages of both methods are discussed. (orig.)

  2. A COMPARATIVE STUDY OF SURGICALLY INDUCED ASTIGMATISM IN FROWN VERSUS CHEVRON INCISION IN MANUAL SMALL INCISION CATARACT SURGERY

    Directory of Open Access Journals (Sweden)

    Prakash

    2013-10-01

    Full Text Available ABSTRACT: PUR POSE : To compare the surgically induced astigmatism following chevron incision versus frown incision in MSICS. METHOD: The study was conducted from January 2012 to December 2012. 200 patients were selected of which 100 patients above the age of 50yrs, with soft cataracts, up to grade 2 nuclear sc lerosis underwent MSICS with chevron incision and t he remaining matched group underwent MSICS with frown incision. For all the patients incision site was chosen based on the pre - op keratometr y readings and the incision length was 6mm. Patients’ keratometry readings were taken at the end of 6 weeks followin g surgery and surgically induced astigmatism was calculated. RESULTS: Post operatively, the surgically induced astigmati sm was 0.75D - 1.0D, in the frown incision group versus 0.5D - 0.75D, in the chevron incision group. CONCLUSION: The Surgically induced asti gmatism with chevron incision is 0.25D - 0.45D less than with frown incision.

  3. Analytic method for the construction of the fundamental mode of a resonator in the form of a Gaussian beam with complex astigmatism

    International Nuclear Information System (INIS)

    Explicit formulas are obtained for a resonator with the fundamental mode in the form of a Gaussian beam with complex astigmatism. The formulas describe the parameters of the beam directly in terms of the ray matrix without using the procedure of finding its eigenvectors. An example is considered. (resonators. modes)

  4. SURGICALLY INDUCED ASTIGMATISM AFTER 2.8 MM TEMPORAL AND NASAL CLEAR CORNEAL INCISIONS IN PHACOEMULSIFICATION CATARACT SURGERY OF SAME PATIENT

    Directory of Open Access Journals (Sweden)

    Preeti

    2015-04-01

    Full Text Available PURPOSE: To evaluate and compare the surgically induced astigmatism in phacoemulsification cataract surgery after 2.8 mm temporal and nasal clear corneal incision of same patient . MATERIAL AND METHOD : This prospective study comprised a consecutive case series of 60 eyes. Eyes from 30 patients with phacoemulsification those were implanted with a 6.00 mm foldable intraocular le ns through a 2.8 mm horizontal clear corneal incision (temporal in the right eye , nasal in the left eye. RESULTS : T he outcome measures were surgically induced astigmatism (SIA and uncorrected visual acuity (UCVA , at 1 and 3 months post - operatively. A 1 month the mean SIA was 0.81 D. for the temporal incision and 0.92 D for nasal incision (P = 0.139 at 3 months the mean SIA was 0.53 D for temporal incision and 0.62 D for nasal incision (P =0.309. The pre - operative parameters i.e. (UCVA , mean keratomet ry & keratometric cylinder between these groups were comparable. There was no statistically significant difference found between three groups pre - operatively . CONCLUSION : After cataract surgery using 2.8mm temporal and nasal horizontal corneal incision , t he induced corneal astigmatic changes was similar in both incision groups. Especially in Asian eyes , both temporal and nasal incisions (2.8 mm or less would be equally favourable for astigmatism neutral cataract surgery

  5. Methods for calculating the vergence of an astigmatic ray bundle in an optical system that contains a freeform surface

    Science.gov (United States)

    Shirayanagi, Moriyasu

    2016-07-01

    A method using the generalized Coddington equations enables calculating the vergence of an astigmatic ray bundle in the vicinity of a skew ray in an optical system containing a freeform surface. Because this method requires time-consuming calculations, however, there is still room for increasing the calculation speed. In addition, this method cannot be applied to optical systems containing a medium with a gradient index. Therefore, we propose two new calculation methods in this paper. The first method, using differential ray tracing, enables us to shorten computation time by using simpler algorithms than those used by conventional methods. The second method, using proximate rays, employs only the ray data obtained from the rays exiting an optical system. Therefore, this method can be applied to an optical system that contains a medium with a gradient index. We show some sample applications of these methods in the field of ophthalmic optics.

  6. Lasik para correção de miopia, astigmatismos e hipermetropia Lasik for myopia, astigmatism and hyperopia

    Directory of Open Access Journals (Sweden)

    Sérgio Kwitko

    2000-02-01

    .Purpose: To report the experience on our first 329 eyes operated with the Lasik technique for myopia, astigmatism and hyperopia, with a minimum postoperative follow-up period of 6 months. Methods: We retrospectively analyzed the results of Lasik surgery of 110 eyes with low myopia (group I, 113 with moderate myopia (group II, 47 with high myopia (group III, 139 with low astigmatism (group IV, 31 with moderate astigmatism (group V, 27 with low hyperopia (group VI and 25 with moderate hyperopia (group VII. Results: Mean preoperative refractive error of each group was, respectively, -3.56 ± 1.25 D, -8.31 ± 1.68 D, -14.95 ± 2.85 D, -1.57 ± 0.49 D, -3.98 ± 0.85 D, +2.32 ± 0.65 D, +5.05 ± 1.02 D. Twelve months after surgery, the mean residual refractive error of each group was, respectively, -0.11 ± 0.69 D, -0.42 ± 0.85 D, -0.69 ± 1.48 D, -0.42 ± 0.73 D, -0.73 ± 1.16 D, +0.35 ± 0.50 D, e +1.32 ± 1.03 D. Regression was clinically insignificant, except for the moderate hyperopia group (0.76 D. Re-operation was necessary in 4.9% of cases (3.4% for undercorrection, 0.6% for overcorrection, and 0.9% for interface cleaning. Loss of one or two best corrected visual acuity occurred in 3.7% of eyes with low myopia, 12.4% in moderate myopia, none in high myopia, 18.5% in low hyperopia and in 20% of the moderate hyperopia group. Other complications were rare: incom-plete disc cut (0.3%, irregular stromal bed because of loss of ring suction (0.3%, free cap (0.3%, regular induced astigmatism (7.4%, irregular induced astigmatism by decentered photoablation (0.3%, interface fragments (0.6%, and disc striae disturbing visual acuity (0.3%. Conclusions: Lasik seems to be a safe, effective, and predictable procedure for a variety of refractive errors.

  7. Study of the emission characteristics of a low-pressure discharge in crossed E x H fields by using an echelle spectrograph with compensated astigmatism

    International Nuclear Information System (INIS)

    In order to prove that thermal ionization is the main mechanism for sustaining a high-current low-pressure diffuse discharge in crossed E x H fields, the ion temperature was estimated by analyzing the Doppler broadening of a spectral line. The emission spectrum from discharge plasma was recorded using a specially designed echelle spectrograph with compensated astigmatism and with a resolution of 0.02 nm

  8. Study of the emission characteristics of a low-pressure discharge in crossed E x H fields by using an Echelle spectrograph with compensated astigmatism

    International Nuclear Information System (INIS)

    To lend support to the ionization thermal mechanism as the basic mechanism to maintain low-pressure high-current diffusion discharge in E x H crossed fields one evaluated temperature of ions on the basis of analysis of the Doppler broadening of the spectral line contour. To record the spectrum of discharge plasma emission one made use of the unique Echelle spectrograph with a compensated astigmatism and 0.02 nm resolution

  9. COMPARISON OF LASER IN SITU KERATOMILEUSIS (LASIK AND PHOTOREFRACTIVE KERATECTOMY (PRK IN CORRECTING LOW TO MODERATE MYOPIA WITH OR WITHOUT ASTIGMATISM

    Directory of Open Access Journals (Sweden)

    Mostafa A. El-Husseiny

    2014-05-01

    Full Text Available Purpose: To compare refractive and visual outcomes in patients treated with Photorefractive keratectomy (PRK and laser in situ keratomileusis (LASIK in cases of mild to moderate myopia with or without astigmatism in a prospective randomized clinical trial. Setting: Research Institute of Ophthalmology (RIO and RCC refractive center, Giza, Egypt. Methods: Refractive and visual acuity results in a cohort of 80 eyes of 40 consecutive patients were randomized to receive either PRK or LASIK by the first two surgeons.

  10. COMPARISON OF LASER IN SITU KERATOMILEUSIS (LASIK) AND PHOTOREFRACTIVE KERATECTOMY (PRK) IN CORRECTING LOW TO MODERATE MYOPIA WITH OR WITHOUT ASTIGMATISM

    OpenAIRE

    Mostafa A. El-Husseiny; Olfat A. Hassanin; Iman M. Eissa a; Mohamed Yasser Farag

    2014-01-01

    Purpose: To compare refractive and visual outcomes in patients treated with Photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) in cases of mild to moderate myopia with or without astigmatism in a prospective randomized clinical trial. Setting: Research Institute of Ophthalmology (RIO) and RCC refractive center, Giza, Egypt. Methods: Refractive and visual acuity results in a cohort of 80 eyes of 40 consecutive patients were randomized to receive either P...

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

    OpenAIRE

    Asim Kumar Kandar

    2014-01-01

    We report a case of 18-year-old male who has undergone phacoemulsification with implantation of toric IOL (AcrySof IQ SN6AT9) after fixation of lens capsule with Cionni′s capsular tension ring (CTR) for subluxated traumatic cataract with high astigmatism after deep anterior lamellar keratoplasty (DALK). He underwent right eye DALK for advanced keratoconus four years earlier. He had history of trauma one year later with displaced clear crystalline lens into  anterior chamber and graft dehiscen...

  12. SURGICALLY INDUCED ASTIGMATISM AFTER 2.8 MM TEMPORAL AND NASAL CLEAR CORNEAL INCISIONS IN PHACOEMULSIFICATION CATARACT SURGERY OF SAME PATIENT

    OpenAIRE

    Preeti*; Chetanya P; Daya Chand

    2015-01-01

    PURPOSE: To evaluate and compare the surgically induced astigmatism in phacoemulsification cataract surgery after 2.8 mm temporal and nasal clear corneal incision of same patient . MATERIAL AND METHOD : This prospective study comprised a consecutive case series of 60 eyes. Eyes from 30 patients with phacoemulsification those were implanted with a 6.00 mm foldable intraocular le ns through a 2.8 mm horizontal clear corneal incision (temporal in the rig...

  13. Comparison of surgically induced astigmatism between horizontal and X-pattern sutures in the scleral tunnel incisions for manual small incision cataract surgery

    Directory of Open Access Journals (Sweden)

    Yadollah Eslami

    2015-01-01

    Full Text Available Background: Two types of popular scleral tunnel sutures in the manual small incision cataract surgery (MSICS are horizontal and X-pattern sutures. Surgically induced corneal astigmatism (SIA is a useful indicator of the suturing effect. Aims: To compare SIA between horizontal and X-pattern sutures in the scleral tunnel incisions for MSICS. Design: Prospective, nonrandomized comparative trial. Materials and Methods: After superior scleral tunnel incision and capsulorhexis, the nucleus was prolapsed into the anterior chamber and delivered. The wound was sutured with either horizontal or X-pattern suture. The simulated keratometry values were derived from the corneal topography preoperatively and 1.5 and 3 months postoperatively. Statistical Analysis: The SIA was calculated by Cartesian coordinates based analysis. Results: Sixty-four patients (32 patients in each group were included in the study. In the horizontal suture group, the SIA centroid values at 1.5 and 3 months after the surgery were 0.87 × 1° and 1.11 × 180°, respectively, showing induction of against-the-rule astigmatism. In the X-pattern suture group, the SIA centroid values at 1.5 and 3 months after the surgery were 0.61 × 97° and 0.66 × 92°, respectively, showing induction of mild with-the-rule astigmatism. The difference between the amount of SIA at 1.5 and 3 months after surgery was small. Conclusion: In the MSICS, the X-pattern sutures were preferred to the horizontal sutures in the patients without significant preoperative steepening in line with the central meridian of the incision. In the cases with significant preoperative steepening, sutureless surgery or horizontal sutures were preferred. Corneal astigmatism in the patients undergoing MSICS was stable at 1.5 months after the surgery.

  14. Comparison of surgically induced astigmatism between horizontal and X-pattern sutures in the scleral tunnel incisions for manual small incision cataract surgery

    OpenAIRE

    Yadollah Eslami; Arash Mirmohammadsadeghi

    2015-01-01

    Background: Two types of popular scleral tunnel sutures in the manual small incision cataract surgery (MSICS) are horizontal and X-pattern sutures. Surgically induced corneal astigmatism (SIA) is a useful indicator of the suturing effect. Aims: To compare SIA between horizontal and X-pattern sutures in the scleral tunnel incisions for MSICS. Design: Prospective, nonrandomized comparative trial. Materials and Methods: After superior scleral tunnel incision and capsulorhexis, the nucleus was pr...

  15. SURGICALLY INDUCED ASTIGMATISM IN 2.8 MM, 5.3 MM PHACOEMULSIFICATION AND 6.0 MM MANUAL SMALL INCISION CATARACT SURGERY

    OpenAIRE

    Ankur; Indu,; Dileep.; Daya Chand

    2014-01-01

    PURPOSE: To evaluate and compare the surgical induced astigmatism in Phacoemulsification done by 2.80 and 5.30 mm clear corneal incision and SICS done through superiorly placed 6.00mm scleral incision. METHODS: Group – 1:2.80 mm clear corneal, sutureless, temporally placed incision with phacoemulsification technique (PE); Group–2:5.30 mm clear corneal, sutureless, temporally placed incision with phacoemulsification technique (PE); Group–3: 6 mm, straight scleral, sutureles...

  16. Dual-color dynamic tracking of GM-CSF receptors/JAK2 kinases signaling activation using temporal focusing multiphoton fluorescence excitation and astigmatic imaging.

    Science.gov (United States)

    Chien, Fan-Ching; Lien, Chi-Hsiang; Dai, Yang-Hong

    2015-11-30

    The dual-color dynamic particle tracking approach that uses temporal focusing multiphoton fluorescence excitation and two-channel astigmatic imaging is utilized to track molecular trajectories in three dimensions to explore molecular interactions. Images of two fluorophores were obtained to extract their positions by optical sectioning excitation using a fast temporal focusing multiphoton excitation microscope (TFMPEM) and by the simultaneous collection of data in two channels. The presented pair of cylindrical lenses, which was used to adjust the astigmatism effect with the minimum shifting of the imaging plane, was more feasible and flexible than single cylindrical lens for aligning two separate detection channels in astigmatic imaging. The lateral and axial positioning resolutions were observed to be approximately 9-13 nm and 23-30 nm respectively, for the two fluorescence channels. The dynamic movement and binding behavior of clusters of GM-CSF receptors and JAK2 kinases in HeLa cells in the presence of GM-CSF ligands were observed. Therefore, the proposed dual-color tracking strategy is useful for the dynamic study of molecular interactions in living specimens with a fast frame rate, less photobleaching, better penetration depth, and minimum optical trapping force. PMID:26698726

  17. Successful toric intraocular lens implantation in a patient with induced cataract and astigmatism after posterior chamber toric phakic intraocular lens implantation: a case report

    Directory of Open Access Journals (Sweden)

    Kamiya Kazutaka

    2012-04-01

    Full Text Available Abstract Introduction We report the case of a patient in whom simultaneous toric phakic intraocular lens removal and phacoemulsification with toric intraocular lens implantation were beneficial for reducing pre-existing astigmatism and acquiring good visual outcomes in eyes with implantable collamer lens-induced cataract and astigmatism. Case presentation A 53-year-old woman had undergone toric implantable collamer lens implantation three years earlier. After informed consent was obtained, we performed simultaneous toric implantable collamer lens removal and phacoemulsification with toric intraocular lens implantation. Preoperatively, the manifest refraction was 0, -0.5 × 15, with an uncorrected visual acuity of 0.7 and a best spectacle-corrected visual acuity of 0.8. Postoperatively, the manifest refraction was improved to 0, -0.5 × 180, with an uncorrected visual acuity of 1.2 and a best spectacle-corrected visual acuity of 1.5. No vision-threatening complications were observed. Conclusion Toric intraocular lens implantation may be a good surgical option for the correction of spherical and cylindrical errors in eyes with implantable collamer lens-induced cataract and astigmatism.

  18. 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

  19. Hard X-ray Spectroscopy and Imaging by a Reflection Zone Plate in the Presence of Astigmatism

    Energy Technology Data Exchange (ETDEWEB)

    Braig, Christoph; Lochel, Heike; Hafner, Aljosa; Firsov, Alexander; Rehanek, Jens; Brzhezinskaya, Maria; Wojcik, Michael; Macrander, Albert; Assoufid, Lahsen; Erko, Alexei

    2016-01-01

    The feasibility of an off-axis x-ray reflection zone plate to perform wavelength-dispersive spectroscopy, on-axis point focusing, and two-dimensional imaging is demonstrated by means of one and the same diffractive optical element (DOE) at a synchrotron radiation facility. The resolving power varies between 3×101 and 4×102 in the range of 7.6 keV to 9.0 keV, with its maximum at the design energy of 8.3 keV. This result is verified using an adjustable entrance slit, by which horizontal (H) and vertical (V) focusing to 0.85 μm(H) and 1.29 μm(V) is obtained near the sagittal focal plane of the astigmatic configuration. An angular and axial scan proves an accessible field of view of at least 0.6 arcmin × 0.8 arcmin and a focal depth of ±0.86 mm. Supported by the grating efficiency of around 17.5% and a very short pulse elongation, future precision x-ray fluorescence and absorption studies of transition metals at their K-edge on an ultrashort timescale could benefit from our findings.

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

    LENUS (Irish Health Repository)

    Dooley, Ian

    2012-02-01

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

  1. Comparison of curative effects of visual perceptual learning and traditional treatment for the children under 8 years with astigmatism amblyopia with rule and astigmatism amblyopia against rule%8岁以下顺、逆规散光性弱视儿童视感知疗法与传统疗法疗效比较

    Institute of Scientific and Technical Information of China (English)

    孔旻; 刘伟民; 林泉; 赵武校

    2011-01-01

    目的:比较8岁以下患儿视感知学习疗法(perceptual learning)与传统疗法治疗顺、逆规散光性弱视的疗效.方法:将252例(504眼)8岁以下顺、逆规散光性弱视患儿,分别行视感知学习(154例,308眼)和传统疗法(98例,196眼)治疗,2年后对结果进行统计学分析.结果:8岁以下的顺、逆规散光性弱视患儿视感知学习疗法组的总有效率均高于传统疗法组,组间比较差异均有统计学意义(P<0.05).结论:8岁以下的顺、逆规散光性弱视患者在视感知学习疗法中的总有效率高于其在传统疗法的总有效率.%Objective: To compare the curative effects of visual perceptual learning and traditional treatment for the children under 8 years with astigmatism amblyopia with rule and astigmatism amblyopia against rule. Methods: 252 children (504 eyes) under 8 years with astigmatism amblyopia with rule and astigmatism amblyopia against rule were divided into visual perceptual learning group (154 children, 308 eyes) and traditional treatment group (98 children, 196 eyes), then the results were analyzed statistically after two years. Results; The total effective rate in visual perceptual learning group was significantly higher than that in traditional treatment group (P < 0. 05) . Conclusion;The total effective rate in the children under 8 years with astigmatism amblyopia with rule and astigmatism amblyopia against rule treated with visual perceptual learning is significantly higher than that treated with traditional treatment

  2. Efficacy, predictability, and safety of laser-assisted subepithelial keratectomy for the treatment of myopia and myopic astigmatism

    Directory of Open Access Journals (Sweden)

    Faisal M Al-Tobaigy

    2012-01-01

    Full Text Available Purpose: The purpose was to report the refractive and visual outcomes of laser-assisted subepithelial keratectomy (LASEK for the treatment of myopia. Materials and Methods: A retrospective, noncomparative consecutive case series of 173 of 91 patients who had undergone LASEK is presented. Primary outcome variables included uncorrected visual acuity (UCVA, best spectacle-corrected visual acuity (BSCVA, manifest refraction, epithelialization time, pain, haze, and complications. Results: Preoperatively, the mean spherical equivalent (SE was −3.71 ± 1.63 D (range, −0.875 D to 8.25 D, and the mean LogMAR BSCVA was −0.0374 ± 0.0767 D (range, −0.47 D to 0.00 D. On the final visit, the mean SE was −0.05 ± 0.335 D (range, −1.63 D to 1.00 D, the mean LogMAR UCVA was 0.04674 ± 0.0771 D (range, −0.3010 D to 0.1249 D and the mean LogMAR BSCVA was −0.0164 ± 0.0497 (range −0.3010 to 0.124. All eyes achieved vision of 20/40 or better, and 83.2% of the eyes achieved a vision of 20/25 or better. One 64 (94.94% and all the eyes were within ± 0.50 D and ± 1.00 D of the attempted correction respectively. Complete epithelialization occurred in 4.70 ± 2.09 days (range, 2-10 days. At the final visit, 79.7% of eyes had a clear cornea. Grade 1 haze developed in 17.34% of the eyes, grade 2 haze developed in 2.89% of eyes developed; no eyes developed grade 3 or 4 haze. Conclusions: LASEK is a safe, effective, and predictable method for the treatment of myopia and myopic astigmatism.

  3. Astigmatismo induzido na cirurgia extracapsular da catarata: acompanhamento a longo prazo Induced astigmatism in extracapsular cataract extraction: long-term follow-up

    Directory of Open Access Journals (Sweden)

    Almir Ghiaroni

    2004-02-01

    Full Text Available OBJETIVO: Estudar o comportamento do astigmatismo induzido a longo prazo em uma série de pacientes submetidos à cirurgia extracapsular da catarata, nos quais foi utilizada incisão límbica posterior superior suturada com pontos separados de mononylon 10-0. MÉTODOS: Foram estudados 38 olhos, de 35 pacientes, sendo 21 do sexo feminino e 14 do sexo masculino, com idades variando entre 47 e 85 anos (média = 70,17 anos. Todos os casos foram operados pelo mesmo cirurgião. O período de acompanhamento pós-operatório variou de 15 a 33 meses (média = 22,07 meses. Nenhum dos casos teve qualquer dos pontos seccionado ou removido. Todos os pacientes atingiram acuidade visual corrigida igual ou superior a 0,5. Para o cálculo do astigmatismo induzido foram consideradas as medidas ceratométricas pré e pós-operatórias e foi utilizado um programa desenvolvido por Jaffe. RESULTADOS: O astigmatismo induzido variou de 0,13 dioptria (D a 2,74 D (média = 1,19 D. Em relação aos eixos, na maioria dos casos houve indução de astigmatismo a favor da regra (60,52%. Foi observada mudança significativa no valor dióptrico do astigmatismo quando foram comparadas as leituras ceratométricas registradas pré-operatoriamente até a segunda semana pós-operatória, entre o primeiro e o terceiro meses pós-operatórios, entre o terceiro e o sexto meses pós-operatórios e após o décimo-segundo mês pós-operatório. CONCLUSÃO: Quando o mononylon 10-0 é utilizado como material de sutura na cirurgia extracapsular da catarata, os valores de astigmatismo a favor da regra inicialmente observados tendem a diminuir com o tempo.PURPOSE: To study the long-term behavior of induced astigmatism in a series of patients who underwent extracapsular extraction in which a superoposterior limbal incision sutured with interrupted 10-0 mononylon sutures was performed. METHODS: 38 eyes of 35 patients were studied, 21 females and 17 males, with ages varying from 47 to 85 year

  4. Amplitude-phase mode structure of an astigmatic Gaussian beam in ring lasers with a nonplanar four-mirror cavity and an aperture

    International Nuclear Information System (INIS)

    The structure of the fundamental mode field in a nonplanar ring four-mirror resonator with an aperture is determined taking into account rotations of the amplitude and phase distributions of an astigmatic Gaussian beam. The rotation angles of the axes of these distributions are calculated upon variations in the characteristic aperture size and the angle of curvature (nonplanarity) of the resonator. The effect of the resonator aperture and nonplanarity on the intensity distribution of the interference pattern behind a mixer is studied. It is shown that interference fringes have a slope depending on the orientations of the amplitude and phase distributions of the mode. (laser beams)

  5. Spatial imaging in the soft x-ray region (20--304 A) utilizing the astigmatism of a grazing incidence concave grating

    International Nuclear Information System (INIS)

    Soft x-ray (20--304--A) astigmatic line shapes were measured in order to evaluate the spatial imaging properties of a Rowland mounted concave grating in grazing incidence. The practicability of coarse 1-D spatial imaging in the soft x-ray region is demonstrated. Spatial resolution equivalent to approx.4 cm at a source distance of 2 m can be achieved with practical parameters (e.g., sensitivity and time resolution) for a fusion diagnostic spectrograph. The results are compared to computer-generated ray tracings and found to be in good agreement. The ray tracing program which models the grazing incidence optics is discussed

  6. The influence of corneal astigmatism on retinal nerve fiber layer thickness and optic nerve head parameter measurements by spectral-domain optical coherence tomography

    OpenAIRE

    Liu Lin; Zou Jun; Huang Hui; Yang Jian-guo; Chen Shao-rong

    2012-01-01

    Abstract Background To evaluate the influence of corneal astigmatism (CA) on retinal nerve fiber layer (RNFL) thickness and optic nerve head(ONH) parameters measured with spectral-domain optical coherence tomography (OCT) in high myopes patients before refractive surgery. Methods Seventy eyes of 35 consecutive refractive surgery candidates were included in this study. The mean age of the subjects was 26.42 ± 6.95 years, the average CA was −1.17 diopters (D; SD 0.64; range −0.2 to-3.3D), All s...

  7. Long-Term Outcomes of Radial Keratotomy, Laser In Situ Keratomileusis, and Astigmatic Keratotomy Performed Consecutively over a Period of 21 Years

    Directory of Open Access Journals (Sweden)

    Priyanka Chhadva

    2015-01-01

    Full Text Available Purpose. To describe a case of 3 refractive procedures performed in one eye over 2 decades. Methods. Case report. Results. A 41-year-old patient presented for refractive surgery evaluation. His ocular history includes bilateral radial keratotomy performed 21 years ago for moderate myopia: spherical equivalence of −4.25 D bilaterally. Postoperative uncorrected visual acuity (UCVA was 20/30; however, over time he developed a hyperopic shift and UCVA decreased to 20/40 in the right eye. Thus, laser-assisted in situ keratomileusis (LASIK was performed at an outside institution 6.5 years later, and the patient had initial improvement of UCVA to 20/25. Due to a change in refractive error, the patient underwent uneventful astigmatic keratotomy 13 years after LASIK in the right eye, and 1.5 years after surgery best-corrected visual acuity was 20/25 with manifest refraction of −1.00+5.50×134°.  Conclusion. We report the outcomes and natural refractive progression in a patient who underwent three corneal refractive procedures over two decades. This case underlines the difficulties of long-term management of post-RK hyperopia and astigmatism.

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

    Directory of Open Access Journals (Sweden)

    Asim Kumar Kandar

    2014-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Mehrdad Mohammadpour

    2013-10-01

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

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

    Science.gov (United States)

    Mc Leod, Roger D.

    2004-03-01

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

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

    Science.gov (United States)

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

    2015-09-01

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

  12. SURGICALLY INDUCED ASTIGMATISM IN 2.8 MM, 5.3 MM PHACOEMULSIFICATION AND 6.0 MM MANUAL SMALL INCISION CATARACT SURGERY

    Directory of Open Access Journals (Sweden)

    Ankur

    2014-05-01

    Full Text Available PURPOSE: To evaluate and compare the surgical induced astigmatism in Phacoemulsification done by 2.80 and 5.30 mm clear corneal incision and SICS done through superiorly placed 6.00mm scleral incision. METHODS: Group – 1:2.80 mm clear corneal, sutureless, temporally placed incision with phacoemulsification technique (PE; Group–2:5.30 mm clear corneal, sutureless, temporally placed incision with phacoemulsification technique (PE; Group–3: 6 mm, straight scleral, sutureless, superiorly placed incision with manual small Incision cataract surgery (MSICS. RESULTS: Keratometric Cylinder (KC: The KC at 1 day, 1 week, 1 month, 3 month, was 1.26±0.54, 1.03±0.44, 0.99±0.36, 0.92±0.36 in group – 1; 1.90±0.41, 1.53±0.29, 1.37±0.28, 1.37±0.28 in group – 2 and 1.62±0.56, 1.43±0.68, 1.23±0.56, 1.21±0.49 in group 3 respectively.; Surgical Induced Astigmatism (SIA: The SIA at 1 week, 1 month, 3 month, was 0.64 ± 0.32, 0.55 ± 0.31, 0.48 ± 0.32 in group – 1; 1.00 ± 0.40, 0.84 ± 0.39, 0.84 ± 0.39 in group – 2 and 1.49 ± 0.77, 1.39 ± 0.46, 1.37 ± 0.40 in group – 3 respectively. After analysis, statistically significant (P<0.05 difference noted in keratometric cylinder & SIA between Group – 1 v/s Group – 2, Group – 1 v/s Group – 3 and Group – 2 v/s Group – 3 from day 1 & subsequent follow up. The preoperative parameters i.e. UCVA, mean keratometry & keratometric cylinder between the three groups were comparable. There was no statistically significant difference found between three groups preoperatively. CONCLUSION: Phacoemulsification 2.80 mm clear corneal temporal incision cataract surgery induces least SIA postoperatively, 5.30 mm incision induces 2nd least SIA & 6.00 mm straight superior scleral manual SICS induces the maximum SIA among the 3 groups.

  13. Wavefront-Guided Photorefractive Keratectomy with the Use of a New Hartmann-Shack Aberrometer in Patients with Myopia and Compound Myopic Astigmatism

    Directory of Open Access Journals (Sweden)

    Steven C. Schallhorn

    2015-01-01

    Full Text Available Purpose. To assess refractive and visual outcomes and patient satisfaction of wavefront-guided photorefractive keratectomy (PRK in eyes with myopia and compound myopic astigmatism, with the ablation profile derived from a new Hartmann-Shack aberrometer. Methods. In this retrospective study, 662 eyes that underwent wavefront-guided PRK with a treatment profile derived from a new generation Hartmann-Shack aberrometer (iDesign aberrometer, Abbott Medical Optics, Inc., Santa Ana, CA were analyzed. The preoperative manifest sphere ranged from −0.25 to −10.75 D, and preoperative manifest cylinder was between 0.00 and −5.25 D. Refractive and visual outcomes, vector analysis of the change in refractive cylinder, and patient satisfaction were evaluated. Results. At 3 months, 91.1% of eyes had manifest spherical equivalent within 0.50 D. The percentage of eyes achieving uncorrected distance visual acuity 20/20 or better was 89.4% monocularly and 96.5% binocularly. The mean correction ratio of refractive cylinder was 1.02 ± 0.43, and the mean error of angle was 0.00 ± 14.86° at 3 months postoperatively. Self-reported scores for optical side effects, such as starburst, glare, halo, ghosting, and double vision, were low. Conclusion. The use of a new Hartmann-Shack aberrometer for wavefront-guided photorefractive keratectomy resulted in high predictability, efficacy, and patient satisfaction.

  14. Spatial distribution measurement of atomic radiation with an astigmatism-corrected Czerny-Turner-type spectrometer in the Large Helical Device

    International Nuclear Information System (INIS)

    Emission lines in the visible/UV wavelength ranges are observed with 80 lines of sight which cover an entire poloidal cross section of the plasma in the Large Helical Device. The emitted light is received with optical fibers having 100 μm diameter and is guided into a 1.33 m Czerny-Turner-type spectrometer based on spherical mirrors for collimating and focusing. A charge-coupled device having 13.3x13.3 mm2 area size is used as the detector and the spectra from all the lines of sight are recorded perpendicularly to the wavelength dispersion. The spectrometer is equipped with optics located in front of the entrance slit to correct the difference between the meridional and sagittal focal points, and thus the astigmatism, which otherwise causes severe cross talk between adjacent optical fiber images on the detector, is corrected. Consequently, simultaneous spectral measurement with 80 lines of sight is realized. The Zeeman splitting of a neutral helium line, λ667.8 nm (2 1P-3 1D), which is caused by the magnetic field for plasma confinement, is measured with the spectrometer. Though the obtained line profile is in general a superposition of several components on the same line of sight, they can be separated according to their different splitting widths. The two-dimensional poloidal distribution of the helium line intensity is obtained with the help of a tomographic technique

  15. Spatial distribution measurement of atomic radiation with an astigmatism-corrected Czerny-Turner-type spectrometer in the Large Helical Device

    Science.gov (United States)

    Goto, Motoshi; Morita, Shigeru

    2006-10-01

    Emission lines in the visible/UV wavelength ranges are observed with 80 lines of sight which cover an entire poloidal cross section of the plasma in the Large Helical Device. The emitted light is received with optical fibers having 100μm diameter and is guided into a 1.33m Czerny-Turner-type spectrometer based on spherical mirrors for collimating and focusing. A charge-coupled device having 13.3×13.3mm2 area size is used as the detector and the spectra from all the lines of sight are recorded perpendicularly to the wavelength dispersion. The spectrometer is equipped with optics located in front of the entrance slit to correct the difference between the meridional and sagittal focal points, and thus the astigmatism, which otherwise causes severe cross talk between adjacent optical fiber images on the detector, is corrected. Consequently, simultaneous spectral measurement with 80 lines of sight is realized. The Zeeman splitting of a neutral helium line, λ667.8nm (2P1-3D1), which is caused by the magnetic field for plasma confinement, is measured with the spectrometer. Though the obtained line profile is in general a superposition of several components on the same line of sight, they can be separated according to their different splitting widths. The two-dimensional poloidal distribution of the helium line intensity is obtained with the help of a tomographic technique.

  16. COMPARISON OF RESULTS OF SURGICALLY INDUCED ASTIGMATISM AND VISUAL ACUITY FOLLOWING TEMPORAL VERSUS SUPERIOR SCLEROCORNEAL INCISIONS IN MANUAL SMALL INCISION SUTURE LESS CATARACT SURGERY

    Directory of Open Access Journals (Sweden)

    Sowbhagya

    2013-06-01

    Full Text Available ABSTRACT : OBJECTIVE: To evaluate the effect of superior and temporal sclerocorneal incisions on astigmatism in small incision cataract surgery. To evaluate the success of different meridional approaches in cataract surgery by changing the sites of incision. To evaluate visual acuity outcomes on temporal versus superior sclerocorneal incisions. DESIGN: Prospective, non - randomized, comparative cli nical study. PARTICIPANTS: One hundred and twenty eyes of 120 patients with cataracts scheduled to undergo routine cataract surgery. METHODS: 120eyes of 120 patients were allocated to two groups of 60 each, Group TI (Temporal incision and Group SI (Superi or incision. Manual Small Incision sutureless Cataract Surgery was (MSICS done. Post operative follow - up was done on day 1, 2 nd , 4 th and 6 th weeks for post - operative clinical findings, visual acuity and keratometry. Data was analyzed by1] Descriptive and in ferential statistical analysis.2] Mean SD (Min - Max. 3] Student T test (Two tailed, independent.4] Chi - Square/Fisher Exact Test

  17. Simultaneous measurement of the geometry and the internal 3D velocity field of a micron sized droplet confined in a channel using Astigmatism-PTV

    Science.gov (United States)

    Mack, Tobias; Cierpka, Christian; Kähler, Christian J.

    2012-11-01

    Astigmatism-PTV is a method that allows to measure with a single camera the fully three-dimensional, three-component velocity field. The technique is ideally suited for microfluidic velocity measurements without errors due to in-plane and out-of-plane averaging (Cierpka et al. Meas Scie Tech 21, 2010). Recently it was shown, that the interface between two fluids or the surrounding fluid and droplets or bubbles can be estimated as well with the technique (Rossi et al., Meas Scie Tech 22, 2010). In this contribution the advantages of both techniques are combined to measure the shape of a droplet inside a micro channel along with the internal 3D flow field of the droplet induced by the surrounding fluid. For the current investigation, particles were only distributed within oil-droplets. Therefore the shape of the droplet could be later reconstructed by the volumetric particle positions and the velocity can be estimated tracking the same particles in consecutive frames of the same dataset. The procedure allows the simultaneous determination of the shape and the droplet velocity as well as the inner flow field and offers a great potential for current research.

  18. The influence of corneal astigmatism on retinal nerve fiber layer thickness and optic nerve head parameter measurements by spectral-domain optical coherence tomography

    Directory of Open Access Journals (Sweden)

    Liu Lin

    2012-05-01

    Full Text Available Abstract Background To evaluate the influence of corneal astigmatism (CA on retinal nerve fiber layer (RNFL thickness and optic nerve head(ONH parameters measured with spectral-domain optical coherence tomography (OCT in high myopes patients before refractive surgery. Methods Seventy eyes of 35 consecutive refractive surgery candidates were included in this study. The mean age of the subjects was 26.42 ± 6.95 years, the average CA was −1.17 diopters (D; SD 0.64; range −0.2 to-3.3D, All subjects in this study were WTR CA. 34 eyes were in the normal CA group with a mean CA was −0.67 ± 0.28D, 36 eyes were in the high CA group with an average CA of −1.65 ± 0.49D. All subjects underwent ophthalmic examination and imaging with the Cirrus HD OCT. Results No significant difference was noted in the average cup-to-disk ratio, vertical cup-to-disk ratio and cup volume (all P values > 0.05. Compared with the normal CA group, the high CA group had a larger disc area and rim area, thinner RNFL thickness in the temporal quadrant, and the superotemporal and inferotemporal peaks were farther to the temporal horizon (All P values P values > 0.05. Conclusions The degree of with-the-rule CA should be considered when interpreting ONH parameters and peripapillary RNFL thickness measured by the Cirrus HD OCT. Virtual slides The virtual slide(s for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1148475676881895

  19. Optical system design of broadband astigmatism-free czerny-turner spectrometer%宽谱段消像散Czerny-Turner光谱仪光学系统设计

    Institute of Scientific and Technical Information of China (English)

    赵意意; 杨建峰; 薛彬; 闫兴涛

    2014-01-01

    针对光谱仪小型化、高分辨率的发展趋势,设计了一种结构简单、宽谱段、消像散的小型光谱仪。具体分析了折叠光路Czerny-Turner光谱仪各种像差的原理和校正方法。推导了柱透镜宽谱段消像散的理论方程。作为实例,设计了一款谱段为300~900 nm、物方数值孔径0.08的小型光谱仪。该光谱仪采用折叠光路结构以减小尺寸,添加柱透镜以消除整个谱段的像散。结果表明:该光谱仪结构简单紧凑,体积小,实现了宽谱段的消像散,全谱段光谱分辨率优于0.5 nm。%For the development trend of miniaturization and high-resolution of spectrometer, an optical design with a simple structure, broadband, astigmatism-corrected micro spectrometer was designed. The principle and correction method of the aberration of crossed beam czerny-turner spectrometer were analyzed in detail. The broadband astigmatism-corrected theory equations using cylindrical lens were deduced. For example, a micro spectrometer operating in 300-900 nm with an object NA of 0.08 has been designed. This spectrometer adopted crossed beam structure to minish its volume and used a cylindrical lens to remove astigmatism over the full bandwidth. The analyzed results demonstrated that this spectrometer with compact configuration and small volume corrected the astigmatism in the wide spectral region. The resolution of the spectrometer was better than 0.5 nm in the whole spectral region.

  20. Epi-LASIK 和 LASIK 治疗近视散光的早期疗效对比观察%Comparative study of Epi -LASIK and LASIK for myopic astigmatism

    Institute of Scientific and Technical Information of China (English)

    罗栋强; 王华; 何书喜; 陈蛟

    2013-01-01

    AIM: To analyze the effects of epipolis laser in situ keratomileusis ( Epi - LASIK ) and laser in situ keratomileusis ( LASIK ) for treatment of myopic astigmatism. METHODS: For treatment of myopic astigmatism, 32 patients (64 eyes) treated by Epi-LASIK and 63 patients (126 eyes) received LASIK.By their degree of astigmatism, the eyes were divided into GroupⅠ(-0.25~-2.75) DC and GroupⅡ(-3.0~-5.0) DC.During the 6-month follow-up, the early effects of the two operations were observed and compared in terms of uncorrected visual acuity ( UCVA) , best corrected visual acuity ( BCVA ) , residual astigmatism, corneal healing, intraocular pressure ( IOP) , corneal topography. RESULTS: In Group Ⅱ, UCVA better than 20/20 was achieved in 87.5%of the eyes subjected to Epi-LASIK and in 63.3% of the eyes subjected to LASIK, with significant difference between them (χ2 =4.055, P<0.05); residual astigmatism was-0.41±0.30D for the Epi-LASIK eyes and-0.74 ±0.36D for the LASIK eyes, with significant difference between them ( t =2.672, P <0.05 );postoperative corneal astigmatism was 0.63±0.34D for the Epi-LASIK eyes and 0.81 ±0.52D for the LASIK eyes with significant difference between them (t=2.234, P<0.05). CONCLUSION: For treatment of high astigmatism (≥-3 .0 0 D ) , Epi-LASIK is more effective and predictive than LASIK.%目的:探讨分析角膜微型刀上皮瓣下准分子激光原位角膜磨镶术( epipolis laser in situ keratomileusis , Epi-LASIK)和准分子激光原位角膜磨镶术( laser in situ keratomileusis , LASIK)治疗近视散光的疗效。方法:近视散光行 Epi-LASIK 治疗的患者32例64眼, LASIK治疗的患者63例126眼,将患者根据柱镜度数分为2组:Ⅰ组(柱镜-0.25~-2.75D,Epi-LASIK 20例、LASIK 48例)、Ⅱ组(柱镜-3.00~-5.00D,Epi-LASIK 12例、LASIK 15例)。随访6 mo观察两种术式的疗效。对比两组患者的术后裸眼视力( uncorrected visual acuity , UCVA

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

    Directory of Open Access Journals (Sweden)

    Ester Sakae Yamazaki

    2007-12-01

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

  2. Efficacy of phacoemulsification combined with intraocular lens implantation for senile cataract with corneal astigmatism%超声乳化联合人工晶状体植入治疗老年白内障合并角膜散光

    Institute of Scientific and Technical Information of China (English)

    董永孝; 黄立; 关小荣; 马艳; 韩文涛; 赵金; 吕菊迎

    2015-01-01

    目的:对老年性白内障合并角膜散光患者采用超声乳化白内障摘除术联合散光型人工晶状体( intraocular lens,IOL)植入的临床疗效进行评估。方法:采用随机数字表法将本院眼科中心收治的64例84眼老年性白内障合并散光患者分为散光型IOL组33例42眼和球面IOL组31例42眼,散光IOL组采用超声乳化白内障摘除术联合散光型人工晶状体植入术治疗,球面IOL组采用常规颞侧透明角膜切口超声乳化白内障摘除球面人工晶状体植入联合陡峭轴位上一对角膜缘松解切口治疗。观察两组手术前、术后3 mo 的视力分布、角膜散光度、球镜及柱镜指标(曲率、轴向、小瞳验光球镜、小瞳验光柱镜、散光轴向)的变化情况。结果:散光型IOL组和球面IOL组在术后第3 mo复查裸眼视力,与同组术前比较视力均提高(P0.05);术后3 mo散光型IOL组的小瞳验光球镜、小瞳验光柱镜值显著低于球面IOL组( P0. 05). Non-mydriatic refraction spherical and non - mydriatic refraction cylindrical of the astigmatism lOL group were significant lower than than in the spherical lOL group at 3mo post-operation(P<0. 05).• CONCLUSlON: Phacoemulsification combined with intraocular lens implantation for senile cataract with corneal astigmatism have a good clinical effect.

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

    Directory of Open Access Journals (Sweden)

    Fernando Leal

    2007-03-01

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

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

    Directory of Open Access Journals (Sweden)

    Flávia Augusta Attié de Castro

    2005-10-01

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

  5. The expression of the correction of corneal astigmatism in the point spread function analysis system of human eyes%人眼角膜散光矫正的点扩散函数分析表达

    Institute of Scientific and Technical Information of China (English)

    姜珺; 毛欣杰; 金成鹏; 吕帆

    2008-01-01

    optical imaging quality among corneal astigmatism subjects under different corrections by using the Point Spread Function analysis system (PSF). Methods PSF 1000 analyzer was used to measure retinal image quality of eyes of 26 subjects with corneal astigmatism ( sphere ranged from - 3.00 to - 6.00 DS, cylinder ranged from - 0. 75 to - 3.00 DC), who were fully corrected with three different methods respectively: spectacles (SPE), rigid gas permeable contact lenses (RGPCL) and toric soft contact lenses (TSCL). The modulation transfer function (MTF) curve was recorded and evaluated. 12 points of the MTF curve (equivalent to the 12 points of Lag Mar VA chart) were chosen for analysis. Equivalent moderate myopia 26 subjects without astigmatism were set up as control group. Results The MTF curve of each eye is enantiomorphous symmetrical Compared with the control group ( < -0. 75D), with 3.0 mm pupil, there's no statistical difference under low spatial frequency, the difference between middle and high frequency is significant ( P < 0.05 ). With 6. 0 mm pupil, there is statistical difference in all frequencies (P < 0.01 ). With simulated 3.0 mm pupil and 6.0 mm pupil, MTF values of all these three methods are statistical different. With 3.0 mm pupil, the MTF value of eyes fitted with RGPCLs is higher than that fitted with TSCLs except in the following frequency 3.00 , 3.78,4. 78,different in all frequencies ( P < 0.05 ). In all these three methods, MTF values with simulated 3.0 mm pupil are significantly higher than that with simulated 6.0 nun pupil ( P < 0.01 ). Conclusions PSF analytical method is available for offering objective data of retina imaging quality. RGPCL and its induced tear film is improved not only correcting the corneal astigmatism, but also enhances the ocular optical quality by reducing diffraction, dispersion and other high order of aberration.

  6. Clinical study on the stability of high myopia cataract with intraocular lens implantation on corneal astigmatism Toric%高度近视并发白内障合并角膜散光植入Toric人工晶状体稳定性的临床研究

    Institute of Scientific and Technical Information of China (English)

    张晓城; 陈茂盛; 李嘉文

    2012-01-01

    Objective To evaluate the Acrysof Toric toric surface artificial lens in cataract with high myopia associated with regular corneal astigmatism in patients with clinical effect and rotational stability.Methods A randomly selected from 2009 June to 2011 August during the cataract and corneal astigmatism in patients,phacoemulsification and implantation of Acrysof Toric IOL operation.The experimental group of 40 patients(43 eyes) ,cataract with high myopia patients (axial length≥26mm,IOL≤15D) implantation degree;optometry mirror ball( - 5.50-10.25)D,average(- 6.25 ± - 0.25)D,column mirror( - 1.25 - 4.25)D,aver-age( - 2.75 + - 0.25)D.A control group of 39 cases (40 eyes) simple astigmatism in cataract patients (axial length≤24mm≥522mm) ,optometry mirror ball ( - 0.25-1.25) ,average( -0.75+ -0.25)D,column mirror (1.50 - 4.25)D,average( - 2.50 +- 0.25)D.Postoperative March fully after mydriasis slit - lamp photography,using Adobe Photoshop software artificial lens axis a-nalysis,were recorded during the preoperative,postoperative observation of uncorrected visual acuity(UCVA) ,best corrected visual acuity(BCVA) ,postoperative corneal astigmatism and whole-eye astigmatism astigmatism,expected and actual residual astigmatism,IOL degree of rotation.Results After March,UCVA>0.5 eyes had no significant difference between two groups(P>0.05).BCVA>0.8 eyes had no significant difference between two groups(P>0.05).Postoperative residual astigmatism in March,the experimental group for the(0.56 + 0.33)D,control group(0.54 ± 0.32)D,the difference was not statistically significant (P>0.05) ; March after intraocular lens degree of rotation,the experimental group was 3.79° + 2.33°,rotation range is( - 6.25°,+ 7.78°) ;the control group was 2.75°+l.38°,rotation range was( - 4.62°,+6.15°),two groups of rotating degree of the differences were statistically significant(P0.05).Conclusion Acrysof Toric IOL March observation indicated that the implant can efficiently and stably

  7. Corneal astigmatism measuring module for slit lamps

    International Nuclear Information System (INIS)

    We have developed an automatic keratometer module for slit lamps that provides automatic measurements of the radii of the corneal curvature. The system projects 72 light spots displayed in a precise circle at the examined cornea. The displacement and deformation of the reflected image of these light spots are analysed providing the keratometry. Measurements in the range of 26.8-75 D can be obtained and a self-calibration system has been specially designed in order to keep the system calibrated. Infrared LEDs indicate automatically which eye is being examined. Volunteer patients (492) have been submitted to the system and the results show that our system has a high correlation factor with the commercially available manual keratometers and the keratometry measurements from a topographer. Our developed system is 95% in agreement with the corneal topographer (Humphrey-Atlas 995 CZM) and the manual keratometer (Topcon OM-4). The system's nominal precision is 0.05 mm for the radii of curvature and 10 for the associated axis

  8. Dark refraction shift with allowance for astigmatism

    Directory of Open Access Journals (Sweden)

    W.D.H. Gillan

    2005-01-01

    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.

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

    Directory of Open Access Journals (Sweden)

    Ricardo de Carvalho Rocha

    2007-12-01

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

  10. 虹膜定位波前引导的LASIK与标准LASIK比较治疗近视散光疗效的Meta分析%Iris-Registration in Wavefront-Guided LASIK versus Conventional LASIK for Correction of Myopia and Myopic Astigmatism: A Meta-Analysis

    Institute of Scientific and Technical Information of China (English)

    李岩; 成拾明; 周霞; 许玲

    2013-01-01

    Objective To systematically evaluate the efficacy and safety of iris-registration in wavefront-guided LASIK (IR+WG LASIK) versus conventional LASIK for correction of myopia accompanied with astigmatism. Methods Such databases as PubMed, EMbase, The Cochrane library (Issue 2, 2012), CBM, CNKI, VIP, and WangFang Data were searched to collect the randomized controlled trials (RCTs) and quasi-RCTs about IR+WG LASIK versus conventional LASIK for correction of myopia accompanied with astigmatism. The retrieval time was from inception to February 2012, and the language was in both Chinese and English. Two reviewers independently screened the literature, extracted the data and assessed the quality of the included studies. Then the meta-analysis was performed by using RevMan 5.1 software. Results A total of 9 studies involving 3 903 eyes were included. The results of meta-analysis showed that, compared with the conventional LASIK group, the IR+WG LASIK group had a higher ratio in patients with postoperative un-corrected visual acuity no less than 1.0 (RR=1.03, 95%CI 1.01 to 1.05, P=0.002), as well as in patients with best-corrected visual acuity gained over 1 line (RR=1.75, 95%CI 1.49 to 2.16, P<0.000 01); it was smaller in the postoperative high order aberration RMS (WMD=-0.16, 95%CI -0.21 to -0.11, P<0.000 01), coma-like RMS (WMD=-0.05, 95%CI -0.11 to 0.00, P=0.07), spherical-like RMS (WMD=-0.15, 95%CI -0.23 to -0.07, P=0.000 2), and residual astigmatism (WMD=0.14, 95%CI 0.10 to 0.18, P<0.000 01); moreover, it was lower in the incidence of postoperative glare (RR=0.27, 95%CI 0.15 to 0.50, P<0.000 1), and it was higher in the subjective satisfaction of patients (RR=1.08, 95%CI 1.04 to 1.13, P=0.000 3). Conclusion Compared with conventional LASIK, IR+WG LASIK can more effectively reduce astigmatism, postoperative high order aberration RMS and spherical-like RMS. It can also get visual function including uncorrected visual acuity and best-corrected visual acuity

  11. 光学诱导散光对视觉信号传导及皮层反应的影响%Electrophysiological research on the effects of optic-induced astigmatism on transmission time and response intensity of visual signals in the visual cortex

    Institute of Scientific and Technical Information of China (English)

    解来青; 徐国旭; 赵堪兴

    2012-01-01

    Objective To evaluate the contribution of different degrees of astigmatism on the latency and amplitude of pattern visual evoked potentials (PVEPs).The effect of astigmatism on the transmission and response intensity of visual signals in the visual cortex was evaluated.Methods It was a random designed study.PVEPs were measured in subjects with normal or normal corrected visual acuity using a checkerboard pattern stimulus under varying conditions using different astigmatic trial lens powers in succession (0-5 D).Paired samples t test,analysis of variance and Pearson correlation was performed.Results When a lower spatial frequency (60' checkerboards stimulus) was used,there was little change in the latency of P100 (F=0.290,P>0.05).However,when a higher spatial frequency (15' checkerboards stimulus) was used,VEP latency increased with a greater degree of astigmatism (F=10.850,P<0.01; r=0.647,P<0.01).There was a gradual reduction of amplitudes of P100 as convex cylindrical lens power increased (when 60' checkerboards were used, F=3.947,P<0.01; r=-0.470,P<0.01; when 15' checkerboards were used,F=14.280,P<0.01; r=-0.699,P<0.01).Conclusion The transmission of visual signals depends on the quality of the visual image formed on the retina.Visual signal transmission time and response intensity in the visual cortex are affected not only by the defocus of the retinal image but also by the spatial frequency of the pattern stimulus.With a high spatial frequency,the transmission of visual signals is faster and the response intensity of the visual cortex is greater if the visual image formed on the retina is clear.%目的 研究光学诱导不同程度散光产生的视觉信号对皮层反应时间及强度的影响;研究散光是否可导致视觉信号传导时程异常,观察视觉信号传导时间及视皮层反应强度与散光程度的量化关系.方法 完全随机设计研究.对视力或矫正视力正常的被检者眼前依次放置0~5 D度数正

  12. Visual Performance in Moderate to Severe Astigmatism : Rigid Gas-permeable Contact Lenses versus Spectacles%透气性硬性接触镜和框架眼镜矫正中高度散光视觉质量的比较

    Institute of Scientific and Technical Information of China (English)

    王雪; 马薇; 杨必; 刘陇黔

    2012-01-01

    Objective To explore whether spectacles or rigid gas-permeable (RGP) contact lenses provide better visual performance for moderate to severe astigmatism. Methods Between June 2008 and May 2011, 20 individuals (40 eyes) were fitted with both RGP lenses and spectacles. They first underwent corneal topography and refractometry, then were fitted with RGP trial lenses and lastly fitted with RGP lenses. When regularly followed up, the corrected visual acuity, wearing condition and eye health were evaluated respectively. For each type of lens, contrast visual acuity was evaluated. Each subject was asked to select the lens type of choice and to rate quality of vision in day-to-day activities through a questionnaire. Results The corrected visual acuity with RGP lenses was better than that with spectacles. But there was no difference in contrast visual acuity in all spatial frequency. Subjectively, there was no difference in vision, but most of the subjects prefer the computer-visual acuity and reading-visual acuity corrected by spectacles. About 40% of patients choose RGP contact lens as the main corrected method, and 45% of patients preferred using RGP lenses and spectacles alternately. About 10% of patients only wear RGP lenses when it was necessary. Two patients dropped out. Conclusions Both RGP lenses and spectacles leads to good results in correcting moderate to severe astigmatism. Though spectacles get higher scores in near vision, because of the better visual performance and appearance offered by RGP contact lens, a majority of patients can insist on wearing it.%目的 比较中高度散光患者配戴框架眼镜和透气性硬性接触镜(RGPCL)的主客观视觉质量.方法 选取2008年6月-2011年5月中高度角膜散光20例共40只眼进行角膜地形图、综合验光仪验光等检查后,选择合适试戴片作配适评估并定制RGPCL.要求患者戴镜后1周、1个月、3个月和6个月复查,记录矫正视力、镜片配

  13. Geometric phases for astigmatic optical modes of arbitrary order

    CERN Document Server

    Habraken, Steven J M

    2010-01-01

    The transverse spatial structure of a basis set of paraxial optical modes is fully characterized by a set of parameters that vary only slowly under free propagation. The parameters specify bosonic ladder operators that connect modes of different order, in analogy to the ladder operators connecting harmonic-oscillator wave functions. The parameter spaces underlying closed subspaces of higher-order modes are carbon copies of the parameter space of the ladder operators. We study the geometry of this space and the geometric phase that arises from it. This phase constitutes the ultimate generalization of the Gouy phase in paraxial wave optics and we recover the ordinary Gouy phase shift and the geometric phase for optical orbital angular momentum states as limiting cases. We discuss an analogy with the Aharonov-Bohm effect that reveals some deep insights in the nature and origin of the generalized Gouy phase shift.

  14. Increase in velocimeter depth of focus through astigmatism

    International Nuclear Information System (INIS)

    Frequently, velocimeter targets are illuminated by a laser beam passing through a hole in a mirror. This mirror is responsible for diverting returning light from a target lens to a velocity interferometer system for any reflector (VISAR). This mirror is often a significant distance from the target lens. Consequently, at certain target focus positions the returning light is strongly vignetted by the hole, causing a loss of signal. We find that we can prevent loss of signal and greatly increase the useful depth of focus by attaching a cylindrical lens to the target lens. copyright 1996 American Institute of Physics

  15. Highly astigmatic, laser-diode end-pumped lasers

    International Nuclear Information System (INIS)

    High power lasers find extensive use in Industry for precision micro machining and cutting, in medical diagnostics for fluorescence detection of dye labelled cells, in medical treatment as laser scalpels and countless research applications. Until recently, if a high power laser was required, several sacrifices had to be made. High power devices are typically large, complicated and expensive to run due to their high power consumption and maintenance requirements. Such devices do not meet the requirements of the end users found in industry, medicine and research. Modern laser-based systems have several requirements which include: low maintenance, stable output, robust, compact, efficient electrical-to-optical efficiency, high beam quality output, and increasingly, high power. The challenge in laser physics today is to produce a high output power device without compromising the other requirements, particularly high beam quality. High quality beams diverge more slowly and can be focussed more tightly than poor quality ones. The only types of lasers that come close to meeting all of these requirements today are laser-diode pumped solid-state lasers. The stability conditions have been determined for the end cylindrical mirror cavity resonator and a new analytic model describing the mode structure in misaligned cavities have been developed. It was demonstrated that the cavities are insensitive to small rotational misalignments. Preliminary experiments have demonstrated that the pump-beam cavity mode overlap is substantially improved in this cavity

  16. Geometric phases in astigmatic optical modes of arbitrary order

    International Nuclear Information System (INIS)

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

  17. Cancellation of RF Coupler-Induced Emittance Due to Astigmatism

    CERN Document Server

    Dowell, David H

    2015-01-01

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

  18. ASTIGMATISM IN PRIMARY PTERYGIUM AND ITS EFFECT ON VISUAL ACUITY

    OpenAIRE

    Devika; Lakshmi; Rajani; Sudhir; Asha,; Ajay

    2015-01-01

    BACKGROUND: Pterygium is a fairly common condition in a tropical country like India with average incidence being 5.2%. Surgery being offered as a treatment for pterygium does not, at present, have a universally accepted indication based on the size. This study was done to make an attempt to define the indication for surgical exicision of pterygium. AIMS: To find out an association between increasing size of pterygium and ...

  19. Comparative clinical study of wavefront-guided laser in situ keratomileusis with versus without iris recognition for myopia or myopic astigmatism%有和无虹膜识别波阵面像差引导的准分子激光原位角膜磨镶术治疗近视或近视散光眼临床对比研究

    Institute of Scientific and Technical Information of China (English)

    王卫群; 张金嵩; 赵晓金

    2011-01-01

    Objective To explore the postoperative visual acuity results of wavefront-guided LASIK with iris recognition for myopia or myopic astigmatism and the changes of higher-order aberrations and contrast sensitivity function (CSF).Methods Series of prospective case studies,158 eyes ( 85 cases) of myopia or myopic astigmatism were divided into two groups:one group underwent wavefront-guided LASIK with iris recognition ( iris recognition group) ; another group underwent wavefront-guided LASIK treatment without iris recognition through the limbus mating point ( non-iris recognition group).To comparative analyze the postoperative visual acuity,residual refraction,the RMS of higher-order aberrations and CSF of two groups.Results There was no statistical significance difference between two groups of the average uncorrected visual acuity( t =0.039,0.058,0.898; P =0.844,0.810,0.343 ),best corrected visual acuity ( t =0.320,0.440,1.515 ; P =0.572,0.507,0.218 ),and residual refraction [ spherical equivalent ( t =0.027,0.215,0.238; P =0.869,0.643,0.626),spherical (t =0.145,0.117,0.038; P =0.704,0.732,0.845) and cylinder( t =1.676,1.936,0.334; P =0.195,0.164,0.563 ) ] at postoperative 10 days,1 month and 3 month.The security index of iris recognition group at postoperative 3 month was 1.06 and non- iris recognition group was 1.03 ; the efficacy index of iris recognition group is 1.01 and non-iris recognition group was 1.00.Postoperative 3 month iris recognition group 93.83% eyes and non-iris recognition group of 90.91% eyes spherical equivalent within ± 0.50 D ( x2 =0.479,P =0.489 ),iris recognition group of 98.77% eyes and non-iris recognition group of 97.40% eyes spherical equivalent within ± 1.00 D( Fisher test,P =0.613).There was no significance difference between the two groups of security,efficacy and predictability.Non-iris recognition group postoperative 1 month and postoperative 3 months 3-order order aberrations root mean square value (RMS) higher than the iris

  20. Quantifying Assessments of Vision Improvements for Myopes, Hypermetropes, Presbyopes, and Astigmats, in Brazil and Elsewhere.

    Science.gov (United States)

    Lopes, Demetriou; D. M., D.; Niemi, Paul N.; D., O.; Mc Leod, Roger D.

    2007-10-01

    Vision can safely, rapidly, and significantly be improved among nearsighted, far-sighted, presbyopic, and astigmatatic individuals, using methods developed for Mc Leod's patent-pending Naturoptics. We hope to calibrate and apply the method in South America, particularly Brazil, using metric standards accessible from ordinary vision assessment charts as used there. This precursor for extension into Hispanic-speaking areas, especially Chile, Guatemala, Honduras, Mexico, Paraguay, Peru, and Puerto Rico, is to establish property-rights protected licensed teaching agreements. Initially, visually impaired potential students of to-be-established not-for-profit Naturopathic medical, surgical, dental, law, science, and arts schools, perhaps named Metocantins or Metaquaratinga University, if in Brazil, will learn to correct their vision; training and licensing them can provide earnings for the self-funding of all associated activities and expenses. We will publish established results that refute claims relating to vision. Mc Leod's spatial Fourier transform model for retinal focal surface electric field amplitude vision explains all phenomena and Land's two-wavelength interval color vision results.

  1. The ABCD matrix for parabolic reflectors and its application to astigmatism free four-mirror cavities

    Science.gov (United States)

    Dupraz, K.; Cassou, K.; Martens, A.; Zomer, F.

    2015-10-01

    The ABCD matrix for parabolic reflectors is derived for any incident angles. It is used in numerical studies of four-mirror cavities composed of two flat and two parabolic mirrors. Constraints related to laser beam injection efficiency, optical stability, cavity-mode, beam-waist size and high stacking power are satisfied. A dedicated alignment procedure leading to stigmatic cavity-modes is employed to overcome issues related to the optical alignment of parabolic reflectors.

  2. Astigmatism compensation in digital holographic microscopy using complex-amplitude correlation

    Science.gov (United States)

    Tamrin, Khairul Fikri; Rahmatullah, Bahbibi; Samuri, Suzani Mohamad

    2015-07-01

    Digital holographic microscopy (DHM) is a promising tool for a three-dimensional imaging of microscopic particles. It offers the possibility of wavefront processing by manipulating amplitude and phase of the recorded digital holograms. With a view to compensate for aberration in the reconstructed particle images, this paper discusses a new approach of aberration compensation based on complex amplitude correlation and the use of a priori information. The approach is applied to holograms of microscopic particles flowing inside a cylindrical micro-channel recorded using an off-axis digital holographic microscope. The approach results in improvements in the image and signal qualities.

  3. Rigorous description of holograms of particles illuminated by an astigmatic elliptical Gaussian beam

    International Nuclear Information System (INIS)

    The digital holography is a non-intrusive optical metrology and well adapted for the measurement of the size and velocity field of particles in the spray of a fluid. The simplified model of an opaque disk is often used in the treatment of the diagrams and therefore the refraction and the third dimension diffraction of the particle are not taken into account. We present in this paper a rigorous description of the holographic diagrams and evaluate the effects of the refraction and the third dimension diffraction by comparison to the opaque disk model. It is found that the effects are important when the real part of the refractive index is near unity or the imaginary part is non zero but small.

  4. High-speed atomic force microscope based on an astigmatic detection system

    International Nuclear Information System (INIS)

    High-speed atomic force microscopy (HS-AFM) enables visualizing dynamic behaviors of biological molecules under physiological conditions at a temporal resolution of 1s or shorter. A small cantilever with a high resonance frequency is crucial in increasing the scan speed. However, detecting mechanical resonances of small cantilevers is technically challenging. In this study, we constructed an atomic force microscope using a digital versatile disc (DVD) pickup head to detect cantilever deflections. In addition, a flexure-guided scanner and a sinusoidal scan method were implemented. In this work, we imaged a grating sample in air by using a regular cantilever and a small cantilever with a resonance frequency of 5.5 MHz. Poor tracking was seen at the scan rate of 50 line/s when a cantilever for regular AFM imaging was used. Using a small cantilever at the scan rate of 100 line/s revealed no significant degradation in the topographic images. The results indicate that a smaller cantilever can achieve a higher scan rate and superior force sensitivity. This work shows the potential for using a DVD pickup head in future HS-AFM technology

  5. Beam spot shift in a dynamic astigmatism correction type (DQ-DAF) electron gun

    International Nuclear Information System (INIS)

    This paper presents the results of an investigation to avoid the convergence error in color CRT guns operating with a dynamic focus correction. The dynamic spot shift as well as the spot coma can be avoided at the same time with a proper arrangement of the quadrupole and main lenses with an oblique incidence of the side beam. The design confirmation is also presented. (orig.)

  6. 3D multifocus astigmatism and compressed sensing (3D MACS) based superresolution reconstruction

    OpenAIRE

    Huang, Jiaqing; Sun, Mingzhai; Gumpper, Kristyn; Chi, Yuejie; Ma, Jianjie

    2015-01-01

    Single molecule based superresolution techniques (STORM/PALM) achieve nanometer spatial resolution by integrating the temporal information of the switching dynamics of fluorophores (emitters). When emitter density is low for each frame, they are located to the nanometer resolution. However, when the emitter density rises, causing significant overlapping, it becomes increasingly difficult to accurately locate individual emitters. This is particularly apparent in three dimensional (3D) localiza...

  7. 3D holographic head mounted display using holographic optical elements with astigmatism aberration compensation.

    Science.gov (United States)

    Yeom, Han-Ju; Kim, Hee-Jae; Kim, Seong-Bok; Zhang, HuiJun; Li, BoNi; Ji, Yeong-Min; Kim, Sang-Hoo; Park, Jae-Hyeung

    2015-12-14

    We propose a bar-type three-dimensional holographic head mounted display using two holographic optical elements. Conventional stereoscopic head mounted displays may suffer from eye fatigue because the images presented to each eye are two-dimensional ones, which causes mismatch between the accommodation and vergence responses of the eye. The proposed holographic head mounted display delivers three-dimensional holographic images to each eye, removing the eye fatigue problem. In this paper, we discuss the configuration of the bar-type waveguide head mounted displays and analyze the aberration caused by the non-symmetric diffraction angle of the holographic optical elements which are used as input and output couplers. Pre-distortion of the hologram is also proposed in the paper to compensate the aberration. The experimental results show that proposed head mounted display can present three-dimensional see-through holographic images to each eye with correct focus cues. PMID:26698993

  8. Flexible generation of optical beams with quasicrystalline structures via astigmatism induced by a tilted lens

    Science.gov (United States)

    Tung, J. C.; Liang, H. C.; Tsou, C. H.; Su, K. W.; Chen, Y. F.

    2012-12-01

    We theoretically show that a family of optical beams with vortex-lattice structures can be reliably generated by tilting the focal lens to introduce the relative phases between the interfering beams. We also experimentally generate the quasicrystal beams to confirm the theoretical analysis. With the analytical wave functions and experimental patterns, a variety of vortex-lattice structures are manifested.

  9. SURGICALLY INDUCED ASTIGMATISM AFTER IMPLANTATION OF FOLDABLE AND NON - FOLDABLE LENSES IN CATARACT SURGERY BY PHACOEMULSIFICATION

    OpenAIRE

    Vikas; Lubna; Chitra; Nikhilesh; Rajesh; Pawar; Seema

    2015-01-01

    This prospective comparative study included 300 matched patients of different grades of senile cataract. All of them willfully underwent phacoemulsification at the hands of a single experienced surgeon, performing with a single and individual technique {Woodcutter’s technique 1 }; half of them were implanted with a foldable intraocular lens and ...

  10. Visual outcomes of conductive keratoplasty to treat hyperopia and astigmatism after laser in situ keratomileusis and photorefractive keratectomy

    Directory of Open Access Journals (Sweden)

    Alireza Habibollahi

    2011-01-01

    Conclusions : CK is a predictable and reliable method to correct hyperopia after LASIK and PRK, however cylinder correction may induce irregular and unpredictable outcomes and a modified nomogram is required for further studies.

  11. Lasik para correção de miopia, astigmatismos e hipermetropia Lasik for myopia, astigmatism and hyperopia

    OpenAIRE

    Sérgio Kwitko; Diane Marinho; Roseli Raskin; Sérgio Sprinz; Moacir Rabin; Samuel Rymer; Antonio Mendez Noble

    2000-01-01

    Objetivo: Relata a experiência em nossos primeiros 329 olhos operados com a técnica de Lasik para miopia, astigmatismo e hipermetropia, com um mínimo de 6 meses de seguimento pós-operatório. Métodos: Foram analisados retrospectivamente os resultados de Lasik em 110 olhos com baixa miopia (grupo I), 113 com miopia moderada (grupo II), 47 com alta miopia (grupo III), 139 com astigmatismo baixo (grupo IV), 31 com astigmatismo moderado (grupo V), 27 com baixa hipermetropia (grupo VI) e 25 com hip...

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

    OpenAIRE

    Je Hwan Yoon; Kyun-Hyung Kim; Jong Yeon Lee; Dong Heun Nam

    2013-01-01

    Aims: To compare the corneal refractive changes induced after 3.0 mm temporal and nasal corneal incisions in bilateral cataract surgery. Materials and Methods: This prospective study comprised a consecutive case series of 60 eyes from 30 patients with bilateral phacoemulsification that were implanted with a 6.0 mm foldable intraocular lens through a 3.0 mm horizontal clear corneal incision (temporal in the right eyes, nasal in the left eyes). The outcome measures were surgically induced astig...

  13. Efficacy, predictability, and safety of laser-assisted subepithelial keratectomy for the treatment of myopia and myopic astigmatism

    OpenAIRE

    Al-Tobaigy, Faisal M.

    2012-01-01

    Purpose: The purpose was to report the refractive and visual outcomes of laser-assisted subepithelial keratectomy (LASEK) for the treatment of myopia. Materials and Methods: A retrospective, noncomparative consecutive case series of 173 of 91 patients who had undergone LASEK is presented. Primary outcome variables included uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest refraction, epithelialization time, pain, haze, and complications. Result...

  14. Understanding Your Vision: The “Imperfect Eye” | NIH MedlinePlus the Magazine

    Science.gov (United States)

    ... spots around the cornea, is an additional treatment. Astigmatism If you have astigmatism, the cornea is more oval than round. This doesn’t allow the eye to focus clearly. Astigmatism is usually accompanied by nearsightedness or farsightedness. Treatment ...

  15. Understanding Your Vision: The "Imperfect Eye"

    Science.gov (United States)

    ... www.nihseniorhealth.gov (click on "Vision and Hearing") Astigmatism If you have astigmatism, the cornea is more oval than round. This doesn't allow the eye to focus clearly. Astigmatism is usually accompanied by nearsightedness or farsightedness. Treatment ...

  16. Laser resonators with several mirrors and lenses with the bow-tie laser resonator with compensation for astigmatism and thermal lens enects as an example

    DEFF Research Database (Denmark)

    Abitan, Haim; Skettrup, Torben

    2005-01-01

    Laser resonators with several mirrors (lenses) have been investigated in a systematic fashion. They have been grouped into classes according to their number n of mirrors/lenses. Stability polynomials, beam waist radii and locations have been obtained for each group up to n = 4. The bow-tie laser...

  17. A COMPARATIVE STUDY OF SURGICALLY INDUCED ASTIGMATISM IN FROWN VERSUS CHEVRA COMPARATIVE STUDY OF SEVOFLURANE VS HALOTHANE FOR GENERAL ANAESTHESIA IN PEDIATRIC PATIENTS

    Directory of Open Access Journals (Sweden)

    Shivani

    2013-11-01

    Full Text Available CONTEXT (BACKGROUND: Halothane has been the induction agent of choice in pediatric age group for nearly five decades. Sevoflurane with low blood gas solubility allows rapid induction and early emergence, its pleasant odour makes it an attractive alternative for inhalational induction in children. AIMS: Comparison of halothane and sevoflurane regarding induction in children, hemodynamic and respiratory study between two agents, emergence, recovery and side effects. This study was c arried out over a period of two years from Dec 2009 to Dec 2011. SETTINGS AND DESIGN: Sixty patients were included and analyzed at our hospital after ethical approval. METHODS AND MATERIAL: Patients in Group I(n=30 received Halothane while Group - II(n=30 patients received Sevoflurane for induction and maintenance. Parameters recorded and analyzed were Time to loss of eyelash reflex, Time to complete induction, Hemodynamic parameters during induction and at regular intervals, Emergence time and Recovery pro file at the end of surgery. STATISTICAL ANALYSIS USED: For the purpose of evaluating the results of the study following statistical tools were used: Mean, S.D., t Test, Confidence Level and Chi - square Test. ANOVA was used to compare observations taken unde r different conditions within the same group. RESULTS: Time to loss of eyelash reflex and time to complete induction were statistically significant in sevoflurane (Group II group. A statistically significant difference was seen between two groups with Gro up I showing significantly higher proportion of complications as compared to Group II (p=0.009. CONCLUSIONS: Sevoflurane is a better inhalational agent than halothane because of faster induction and rapid recovery. Hemodynamic stability was better, with l ess incidence of complications than halothane.

  18. Astigmatismo induzido na cirurgia extracapsular da catarata: acompanhamento a longo prazo Induced astigmatism in extracapsular cataract extraction: long-term follow-up

    OpenAIRE

    Almir Ghiaroni; José Belmiro de Castro Moreira

    2004-01-01

    OBJETIVO: Estudar o comportamento do astigmatismo induzido a longo prazo em uma série de pacientes submetidos à cirurgia extracapsular da catarata, nos quais foi utilizada incisão límbica posterior superior suturada com pontos separados de mononylon 10-0. MÉTODOS: Foram estudados 38 olhos, de 35 pacientes, sendo 21 do sexo feminino e 14 do sexo masculino, com idades variando entre 47 e 85 anos (média = 70,17 anos). Todos os casos foram operados pelo mesmo cirurgião. O período de acompanhament...

  19. Perbandingan Kejadian Astigmatisma Pasca Operasi Katarak Dengan Menggunakan Tehnik Fakoemulsifikasi Dan Small Incision Cataract Surgery

    OpenAIRE

    Marlinda, Sri

    2013-01-01

    Backgraund : Astigmatism change after cataract surgery is common, but if the astigmatism is too high it can effect the visual acuity. The astigmatism change depends on the incision methods, sclera rigidity, and age Objective : To compare the astigmatism change between scleral on the SICS and clearcorneal incision methods on facoemulsification after cataract surgery and intraocular lens implantation. Method : Sixty patients after cataract surgery with IOL implantation were evaluated....

  20. The experimental investigation of orbital angular momentum of complex astigmatic elliptical beams%复杂像散椭圆光束的轨道角动量的实验研究

    Institute of Scientific and Technical Information of China (English)

    董一鸣; 徐云飞; 张璋; 林强

    2006-01-01

    提出一种直接测量光束的轨道角动量的方法,其原理是把具有轨道角动量的光束照射到一个金属靶上,使其在光束的角动量作用下发生转动.通过测量靶转动的角度来计算光束的角动量值.对几种不同参数的光束的轨道角动量进行了测量,获得了轨道角动量与光束参数之间的关系,实验结果与理论分析较好地符合.

  1. 新型人工晶体推送器对白内障术后角膜散光影响的临床研究%Clinical study on the effect of new type intraocular lens unfolder on postoperative astigmatism

    Institute of Scientific and Technical Information of China (English)

    汤欣; 杨瑞波; 孙慧敏

    2004-01-01

    目的:评价2.6mm口径的新型人工晶体推送器(Emerald T推送器)对白内障超声乳化人工晶体植入术后角膜散光的影响.方法:将160例(160眼)老年性白内障患者随机分为两组:A组为2.6mm口径的Emerald T人工晶体推送器组;B组为3.2mm口径的Sapphire人工晶体推送器组.所有患者均行经透明角膜超声乳化人工晶体植入术,术后1周、1月、3月采用角膜地形图仪比较两组角膜散光的变化情况.结果:A、B两组术后1周、1月、3月平均手术源性角膜散光(D)分别为:0.36 0.20、0.33 0.23、0.31 0.22;0.78 0.61、0.69 0.58、0.58 0.44;两组间差别有统计学意义(P<0.05).术后1周及1月,A、B两组裸眼视力≥0.5者分别为:74眼(92.50%)、77眼(96.25%);62眼(77.50%)、70眼(87.50%),两组间差别有统计学意义(P<0.05),术后3月两组裸眼视力≥0.5者分别为:77眼(96.25%)、73眼(91.25%),两组间差别无统计学意义(P>0.05).结论:2.6mm口径的Emerald T人工晶体推送器所需手术切口小、术后散光小、视力恢复快且稳定,是目前较为理想的小切口人工晶体植入装置.

  2. Corneal relaxing incision combined with phacoemulsification and IOL implantation

    Institute of Scientific and Technical Information of China (English)

    沈晔; 童剑萍; 李毓敏

    2004-01-01

    Objective: To analyze the effectiveness and safety of corneal relaxing incisions (CRI) in correcting keratometric astigmatism during cataract surgery. Methods: A prospective study of two groups: control group and treatment group. A treatment group included 25 eyes of 25 patients who had combined clear corneal phacoemulsification, IOL implantation and CRI. A control group included 25 eyes of 25 patients who had clear corneal phacoemulsification and IOL implantation.Postoperative keratometric astigmatism was measured at 1 week, 1 month, 3 months and 6 months. Results: CRI significantly decreased keratometric astigmatism in patients with preexisting astigmatism compared with astigmatic changes in the control group. In eyes with CRI, the mean keratometric astigmatism was 0.29±0.17 D (range 0 to 0.5 D) at 1 week, 0.41±0.21 D (range 0 to 0.82 D) at 1 month, respectively reduced by 2.42 D and 2.30 D at 1 week and 1 month postoperatively (P=0.000, P=0.000), and postoperative astigmatism was stable until 6 months follow-up. The keratometric astigmatism of all patients decreased to less than 1.00 D postoperatively. Conclusions: CRI is a practical, simple, safe and effective method to reduce preexisting astigmatism during cataract surgery. A modified nomogram is proposed. The long-term effect of CRI should be investigated.

  3. Corneal relaxing incision combined with phacoemulsification and IOL implantation

    Institute of Scientific and Technical Information of China (English)

    沈晔; 童剑萍; 李毓敏

    2004-01-01

    Objective: To analyze the effectiveness and safety of corneal relaxing incisions (CRI) in correcting keratometric astigmatism during cataract surgery. Methods: A prospective study of two groups: control group and treatment group. A treatment group included 25 eyes of 25 patients who had combined clear corneal phacoemulsification, IOL implantation and CRI. A control group included 25 eyes of 25 patients who had clear corneal phacoemulsification and IOL implantation.Postoperative keratometric astigmatism was measured at 1 week, 1 month, 3 months and 6 months. Results: CRI signifi-cantly decreased keratometric astigmatism in patients with preexisting astigmatism compared with astigmatic changes in the control group. In eyes with CRI, the mean keratometric astigmatism was 0.29±0.17 D(range 0 to 0.5 D) at 1 week, 0.41±0.21 D (range 0 to 0.82 D) at 1 month, respectively reduced by 2.42 D and 2.30 D at 1 week and 1 month postoperatively (P=0.000, P=0.000), and postoperative astigmatism was stable until 6 months follow-up. The keratometric astigmatism of all patients decreased to less than 1.00 D postoperatively. Conclusions: CRI is a practical, simple, safe and effective method to reduce preexisting astigmatism during cataract surgery. A modified nomogram is proposed. The long-term effect of CRI should be investigated.

  4. Small-incision lenticule extraction (SMILE)

    DEFF Research Database (Denmark)

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

    2016-01-01

    PURPOSE: To study the outcomes of small-incision lenticule extraction (SMILE) for treatment of myopia and myopic astigmatism. METHODS: Retrospective study of patients treated for myopia or myopic astigmatism with SMILE, using a VisuMax(®) femtosecond laser (Carl Zeiss Meditec, Jena, Germany), at...

  5. Comparison of the curative effect between IR-LASIK and LASIK in high astigmatism treatment%高度散光患者虹膜定位波前引导的LASIK与常规LASIK手术疗效的比较

    Institute of Scientific and Technical Information of China (English)

    李耀宇; 翟国光; 邱岩; 邸玉兰; 屈哲; 黄耀辉

    2008-01-01

    目的:比较高度散光患者虹膜定位波前引导的LASIK(IR-LASIK)手术与常规LASIK手术的临床效果.方法:≥2.0DC的高度散光患者分别使用VISX S4-IR准分子激光机进行IR-LASIK手术(204例338眼)和常规LASIK手术(180例335眼),对术后裸眼视力和残留散光度数进行比较,IR手术组检查了眼球旋转的角度.结果:IR-LASIK手术组术后2d裸眼视力(≥1.0者89.1%)明显优于常规LASIK手术组(≥1.0者83.6%,P<0.05),术后残留散光度数也明显小于常规LASIK手术组(0.56DC vs1.15DC,P<0.01).IR-LASIK手术组波前像差检查的散光度数和轴位均与显然验光结果有一定的差别,所有患眼手术时均发生了眼球旋转.这可能是IR手术后疗效较好的重要原因.结论:IR-LASIK手术能够明显改善高度散光患者术后裸眼视力,减轻术后的散光残留.

  6. Causes of subnormal vision in patients following cataract surgery at a tertiary hospital in Kashmir.

    Science.gov (United States)

    Ahangar, Andleeb; Sufi, Aalia Rasool; Nabi, Mushood; Rather, Muddasar Hassan

    2014-10-01

    Cataract surgery is aimed at restoring sight to near normal vision. This study, conducted at the Department of Ophthalmology, Government Medical College, Srinagar, is an attempt to determine the causes of subnormal vision in patients following cataract surgery at a tertiary hospital in Kashmir. One hundred patients who underwent cataract surgery with an unaided visual acuity of <6/9 at 16 weeks postoperatively were included in the study. Postoperative follow-up examinations were conducted until the 16th week. Intraoperative and postoperative complications were recorded to determine the cause of subnormal vision. Of 100 patients, 40 underwent extracapsular cataract extraction (ECCE), 30 underwent small incision cataract surgery (SICS) and 30 underwent phacoemulsification. Seventy-five percent of the patients who underwent ECCE had postoperative astigmatism with a mean astigmatism of 2.2 ± 0.81 diopters at 16 weeks, with the majority having with-the-rule astigmatism. In the SICS group, 17 (56.6 %) patients had a mean postoperative astigmatism of 0.75 ± 0.40 diopters, with the majority (82.3 %) having against-the-rule (ATR) astigmatism. In the phacoemulsification group, 13 (43.3 %) of the patients had a mean postoperative astigmatism of 0.48 ± 0.23 diopters with the majority having ATR astigmatism. Other causes of subnormal vision were pseudophakic ametropia, posterior capsular opacity and intraoperative complications like posterior capsular rent and vitreous loss. Postoperative astigmatism was the major cause of subnormal vision with greater astigmatism seen in the ECCE group. Therefore, procedures like smaller incision sutureless surgery and careful biometry are advocated to improve visual outcome and patient satisfaction. PMID:24522881

  7. A comparison of designs of off-axis Gregorian telescopes for mm-wave large focal plane arrays

    CERN Document Server

    Hanany, S; Hanany, Shaul; Marrone, Daniel P.

    2002-01-01

    We compare the diffraction-limited field of view (FOV) provided by four types of off-axis Gregorian telescopes: the classical Gregorian, the aplanatic Gregorian, and designs that cancel astigmatism and both astigmatism and coma. The analysis is carried out using telescope parameters that are appropriate for satellite and balloon-borne millimeter and sub-millimeter wave astrophysics. We find that the design that cancels both coma and astigmatism provides the largest flat FOV, about 21 square degrees. We also find that the FOV can be increased by about 15% by optimizing the shape and location of the focal surface.

  8. Ring lens focusing and push-pull tracking scheme for optical disk systems

    Science.gov (United States)

    Gerber, R.; Zambuto, J.; Erwin, J. K.; Mansuripur, M.

    1993-01-01

    An experimental comparison of the ring lens and the astigmatic techniques of generating focus-error-signal (FES) in optical disk systems reveals that the ring lens generates a FES over two times steeper than that produced by the astigmat. Partly due to this large slope and, in part, because of its diffraction-limited behavior, the ring lens scheme exhibits superior performance characteristics. In particular the undesirable signal known as 'feedthrough' (induced on the FES by track-crossings during the seek operation) is lower by a factor of six compared to that observed with the astigmatic method. The ring lens is easy to align and has reasonable tolerance for positioning errors.

  9. Design of an Optical System for High Power CO2 Laser Cutting

    DEFF Research Database (Denmark)

    de Lange, D.F.; Meijer, J.; Nielsen, Jakob Skov

    2003-01-01

    considerable astigmatism (basically coma). In addition , unavoidable manufacuring tolerances contribute to deteriorate the optical quality. However, it is shown that the particular combination of two aspherical elementscompensate each other, leading to a high quality optical performance, which is virtually...

  10. Higher-order aberration corrector for an image-forming system in a transmission electron microscope

    International Nuclear Information System (INIS)

    We developed a new electron optical system with three dodecapoles to compensate for spherical aberration and six-fold astigmatism, which generally remains in a two-hexapole type corrector. In this study, we applied the corrector for image-forming system in transmission electron microscope. Compensation for higher-order aberration was demonstrated through a diffractogram tableau using a triple three-fold astigmatism field system, which was then compared with a double hexapole field system. Using this electron optical system, six-fold astigmatism was measured to be less than 0.1 mm at an acceleration voltage of 60 kV, showing that the system successfully compensated for six-fold astigmatism.

  11. Keratoconus

    Science.gov (United States)

    ... worse over time. As the problem gets worse, astigmatism develops. Keratoconus is often discovered during the teenage ... Corneal cross-linking is an experimental treatment that causes the cornea to become hard. This stops the ...

  12. Get Your Eyes Tested

    Science.gov (United States)

    ... objects are easier to see than near ones Astigmatism – a condition that makes it hard to see ... diabetes and high blood pressure . These diseases can cause eye problems if they aren’t treated. Lower ...

  13. Keratoconus Treatment Options

    Science.gov (United States)

    ... be used to correct the mild nearsightedness and astigmatism caused by keratoconus in its earliest stage, however ... options for Keratoconus which focus on correcting vision cause my the bulging and thinning of the cornea. ...

  14. Distortion of ultrashort pulses caused by aberrations

    Science.gov (United States)

    Horváth, Z. L.; Kovács, A. P.; Bor, Zs.

    The effect of the primary wave aberrations (spherical aberration, astigmatism and coma) on ultrashort pulses is studied by the Nijboer-Zernike theory. The results of the geometrical and the wave optical treatments are compared.

  15. Genetics Home Reference: isolated ectopia lentis

    Science.gov (United States)

    ... isolated ectopia lentis . Affected individuals often have nearsightedness (myopia) and can have an irregular curvature of the lens or a structure that covers the front of the eye (the cornea), which causes blurred vision (astigmatism). They may also develop clouding ...

  16. 78 FR 14557 - Guidance for Industry and Food and Drug Administration Staff: Investigational Device Exemption...

    Science.gov (United States)

    2013-03-06

    ... of April 17, 2009 (74 FR 17872), FDA announced the availability of the draft guidance. Comments on... (myopia, astigmatism, presbyopia). This guidance is intended to assist device manufacturers who plan...

  17. Optimization of an External Cavity Quantum Cascade Laser for Chemical Sensing Applications

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, Mark C.; Bernacki, Bruce E.; Taubman, Matthew S.; Cannon, Bret D.; Schiffern, John T.; Myers, Tanya L.

    2010-03-01

    We describe and characterize an external cavity quantum cascade laser designed for detection of multiple airborne chemicals, and used with a compact astigmatic Herriott cell for sensing of acetone and hydrogen peroxide.

  18. LASIK eye surgery

    Science.gov (United States)

    LASIK is most often done on people who use glasses or contact lenses because of nearsightedness (myopia). It is sometimes used to correct farsightedness. It may also correct astigmatism. The FDA and American ...

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

    NARCIS (Netherlands)

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

    2005-01-01

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

  20. Contact Lens Visual Rehabilitation in Keratoconus and Corneal Keratoplasty

    Directory of Open Access Journals (Sweden)

    Yelda Ozkurt

    2012-01-01

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

  1. Eyelid Problems

    Science.gov (United States)

    ... in Action Medical Editor & Editorial Advisory Board Sponsors Sponsorship Opporunities Spread the Word Shop AAP Find a ... irregular shape (astigmatism), it will threaten normal vision development and must be corrected as early as possible. ...

  2. Disease: H00690 [KEGG MEDICUS

    Lifescience Database Archive (English)

    Full Text Available (AIED) is an X-linked form of ocular hypopigmentation. Affected males demonstrate nystagmus, decreased visual acuity, myopia, astigm...atism, achromatopsia, and fundus hypopigmentation. Eye disease CACNA1F [HSA:778] [K

  3. Line focusing for soft x-ray laser-plasma lasing

    OpenAIRE

    Bleiner, Davide; Balmer, Jürg; Staub, Felix

    2011-01-01

    A computational study of line-focus generation was done using a self-written ray-tracing code and compared to experimental data. Two line-focusing geometries were compared, i.e., either exploiting the sagittal astigmatism of a tilted spherical mirror or using the spherical aberration of an off-axis- illuminated spherical mirror. Line focusing by means of astigmatism or spherical aberration showed identical results as expected for the equivalence of the two frames of reference. The variation o...

  4. Up-to-date analysis of school myopia, 6

    International Nuclear Information System (INIS)

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

  5. The effect of pterygium surgery on wavefront analysis

    OpenAIRE

    Hasan Razmjoo; Mohammad-Hadi Vaezi; Alireza Peyman; Nima Koosha; Zahra Mohammadi; Maryam Alavirad

    2014-01-01

    Background: Pterygium is a common disorder of the ocular surface. It causes vision impairment -usually irregular type astigmatism- through different mechanisms. In addition, it is believed that surgical excision of the pterygium improves visual problems. The appropriate method to investigate irregular astigmatism is using wavefront analysis. This study was aimed to evaluate wavefront analysis pre and post pterygium surgery. Materials and Methods: This study was performed on 32 patients wh...

  6. Enhancement of femtosecond lenticule extraction for visual symptomatic eye after myopia correction

    OpenAIRE

    Zhao, Jing; Yao, Peijun; Chen, Zhi; Li, Meiyan; Shen, Yang; Miao, Huamao; Zhou, Xingtao

    2014-01-01

    Background The novel Femtosecond lenticule extraction (FLEx) procedure has been considered safe, predictable, and effective in treating myopia and myopic astigmatism, with few complications. However, an enhancement procedure after FLEx may be required in some cases, but has not been reported in detail. Case presentation A 24-year-old woman who had undergone bilateral FLEx with the VisuMax femtosecond laser treatment for myopic astigmatism complained of double vision in her left eye after the ...

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

    Directory of Open Access Journals (Sweden)

    Gundersen Kjell

    2012-07-01

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

  8. Clinical research of limbal relaxing incision during implantable collamer lens surgery

    Directory of Open Access Journals (Sweden)

    Zhen Li

    2015-02-01

    Full Text Available AIM: To evaluate the efficacy and safety of limbal relaxing incision(LRIfor correcting corneal astigmatism during implantable collamer lens(ICLsurgery.METHODS: A total of 185 eyes of 105 patients with high myopia and corneal keratometric astigmatism were included in the study. ICL surgery with concomitant relaxing incision was performed in 105 eyes of 60 patients in LRIs group(Group A. Eighty eyes of 45 patients only underwent ICL surgery were in control group(Group B. All patients undergone ophthalmic examination that included uncorrected visual acuity(UCVA, best-corrected visual acuity(BCVA, Pentacam analysis system to observe the changes of corneal astigmatism before and 1wk, 1 and 3mo after surgery.RESULTS: Respectively comparing UCVA between two groups in 1 and 3mo postoperatively, the P values were considered statistically significant(PP values were considered no statistically significant(P>0.05. Preoperative corneal astigmatism was 1.52±0.55D in group A and 1.48±0.57D in group B, there was no statistically significant difference(P>0.05. One week postoperatively, the astigmatism was 0.55±0.41D in group A and 1.20±0.48D in group B. One month postoperatively, the astigmatism was 0.60±0.38D in group A and 0.93±0.47D. Three months postoperatively, the astigmatism was 0.51±0.32D in group A and 0.96±0.40D in group B. The difference between the two groups were statistically significant(PPPCONCLUSION: LRIs performed during ICL surgery appeared to be an effective and safer procedure to reduce pre-existing corneal astigmatism and improve UCVA as well as the visual quality.

  9. Keratometry device for surgical support

    OpenAIRE

    Saia Paula; De Groote Jean-Jacques; Ventura Liliane; Faria e Sousa Sidney J

    2009-01-01

    Abstract Background High astigmatisms are usually induced during corneal suturing subsequent to tissue transplantation or any other surgery which involves corneal suturing. One of the reasons is that the procedure is intimately dependent on the surgeon's skill for suturing identical stitches. In order to evaluate the influence of the irregularity on suturing for the residual astigmatism, a prototype for ophthalmic surgical support has been developed. The final intention of this prototype is t...

  10. Identical twins with “mirror image” anisometropia and esotropia

    Directory of Open Access Journals (Sweden)

    Stanković-Babić Gordana

    2011-01-01

    Full Text Available Introduction. Identical twins account for 0.2% of the world population and 8% of all twins. A “mirror image” variation can be found in 25% of identical twins. Studies of twins assume a special place in human genetics due to the possibility of comparing genetic and other factors. We present two pairs of identical male twins with mirror-image astigmatism and esotropia. Case Outline. The first was a pair of twelve-year old identical twins with “mirror image” myopic astigmatism. The Twin 1 had myopic astigmatism in the right eye, while the Twin 2 was affected by the left eye myopic astigmatism. The second was a pair of six-year old identical twins with esotropia and hypermetropic astigmatism. The Twin 1 had esotropia in the left eye, while the right eye was affected in the Twin 2. Esotropia was surgically corrected. Conclusion. In this study we pointed to the role of genetic factors in the development of refractive error, as well as the type of strabismus. Refraction anomalies (myopia, hypermetropia and astigmatism are complex heterogeneous disorders and ideal for genetic investigation. The knowledge of genetic mechanisms involved in refractive error susceptibility may allow treatment to prevent progression or to further examine gene-environment interactions. We hope that this paper will initiate further investigation of refraction anomalies in twins and future multicentre studies, which, to our knowledge, have not been conducted in our country so far.

  11. Factors Influencing Efficacy of Peripheral Corneal Relaxing Incisions during Cataract Surgery

    Directory of Open Access Journals (Sweden)

    Nino Hirnschall

    2015-01-01

    Full Text Available Purpose. To evaluate influencing factors on the residual astigmatism after performing peripheral corneal relaxing incisions (PCRIs during cataract surgery. Methods. This prospective study included patients who were scheduled for cataract surgery with PCRIs. Optical biometry (IOLMaster 500, Carl Zeiss Meditec AG, Germany was taken preoperatively, 1 week, 4 months, and 1 year postoperatively. Additionally, corneal topography (Atlas model 9000, Carl Zeiss Meditec AG, Germany, ORA (Ocular Response Analyzer, Reichert Ophthalmic Instruments, USA, and autorefraction (Autorefractometer RM 8800 Topcon were performed postoperatively. Results. Mean age of the study population n=74 was 73.5 years (±9.3; range: 53 to 90 and mean corneal astigmatism preoperatively was −1.82 D (±0.59; 1.00 to 4.50. Mean corneal astigmatism was reduced to 1.14 D (±0.67; 0.11 to 3.89 4 months postoperatively. A partial least squares regression showed that a high eccentricity of the cornea, a large deviation between keratometry and topography, and a high preoperative astigmatism resulted in a larger postoperative error concerning astigmatism. Conclusions. PCRI causes a reduction of preoperative astigmatism, though the prediction is difficult but several factors were found to be a relevant source of error.

  12. Prevalence of Refractive Errors; the Yazd Eye Study

    Directory of Open Access Journals (Sweden)

    Hossein Ziaei

    2013-01-01

    Full Text Available Purpose: To determine the prevalence of refractive errors in Yazd, central Iran. Methods: This population-based study was performed in 2010-2011 and targeted adults aged 40 to 80 years. Multi-stage random cluster sampling was applied to select samples from urban and rural residents of Yazd. Manifest refraction, visual acuity measurement, retinoscopy and funduscopy were performed for all subjects. Myopia, hyperopia, astigmatism and anisometropia were defined as spherical equivalent (SE +0.50 D, cylindrical error >0.5 D and SE difference ≥1 D between fellow eyes, respectively. Results: From a total of 2,320 selected individuals, 2,098 subjects (90.4% participated out of which 198 subjects were excluded due to previous eye surgery. The prevalence (95% confidence interval for myopia, hyperopia, astigmatism, anisometropia, -6 D myopia or worse, and 4 D hyperopia or worse was 36.5% (33.6-39.4%, 20.6% (17.9- 23.3%, 53.8% (51.3-56.3%, 11.9% (10.4-13.4%, 2.3% (1.6-2.9% and 1.2% (0.6-1.8%, respectively. The prevalence of hyperopia, astigmatism and anisometropia increased with age. The prevalence of myopia was significantly higher in female subjects. The prevalence of with-the-rule, against-the-rule and oblique astigmatism was 35.7%, 13.4% and 4.6%, respectively. The prevalence of against-the-rule astigmatism increased with age (P<0.001; with-the-rule astigmatism was more common in women (P=0.038. Conclusion: More than half of the study population had refractive errors; the prevalence of myopia and astigmatism was higher than earlier studies in Iran. Since refractive errors are a major cause of avoidable visual impairment, their high prevalence in this survey is important from a public health perspective.

  13. Keratometry device for surgical support

    Directory of Open Access Journals (Sweden)

    Saia Paula

    2009-12-01

    Full Text Available Abstract Background High astigmatisms are usually induced during corneal suturing subsequent to tissue transplantation or any other surgery which involves corneal suturing. One of the reasons is that the procedure is intimately dependent on the surgeon's skill for suturing identical stitches. In order to evaluate the influence of the irregularity on suturing for the residual astigmatism, a prototype for ophthalmic surgical support has been developed. The final intention of this prototype is to be an evaluation tool for guided suture and as an outcome diminish the postoperative astigmatism. Methods The system consists of hand held ring with 36 infrared LEDs, that is to be projected onto the lachrymal film of the cornea. The image is reflected back through the optics of the ocular microscope and its distortion from the original circular shape is evaluated by developed software. It provides keratometric and circularity measurements during surgery in order to guide the surgeon for uniformity in suturing. Results The system is able to provide up to 23D of astigmatism (32D - 55D range and is ± 0.25D accurate. It has been tested in 14 volunteer patients intraoperative and has been compared to a commercial keratometer Nidek Oculus Hand-held corneal topographer. The correlation factors are 0.92 for the astigmatism and 0.97 for the associated axis. Conclusion The system is potentially efficient for guiding the surgeon on uniformity of suturing, presenting preliminary data indicating an important decrease on the residual astigmatism, from an average of 8D - for patients not submitted to the prototype guidance - to 1.4D - for patients who have actually been submitted to the prototype guidance - after the first 24 hours post-surgery and in the subsequent weeks. It also indicates that the surgeon should achieve circularity greater or equal to 98% in order to avoid postoperative astigmatisms over 1D. Trial Registration Trial registration number: CAAE - 0212.0.004.000-09.

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

    International Nuclear Information System (INIS)

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

  15. Effects of different types of refractive errors on bilateral amblyopia

    Directory of Open Access Journals (Sweden)

    Mücella Arıkan Yorgun

    2012-12-01

    Full Text Available Objectives: Identifying effects of different types of refractiveerrors on final visual acuity and stereopsis levels inpatients with bilateral amblyopia.Materials and methods: Patients with bilateral amblyopialower than ≥1.5 D anisometropia were included. Thepatients were classified according to the level of sphericalequivalent (0-4 D and >4 D of hypermetropia, the levelof astigmatism (below and above 2D in positive cylinderand type of composed refractive error [ 4 D of hypermetropiaand 2 D of astigmatism (group III]. Initialand final binocular best corrected visual acuities (BCVAwere compared between groups.Results: The initial binocular BCVA levels were significantlylower in patients with > 4 D of hypermetropia(p=0.028, without correction after treatment (p=0.235.The initial binocular BCVA was not different betweenastigmatism groups, but final BCVA levels were significantlylower in 4-6D of astigmatism compared with 2-4D of astigmatism (p=0.001. During comparison of composedrefractive errors, only the initial binocular BCVAwas significantly lower in group I compared to group II(p=0.015. The final binocular BCVA levels were not differentbetween groups I and III (p>0.05.Conclusions: Although the initial BCVA is lower in patientswith higher levels of hypermetropia, the response ofpatients to treatment with glasses is good. The responseof patients with high levels of astigmatism seems to belimited. J Clin Exp Invest 2012; 3(4: 467-471Key words: Amblyopia, isoametropic amblyopia, hypermetropia,refractive amblyopia, visual acuity

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-04-15

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

  17. Monte Carlo simulation of expected outcomes with the AcrySof® toric intraocular lens

    Directory of Open Access Journals (Sweden)

    Potvin Richard

    2008-10-01

    Full Text Available Abstract Background To use a Monte Carlo simulation to predict postoperative results with the AcrySof® Toric lens, evaluating the likelihood of over- or under-correction using various toric lens selection criteria. Methods Keratometric data were obtained from a large patient population with preoperative corneal astigmatism Results This simulation demonstrated that random errors in alignment, surgically induced astigmatism and lens rotation slightly reduced the overall effect of the toric lens. Residual astigmatism was statistically significantly higher under the simulation of surgery relative to an exact calculation (p Conclusion Monte Carlo simulation suggests that surgical variability and lens orientation/rotation variability may combine to produce small reductions in the correction achieved with the AcrySof® Toric® IOL. Adopting more aggressive lens selection criteria may yield significantly lower residual astigmatism values for many patients, with negligible overcorrections. Surgeons are encouraged to evaluate their AcrySof® Toric® outcomes to determine if they should modify their individual lens selection criteria, or their default surgically induced astigmatism value, to benefit their patients.

  18. In vivo and in vitro analysis of topographic changes secondary to DSAEK venting incisions

    Directory of Open Access Journals (Sweden)

    Church D

    2011-08-01

    Full Text Available Majid Moshirfar, Monette T Lependu, Dane Church, Marcus C Neuffer John A Moran Eye Center, University of Utah, Salt Lake City, UT, USA Introduction: Descemet’s stripping automated endothelial keratoplasty (DSAEK venting incisions may induce irregular corneal astigmatism. The study examines in vivo and in vitro astigmatic effects of venting incisions. Patients and methods: In vivo analysis examined eleven eyes of eleven patients who had received DSAEK with venting incisions. A chart review of the eleven eyes including assessment of pre and postoperative refraction and topography was performed. In vitro analysis examined three cadaver eyes which received topographic imaging followed by venting incisions at 4 mm, 6 mm, and 7 mm optical zones. Topographic imaging was then performed again after the incisions. Results: Postoperative topographies of eleven eyes demonstrated localized flattening at incision sites and cloverleaf pattern astigmatism. There was a significant difference in corneal irregularity measurement (P = 0.03, but no significant difference in shape factor or change of topographic cylinder. The cloverleaf pattern was found in cadaver eyes with incisions placed at 4 mm and 6 mm optical zones but not at the 7 mm zone. Conclusion: DSAEK venting incisions can cause irregular corneal astigmatism that may affect visual outcomes. The authors recommend placement of venting incisions near the 7 mm optical zone. Keywords: DSAEK, venting incisions, endothelial keratoplasty, astigmatism, endothelium, endothelial transplant

  19. Infantile nystagmus and visual deprivation

    DEFF Research Database (Denmark)

    Fledelius, Hans C; Jensen, Hanne

    2014-01-01

    , astigmatism, and age were further considered. The series comprised 48 children with nystagmus as single diagnosis, whereas 42 had clinical colabels (Down syndrome [13], dysmaturity [9], and mental retardation, encephalopathy [20]). RESULTS: Median binocular visual acuity was 0.3 in the full series, and median...... refraction was emmetropia in all subgroups. Compared with Danish control data, myopia was over-represented, and generally of juvenile onset. The Down syndrome subgroup was separated from the remainder by an even higher myopia prevalence. Astigmatism above 1 D cylinder value was recorded in 52% of all cases....... CONCLUSIONS: The prevalence of myopia and astigmatism was higher among children with nystagmus than in controls. Myopia was mainly juvenile, and not related to the period of infancy when the motor foveal smear is considered most disturbing and possibly influencing visual development....

  20. Focused high-intensity proton beam from a lithium source by using an ExB stigmatic selector

    International Nuclear Information System (INIS)

    This article describes the design and operation of a system that produces a high-intensity proton beam. The system consists of a lithium proton source and an ExB stigmatic selector that produces a stigmatic proton beam at the mass focus. The protons are produced by bombarding electrons against a lithium surface. These protons are accelerated toward a special tilted-pole Wien filter (stigmatic selector), which eliminates astigmatism in the proton beam at the mass focus. The stigmatic ExB selector was also tested with electron beams, and their astigmatism was also eliminated. A classical ExB Wien filter with parallel poles (astigmatic selector) was used for comparison. The experimental spectral curves of both the proton current and the electron current, each using both types of selectors, are shown

  1. Design of aspherical surfaces for panoramic imagers using multi-populations genetic algorithm

    Science.gov (United States)

    Wang, Li-Ping; Liang, Zhong-zhu; Jin, Chun-Shui

    2009-05-01

    A design method of aspherical surface for panoramic imaging system with two mirrors using multi-populations genetic algorithms is proposed. Astigmatism induced by mirrors may significantly compromise image resolution. To solve this problem, we induced algebraic expression of astigmatism in panoramic imager based on generalized Coddington equation and theory of geometric optics. Then, we propose an optimization process for mirror profile design to eliminate astigmatism and provide purposely-designed projection formula with aid of MPGA. A series of polynomial expressions of aspherical surfaces are obtained and procedures of the design are presented. In order to facilitate ray tracing and aberration calculation, even asphere surface model is obtained by using of hybrid schemes combining MPGA and damped least squares. Finally, a prototype of the catadioptric panoramic imager has been developed and panoramic ring image is obtained.

  2. Cyclopentolate as a cycloplegic drug in determination of refractive error

    Directory of Open Access Journals (Sweden)

    Bolinovska Sofija

    2008-01-01

    Full Text Available Cycloplegia is loss of the power of accommodation with inhibition of a ciliary muscle. We obtain in this way the smallest refraction of the lens and make it possible to determine the presence and size of the particular refractive error in cycloplegia by using cyclopentolate. Cyclopentolate is a synthetic anticholinergic drug and antagonist of the muscarine receptors. If applied in the eye, it blocks the effect of cholinergic stimulation on the sphincter pupillae muscle and ciliary muscle. It provokes severe mydriasis (dilation of the pupil and cycloplegia (paralysis of the accommodation. Cyclopentolate has been used occasionaly in diagnostic purposes: defining ocular refraction and in ophthalmoscopy. This is the prospective study which included 200 children (400 eyes aged 3-18 years, carried out in one ambulatory ophthalmological examination. The results were analysed using standard statistical methods. The most often refractive error in the examined group of children is hyperopia with hyperopic astigmatism, then myopia with myopic astigmatism and mixtus astigmatism are the most often in the oldest group of children. The mean value of corneal astigmatism on the right eye was 1.24 D, on the left eye 1.23 D. Anisometropy was found in 40% children. The presence of myopia, myopic and astigmatism mixtus tended to increase, and hyperopia and hyperopic astigmatism tended to decrease toward older groups of children. Refractive error could result in a poor development of visual acuity, causing amblyopia and strabismus, and because of that represents an important public health problem. As one of amblyogenic risk factors in children, it can be prevented with screening program and appropriate treatment, thus providing prevention of amblyopia as one form of blindness.

  3. Unveiling orbital angular momentum and acceleration of light beams and electron beams

    Science.gov (United States)

    Arie, Ady

    Special beams, such as the vortex beams that carry orbital angular momentum (OAM) and the Airy beam that preserves its shape while propagating along parabolic trajectory, have drawn significant attention recently both in light optics and in electron optics experiments. In order to utilize these beams, simple methods are needed that enable to easily quantify their defining properties, namely the OAM for the vortex beams and the nodal trajectory acceleration coefficient for the Airy beam. Here we demonstrate a straightforward method to determine these quantities by astigmatic Fourier transform of the beam. For electron beams in a transmission electron microscope, this transformation is easily realized using the condenser and objective stigmators, whereas for light beam this can be achieved using a cylindrical lens. In the case of Laguerre-Gauss vortex beams, it is already well known that applying the astigmatic Fourier transformation converts them to Hermite-Gauss beams. The topological charge (and hence the OAM) can be determined by simply counting the number of dark stripes of the Hermite-Gauss beam. We generated a series of electron vortex beams and managed to determine the topological charge up to a value of 10. The same concept of astigmatic transformation was then used to unveil the acceleration of an electron Airy beam. The shape of astigmatic-transformed depends only on the astigmatic measure and on the acceleration coefficient. This method was experimentally verified by generating electron Airy beams with different known acceleration parameters, enabling direct comparison to the deduced values from the astigmatic transformation measurements. The method can be extended to other types of waves. Specifically, we have recently used it to determine the acceleration of an optical Airy beams and the topological charge of so-called Airy-vortex light beam, i.e. an Airy light beam with an embedded vortex. This work was supported by DIP and the Israel Science

  4. Effect of Orbital Decompression on Corneal Topography in Patients with Thyroid Ophthalmopathy.

    Directory of Open Access Journals (Sweden)

    Su Ah Kim

    Full Text Available To evaluate changes in corneal astigmatism in patients undergoing orbital decompression surgery.This retrospective, non randomized comparative study involved 42 eyes from 21 patients with thyroid ophthalmopathy who underwent orbital decompression surgery between September 2011 and September 2014. The 42 eyes were divided into three groups: control (9 eyes, two-wall decompression (25 eyes, and three-wall decompression (8 eyes. The control group was defined as the contralateral eyes of nine patients who underwent orbital decompression surgery in only one eye. Corneal topography (Orbscan II, Hertel exophthalmometry, and intraocular pressure were measured at 1 month before and 3 months after surgery. Corneal topographic parameters analyzed were total astigmatism (TA, steepest axis (SA, central corneal thickness (CCT, and anterior chamber depth (ACD.Exophthalmometry values and intraocular pressure decreased significantly after the decompression surgery. The change (absolute value (|x| of the difference in astigmatism at the 3 mm zone was significantly different between the decompression group and the controls (p = 0.025. There was also a significant change in the steepest axis at the 3 mm zone between the decompression group and the controls (p = 0.033. An analysis of relevant changes in astigmatism showed that there was a dominant tendency for incyclotorsion of the steepest axis in eyes that underwent decompression surgery. Using Astig PLOT, the mean surgically induced astigmatism (SIA was 0.21±0.88 D with an axis of 46±22°, suggesting that decompression surgery did change the corneal shape and induced incyclotorsion of the steepest axis.There was a significant change in corneal astigmatism after orbital decompression surgery and this change was sufficient to affect the optical function of the cornea. Surgeons and patients should be aware of these changes.

  5. Novel approach for phacoemulsification during combined phacovitrectomy

    Directory of Open Access Journals (Sweden)

    Ewais WA

    2015-12-01

    Full Text Available Wael Ahmed Ewais, Ashraf Abdel Maqsoud Nossair, Lamia Samy Ali Department of Ophthalmology, Faculty of Medicine, Cairo University, Cairo, Egypt Purpose: To evaluate the safety and efficacy of surgeon’s superior sitting position during temporal clear corneal incision (TCCI phacoemulsification, with a 90° working angle, during combined phacovitrectomy. Methods: Prospective interventional case series were performed on 65 eyes of 63 patients. TCCI phacoemulsification was done in all cases (whether right or left eyes, while the surgeon was sitting superiorly to the operating table. Outcome measures included: Shift in sitting position, keratometric astigmatism, surgically induced astigmatism, posterior capsule integrity, and intraocular lens centration. Results: Phacoemulsification was performed completely in all cases (100%. Shift in position to temporal sitting position happened in two cases (3%. The keratometric astigmatism showed mean changes of 1.09 D (0.25–3.75 D to 0.84 D (0.00–3.25 D at 1 month, which remained stable at 6 months; 0.84 D (0.16–3.21 D. The surgically induced astigmatism was 0.25 DC (-0.50 to 1.0 DC at 1 month, which stayed stable at 6 months; 0.25 D (-0.63 D to 0.98 D. Posterior capsular rupture occurred in one case (the second case (1.5%. The intraocular lens was centered in all cases (100%. Conclusion: Superior sitting TCCI phacoemulsification, with a wide working angle, during combined phacovitrectomy proved safe and easy, without the burden of changing and disrupting the operative setting. The anatomical and optical outcomes were acceptable. Keywords: clear corneal incisions, temporal nasal horizontal superior, surgically induced astigmatism, keratometric astigmatism, superior sitting position, working angle

  6. Identical twins with “mirror image” anisometropia and esotropia

    OpenAIRE

    Stanković-Babić Gordana; Vujanović Milena; Cekić Sonja

    2011-01-01

    Introduction. Identical twins account for 0.2% of the world population and 8% of all twins. A “mirror image” variation can be found in 25% of identical twins. Studies of twins assume a special place in human genetics due to the possibility of comparing genetic and other factors. We present two pairs of identical male twins with mirror-image astigmatism and esotropia. Case Outline. The first was a pair of twelve-year old identical twins with “mirror image” myopic astigmatism. The Twin 1 ...

  7. Rows of optical vortices from elliptically perturbing a high-order beam

    CERN Document Server

    Dennis, M R

    2006-01-01

    An optical vortex (phase singularity) with a high topological strength resides on the axis of a high-order light beam. The breakup of this vortex under elliptic perturbation into a straight row of unit strength vortices is described. This behavior is studied in helical Ince-Gauss beams and astigmatic, generalized Hermite-Laguerre-Gauss beams, which are perturbations of Laguerre-Gauss beams. Approximations of these beams are derived for small perturbation, in which a neighborhood of the axis can be approximated by a polynomial in the complex plane: a Chebyshev polynomial for Ince-Gauss beams, and a Hermite polynomial for astigmatic beams.

  8. Correction of monochromatic aberrations in human eyes - report on work in progress

    International Nuclear Information System (INIS)

    In the excimer laser photorefractive keratectomy the laser removes tissues across the anterior corneal surface. The result is a change in the anterior corneal curvature which is used to correct ocular image errors such as myopia and astigmatism. Unfortunately, there are additional aberrations as higher order coma-like and spherical aberration-like image errors limiting the visual acuity. Actually we are investigating how to fit the excimer laser photorefractive ablation profiles for correction of myopia and astigmatism to those for minimizing higher order coma and spherical aberration. Our approach is an aberrometry-guided corneal refractive surgery using a scanning spot ArF excimer laser. (author)

  9. Optical design methods to suppress aberrations which are caused by change of object distance

    Science.gov (United States)

    Hase, Shunsuke; Shibuya, Masato; Maehara, Kazuhisa; Oka, Mikio; Nakadate, Suezou

    2011-10-01

    An object distance range within which fine image can be obtained by focus adjustment is limited since aberrations are caused by change of object distance. We have developed a novel optical design method to suppress variation of coma, astigmatism and field curvature induced by change of object distance. Variation of astigmatism and field curvature can be suppressed by introducing appropriate distortion. Also variation of coma caused by change of object distance can be suppressed by using spherical image surface which pivot is located at the center of exit pupil.

  10. A simple method for creating a robust optical vortex beam with a single cylinder lens

    Science.gov (United States)

    Nam, Hannarae Annie; Cohen, Martin G.; Noé, John W.

    2011-06-01

    We describe a simple method for creating Laguerre-Gauss (LG) optical vortex beams from Hermite-Gauss (HG) modes with a single cylinder lens. The diverging vortex created by the cylinder lens has the correct intensity distribution in the far-field but its residual longitudinal astigmatism causes the vortex to revert to the original HG mode when it is brought to a focus. We show that an appropriate small tilt of the focusing lens can prevent this effect by introducing a compensating astigmatism. The corrected vortex is a good approximation to an exact LG mode and should be useful for a variety of demonstrations and experiments.

  11. Modeling aberrations in the Advanced Camera for Surveys

    Science.gov (United States)

    Houairi, K.; Casertano, S.; Lallo, M.; Makidon, R. B.

    2006-10-01

    We present an analysis of the optical model for HST and ACS that shows the possible impact of misalignments of various optical elements on apparent image aberrations. The analysis was aimed at identifying possible causes for apparent variations in coma and astigmatism seen on orbital time scales in HST images. Results indicate that any combinations of mirrors and motions that reproduce the observed coma and astigmatism changes, also predict either large shifts in the image, which is not observed, or require unrealistically large movements of the elements.

  12. A simple method for creating a robust optical vortex beam with a single cylinder lens

    International Nuclear Information System (INIS)

    We describe a simple method for creating Laguerre–Gauss (LG) optical vortex beams from Hermite–Gauss (HG) modes with a single cylinder lens. The diverging vortex created by the cylinder lens has the correct intensity distribution in the far-field but its residual longitudinal astigmatism causes the vortex to revert to the original HG mode when it is brought to a focus. We show that an appropriate small tilt of the focusing lens can prevent this effect by introducing a compensating astigmatism. The corrected vortex is a good approximation to an exact LG mode and should be useful for a variety of demonstrations and experiments

  13. Simple mathematical model for designing laser diode focusing optics with a large numerical aperture

    Science.gov (United States)

    Sun, Haiyin

    2014-10-01

    A simple mathematical model is derived for conveniently designing laser diode focusing optics with a large numerical aperture. The astigmatism of laser diode beams and the lens truncation effects are considered in the model. The linearly polarized nature of laser diode beams is also included. Two design examples using this model are presented. Design results show that the lens truncation will increase the size of the focused spot and the value of the M2 factor, and the lens truncation caused a focal shift, which is not enough to correct laser diode beam astigmatism.

  14. Off-axis reflecting telescope with axially-symmetric optical property and its applications

    Science.gov (United States)

    Chang, Seunghyuk

    2006-06-01

    The basic concept and fundamental result of a recently developed geometric aberration theory for classical off-axis reflecting telescopes and imaging systems are presented. It is shown that a classical off-axis reflecting telescope can be designed to have practically axially-symmetric optical property by eliminating the dominant aberration (linear astigmatism) caused by the asymmetric geometry. A simple closed-form equation for elimination of linear astigmatism is presented. Also, to show how the developed aberration theory can be applied to current and future telescopes, several off-axis reflecting telescopes and imaging systems are designed and analyzed.

  15. Wide viewing-zone-angle full-color electronic holography system using very high resolution liquid crystal display panels

    Science.gov (United States)

    Senoh, Takanori; Mishina, Tomoyuki; Yamamoto, Kenji; Oi, Ryutaro; Kurita, Taiichiro

    2011-02-01

    A wide viewing-zone-angle full-color electronic holography reconstruction system is developed. Time division multiplexing of RGB color light and space division multiplexing of viewing-zone-angles are adopted to keep the optical system compact. Undesirable light such as illumination light, phase conjugate light, and high-order diffraction light are eliminated by half-zone-plate hologram generation and single sideband beam reconstruction. Color aberration and astigmatism caused by the reproduction optical system are analyzed and reduced. The developed system expands viewing-zone-angle of full-color holographic image three times wider than the original, suppressing undesirable light, color aberration, and astigmatism.

  16. Advances in femtosecond laser technology

    Directory of Open Access Journals (Sweden)

    Callou TP

    2016-04-01

    Full Text Available Thais Pinheiro Callou, Renato Garcia, Adriana Mukai, Natalia T Giacomin, Rodrigo Guimarães de Souza, Samir J Bechara Department of Ophthalmology, University of Sao Paulo, Sao Paulo, Brazil Abstract: Femtosecond laser technology has become widely adopted by ophthalmic surgeons. The purpose of this study is to discuss applications and advantages of femtosecond lasers over traditional manual techniques, and related unique complications in cataract surgery and corneal refractive surgical procedures, including: LASIK flap creation, intracorneal ring segment implantation, presbyopic treatments, keratoplasty, astigmatic keratotomy, and intrastromal lenticule procedures. Keywords: laser therapy, refractive surgical procedures, intracorneal ring, laser in situ keratomileusis, keratoplasty, presbyopia, cataract extraction, astigmatism surgery

  17. Laser In Situ keratomileusis (LASIK) for the treatment of low moderate, and high myopia.

    OpenAIRE

    Lindstrom, R L; Hardten, D R; Chu, Y R

    1997-01-01

    PURPOSE: To evaluate the efficacy, safety and predictability of LASIK in the treatment of low, moderate and high myopia. METHODS: A perspective study of LASIK for low myopia of -0.75 to -6.00 with less than +1 D of astigmatism and for moderate and high myopia of -6.12 to -20 D with astigmatism up to +4.50 D was performed at our institution from March through November, 1996. The Chiron automated corneal shaper was used for the initial flap, and either the Summit or VISX laser was used for the ...

  18. Seven year follow-up after advanced surface ablation with excimer laser for treatment of myopia: Long-term outcomes of cooling PRK and LASEK

    DEFF Research Database (Denmark)

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

    , Odense University Hospital. Inclusion criteria: Age 20-50 years at time of surgery, pre-operative CDVA ≤ 0.10 (logMAR) and no other ocular conditions than myopia with or without astigmatism of maximum 3 D. Exclusion criteria: Pregnancy and eyes having undergone re-treatment. A MEL80 flying-spot excimer...... were satisfied or very satisfied with the surgery 5 to 7 years after surgery. Conclusions: Both cPRK and LASEK seemed safe up to 7 years after surgery for treatment of myopia and low degrees of astigmatism. Results were comparable concerning refractive predictability, visual acuity, corneal haze...

  19. Corneal topography, refractive state, and accommodation in harbor seals (Phoca vitulina).

    Science.gov (United States)

    Hanke, Frederike D; Dehnhardt, Guido; Schaeffel, Frank; Hanke, Wolf

    2006-03-01

    Corneal topography of a harbor seal measured with a Placido's disc shows a central flattened stripe in the vertical meridian. Together with a pupil that can form a vertical slit, the flat vertical meridian can minimize the optical effects caused by the transition from water to air. Using infrared (IR) photoretinoscopy, we analyzed the refractive state of harbor seals and revealed a high degree of myopia and astigmatism in air, but emmetropia or slight hyperopia with little astigmatism underwater. The brightness distribution in the pupils suggest the presence of a multifocal dioptric apparatus in air and underwater. We found a first indication for accommodation by dynamic recordings underwater. PMID:16256164

  20. Symbolic algebra approach to the calculation of intraocular lens power following cataract surgery

    Science.gov (United States)

    Hjelmstad, David P.; Sayegh, Samir I.

    2013-03-01

    We present a symbolic approach based on matrix methods that allows for the analysis and computation of intraocular lens power following cataract surgery. We extend the basic matrix approach corresponding to paraxial optics to include astigmatism and other aberrations. The symbolic approach allows for a refined analysis of the potential sources of errors ("refractive surprises"). We demonstrate the computation of lens powers including toric lenses that correct for both defocus (myopia, hyperopia) and astigmatism. A specific implementation in Mathematica allows an elegant and powerful method for the design and analysis of these intraocular lenses.

  1. Relationship between wave aberrations and histological features in ex vivo porcine crystalline lenses

    Science.gov (United States)

    Acosta, Eva; Bueno, Juan M.; Schwarz, Christina; Artal, Pablo

    2010-09-01

    Wave aberrations of isolated ex vivo porcine crystalline lenses were measured by using a point-diffraction interferometer. This method allowed us to gain greater insight into the detailed aberration structure of eye lenses showing systematic presence of some dominant aberrations. In order of significance, astigmatism together with spherical aberration, coma, and trefoil are the main aberrations present in all lenses. We found a high correlation between the axis of both astigmatism and trefoil with the Y-shaped suture planes of the lens, revealing a subtle relationship between the induced aberrations and the histological features.

  2. TARGET EMMETROPIA IN MANUAL SMALL INCISION CATARACT SURGERY

    Directory of Open Access Journals (Sweden)

    Sathish

    2013-04-01

    Full Text Available INTRODUCTION: Patient dissatisfaction is very common even with go od cataract surgery. Cataract surgery done by phacoemulsification with f oldable IOL implantation results in minimal astigmatism. This results in early rehabilitation t hereby rendering the patient nearly emmetropic for both distant and near work. But the drawbacks of this surgical technique are high cost, steep learning curve and is entirely mach ine dependent. This study has been conducted to know if it is possi ble to achieve minimal astigmatism with MSICS with rigid PMMA IOL in selected cases th us achieving cost effectiveness and reducing the duration of surgery.

  3. Design of high power solid-state pulsed laser resonators

    International Nuclear Information System (INIS)

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

  4. Diving with microparticles in acoustic fields

    DEFF Research Database (Denmark)

    Marin, Alvaro; Rossi, Massimiliano; Barnkob, Rune;

    2012-01-01

    technique is called Astigmatism Particle Tracking Velocimetry and it consists in the use of cylindrical lenses to induce a deformation in the particle shape, which will be then correlated with its distance from the observer. With this method we are able to dive with the particles and observe in detail...

  5. Expressions for third-order aberration theory for holographic images

    Indian Academy of Sciences (India)

    S K Tripathy; S Ananda Rao

    2003-01-01

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

  6. Visual outcomes and optical quality after implantation of a diffractive multifocal toric intraocular lens

    Science.gov (United States)

    Chen, Xiangfei; Zhao, Ming; Shi, Yuhua; Yang, Liping; Lu, Yan; Huang, Zhenping

    2016-01-01

    Background: This study evaluated the visual function after implantation of a multifocal toric intraocular lenses (IOLs). Materials and Methods: This study involved 10 eyes from eight cataract patients with corneal astigmatism of 1.0 diopter (D) or higher who had received phacoemulsification with implantation of an AcrySof IQ ReSTOR Toric IOL. Six-month evaluations included visual acuity, spherical equivalent (SE), defocus curve, residual astigmatism, IOL rotation, contrast sensitivity (CS), wavefront aberrations, modulation transfer function (MTF), and patient satisfaction assessments. Results: At 6 months postoperatively, uncorrected distance visual acuity (logarithm of the minimum angle of resolution) was 0.09 ± 0.04, corrected distance visual acuity was 0.02 ± 0.11, and uncorrected near visual acuity was 0.12 ± 0.07. The mean SE was −0.095 ± 0.394 D (±0.50 D in 90%). Refractive astigmatism at the 6-month follow-up visit was significantly reduced to 0.35 ± 0.32 D from 1.50 ± 0.41 D presurgery (P 0.05). There was an increase in MTF results between preoperative and postoperative evaluations at all spatial frequencies. Conclusions: The diffractive multifocal toric IOL is able to provide a predictable astigmatic correction with apparently outstanding levels of optical quality after implantation. PMID:27221680

  7. Experimental and analytical characterization of the 3D motion of particles in acoustofluidic devices

    DEFF Research Database (Denmark)

    Rossi, M.; Barnkob, Rune; Augustsson, P.; Marín, Á. G.; Muller, Peter Barkholt; Bruus, Henrik; Laurell, T.; Kähler, C. J.

    2012-01-01

    . Astigmatism Particle Tracking Velocimetry (APTV) was used to measure the three-dimensional trajectories, velocities and accelerations of the particles. The experiments show how the acoustic radiation force dominates for the large 5-µm particles, whereas the drag force from the acoustic streaming dominates for...

  8. The effect of pterygium surgery on contrast sensitivity and corneal topographic changes

    Directory of Open Access Journals (Sweden)

    Joo Youn Oh

    2010-04-01

    Full Text Available Joo Youn Oh, Won Ryang WeeDepartment of Ophthalmology, Seoul National University Hospital, Seoul, KoreaPurpose: To investigate the effect of pterygium surgery on corneal topography and contrast sensitivity.Patient and methods: The IRB approved this prospective, nonrandomized, self-controlled study. Computerized videokeratography (Orbscan II was performed in 36 patients with primary pterygia, both before and 1 month after pterygium excision with limbal-conjunctival autografting. The topographic parameters were compared. Spatial contrast sensitivity testing was performed using VCTS 6500. Differences between preoperative and postoperative values were evaluated statistically.Results: The mean Sim K astigmatism and irregularity index, significantly decreased after pterygium surgery. The mean refractive power significantly increased after the operation. The “with-the-rule” astigmatism induced by pterygium became “against-the-rule” astigmatism after pterygium removal (P = 0.041. The contrast sensitivity of 6, 12, and 18 cycles per degree, significantly increased from 1.55 ± 0.28, 0.97 ± 0.47, and 0.29 ± 0.16 to 1.72 ± 0.18, 1.21 ± 0.44, and 0.65 ± 0.48, respectively (P = 0.007, <0.001, <0.001, respectively.Conclusions: Pterygium surgery significantly reduces corneal topographic astigmatism and improves contrast sensitivity.Keywords: corneal topography, visual acuity

  9. Optical behavior of surface bubbles

    Science.gov (United States)

    Straulino, Samuele; Gambi, Cecilia M. C.; Molesini, Giuseppe

    2015-11-01

    The observation of diamond-like light spots produced by surface bubbles obliquely illuminated is reported. The phenomenon is discussed in terms of geometrical optics, and an explanation is provided attributing the effect to the astigmatism introduced by the deformation of the liquid surface surrounding the bubble. An essential ray tracing program is outlined and used to reconstruct the observed phenomenon numerically.

  10. Refraction and visual acuity in a national Danish cohort of 4-year-old children of extremely preterm delivery

    DEFF Research Database (Denmark)

    Fledelius, Hans C; Bangsgaard, Regitze; Slidsborg, Carina; laCour, Morten

    2015-01-01

    refractive distribution presented a myopic tail (4.5%) and a hyperopic tail (11.9% ≥+2.5 D) as special preterm features, and corneas were more curved. Astigmatism and anisometropia were only marginally increased, and visual acuities were generally good. Best-corrected binocular median logMAR visual acuity...

  11. Alignment and assembly process for primary mirror subsystem of a spaceborne telescope

    Science.gov (United States)

    Lin, Wei-Cheng; Chang, Shenq-Tsong; Chang, Sheng-Hsiung; Chang, Chen-Peng; Lin, Yu-Chuan; Chin, Chi-Chieh; Pan, Hsu-Pin; Huang, Ting-Ming

    2015-11-01

    In this study, a multispectral spaceborne Cassegrain telescope was developed. The telescope was equipped with a primary mirror with a 450-mm clear aperture composed of Zerodur and lightweighted at a ratio of approximately 50% to meet both thermal and mass requirements. Reducing the astigmatism was critical for this mirror. The astigmatism is caused by gravity effects, the bonding process, and deformation from mounting the main structure of the telescope (main plate). This article presents the primary mirror alignment, mechanical ground-supported equipment (MGSE), assembly process, and optical performance test used to assemble the primary mirror. A mechanical compensated shim is used as the interface between the bipod flexure and main plate. The shim was used to compensate for manufacturer errors found in components and differences between local coplanarity errors to prevent stress while the bipod flexure was screwed to the main plate. After primary mirror assembly, an optical performance test method called a bench test with an algorithm was used to analyze the astigmatism caused by the gravity effect and deformation from the mounting or supporter. The tolerance conditions for the primary mirror assembly require the astigmatism caused by gravity and mounting force deformation to be less than P-V 0.02 λ at 632.8 nm. The results demonstrated that the designed MGSE used in the alignment and assembly processes met the critical requirements for the primary mirror assembly of the telescope.

  12. Criteria for admissible values of smooth aberrations for nondiffractive laser beams

    Energy Technology Data Exchange (ETDEWEB)

    Malashko, Ya I; Khabibulin, V M [JSC ' Concern PVO ' Almaz-Antey' , Moscow (Russian Federation)

    2014-04-28

    We have derived analytical expressions, verified by the methods of numerical simulation, to evaluate the angular divergence of nondiffractive laser beams containing smooth aberrations, i.e., spherical defocusing, astigmatism and toroid. Using these expressions we have formulated the criteria for admissible values of smooth aberrations. (laser applications and other topics in quantum electronics)

  13. Mass spectrometers with energy focusing: Combinations of magnetic and electric sector fields whose mean planes of deflection are tilted with respect to each other

    International Nuclear Information System (INIS)

    First a combination of two sector fields is considered, for instance a homogeneous magnetic field followed by an electric cylinder condenser. The mean planes of deflection of the fields are tilted with respect to each other by an oblique angle. Such a combination has astigmatic focusing properties for paraxial rays of ions of certain mass and energy coming from an object point assumed at a certain distance before the first field on the incoming central ray. At different distances from the field combination are formed, calculated in first order, two real or virtual straight astigmatic focusing lines which are perpendicular to each other and to the outgoing central ray. By proper assumptions of the dimensions of the combination it can be arranged that its first order energy dispersion and one real of its astigmatic focusing lines have exactly the same direction. Then by addition of a third sector field (again a homogeneous magnetic field) it can be achieved that the astigmatic focusing will be changed into a stigmatic one while at the same time the energy dispersion can be reduced to small values. The mass dispersion of this three field combination in the given numerical example is about perpendicular to the direction of the energy dispersion. (orig.)

  14. Advances in femtosecond laser technology

    Science.gov (United States)

    Callou, Thais Pinheiro; Garcia, Renato; Mukai, Adriana; Giacomin, Natalia T; de Souza, Rodrigo Guimarães; Bechara, Samir J

    2016-01-01

    Femtosecond laser technology has become widely adopted by ophthalmic surgeons. The purpose of this study is to discuss applications and advantages of femtosecond lasers over traditional manual techniques, and related unique complications in cataract surgery and corneal refractive surgical procedures, including: LASIK flap creation, intracorneal ring segment implantation, presbyopic treatments, keratoplasty, astigmatic keratotomy, and intrastromal lenticule procedures. PMID:27143847

  15. Ultrasound-induced acoustophoretic motion of microparticles in three dimensions

    DEFF Research Database (Denmark)

    Muller, Peter Barkholt; Rossi, M.; Marín, Á. G.; Barnkob, Rune; Augustsson, P.; Laurell, T.; Kähler, C. J.; Bruus, Henrik

    2013-01-01

    D particle motion was recorded using astigmatism particle tracking velocimetry under controlled thermal and acoustic conditions in a long, straight, rectangular microchannel actuated in one of its transverse standing ultrasound-wave resonance modes with one or two half-wavelengths. The acoustic...

  16. Quality control of JEOL JBX-9500FSZ e-beam lithography system in a multi-user laboratory

    DEFF Research Database (Denmark)

    Greibe, Tine; Anhøj, Thomas Aarøe; Johansen, Leif; Han, Anpan

    2016-01-01

    designed quality control procedure characterized using a scanning electron microscope. We inspect position accuracy, dynamic focus, and dynamic astigmatism, as well as single and multi-pixel lines in thin resist. Beam shape quality is inspected in the corners of the writing field at 6 different beam...

  17. Towards quantitative off-axis electron holographic mapping of the electric field around the tip of a sharp biased metallic needle

    DEFF Research Database (Denmark)

    Beleggia, Marco; Kasama, Takeshi; Larson, D. J.; Kelly, T. F.; Dunin-Borkowski, R. E.; Pozzi, G.

    2014-01-01

    maps and Fresnel (out-of-focus) images for comparison with experimental measurements. While the overall agreement is excellent, the simulations also highlight the presence of an unexpected astigmatic contribution to the intensity in a highly defocused Fresnel image, which is thought to result from the...

  18. Facts about Refractive Errors

    Science.gov (United States)

    ... the cornea, or aging of the lens can cause refractive errors. What is refraction? Refraction is the bending of ... for objects at any distance, near or far. Astigmatism is a condition in ... This can cause images to appear blurry and stretched out. Presbyopia ...

  19. The effect of pterygium surgery on wavefront analysis

    Directory of Open Access Journals (Sweden)

    Hasan Razmjoo

    2014-01-01

    Full Text Available Background: Pterygium is a common disorder of the ocular surface. It causes vision impairment -usually irregular type astigmatism- through different mechanisms. In addition, it is believed that surgical excision of the pterygium improves visual problems. The appropriate method to investigate irregular astigmatism is using wavefront analysis. This study was aimed to evaluate wavefront analysis pre and post pterygium surgery. Materials and Methods: This study was performed on 32 patients who underwent surgical excision of pterygium in January 2012. Data were recorded and compared after pre and postoperative comprehensive ophthalmologic examinations including uncorrected and best corrected visual acuity, Orbscan, wavefront analysis and autorefraction to figure out the effects of surgery on different parameters. Results: Comparison of pre and postoperative parameters showed that surgical treatment of the pterygium improves numerous parameters significantly including uncorrected and best corrected visual acuity, spherical and cylinder refractive error, higher order aberration, quadrafoil (Z440, corneal astigmatism and 3 and 5 mm central zone corneal irregularity (all P-values < 0.0001. In addition, it improves vertical coma (P:0.003 and secondary astigmatism (Z420 (P:0.004. Conclusion: It is concluded that surgical excision of the pterygium improves visual acuity, refractive errors and most of the corneal topographic indices and wavefront analysis parameters.

  20. RESONATORS, MODES, BEAMS: Gain saturation of laser beams and production and decay of phase dislocations

    Science.gov (United States)

    Malyutin, A. A.

    2006-02-01

    The distortion of the distribution of initially pure laser modes caused by the gain saturation is simulated numerically. It is shown that the gain saturation results in a considerable enrichment of the modal spectrum of radiation accompanied by the production and decay of phase dislocations in the far-field domain and at the output of an astigmatic π/2-mode converter.

  1. Anterior segment study with the pentacam scheimpflug camera in refractive surgery candidates

    Directory of Open Access Journals (Sweden)

    Masih Hashemi

    2013-01-01

    Conclusions: Myopic eyes had steeper corneas than hyperopic eyes and anterior chamber measurements were significantly higher in the myopic eyes. In myopic eyes, AE max and PE max and K max measurements were higher, and ACD measurements were lower in the astigmatic groups.

  2. Creation, doubling, and splitting, of vortices in intracavity second harmonic generation

    CERN Document Server

    Lim, O K; Saffman, M; Królikowski, W

    2003-01-01

    We demonstrate generation and frequency doubling of unit charge vortices in a linear astigmatic resonator. Topological instability of the double charge harmonic vortices leads to well separated vortex cores that are shown to rotate, and become anisotropic, as the resonator is tuned across resonance.

  3. Ptosis - infants and children

    Science.gov (United States)

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

  4. Manual intrastromal corneal keratotomy: An alternate encouraging approach for refractive error correction

    Directory of Open Access Journals (Sweden)

    Saravana Kodandapani

    2014-01-01

    Full Text Available Results of femtosecond based intrastromal astigmatic keratotomy have been reported to be encouraging for correction of Astigmatism. We report a new surgical technique-manual intrastromal corneal keratotomy (MICK for correction of simple refractive astigmatism (−1.5 DC against the rule. The technique involves the creation of a 100 μm thickness corneal flap creation using Moria M2 evolution LSK MicroKeratome and 300 μm depth, 4 mm long manual transverse astigmatic keratotomy on both sides of the steep axis 3 mm from the pupillary center along with four incision peripheral radial keratotomy outside the optic zone (based on the mesopic pupil. The flap was repositioned and routine post-operative regimen was followed. Patient achieved 20/20 vision in both eyes post-operatively on the first day, which was maintained even at the 1 month follow-up. This simple technique could be useful as an alternative method for correction of refractive errors in patients not suitable for excimer and/or femtosecond laser treatment.

  5. Excimer laser system Profile-500

    Science.gov (United States)

    Atejev, V. V.; Bukreyev, V. S.; Vartapetov, Serge K.; Semenov, A. D.; Sugrobov, V. A.; Turin, V. S.; Fedorov, Sergei N.

    1999-07-01

    The description of ophthalmological excimer laser system 'PROFILE-500' for photorefractive and physiotherapeutic keratectomy is presented. Excimer Laser Systems 'PROFILE- 500' are optical system that use ArF excimer lasers to perform photorefractive keratectomy or LASIK; surgical procedures used to correct myopia, hyperopia and astigmatism.

  6. Ball lens reflections by direct solution of Maxwell's equations

    International Nuclear Information System (INIS)

    We calculate ball lens reflections, using the exact solution of Maxwell's equations for the scattering of a beam from a dielectric sphere. Our results are consistent to within 1 dB with measurements of backreflection to a single-mode fiber. We also calculate backreflection to an astigmatic spot laser diode. copyright 1995 Optical Society of America

  7. Orthokeratology vs. spectacles: Adverse events and discontinuations

    OpenAIRE

    Santodomingo Rubido, Jacinto; Villa Collar, César; Gilmartin, Bernard; Gutiérrez Ortega, Ángel Ramón

    2012-01-01

    Purpose. To assess the relative clinical success of orthokeratology contact lenses (OK) and distance single-vision spectacles (SV) in children in terms of incidences of adverse events and discontinuations over a 2-year period. Methods. Sixty-one subjects 6 to 12 years of age with myopia of - 0.75 to - 4.00DS and astigmatism

  8. Meta-analysis to compare the safety and efficacy of manual small incision cataract surgery and phacoemulsification

    Directory of Open Access Journals (Sweden)

    Parikshit Gogate

    2015-01-01

    Conclusion: The outcome of this meta-analysis indicated there is no difference between phacoemulsification and SICS for BCVA and UCVA of 6/18 and 6/60. Endothelial cell loss and intraoperative and postoperative complications were similar between procedures. SICS resulted in statistically greater astigmatism and UCVA of 6/9 or worse, however, near UCVA was better.

  9. High-performance thermal imaging with a singlet and pupil plane encoding

    Science.gov (United States)

    Muyo, Gonzalo; Harvey, Andrew R.; Singh, Amritpal

    2005-10-01

    Pupil plane encoding enables extended depth of field and greatly reduced sensitivity to aberrations in an imaging system (field curvature, thermally induced defocus, astigmatism, etc.). The application of pupil plane encoding has potential in thermal imaging where it can enable the use of simple, low-cost, light-weight lens systems. We present numerical and modelling studies of the application of this technique to an uncooled LWIR imaging system, F/1, 75mm focal length, germanium singlet with a detector array size of 240x320 with 50 micron pixel. The initial singlet is corrected from coma and spherical aberration, but its performance across the field of view is greatly limited by astigmatism. The introduction of an encoding asymmetrical germanium phase mask at the aperture stop of the system, combined with digital image processing, allows the removal of astigmatism and improved imaging performance across the field of view. This improvement is subject to a noise amplification in the digitally restore image. There is as a tradeoff between the maximum correction to astigmatism and reduced signal-to-noise ratio in the recovered image.

  10. Surgical device for supporting corneal suturing

    Science.gov (United States)

    Ventura, Liliane; Oliveira, Gunter C. D.; De Groote, Jean-Jacques; Sousa, Sidney J. F.; Saia, Paula

    2009-02-01

    A system for ophthalmic surgery support has been developed in order to minimize the residual astigmatism due to the induced irregular shape of the cornea by corneal suture. The system projects 36 light spots, from LEDs, displayed in a precise circle at the lachrymal film of the examined cornea. The displacement, the size and deformation of the reflected image of these light spots are analyzed providing the keratometry and the circularity of the suture. Measurements in the range of 32D - 55D (up to 23D of astigmatism are possible to be obtained) and a self-calibration system has been designed in order to keep the system calibrated. Steel precision spheres have been submitted to the system and the results show 99% of correlation with the fabricant's nominal values. The system has been tested in 13 persons in order to evaluate its clinical applicability and has been compared to a commercial keratometer Topcon OM-4. The correlation factors are 0,92 for the astigmatism and 0.99 for the associated axis. The system indicates that the surgeon should achieve circularity >=98% in order to do not induce astigmatisms over 3D.

  11. Monte Carlo simulation of expected outcomes with the AcrySof® toric intraocular lens

    OpenAIRE

    Potvin Richard; Hill Warren

    2008-01-01

    Abstract Background To use a Monte Carlo simulation to predict postoperative results with the AcrySof® Toric lens, evaluating the likelihood of over- or under-correction using various toric lens selection criteria. Methods Keratometric data were obtained from a large patient population with preoperative corneal astigmatism

  12. Use of preoperative assessment of positionally induced cyclotorsion: a video-oculographic study

    OpenAIRE

    Becker, R.; Krzizok, T H; Wassill, H

    2004-01-01

    Purpose: Positionally induced cyclotorsion could be an important factor concerning correction of astigmatism in refractive surgery. The method of binocular three dimensional infrared video-oculography (3D-VOG) was used to determine a possible influence of body position on cyclotorsion.

  13. Primary aberrations in focused radially polarized vortex beams

    Science.gov (United States)

    Biss, David P.; Brown, T. G.

    2004-02-01

    We study the effect of primary aberrations on the 3-D polarization of the electric field in a focused lowest order radially polarized beam. A full vector diffraction treatment of the focused beams is used. Attention is given to the effects of primary spherical, astigmatic, and comatic aberrations on the local polarization, Strehl ratio, and aberration induced degradation of the longitudinal field at focus

  14. Safety and efficacy of the transition from extracapsular cataract extraction to manual small incision cataract surgery in prevention of blindness campaigns

    Directory of Open Access Journals (Sweden)

    Isabel Signes-Soler

    2016-01-01

    Conclusion: Transitioning from ECCE to MSICS for experienced cataract surgeons in surgical campaigns is safe. The rate of complications is similar for both techniques. Slightly better visual and refractive outcomes can be achieved due to the decreased induction of corneal astigmatism.

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

    Directory of Open Access Journals (Sweden)

    Kai-jian CHEN

    2011-04-01

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

  16. Rotational stability of the AcrySof SA60TT toric intraocular lenses: A cohort study

    Directory of Open Access Journals (Sweden)

    Gale Richard

    2008-05-01

    Full Text Available Abstract Background To evaluate the rotational stability of the three types of AcrySof SA60TT toric intraocular lenses (Alcon, Switzerland in cataract surgery after the first postoperative week. Methods A retrospective study of 44 eyes in 33 patients. All patients underwent similar uncomplicated phacoemulsification cataract surgery. Seven eyes with corneal astigmatism of less than 1.5 D were implanted with the AcrySof SA60T3 intraocular lens. Seventeen eyes with astigmatism between 1.5 D and 2.25 D received the SA60T4 intraocular lens, and 20 eyes with more than 2.25 D of corneal astigmatism received the SA60T5 intraocular lens. Intraoperatively, the axis of the toric lens was aligned to the steepest axis of the corneal astigmatism. Main outcome measure was the postoperative position of the lens, assessed at 1 week and 3 months, using a specially designed angle measuring eyepiece for the slit lamp. Results There was no significant difference in the rotational stability of the three types of toric intraocular lenses. Overall, the postoperative rotation was within 5 degrees in 95% and within 2 degrees in 68% of eyes. The mean absolute rotation was 2.2 ± 2.2 degrees. No lens showed more than 9 degrees of rotation, and no lens required secondary repositioning. There was no trend for either clockwise or anti-clockwise rotation. The surgical procedure did not change the corneal astigmatism. Conclusion Once placed to it's position, each of the three types of the AcrySof SA60TT toric intraocular lenses demonstrate rotational stability in the capsular bag.

  17. Higher-Order Aberrations in Myopic Eyes

    Directory of Open Access Journals (Sweden)

    Farid Karimian

    2010-01-01

    Full Text Available Purpose: To evaluate the correlation between refractive error and higher-order aberrations (HOAs in patients with myopic astigmatism. Methods: HOAs were measured using the Zywave II aberrometer over a 6 mm pupil. Correlations between HOAs and myopia, astigmatism, and age were analyzed. Results: One hundred and twenty-six eyes of 63 subjects with mean age of 26.4±5.9 years were studied. Mean spherical equivalent refractive error and refractive astigmatism were -4.94±1.63 D and 0.96±1.06 D, respectively. The most common higher-order aberration was primary horizontal trefoil with mean value of 0.069±0.152 μm followed by spherical aberration (-0.064±0.130 μm and primary vertical coma (-0.038±0.148 μm. As the order of aberration increased from third to fifth, its contribution to total HOA decreased: 53.9% for third order, 31.9% for fourth order, and 14.2% for fifth order aberrations. Significant correlations were observed between spherical equivalent refractive error and primary horizontal coma (R=0.231, P=0.022, and root mean square (RMS of spherical aberration (R=0.213, P=0.031; between astigmatism and RMS of total HOA (R=0.251, P=0.032, RMS of fourth order aberration (R=0.35, P<0.001, and primary horizontal coma (R=0.314, P=0.004. Spherical aberration (R=0.214, P=0.034 and secondary vertical coma (R=0.203, P=0.031 significantly increased with age. Conclusion: Primary horizontal trefoil, spherical aberration and primary vertical coma are the predominant higher-order aberrations in eyes with myopic astigmatism.

  18. CHARACTERISTIC OF PATIENTS WITH REFRACTIVE DISORDER AT EYE CLINIC OF SANGLAH GENERAL HOSPITAL DENPASAR, BALI-INDONESIA

    Directory of Open Access Journals (Sweden)

    T Handayani-Ariestanti

    2012-09-01

    Full Text Available Objective: Refractive disorders are one of the most common causes of visual impairment worldwide and become the second leading cause of blindness that can be cured. This study aims to know the characteristic of refractive errors patients in Sanglah General Hospital in the period of 1st January until 31st December 2011.Method: This is a retrospective analytical descriptive study. Data were collected retrospectively from patient’s medical records with refractive errors and shown as frequency andpercentage. Visual acuity before and after corrections were investigated and analyzed using McNemar Test.Results: from 579 patients, the most common diagnosis was astigmatism (40.1%, 63% were woman, 39.7% were older than 40 years old, and 60.2% live in Denpasar. In myopia cases, 69.7% patients were woman and 25.1% were between 11-20 years old. In astigmatism cases, 63.4% were woman, 57% were older than 40 years old. Of the hypermetropic cases, 61,3% were woman, 79.5% were older than 40 years. Among presbyopia cases, 53.2% patients were woman with 84.4% were older than 40 years. In McNemar test, there were a significant difference between visual acuity before and after correction in both eyes (p=0.0001. Most astigmatism was with the rule cases on both eyes. On the right eye 54.3% shows mild astigmatism, whereas on the left eye 50.8% shows moderate astigmatism. In hypermetropic cases 92.4% are mild degrees. While 55.5% presbyopic patients needadditional glasses of +1.00 D up to +2.00 D. About 97.9% patients with refractive error were given glasses prescription. Conclusion: mostly refractive errors patient are woman and the most common diagnosis is astigmatism. There were significant differences of visual acuity before and aftercorrection on both eyes (p=0.001.

  19. Refractive cylinder outcomes after calculating toric intraocular lens cylinder power using total corneal refractive power

    Directory of Open Access Journals (Sweden)

    Davison JA

    2015-08-01

    Full Text Available James A Davison,1 Richard Potvin21Wolfe Eye Clinic, Marshalltown, IA, USA; 2Science in Vision, Akron, NY, USAPurpose: To determine whether the total corneal refractive power (TCRP value, which is based on measurement of both anterior and posterior corneal astigmatism, is effective for toric intraocular lens (IOL calculation with AcrySof® Toric IOLsPatients and methods: A consecutive series of cataract surgery cases with AcrySof toric IOL implantation was studied retrospectively. The IOLMaster® was used for calculation of IOL sphere, the Pentacam® TCRP 3.0 mm apex/ring value was used as the keratometry input to the AcrySof Toric IOL Calculator and the VERION™ Digital Marker for surgical orientation. The keratometry readings from the VERION reference unit were recorded but not used in the actual calculation. Vector differences between expected and actual residual refractive cylinder were calculated and compared to simulated vector errors using the collected VERION keratometry data.Results: In total, 83 eyes of 56 patients were analyzed. Residual refractive cylinder was 0.25 D or lower in 58% of eyes and 0.5 D or lower in 80% of eyes. The TCRP-based calculation resulted in a statistically significantly lower vector error (P<0.01 and significantly more eyes with a vector error ≤0.5 D relative to the VERION-based calculation (P=0.02. The TCRP and VERION keratometry readings suggested a different IOL toric power in 53/83 eyes. In these 53 eyes the TCRP vector error was lower in 28 cases, the VERION error was lower in five cases, and the error was equal in 20 cases. When the anterior cornea had with-the-rule astigmatism, the VERION was more likely to suggest a higher toric power and when the anterior cornea had against-the-rule astigmatism, the VERION was less likely to suggest a higher toric power.Conclusion: Using the TCRP keratometry measurement in the AcrySof toric calculator may improve overall postoperative refractive results

  20. Line focusing for soft x-ray laser-plasma lasing.

    Science.gov (United States)

    Bleiner, Davide; Balmer, Jürg E; Staub, Felix

    2011-12-20

    A computational study of line-focus generation was done using a self-written ray-tracing code and compared to experimental data. Two line-focusing geometries were compared, i.e., either exploiting the sagittal astigmatism of a tilted spherical mirror or using the spherical aberration of an off-axis-illuminated spherical mirror. Line focusing by means of astigmatism or spherical aberration showed identical results as expected for the equivalence of the two frames of reference. The variation of the incidence angle on the target affects the line-focus length, which affects the amplification length such that as long as the irradiance is above the amplification threshold, it is advantageous to have a longer line focus. The amplification threshold is physically dependent on operating parameters and plasma-column conditions and in the present study addresses four possible cases. PMID:22193201

  1. Topography-guided custom ablation treatment for treatment of keratoconus

    Directory of Open Access Journals (Sweden)

    Rohit Shetty

    2013-01-01

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

  2. Adaptive wavefront sensor based on the Talbot phenomenon.

    Science.gov (United States)

    Podanchuk, Dmytro V; Goloborodko, Andrey A; Kotov, Myhailo M; Kovalenko, Andrey V; Kurashov, Vitalij N; Dan'ko, Volodymyr P

    2016-04-20

    A new adaptive method of wavefront sensing is proposed and demonstrated. The method is based on the Talbot self-imaging effect, which is observed in an illuminating light beam with strong second-order aberration. Compensation of defocus and astigmatism is achieved with an appropriate choice of size of the rectangular unit cell of the diffraction grating, which is performed iteratively. A liquid-crystal spatial light modulator is used for this purpose. Self-imaging of rectangular grating in the astigmatic light beam is demonstrated experimentally. High-order aberrations are detected with respect to the compensated second-order aberration. The comparative results of wavefront sensing with a Shack-Hartmann sensor and the proposed sensor are adduced. PMID:27140122

  3. Characterization of the thermal lens in 3 at.%Tm:KLu(WO4)2 and microchip laser operation

    International Nuclear Information System (INIS)

    A comparative study of the thermal lensing effect is performed for monoclinic 3 at.%Tm:KLu(WO4)2 crystals cut along the three principal axes of the optical indicatrix, Np, Nm and Ng. Optical power, sensitivity factors and astigmatism of the thermal lens are determined. It is found that the thermal lens is differently signed for beam propagation along Np and Nm (for m- and p-polarizations, respectively). In contrast, beam propagation along Ng possesses a positive lens with nearly two-times reduced astigmatism (m-polarization). The results are utilized in the first realization of a continuous-wave quasi-microchip 3 at.%Tm:KLu(WO4)2 laser delivering 880 mW output power at 1.95 μm with a slope efficiency of 44%, and an M2 factor below 1.05. (letter)

  4. Space-resolved extreme ultraviolet (XUV) spectroscopy using a toroidal mirror

    International Nuclear Information System (INIS)

    In order to collect radiation from a distant light source and to compensate astigmatism, a toroidal mirror is often placed in front of a grazing-incidence spectrograph. In this study, characteristics of space-resolved spectra obtained with such a system have been investigated using a ray-tracing analysis. The following was found: in the stigmatic focal region of the spectrum, the spatial resolution along the sagittal direction is excellent but that along the meridional direction is poor; on the other hand, in the astigmatic wavelength region, the trend is reversed, i.e., the spatial resolution along the sagittal direction is poor but that along the meridional direction is good, particularly in the wavelength region which is far from the stigmatic focus. The method was successfully applied to the space-resolved spectroscopic study of a capillary discharge plasma. copyright 1995 American Institute of Physics

  5. Design and simulation of the active support system for a 1.2m meniscus primary mirror

    Science.gov (United States)

    Liu, Haitao; Fan, Bin; Zeng, Zhige; Li, Xiaojin; Wang, Hongqiao; Liu, Rong

    2015-07-01

    Thin meniscus primary mirrors with active support have been used successfully in many large telescopes, and also draw attention of many optical fabricators. Because the active support system can correct the low order figure errors, such as astigmatism, coma, trefoil 3rd astigmatism, the optical fabricators can just focus on to remove high order figure errors. This will shorten the fabrication time. In this paper, we present an active support system for a 1.2m meniscus parabolic primary mirror. It contains 37 axial push-pull force supports, 3 axial fixed points, and 4 lateral restraints. Some basic performance of the active support system is analyzed and the figure error correction capability is also studied based on Zernike modes.

  6. Segmented Vortex Telescope and its Tolerance to Diffraction Effects and Primary Aberrations

    CERN Document Server

    Treviño, Juan P; Chávez-Cerda, Sabino

    2013-01-01

    We propose the segmented Large Millimeter Telescope (LMT/GTM),as the largest spatial light modulator capable of producing vortex beams of integer topological charge. This observing mode could be applied for direct exoplanet searches in the millimeter or submillimeter regimes. We studied the stability of the vortex structure against aberrations and diffraction effects inherent to the size and segmented nature of the collector mirror. In the presence of low order aberrations the focal distribution of the system remains stable. Our results show that these effects depend on the topological charge of the vortex and the relative orientation of the aberration with respect to the antenna axis. Coma and defocus show no large effects in the image at the focal plane, nevertheless the system is very sensitive to astigmatism. Heat turbulence, simulated by random aberrations, shows that the system behaves in a similar way as astigmatism dissociating the vortices. We propose the Segmented Vortex Telescope as a novel approac...

  7. A study on the diagonal beam quality of a fiber laser pumped source

    International Nuclear Information System (INIS)

    Improving diode laser fiber coupling efficiency is the key to improving the efficiency of fiber lasers. We have demonstrated a new expression for the diagonal beam quality of a rectangular spot beam of a diode laser, which reflects the actual value approached. By considering the application of fiber coupling and the astigmatism characteristics of the diode laser, we have introduced an astigmatism factor, using the extreme value and the approximation of the overall divergence angle in the offset direction. From this we have obtained a new universal expression for the diagonal beam parameters of the diode laser. The degree of matching between the theoretical value and the experimentally measured value was greater than 99.7%. (paper)

  8. Transport of a high brightness proton beam through the Munich tandem accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Moser, M., E-mail: marcus.moser@unibw.de [Universität der Bundeswehr München, Institut für Angewandte Physik und Messtechnik LRT2, Department für Luft- und Raumfahrttechnik, 85577 Neubiberg (Germany); Greubel, C. [Universität der Bundeswehr München, Institut für Angewandte Physik und Messtechnik LRT2, Department für Luft- und Raumfahrttechnik, 85577 Neubiberg (Germany); Carli, W. [Beschleunigerlabor MLL, 85478 Garching (Germany); Peeper, K.; Reichart, P.; Urban, B.; Vallentin, T. [Universität der Bundeswehr München, Institut für Angewandte Physik und Messtechnik LRT2, Department für Luft- und Raumfahrttechnik, 85577 Neubiberg (Germany); Dollinger, G., E-mail: guenther.dollinger@unibw.de [Universität der Bundeswehr München, Institut für Angewandte Physik und Messtechnik LRT2, Department für Luft- und Raumfahrttechnik, 85577 Neubiberg (Germany)

    2015-04-01

    Basic requirement for ion microprobes with sub-μm beam focus is a high brightness beam to fill the small phase space usually accepted by the ion microprobe with enough ion current for the desired application. We performed beam transport simulations to optimize beam brightness transported through the Munich tandem accelerator. This was done under the constraint of a maximum ion current of 10 μA that is allowed to be injected due to radiation safety regulations and beam power constrains. The main influence of the stripper foil in conjunction with intrinsic astigmatism in the beam transport on beam brightness is discussed. The calculations show possibilities for brightness enhancement by using astigmatism corrections and asymmetric filling of the phase space volume in the x- and y-direction.

  9. Image transfer with spatial coherence for aberration corrected transmission electron microscopes.

    Science.gov (United States)

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

    2016-08-01

    The formula of spatial coherence involving an aberration up to six-fold astigmatism is derived for aberration-corrected transmission electron microscopy. Transfer functions for linear imaging are calculated using the newly derived formula with several residual aberrations. Depending on the symmetry and origin of an aberration, the calculated transfer function shows characteristic symmetries. The aberrations that originate from the field's components, having uniformity along the z direction, namely, the n-fold astigmatism, show rotational symmetric damping of the coherence. The aberrations that originate from the field's derivatives with respect to z, such as coma, star, and three lobe, show non-rotational symmetric damping. It is confirmed that the odd-symmetric wave aberrations have influences on the attenuation of an image via spatial coherence. Examples of image simulations of haemoglobin and Si [211] are shown by using the spatial coherence for an aberration-corrected electron microscope. PMID:27155359

  10. Measurement of the atmospheric primary aberrations by 4-aperture DIMM

    CERN Document Server

    Shomali, Ramin; Darudi, Ahmad

    2011-01-01

    The present paper investigates and discusses the ability of the Hartmann test with 4-aperture DIMM to measure the atmospheric primary aberrations which, in turn, can be used for calculation of the atmospheric coherence time. Through performing numerical simulations, we show that the 4-aperture DIMM is able to measure the defocus and astigmatism terms correctly while its results are not reliable for the coma. The most important limitation in the measurement of the primary aberrations by 4-aperture DIMM is the centroid displacements of the spots which are caused by the higher order aberrations. This effect is negligible in calculating of the defocus and astigmatisms, while, it cannot be ignored in the calculation of the coma.

  11. Transport of a high brightness proton beam through the Munich tandem accelerator

    International Nuclear Information System (INIS)

    Basic requirement for ion microprobes with sub-μm beam focus is a high brightness beam to fill the small phase space usually accepted by the ion microprobe with enough ion current for the desired application. We performed beam transport simulations to optimize beam brightness transported through the Munich tandem accelerator. This was done under the constraint of a maximum ion current of 10 μA that is allowed to be injected due to radiation safety regulations and beam power constrains. The main influence of the stripper foil in conjunction with intrinsic astigmatism in the beam transport on beam brightness is discussed. The calculations show possibilities for brightness enhancement by using astigmatism corrections and asymmetric filling of the phase space volume in the x- and y-direction

  12. Imaging with Spherically Bent Crystals or Reflectors

    International Nuclear Information System (INIS)

    This paper consists of two parts: Part I describes the working principle of a recently developed x-ray imaging crystal spectrometer, where the astigmatism of spherically bent crystals is being used with advantage to record spatially resolved spectra of highly charged ions for Doppler measurements of the ion-temperature and toroidal plasmarotation- velocity profiles in tokamak plasmas. This type of spectrometer was thoroughly tested on NSTX and Alcator C-Mod, and its concept was recently adopted for the design of the ITER crystal spectrometers. Part II describes imaging schemes, where the astigmatism has been eliminated by the use of matched pairs of spherically bent crystals or reflectors. These imaging schemes are applicable over a wide range of the electromagnetic radiation, which includes microwaves, visible light, EUV radiation, and x-rays. Potential applications with EUV radiation and x-rays are the diagnosis of laserproduced plasmas, imaging of biological samples with synchrotron radiation, and lithography.

  13. Thermal lensing in Er, Yb : YVO4 crystal

    International Nuclear Information System (INIS)

    A thermal lens is characterized in 0.7 at.%Er, 3 at.%Yb : YVO4 yttrium vanadate crystal cut along the [1 0 0] crystallographic axis, for π and σ laser polarizations, by a probe beam method. For a pump spot radius of 100 μm and π-polarization, sensitivity factors of the thermal lens equal 5.7 and 7.9 m−1 W−1 (parallel and perpendicular to the [0 0 1]-axis, respectively); the astigmatism degree is 28%. The fractional heat load is determined by ISO-standard laser calorimetry, ηh = 0.63  ±  0.05. The anisotropy of the photo-elastic effect plays a dominant role in the formation of the astigmatic thermal lens. (letter)

  14. Influence of eye micromotions on spatially resolved refractometry

    Science.gov (United States)

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

    2001-01-01

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

  15. A compensation alignment method for surface irregularity based on Zernike coefficients

    Science.gov (United States)

    Li, Lian; Ma, TianMeng

    2014-11-01

    Surface irregularity of optical elements is one of the errors caused in manufacturing process. The primary aberration caused by surface irregularity is astigmatism which can hardly be removed in traditional alignment method. An alignment method by rotating the lens for compensating the deterioration of the image quality caused by surface irregularity is put forward in the paper, and the mathematical model of the method is established. The calculation of the rotate angle is described in detail. A numerical simulation of the method has been performed for a four-lens precision optical system to verify the ability and accuracy of the method. The results show that the astigmatism of the optical system caused by the surface irregularity can completely be removed, and the image quality can be improved effectively. The method is especially suitable for the optical system which demands a very high image quality.

  16. Measurement of the atmospheric primary aberrations by a 4-aperture differential image motion monitor

    Science.gov (United States)

    Shomali, Ramin; Nasiri, Sadollah; Darudi, Ahmad

    2011-05-01

    The present paper investigates and discusses the ability of the Hartmann test with a 4-aperture differential image motion monitor (DIMM) to measure the atmospheric primary aberrations which, in turn, can be used for the calculation of the atmospheric coherence time. Through performing numerical simulations, we show that the 4-aperture DIMM is able to measure the defocus and astigmatism terms correctly whereas its results are not reliable for the coma. The most important limitations in the measurement of the primary aberrations by the 4-aperture DIMM are the centroid displacements of the spots which are caused by the higher order aberrations. This effect is negligible in the calculation of the defocus and astigmatisms, whereas it cannot be ignored in the calculation of the coma.

  17. Low-Order Aberration Sensitivity of Eighth-Order Coronagraph Masks

    Science.gov (United States)

    Shaklan, Stuart B.; Green, Joseph J.

    2005-07-01

    In a recent paper, Kuchner, Crepp, and Ge describe new image-plane coronagraph mask designs that reject to eighth order the leakage of starlight caused by image motion at the mask, resulting in a substantial relaxation of image centroiding requirements compared to previous fourth-order and second-order masks. They also suggest that the new masks are effective at rejecting leakage caused by low-order aberrations (e.g., focus, coma, and astigmatism). In this paper, we derive the sensitivity of eighth-order masks to aberrations of any order and provide simulations of coronagraph behavior in the presence of optical aberrations. We find that the masks leak light as the fourth power of focus, astigmatism, coma, and trefoil. This has tremendous performance advantages for the Terrestrial Planet Finder Coronagraph.

  18. Analytical beam-width characteristics of distorted cat-eye reflected beam

    Science.gov (United States)

    Zhao, Yanzhong; Shan, Congmiao; Zheng, Yonghui; Zhang, Laixian; Sun, Huayan

    2015-02-01

    The analytical expression of beam-width of distorted cat-eye reflected beam under far-field condition is deduced using the approximate three-dimensional analytical formula for oblique detection laser beam passing through cat-eye optical lens with center shelter, and using the definition of second order moment, Gamma function and integral functions. The laws the variation of divergence angle and astigmatism degree of the reflected light with incident angle, focal shift, aperture size, and center shelter ratio are established by numerical calculation, and physical analysis. The study revealed that the cat-eye reflected beam is like a beam transmitted and collimated by the target optical lens, and has the same characteristics as that of Gaussian beam. A proper choice of positive focal shift would result in a divergence angle smaller than that of no focal shift. The astigmatism is mainly caused by incidence angle.

  19. Measurement of the atmospheric primary aberrations by a 4-aperture differential image motion monitor

    International Nuclear Information System (INIS)

    The present paper investigates and discusses the ability of the Hartmann test with a 4-aperture differential image motion monitor (DIMM) to measure the atmospheric primary aberrations which, in turn, can be used for the calculation of the atmospheric coherence time. Through performing numerical simulations, we show that the 4-aperture DIMM is able to measure the defocus and astigmatism terms correctly whereas its results are not reliable for the coma. The most important limitations in the measurement of the primary aberrations by the 4-aperture DIMM are the centroid displacements of the spots which are caused by the higher order aberrations. This effect is negligible in the calculation of the defocus and astigmatisms, whereas it cannot be ignored in the calculation of the coma

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

    International Nuclear Information System (INIS)

    Alignment by means of current commutating and defocusing of the objective does not yield the desired rotational symmetry of the imaging pencils. This was found while aligning a transmission electron microscope with a single field condenser objective. A series of optical diffractograms of micrographs taken under the same tilted illumination yet under various azimuths have been arranged in a tableau, wherein strong asymmetry is exhibited. Quantitative evaluation yields the most important asymmetric aberration to be the axial coma, which becomes critical when a resolution better than 5 A0 is obtained. The tableau also allows an assessment of the three-fold astigmatism. A procedure has been developed which aligns the microscope onto the coma-free and dispersion-free pencil axis and does not rely on current communication. The procedure demands equal appearance of astigmatic carbon film images produced under the same tilt yet diametrical azimuth. (Auth.)

  1. Deep anterior lamellar keratoplasty for the management of iatrogenic keratectasia occurring after hexagonal keratotomy

    Directory of Open Access Journals (Sweden)

    Paras Mehta

    2012-01-01

    Full Text Available Iatrogenic keratectasia has been reported subsequent to refractive surgery or trauma. Hexagonal keratotomy (HK is a surgical incisional technique to correct hyperopia. A number of complications have been reported following this procedure, including irregular astigmatism, wound healing abnormalities and corneal ectasia. When visual acuity is poor because of ectasia or irregular astigmatism and contact lens fitting is not possible, penetrating or lamellar keratoplasty can be performed. Since incisions in refractive keratotomy are set at 90-95% depth of cornea, intraoperative microperforations are known to occur and lamellar keratoplasty may become difficult. We describe deep anterior lamellar keratoplasty (DALK used to successfully manage keratectasia after HK. Pre DALK vision was 20/400 and post DALK vision was 20/30 two months after surgery. This report aims to show improved visual outcome in corneal ectasia secondary to HK. DALK can be a procedure of choice with proper case selection.

  2. Refractive lens exchange in modern practice: when and when not to do it?

    Science.gov (United States)

    Alió, Jorge L; Grzybowski, Andrzej; Romaniuk, Dorota

    2014-01-01

    Cataract surgery due to advances in small incision surgery evolved from a procedure concerned with the primary focus on the safe removal of cataractous lens to a procedure focused on the best possible postoperative refractive result. As the outcomes of cataract surgery became better, the use of lens surgery as a refractive modality in patients without cataracts has increased in interest and in popularity. Removal of the crystalline lens for refractive purposes or refractive lens exchange (RLE) presents several advantages over corneal refractive surgery. Patients with high degrees of myopia, hyperopia and astigmatism are still not good candidates for laser surgery. Moreover, presbyopia can currently only be corrected with monovision or reading spectacles. RLE supplemented with multifocal or accommodating intraocular lenses (IOLs) in combination with corneal astigmatic procedures might address all refractive errors including presbyopia, and eliminate the future need for cataract surgery. PMID:26605356

  3. Simultaneous pterygium and cataract surgery.

    Directory of Open Access Journals (Sweden)

    Gulani A

    1995-01-01

    Full Text Available In our country both pterygium and cataract have a high incidence. Hence in this study, thirty patients with pterygium and cataract were treated with a simultaneous pterygium excision and cataract extraction procedure. These patients after pterygium excision were treated intra-operatively with 500 rads of beta radiation over the pterygium site. Then, the cataract was extracted and the patients were treated post-operatively with topical betamethasone 0.1% for a duration of three months. They were followed up for a duration of 6 months postoperatively. Nineteen patients (63% had visual recovery to 6/12. Twelve of 30 patients (40% had recurrence of pterygium. The combined procedure did not result in any surgical complications following cataract removal. Post-operatively, after 6 months 13 patients had with the rule astigmatism (WRA for a mean WRA of 1.3 D, and 17 had against the rule astigmatism (ARA for a mean ARA of 1.2 D.

  4. Pterygium-induced corneal refractive changes

    Directory of Open Access Journals (Sweden)

    Maheshwari Sejal

    2007-01-01

    Full Text Available To study the effect of pterygium on corneal topography, a retrospective analysis of 151 eyes with primary pterygia was done. All cases underwent videokeratography preoperatively and one month postoperatively. Statistical analysis of average corneal power (ACP, corneal astigmatism, surface regularity index (SRI and surface asymmetry index (SAI was done before and one month after surgery. Topographic indices were compared statistically for various grades of pterygia. Increase in the grade of pterygia had a significant effect on topographic indices. Corneal astigmatism reduced from 4.40±3.64 diopter (D to 1.55±1.63D ( P value < 0.001 following surgery. The regularity of corneal surface improved and asymmetry of the cornea reduced one month after surgery. Pterygium leads to significant changes in corneal refractive status, which increase with the increase in the grade of pterygia and improve following pterygium excision.

  5. Subwavelength-grating-induced wavefront aberrations: a case study

    Science.gov (United States)

    Crabtree, Karlton; Chipman, Russell A.

    2007-07-01

    The on-axis wavefront aberrations of a one-dimensional subwavelength-grating antireflection coating on an f/1.7 lens surface are shown to be small with noticeable contributions of defocus, astigmatism, and piston. The astigmatism is 0.02 wave, and the magnitude of the piston approaches one wave peak-to-valley. The difference in aberrations between orthogonally polarized wavefronts, or the retardance aberration, shows 0.01 wave of astigmatismlike variation and more than 0.01 wave of retardance-induced defocuslike variation. A small coupling between polarization states occurs in the form of the familiar Maltese cross, yielding a maximum of 3% coupling in the four diagonal edges of the pupil.

  6. Study of bonding positions of isostatic mounts on a lightweight primary mirror

    Science.gov (United States)

    Chan, C. Y.; Chen, Y. C.; Chang, S. T.; Huang, T. M.; Hsu, M. Y.

    2012-10-01

    The bonding positions of three isostatic mounts on the primary mirror of a Cassegrain telescope under self-weight loading have both been studied in the paper. Finite element method and Zernike polynomial fitting are complementarily applied to the ZERODUR® primary mirror with a pre-designed lightweight configuration on the back. Eight bonding positions of isostatic mounts with respect to the center of gravity of the mirror have been chosen to investigate the mirror surface deforms as well as the induced optical aberrations. It is found that astigmatism becomes remarkably higher than other optical aberrations under self-weight loading. The optimum bonding position with the least astigmatism value has also been obtained.

  7. Creation and doubling of vortices in intracavity second harmonic generation

    Science.gov (United States)

    Lim, Oo-Kaw; Boland, Brian; Saffman, Mark; Krolikowski, Wieslaw

    2004-05-01

    Optical vortices are topological objects whose transformation properties under propagation in linear and nonlinear optical media have been the subject of much recent interest. In this work we demonstrate generation and frequency doubling of unit charge vortices in a linear astigmatic resonator. By appropriate alignment of a near confocal cavity we couple a fundamental laser beam at 860nm to a vortical resonator mode. With a nonlinear crystal in the resonator a doubly charged vortex at the second harmonic frequency is generated. Topological instability of the double charge harmonic vortices leads to well separated vortex cores that are shown to rotate and become anisotropic, as the resonator is tuned across resonance. A simple theory that accounts for crystal induced astigmatism agrees well with the experimental measurements.

  8. Fast Three-Dimensional Single-Particle Tracking in Natural Brain Tissue.

    Science.gov (United States)

    Sokoll, Stefan; Prokazov, Yury; Hanses, Magnus; Biermann, Barbara; Tönnies, Klaus; Heine, Martin

    2015-10-01

    Observation of molecular dynamics is often biased by the optical very heterogeneous environment of cells and complex tissue. Here, we have designed an algorithm that facilitates molecular dynamic analyses within brain slices. We adjust fast astigmatism-based three-dimensional single-particle tracking techniques to depth-dependent optical aberrations induced by the refractive index mismatch so that they are applicable to complex samples. In contrast to existing techniques, our online calibration method determines the aberration directly from the acquired two-dimensional image stream by exploiting the inherent particle movement and the redundancy introduced by the astigmatism. The method improves the positioning by reducing the systematic errors introduced by the aberrations, and allows correct derivation of the cellular morphology and molecular diffusion parameters in three dimensions independently of the imaging depth. No additional experimental effort for the user is required. Our method will be useful for many imaging configurations, which allow imaging in deep cellular structures. PMID:26445447

  9. Optical design of Kirkpatrick-Baez microscope for ICF

    International Nuclear Information System (INIS)

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

  10. SURGICAL AND VISUAL OUTCOME OF PHACOEMULSIFICATION SURGERY (ROUTINE AND MICRO - PHACO (BIMANUAL PHACO: A COMPARATIVE STUDY

    Directory of Open Access Journals (Sweden)

    Sudha

    2015-03-01

    Full Text Available Cataract surgery has evolved over the past few decades with progressive decrease in the size of the incision. Originally from 12 mm intracapsular incision to bimanual phacoemulsification (Micro - Phaco that has incision size of just 700 microns. In the pres ent comparative PROSPECTIVE study best corrected visual acuity postoperatively and surgically induced astigmatism were compared in routine Phacoemulsification technique and bimanual phaco (Micro - Phaco 60 eyes were studied. There was no statistically signi ficant difference in postoperative best corrected visual acuity (BCVA of patients operated with Micro - Phaco or routine Phacoemulsification. There was difference in surgically induced astigmatism (SIA ; average SIA in microphaco was 0.5972 as against 0.832 8 in routine Phacoemulsification.

  11. Fibrin-glue assisted multilayered amniotic membrane transplantation in surgical management of pediatric corneal limbal dermoid: a novel approach

    OpenAIRE

    Pirouzian, Amir; Ly, Hang; Holz, Huck; Sudesh, Rattehalli S.; Chuck, Roy S.

    2010-01-01

    Purpose To report a new surgical technique for excising pediatric corneal limbal dermoid and the post-resection ocular surface reconstruction. Methods We describe a method of deep lamellar excision followed by sutureless multilayered amniotic membrane transplantation in surgical management of corneal limbal dermoid. Result This technique achieves a rapid corneal re-epithelization, reduces post-operative pain, and will diminish post-operative scarring. Preoperative corneal astigmatism will per...

  12. Velocity map imaging of a slow beam of ammonia molecules inside a quadrupole guide

    OpenAIRE

    Quintero-Pérez, Marina; Jansen, Paul; Bethlem, Hendrick L.

    2012-01-01

    Velocity map imaging inside an electrostatic quadrupole guide is demonstrated. By switching the voltages that are applied to the rods, the quadrupole can be used for guiding Stark decelerated molecules and for extracting the ions. The extraction field is homogeneous along the axis of the quadrupole while it defocuses the ions in the direction perpendicular to both the axis of the quadrupole and the axis of the ion optics. To compensate for this astigmatism, a series of planar electrodes with ...

  13. Evaluating the method increasing of toric intraocular lenses rotational stability

    OpenAIRE

    G. A. Fedjashev

    2015-01-01

    Purpose. To suggest a safe and effective way to improve the rotational stability of the position of toric the intraocular lenses in the capsular bag.Patients and methods.86 patients (97 eyes) with corneal astigmatism undergoing cataract surgery and Acrysof Toric (Alcon, USA) intraocular lens implantation. In 42 patients (47 eyes), the intraocular lens (IOL) were implanted in accordance with the proposed invention.Results. Average rotation angle IOL implanted by traditional technology was 2,2±...

  14. Changes in Corneal Topography after 25-Gauge Transconjunctival Sutureless Vitrectomy versus after 20-Gauge Standard Vitrectomy

    OpenAIRE

    Okamoto, F; Okamoto, C.; Sakata, N.; Hiratsuka, K; Yamane, N; Hiraoka, T.; Kaji, Y; Oshika, T.

    2007-01-01

    PurposeTo evaluate the changes in regular and irregular corneal astigmatism after 25-gauge transconjunctival sutureless vitrectomy and 20-gauge standard vitrectomy.DesignProspective observational comparative case series.ParticipantsThirty-two eyes of 32 patients undergoing 25-gauge transconjunctival sutureless vitrectomy and 25 eyes of 24 patients undergoing 20-gauge standard vitrectomy.MethodsCorneal topography was obtained preoperatively and at 2 weeks and 1 month postoperatively.Main Outco...

  15. Orbital angular momentum exchange in an optical parametric oscillator

    OpenAIRE

    Martinelli, M.; Huguenin, J. A. O.; Nussenzveig, P.; Khoury, A. Z.

    2004-01-01

    We present a study of orbital angular momentum transfer from pump to down-converted beams in a type-II Optical Parametric Oscillator. Cavity and anisotropy effects are investigated and demostrated to play a central role in the transverse mode dynamics. While the idler beam can oscillate in a Laguerre-Gauss mode, the crystal birefringence induces an astigmatic effect in the signal beam that prevents the resonance of such mode.

  16. High Prevalence of Refractive Errors in 7 Year Old Children in Iran

    Directory of Open Access Journals (Sweden)

    Hassan HASHEMI

    2016-02-01

    Full Text Available Background: The latest WHO report indicates that refractive errors are the leading cause of visual impairment throughout the world. The aim of this study was to determine the prevalence of myopia, hyperopia, and astigmatism in 7 yr old children in Iran.Methods: In a cross-sectional study in 2013 with multistage cluster sampling, first graders were randomly selected from 8 cities in Iran. All children were tested by an optometrist for uncorrected and corrected vision, and non-cycloplegic and cycloplegic refraction. Refractive errors in this study were determined based on spherical equivalent (SE cyloplegic refraction.Results: From 4614 selected children, 89.0% participated in the study, and 4072 were eligible. The prevalence rates of myopia, hyperopia and astigmatism were 3.04% (95% CI: 2.30-3.78, 6.20% (95% CI: 5.27-7.14, and 17.43% (95% CI: 15.39-19.46, respectively. Prevalence of myopia (P=0.925 and astigmatism (P=0.056 were not statistically significantly different between the two genders, but the odds of hyperopia were 1.11 (95% CI: 1.01-2.05 times higher in girls (P=0.011. The prevalence of with-the-rule astigmatism was 12.59%, against-the-rule was 2.07%, and oblique 2.65%. Overall, 22.8% (95% CI: 19.7-24.9 of the schoolchildren in this study had at least one type of refractive error.Conclusion: One out of every 5 schoolchildren had some refractive error. Conducting multicenter studies throughout the Middle East can be very helpful in understanding the current distribution patterns and etiology of refractive errors compared to the previous decade. Keyword: Refractive errors, Cross-sectional study, Iran

  17. Rotationally induced vortices in optical cavity modes

    CERN Document Server

    Habraken, Steven J M

    2008-01-01

    We show that vortices appear in the modes of an astigmatic optical cavity when it is put into rotation about its optical axis. We study the properties of these vortices and discuss numerical results for a specific realization of such a set-up. Our method is exact up to first order of the time-dependent paraxial approximation and involves bosonic ladder operators in the spirit of the quantum-mechanical harmonic oscillator.

  18. Topical timolol maleate 0.5% solution for the management of deep periocular infantile hemangiomas.

    Science.gov (United States)

    Painter, Sally L; Hildebrand, Göran Darius

    2016-04-01

    This retrospective, consecutive, clinical case series examined the use of topical timolol in the treatment of 5 children with deep, periocular infantile hemangiomas that caused astigmatism, change in head posture, or ptosis. All patients were treated with timolol maleate solution 0.5% twice daily until the lesions had regressed. All 5 children showed regression of the lesion and improvement in amblyogenic risk factors within 2 weeks. PMID:27079600

  19. Rotational stabilization and destabilization of an optical cavity

    CERN Document Server

    Habraken, Steven J M

    2008-01-01

    We investigate the effects of rotation about the axis of an astigmatic two-mirror cavity on its optical properties. This simple geometry is the first example of an optical system that can be destabilized and, more surprisingly, stabilized by rotation. As such, it has some similarity with both the Paul trap and the gyroscope. We illustrate the effects of rotational (de)stabilization of a cavity in terms of the spatial structure and orbital angular momentum of its modes.

  20. Controlled reshaping of the front surface of the cornea through its full-area ablation outside of the optical zone with a Gaussian ArF excimer laser beam

    International Nuclear Information System (INIS)

    We studied in vitro the response of the topography of the cornea to its full-area laser ablation (the laser beam spot diameter is commensurable with the size of the interface) outside of the central zone with an excimer laser having a Gaussian fluence distribution across the beam. Subject to investigation were the topographically controlled surface changes of the anterior cornea in 60 porcine eyes with a 5 ± 1.25-diopter artificially induced astigmatism, the changes being caused by laser ablation of the stromal collagen in two 3.5-mm-dia. circular areas along the weaker astigmatism axis. Experimental relationships are presented between the actual astigmatism correction and the expected correction for the intact optical zones 1, 2, 3, and 4 mm in diameter. The data for each zone were approximated by the least-squares method with the function d = a + bx. The coefficient b is given with the root-mean-square error. The statistical processing of the data yielded the following results: d = (0.14 ± 0.037)x for the 1-mm-dia. optical zone, (1.10 ± 0.036)x for the 2-mm-dia. optical zone, (1.04 ± 0.020)x for the 3-mm-dia. optical zone, and (0.55 ± 0.04)x for the 4-mm-dia. optical zone. Full astigmatism correction was achieved with ablation effected outside of the 3-mm-dia. optical zone. The surface changes of the cornea are shown to be due not only to the removal of the corneal tissue, but also to the biomechanical topographic response of the cornea to its strain caused by the formation of a dense pseudomembrane in the ablation area. (letter)