Clinical Evaluation of Large Diameter Rigid-Gas Permeable Versus Soft Toric Contact Lenses for the Correction of Refractive Astigmatism. A MultiCenter Study.

PURPOSE: This study aims to address the clinical performance of a large diameter rigid gas permeable lens (LRGP) in a group of subjects with low-to-moderate (0.75-2.75 D) refractive astigmatism. An additional goal was to determine whether soft toric or LRGP contact lenses performed better objectively in the correction of astigmatism and to determine which modality is preferred by subjects. METHODS: This was a multisite prospective cross-over clinical study. Ten asymptomatic contact lens wearers per site (four university clinics) were recruited and randomly assigned to group A or group B. Group A was assigned to start wearing Comfilcon A soft toric lens first, for two weeks, and then crossed over to LRGP lenses (Boston XO, 14.3 mm diameter miniscleral lens). Group B initially wore LRGP lenses and then crossed over to soft toric lenses. For each type of lens worn, low-contrast and high-contrast visual acuity (VA) were evaluated at distance. At the conclusion of the study, after two months, all subjects completed a questionnaire in which they were asked to indicate their preference for one type of lens (soft toric or LRGP) and to rate the quality of vision in day-to-day activities. RESULTS: Thirty-six of 38 (94.7%) subjects completed the study with 75% preferring the vision of the LRGP lens as compared to the soft toric lenses worn in the study. 52.7% expressed a preference to continue with this modality despite only 38.8% reporting that these LRGP lenses are easy or very easy to handle. Wear time, subjective comfort, and subjective vision ratings exhibited no significant difference between the two groups. CONCLUSIONS: In a population of asymptomatic contact lens wearers, LRGP lenses can be considered as a good alternative to soft toric lenses for the correction of refractive astigmatism.

Clinical Performance of a Spherical Hybrid Lens Design in High Regular Astigmatism.

OBJECTIVES: To evaluate safety, efficacy, and comfort of a spherical hybrid contact lens design in management of the regular astigmatic cornea. METHODS: This prospective study included 18 eyes from 18 subjects with regular corneal astigmatism greater than -3.00 diopters. All patients were fitted with optimal hybrid contact lenses. Demographic data and fitting parameters were recorded. Patient refraction, visual outcomes, contrast sensitivity, and glare levels were measured 2 weeks, 3 months, and 6 months after the start of lens use. Duration of lens use, comfort grades, causes of lens discontinuation, and any noticed complications were recorded. RESULTS: An average of 1.8 lenses (range 1-3) was required to achieve the optimal fit. Average logMAR visual acuity had improved significantly from 0.92±0.03 to 0.03±0.04 (P<0.001) at the last follow-up. Contrast sensitivity and glare tests were also significantly improved. Statistical analysis of the subjective responses indicated a strong acceptance of the lens by most of the patients. Mean wearing time of lenses was 10.1±3.2 hr/d. Causes of discontinuation were discomfort (2 patients), high lens price (2 patients), and handling problems (1 patient). Minimal complications were demonstrated in wearers of the lenses during follow-up visits. CONCLUSION: Spherical hybrid contact lenses provide a good option for patients with regular astigmatic corneas. They provide optimal visual function with high comfort and patient satisfaction, especially when surgery is undesirable or contraindicated.

In vitro optical quality of monofocal aspheric toric intraocular lenses: effect of cylindrical power.

PURPOSE: To assess the in vitro optical quality of monofocal aspheric toric intraocular lenses (IOLs) as a function of the cylindrical power. METHODS: The in vitro optical quality of the AcrySof IQ Toric IOLs SN6AT2, SN6AT3, SN6AT4, SN6AT5 and SN6AT6 (Alcon Laboratories Inc., Forth Worth, TX, USA) was assessed with an instrument conceived for measuring Zernike's coefficients at 3.0- and 5.0-mm apertures. As a reference, the aspheric monofocal lens AcrySof IQ Aspheric SN60WF (Alcon Laboratories Inc., Forth Worth, TX, USA) was also measured. The area of visibility and cut-off frequency were used to describe the modulation transfer function (MTF) of each lens; meanwhile, the light in the bucket and the diameter of a circular area centred on the point-spread function (PSF) peak that captures 50% of the light energy were used to describe the PSF of each lens. Finally, an image simulation was computed from the Zernike values with reference purposes. RESULTS: Small differences were found on the metrics used for describing the MTF and PSF of the lenses at both tested apertures, but these were not statistically significant (p > 0.05). Furthermore, the image simulation showed that these differences would not have clinical relevance at all. CONCLUSIONS: The optical performance of the AcrySof IQ toric IOLs in terms of MTF and PSF is good and seems to be independent of the cylindrical power and similar to a non-toric aspheric lens.

Optimizing precision in toric lens selection by combining keratometry techniques.

PURPOSE: To increase precision in toric intraocular lens selection by reducing the frequency of outliers that arise from technology-dependent variability during the preoperative assessment for routine cataract surgery. METHODS: Mean preoperative values for absolute sphere, amount of astigmatism, and steepest cylindrical axis were obtained for 87 eyes (54 patients) each with a manual keratometer and four automated keratometers. The mean sphere, amount of astigmatism, and steepest cylindrical axis across five technologies for each eye were defined as the meld sphere, meld astigmatism, and meld axis, respectively. Each technology was evaluated against the meld by Bland­Altman analysis, Student's paired t test, and correlation coefficients. Further comparison between individual technologies and the meld quantified the number of outlier measurements each technology produced. RESULTS: The number of outliers between individual keratometers and the meld differed with specific measurement of sphere, axis, or amount of astigmatism. Although statistical analysis using Bland­Altman plots, correlation coefficients, and paired t tests suggested insignificant difference from meld measurements for each parameter, precision-guided analysis presented more clinically significant outliers. The number of outliers can be reduced for sphere (range: 2%-46% to 1%-6%), astigmatism (range: 6%-23% to 0%-2%), and axis outliers (range: 15%-27% to 3%-6%) by averaging measurements from automated and manual keratometers. CONCLUSIONS: Although multiple keratometry technologies produced similar, average measurements, the authors found a disturbing number of outliers that may be overlooked when employing a single technology. Measurement errors can be dramatically reduced by averaging measurements from manual keratometry with any automated technology to make toric lens selection more precise.

Clinical evaluation of fitting toric soft contact lenses to current non-users.

PURPOSE: To evaluate the ease with which astigmats from three groups of current non-wearers of toric contact lenses can be fitted with current toric soft lenses, and to determine toric lens-wearing success. METHODS: This was a 1-month, randomized, bilateral, open-label, daily wear study involving 200 subjects and 16 investigational sites in the UK. Three groups of astigmatic subjects aged from 16 to 60 and with a mean age of 36 years (67 spherical soft contact lens users, SW; 72 contact lens drop-outs, DO; and 61 neophytes, Neo) were fitted with one of two toric soft lens types: a daily disposable toric soft lens (1 Day Acuvue Moist for Astigmatism, Johnson & Johnson Vision Care) or a 2-weekly replacement, re-usable toric soft lens (Acuvue Oasys for Astigmatism, Johnson & Johnson Vision Care). Subjects were evaluated after 1 month of wear and success rates calculated according to pre-set criteria for acceptable fit, orientation stability, visual acuity, quality of vision, and overall comfort. RESULTS: Eighty-eight percent of lenses were fitted at the first attempt. Of 198 subjects dispensed with lenses, 182 (92%) completed the study. When analysed by subject group, the success rates according to the pre-set criteria were 80% (53/66), 74% (52/70), and 70% (39/56) for the SW, DO and Neo groups respectively. Comfort was the most common reason for failure with all three groups; however, visual problems were more common in the DO and Neo groups (13% vs 6%). VA with the study lenses was significantly better in the SW group compared to their habitual lenses. For the DO and Neo groups combined (i.e. spectacle wearers), visual acuity was comparable to their habitual spectacles. CONCLUSIONS: A high proportion of astigmats who are not using toric soft contact lenses can be fitted with current lenses. Previous contact lens drop-outs and neophyte wearers achieve visual acuity comparable to spectacles when fitted with toric soft lenses. Spherical contact lens wearing astigmats achieve superior visual acuity when refitted with toric soft lenses. These findings suggest that many astigmats who are not currently using toric soft contact lenses could do so successfully.

Wearing time as a measure of success of scleral lenses for patients with irregular astigmatism.

OBJECTIVES: To evaluate the visual correction and clinical performance with scleral contact lenses (CL) for the visual rehabilitation of irregular astigmatism and to report the effect of brief wearing breaks on the wearing time and success rate. METHODS: A retrospective review was performed on consecutive patients who were fitted with scleral CL because of irregular astigmatism following failure of other optical corrections. Visual acuity (VA) and wearing times were abstracted. RESULTS: The 97 consecutive identified patients (155 eyes) were divided according to the diagnosis: (1) keratoconus (105 eyes; 67.7%), (2) postpenetrating keratoplasty (PK) (28 eyes; 18.1%); (3) multiple diagnoses (22 eyes; 14.2%)-postradial keratotomy, keratoglobus, pellucid marginal degeneration, PK with aphakia, and iatrogenic ectasia. The mean follow-up was 34.9 ± 18.5 months (range, 2-71 months). There was a significant increase in best VA-scleral when compared with the previous best VA-prescleral (P<0.001). The best VA-scleral was similar in the 3 groups (P>0.5). Patients who took brief breaks every 4 to 5 continuous wearing hours had a significantly higher success rate (P<0.001) among all diagnosis groups. The success rate in wearing time in the keratoconus group was significantly higher than in the PK group (P<0.001). Twenty-six patients (27%) discontinued to wear scleral lenses. CONCLUSION: Scleral lenses can be used successfully for visual rehabilitation and management of irregular astigmatism from various causative factors. The daily wearing time was significantly improved by taking brief breaks for replenishing the CL.

An international survey of toric contact lens prescribing.

OBJECTIVES: To characterize toric contact lens prescribing worldwide. METHODS: Up to 1,000 survey forms were sent to contact lens fitters in up to 39 countries between January and March every year for 5 consecutive years (2007-2011). Practitioners were asked to record data relating to the first 10 contact lens fits or refits performed after receiving the survey form. Only data for toric and spherical soft lens fits were analyzed. Survey data collected since 1996 were also analyzed for 7 nations to assess toric lens fitting trends since that time. RESULTS: Data were collected in relation to 21,150 toric fits (25%) and 62,150 spherical fits (75%). Toric prescribing ranged from 6% of lenses in Russia to 48% in Portugal. Compared with spherical fittings, toric fittings can be characterized as follows: older age (29.8 ± 11.4 years vs. 27.6 ± 10.8 years for spherical lenses); men are overrepresented (38% vs. 34%); greater proportion of new fits (39% vs. 32%); use of silicone hydrogel lenses (49% vs. 39%); and lower proportion of daily disposable lenses (14% vs. 28%). There has been a continuous increase in toric lens prescribing between 1996 and 2011. The proportion of toric lens fits was positively related to the gross domestic product at purchasing power parity per capita for year 2011 (r = 0.21; P=0.004). CONCLUSIONS: At the present time, in the majority of countries surveyed, toric soft contact lens prescribing falls short of that required to correct clinically significant astigmatism (≥ 0.75 diopters) in all lens wearers.

Peripheral aberrations and image quality for contact lens correction.

PURPOSE: Contact lenses (CLs) reduced the degree of hyperopic field curvature present in myopic eyes and rigid CLs reduced spherocylindrical image blur on the peripheral retina, but their effect on higher order aberrations and overall optical quality of the eye in the peripheral visual field is still unknown. The purpose of our study was to evaluate peripheral wavefront aberrations and image quality across the visual field before and after CL correction. METHODS: A commercial Hartmann-Shack aberrometer was used to measure ocular wavefront errors in 5° steps out to 30° of eccentricity along the horizontal meridian in uncorrected eyes and when the same eyes are corrected with soft or rigid CLs. Wavefront aberrations and image quality were determined for the full elliptical pupil encountered in off-axis measurements. RESULTS: Ocular higher order aberrations (HOA) increase away from fovea in the uncorrected eye. Third-order aberrations are larger and increase faster with eccentricity compared with the other HOA. CLs increase all HOA except third-order Zernike terms. Nevertheless, a net increase in image quality across the horizontal visual field for objects located at the foveal far point is achieved with rigid lenses, whereas soft CLs reduce image quality. CONCLUSIONS: Second-order aberrations limit image quality more than HOA in the periphery. Although second-order aberrations are reduced by CLs, the resulting gain in image quality is partially offset by increased amounts of HOA. To fully realize the benefits of correcting HOA in the peripheral field requires improved correction of second-order aberrations as well.

Adaptive astigmatism-correcting device for eyepieces.

PURPOSE: We describe how to construct a low-cost and robust variable astigmatism-correcting device manufactured using a pair of identical commercial ophthalmic lenses. METHODS: Variable astigmatism power can be obtained by relative rotation of two cross cylinders with the same prescription (for this work: S = +2.00 D, C = -4.00 D was used). The rotation of the whole ensemble allows the user to choose the astigmatism axis. RESULTS: The lens system presented here is able to correct astigmatism for eyepieces, compensating eyeglasses prescriptions from -8.00 to 0.00 D without generation of higher order aberrations and always with mean sphere power close to 0. Theoretical description of the piece, calibration, measurement of aberrations, and examples of use within a microscope are included. CONCLUSIONS: An inexpensive and robust variable-astigmatism device for eyepieces can be manufactured using two equal ophthalmic lenses. The system is robust in the sense that small misalignments only minimally affect mean sphere power and do not affect higher order aberrations. This unique device can be adapted to many users.

Third-order theory of spectacle lenses applied to correction of peripheral refractive errors.

PURPOSE: To demonstrate that relatively simple third-order theory can provide a framework which shows how peripheral refraction can be manipulated by altering the forms of spectacle lenses. METHODS: Third-order equations were used to yield lens forms that correct peripheral power errors, either for the lenses alone or in combination with typical peripheral refractions of myopic eyes. These results were compared with those of finite raytracing. RESULTS: The approximate forms of spherical and conicoidal lenses provided by third-order theory were flatter over a moderate myopic range than the forms obtained by rigorous raytracing. Lenses designed to correct peripheral refractive errors produced large errors when used with foveal vision and a rotating eye. Correcting astigmatism tended to give large errors in mean oblique error and vice versa. When only spherical lens forms are used, correction of the relative hypermetropic peripheral refractions of myopic eyes that are observed experimentally, or the provision of relative myopic peripheral refractions in such eyes, appears impossible in the majority of cases. CONCLUSIONS: The third-order spectacle lens design approach can readily be used to show trends in peripheral refraction.

Prevalence of astigmatism in relation to soft contact lens fitting.

PURPOSE: To estimate the proportion of potential soft contact lens wearers requiring an astigmatic correction and to estimate the proportion of astigmats who can be accommodated with toric soft lenses of varying prescription range. METHOD: A database of 11,624 spectacle prescriptions was used to calculate the prevalence of astigmatism for various thresholds (0.50-2.00 DC) by eye and by patient. The coverage of various prescription ranges was estimated using a subset of the database comprising those patients with at least 0.75 D of astigmatism in at least one eye (n = 5,444). RESULTS: The prevalence of patients showing astigmatism of 0.75 and 1.00 D or greater in at least one eye was 47.4% and 31.8% and, in both eyes, 24.1% and 15.0%, respectively. The proportion of eyes showing astigmatism greater than or equal to 0.75, 1.00, 1.50, and 2.00 D was 35.7%, 23.4%, 10.8%, 5.6%, respectively. The prevalence of astigmatism of 0.75 D or greater was almost double in myopes compared with hyperopes: 31.7% vs. 15.7%. The prevalence of with-the-rule (WTR) astigmatism was higher than against-the-rule (32.9% vs. 29.1%); the proportion was also higher for WTR in eyes with astigmatism ≥0.75 D (15.3% vs. 14.5%). We estimate that approximately one third of potential contact lens wearers require astigmatic correction. A stock range of toric soft lenses in sphere powers +6.00 to -9.00 D, three cylinder powers, and 18 axes requires nearly 3,000 prescriptions and provides coverage for 90% of astigmats. CONCLUSION: These findings provide an estimate of the proportion of soft contact lens patients requiring an astigmatic correction and some useful insights into the proportion of astigmats covered by toric soft lens stocks of varying range.

Transferences of heterocentric astigmatic catadioptric systems including Purkinje systems.

PURPOSE: To develop the linear optics of general catadioptric systems with allowance for both astigmatism and heterocentricity. METHODS: Reflecting elements partition a catadioptric system into subsystems of four distinct types: (unreversed) dioptric subsystems, anterior catoptric subsystems, reversed dioptric subsystems, and posterior catoptric systems. Differential geometry of an arbitrary astigmatic and tilted or decentered surface is used to determine the anterior and posterior catoptric transferences of a surface. RESULTS: The transference of a catadioptric system is obtained by multiplication of the transferences of unreversed and reversed dioptric subsystems and anterior and posterior catoptric transferences of reflecting elements. Formulae are obtained for the transferences of the visual system of an eye and of six nonvisual systems including the four Purkinje systems. CONCLUSIONS: The transference can be calculated for a catadioptric system, and from it, one can obtain other optical properties of the system including the dioptric power and the locations of the optical axis and cardinal structures.

Amblyopia in astigmatic infants and toddlers.

PURPOSE: To determine whether reduced astigmatism-corrected acuity for vertical (V) and/or horizontal (H) gratings and/or meridional amblyopia (MA) are present before 3 years of age in children who have with-the-rule astigmatism. METHODS: Subjects were 448 children, 6 months through 2 years of age with no known ocular abnormalities other than with-the-rule astigmatism, who were recruited through Women, Infants and Children clinics on the Tohono O'odham reservation. Children were classified as non-astigmats (< or =2.00 diopters) or astigmats (>2.00 diopters) based on right eye non-cycloplegic autorefraction measurements (Welch Allyn SureSight). Right eye astigmatism-corrected grating acuity for V and H stimuli was measured using the Teller Acuity Card procedure while children wore cross-cylinder lenses to correct their astigmatism or plano lenses if they had no astigmatism. RESULTS: Astigmatism-corrected acuity for both V and H gratings was significantly poorer in the astigmats than in the non-astigmats, and the reduction in acuity for astigmats was present for children in all three age groups examined (6 months to <1 year, 1 to <2 years, and 2 to <3 years). There was no significant difference in V-H grating acuity (no evidence of MA) for the astigmatic group as a whole, or when data were analyzed for each age group. CONCLUSIONS: Even in the youngest age group, astigmats tested with astigmatism correction showed reduced acuity for both V and H gratings, which suggests that astigmatism is having a negative influence on visual development. We found no evidence of orientation-related differences in astigmatism-corrected grating acuity, indicating either that MA does not develop before 3 years of age, or that most of the astigmatic children had a type of astigmatism, i.e., hyperopic, that has proven to be less likely than myopic or mixed astigmatism to result in MA.

Peripheral refraction with and without contact lens correction.

PURPOSE: Peripheral refractive error degrades the quality of retinal images and has been hypothesized to be a stimulus for the development of refractive error. The purpose of this study was to investigate the changes in refractive error across the horizontal visual field produced by contact lenses (CLs) and to quantify the effect of CLs on peripheral image blur. METHODS: A commercial Shack-Hartmann aberrometer measured ocular wavefront aberrations in 5 degrees steps across the central 60 degrees of visual field along the horizontal meridian before and after CLs correction. Wavefront refractions for peripheral lines-of-sight were based on the full elliptical pupil encountered in peripheral measurements. Curvature of field is the change in peripheral spherical equivalent relative to the eye's optical axis. RESULTS: Hyperopic curvature of field in the naked eye increases with increasing amounts central myopic refractive error as predicted by Atchison (2006). For an eccentricity of E degrees, field curvature is approximately E percent of foveal refractive error. Rigid gas permeable (RGP) lenses changed field curvature in the myopic direction twice as much as soft CLs (SCLs). Both of these effects varied with CLs power. For all lens powers, SCL cut the degree of hyperopic field curvature in half whereas RGP lenses nearly eliminated field curvature. The benefit of reduced field curvature was partly offset by increased oblique astigmatism. The net reduction of retinal blur because of CLs is approximately constant across the visual field. CONCLUSIONS: Both SCL and RGP lenses reduced the degree of hyperopic field curvature present in myopic eyes, with RGP lenses having greater effect. The tradeoff between field curvature and off-axis astigmatism with RGP lenses may limit their effectiveness for control of myopia progression. These results suggest that axial growth mechanisms that depend on retinal image quality will be affected more by RGP than by SCL lenses.

Visual performance with real-life tasks under adaptive-optics ocular aberration correction.

We measured the effect of the correction of the natural aberrations of the eye by means of adaptive optics on the subject's performance on three different visual tasks: subjective sharpness assessment of natural images, familiar face recognition, and facial expression recognition. Images were presented through a dedicated psychophysical channel and viewed through an electromagnetic deformable mirror. Experiments were performed on 17 normal subjects. Ocular aberrations (astigmatism and higher order aberrations) were reduced on average from 0.366 +/- 0.154 to 0.101 +/- 0.055 mum for a 5-mm pupil diameter. On average, subjects considered to be sharper 84 +/- 14% of the images viewed under AO correction, and there was a significant correlation between the amount of corrected aberrations and the percentage of images that the subject considered sharper when observed under AO-corrected aberrations. In all eyes (except one), AO correction improved familiar face recognition, by a factor of x1.13 +/- 0.12 on average. However, AO correction did not improve systematically facial expression recognition.

Correction of astigmatism at the time of cataract surgery.

PURPOSE OF REVIEW: There are several options for correcting astigmatism at the time of cataract surgery. They include incision placement on the steep axis of corneal astigmatism, single or paired peripheral corneal relaxing incisions, and toric intraocular lens implantation. The aim of this review is to update readers on advances reported during the last year. RECENT FINDINGS: Phacoemulsification incision placement on the steep corneal axis corrects small amounts of astigmatism and is sufficient for most eyes. Peripheral corneal relaxing incisions correct greater amounts of astigmatism. They may be necessary when implanting multifocal intraocular lenses in eyes with more than 1 diopter of astigmatism. Toric intraocular lenses are also safe and effective for treating more than 1 diopter of astigmatism, and they now have excellent rotational stability. SUMMARY: Good uncorrected postoperative distance visual acuity can be obtained for a high percentage of cataract patients with preexisting corneal astigmatism. Postoperative keratorefractive surgery is available to enhance the condition of patients who achieve less-than-optimal astigmatic results.

Influence of adaptive-optics ocular aberration correction on visual acuity at different luminances and contrast polarities.

We evaluated the visual benefit of correcting astigmatism and high-order aberrations with adaptive optics (AO) on visual acuity (VA) measured at 7 different luminances (ranging from 0.8 to 50 cd/m(2)) and two contrast polarities (black letters on white background, BoW, and white letters on black background, WoB) on 7 subjects. For the BoW condition, VA increased with background luminance in both natural and AO-corrected conditions, and there was a benefit of AO correction at all luminances (by a factor of 1.29 on average across luminances). For WoB VA increased with foreground luminance but decreased for the highest luminances. In this reversed polarity condition AO correction increased VA by a factor of 1.13 on average and did not produce a visual benefit at high luminances. The improvement of VA (averaged across conditions) was significantly correlated (p = 0.04) with the amount of corrected aberrations (in terms of Strehl ratio). The improved performance with WoB targets with respect to BoW targets is decreased when correcting aberrations, suggesting a role of ocular aberrations in the differences in visual performance between contrast polarities.

[Determination of toric intraocular lenses]. / Berechnung torischer Intraokularlinsen.

BACKGROUND: In the last decades, toric posterior chamber lenses (TPCLs) for cataract surgery and phakic toric lenses (PTLs) for refractive surgery have become more and more popular for correcting high or excessive corneal astigmatism. The purpose of this article is to present a vergence-based calculation scheme for TPCLs and PTLs. METHODS: In Gaussian optics (in the paraxial space), spherocylindrical optical surfaces can be described in a mathematically equivalent formulation as vergences. There are dual notations: The standard notation is used for transforming vergences through a homogeneous optical medium, and the component notation is applied to add up the power of a refractive surface to the vergence. Both notations can be used interchangeably. For calculating TPCLs, the vergences in front of and behind the predicted pseudophakic lens position are determined and subtracted. For calculating PTLs, the anterior vergence at the predicted lens position is estimated for the preoperative and postoperative states, and the difference between the two yields the desired lens power. WORKING EXAMPLES: In the 1(st) example, the power of a thin TPCL is determined step by step by applying the presented calculation scheme, which was designed to be transferred directly to a simple computer program (e.g., Microsoft Excel). In the 2(nd) example, the postoperative refraction is estimated for a simulation in which a TPCL similar to that in example 1 is implanted in a slightly misaligned orientation. In a 3(rd) example, the power of a PTL is determined step by step using the above-mentioned calculation scheme. CONCLUSIONS: The presented calculation scheme allows determination of"thin" TPCLs or PTLs to achieve spherocylindrical target refraction with a cylinder axis at random or to predict the postoperative refraction for any toric lens implanted in any axis. The concept can be easily generalized to"thick" toric intraocular lenses if the geometric data and refraction index of the material are known.

[Use of multifocal intraocular lenses and criteria for patient selection]. / Einsatzmöglichkeiten intraokularer Multifokallinsen und Kriterien der Patientenselektion.

Multifocal intraocular lenses (MIOL) are increasingly being used as a therapeutic approach to correct presbyopia. To guarantee patient satisfaction, it is important to be aware of the different IOL properties and patient inclusion criteria. A differentiated patient selection in combination with optimized perioperative and postoperative management is necessary to achieve appropriate postoperative refractive results and patient satisfaction.

[Limbal relaxing incision or the more curved meridian incision associated to phacoemulsification with multifocal intraocular lens implant: three case reports]. / Incisões relaxantes limbares ou incisões no meridiano mais curvo associadas a facoemulsificação com implante de lente intra-ocular multifocal: relato de três casos.

The use of multifocal intraocular lenses (IOLs) is a great advance in the treatment of patients with cataract allowing near and distance uncorrected visual acuity recovery. However patients with some degrees of corneal astigmatism have some limitations. We present 3 cases that were indicated for phacoemulsitfication and multifocal intraocular lens implant (AcrySof Restor, Alcon Labs) after limbal relaxing incision (LRI) in the dominant eye and axis topographic incision in the fellow eye. There was no similar case report in the literature. It is believed that this association can extend the indications for multifocal intraocular lens implants in patients with significant corneal astigmatism and this possibility should be confirmed by future studies.