Simulation of daily soft multifocal contact lenses using SimVis Gekko: from in-vitro and computational characterization to clinical validation.

Multifocal contact lenses (MCLs) are one of the solutions to correct presbyopia, but their adoption is not widespread. To address this situation, visual simulators can be used to refine the adaptation process. This study aims to obtain accurate simulations for a visual simulator (SimVis Gekko; 2EyesVision) of daily soft MCL designs from four manufacturers. In-vitro characterization of these MCLs-several powers and additions- was obtained using NIMO TR-1504. From the averaged relative power profiles across powers, phase maps were reconstructed and the Through-Focus Visual Strehl metric was calculated for each MCL design. The SimVis Gekko simulation corresponding to each MCL design was obtained computationally and bench-validated. Finally, the MCL simulations were clinically validated involving presbyopic patients. The clinical validation results show a good agreement between the SimVis Gekko simulations and the real MCLs for through-focus visual acuity (TF-VA) curves and VA at three real distances. All MCL designs showed a partial correlation higher than 0.90 and a Root Mean Square Error below 0.07 logMAR between the TF-VA of simulations and Real MCLs across subjects. The validity of the simulation approach using SimVis Gekko and in-vitro measurements was confirmed in this study, opening the possibility to accelerate the adaptation of MCLs.

Defocus flicker of chromatic stimuli deactivates accommodation.

Tunable lenses, optical elements able to change their optical power within milliseconds, constitute an emerging technology increasingly used in ophthalmic applications. In this study, 25 subjects looked through tunable lenses at a chromatic stimulus to evaluate the perceptual response of the human visual system to periodic changes in defocus of 0.25D of amplitude and 15 Hz of temporal frequency. These defocus changes produce flicker and chromatic distortions that change with the overall level of defocus. The task in this study was to minimize the flicker by varying the average optical power, and it was performed for different myopic and hyperopic starting points. Subjects also performed a blur-minimization task in a black-and-white stimulus of the same geometry. The flicker-minimization task is more repeatable than the blur-minimization task (standard deviations ±0.17D and ±0.49D). The time per repetition of the flicker-minimization task is only 38s. Cycloplegia severely affects the blur-minimization, but not the flicker-minimization task, confirming that defocus flicker deactivates the accommodative system. This discovery can be used to develop new methods for measuring the refractive error of the eye that does not require supervision and can potentially improve existing subjective methods in terms of accuracy, precision, and measurement time.

Spatiotemporal defocus sensitivity function of the human visual system.

Tunable lenses make it possible to measure visual sensitivity to rapid changes in optical power, surpassing the limits imposed by mechanical elements. Using a tunable lens system, we measured, for the first time, the spatiotemporal defocus sensitivity function (STDSF), and the limits of human defocus perception. Specifically, we measured defocus sensitivity using a QUEST adaptive psychophysical procedure for different stimuli (Gabor patches of different spatial frequencies, natural images, and edges) and we developed descriptive models of defocus perception. For Gabor patches, we found on average (across seven subjects) that the maximum sensitivity to defocus is 0.22 D at 14 cpd and 10 Hz, and that the upper limits of sensitivity are 40 cpd and 40 Hz. Our results suggest that accommodation remains fixed while performing the defocus flicker-detection task. These results have implications for new technologies whose working principles make use of fast changes to defocus.

Case report of the evidence of a spontaneous Reverse Pulfrich effect in monovision after cataract surgery.

BACKGROUND: Cataracts affect the optics of the eye in terms of absorption, blur, and scattering. When cataracts are unilateral, they cause differences between the eyes that can produce visual discomfort and harm binocular vision. These interocular differences can also induce differences in the processing speed of the eyes that may cause a spontaneous Pulfrich effect, a visual illusion provoking important depth misperceptions. Interocular differences in light level, like those present in unilateral cataracts, can cause the Classic Pulfrich effect, and interocular differences in blur, like those present in monovision, a common correction for presbyopia, can cause the Reverse Pulfrich effect. The visual system may be able to adapt, or not, to the new optical condition, depending on the degree of the cataract and the magnitude of the monovision correction. CASE PRESENTATION: Here, we report a unique case of a 45-year-old patient that underwent unilateral cataract surgery resulting in a monovision correction of 2.5 diopters (D): left eye emmetropic after the surgery compensated with a monofocal intraocular lens and right eye myopic with a spherical equivalent of -2.50 D. This patient suffered severe symptoms in binocular vision, which can be explained by a spontaneous Pulfrich effect (a delay measured of 4.82 ms, that could be eliminated with a 0.19 optical density filter). After removing the monovision with clear lens extraction in the second eye, symptoms disappeared. We demonstrate that, at least in this patient, both Classic and Reverse Pulfrich effects coexist after unilateral cataract surgery and that can be readapted by reverting the interocular differences. Besides, we report that the adaptation/readaptation process to the Reverse Pulfrich effect happens in a timeframe of weeks, as opposed to the Classic Pulfrich effect, known to have timeframes of days. Additionally, we used the illusion measured in the laboratory to quantify the relevance of the spontaneous Pulfrich effect in different visual scenarios and tasks, using geometrical models and optic flow algorithms. CONCLUSIONS: Measuring the different versions of the Pulfrich effect might help to understand the visual discomfort reported by many patients after cataract surgery or with monovision and could guide compensation or intervention strategies.

Monovision Correction Preference and Eye Dominance Measurements.

Purpose: To propose new methods for eye selection in presbyopic monovision corrections. Methods: Twenty subjects with presbyopia performed two standard methods of binary eye dominance identification (sensory with +1.50 diopters [D ]and +0.50 D and sighting with "hole-in-the-card") and two psychophysical methods of perceived visual quality: (1) the Preferential test, 26 natural images were judged with the near addition in one eye or in the other in a 2-interval forced-choice task, and the Eye Dominance Strength (EDS) defined as the proportion of trials where one monovision is preferred over the other; (2) the Multifocal Acceptance Score (MAS-2EV) test, the perceived quality of a natural images set (for 2 luminance levels and distances) was scored and EDS defined as the score difference between monovision in one eye or the other. Left-eye and right-eye dominance are indicated with negative and positive values, respectively. Tests were performed using a Simultaneous Vision Simulator, which allows rapid changes between corrections. Results: Standard sensory and sighting dominances matched in only 55% of subjects. The Preferential EDS (ranging from -0.7 to +0.9) and MAS-2EV EDS (ranging from -0.6 to +0.4) were highly correlated. Selecting the eye for far in monovision with the MAS-2EV, sensory, or sighting tests would have resulted in 79%, 64%, and 43% success considering the Preferential test as the gold standard. Conclusions: Tests based on perceptual preference allow selection of the preferred monovision correction and measurement of dominance strength. Translational Relevance: The binocular visual simulator allows efficient implementation of eye preference tests for monovision in clinical use.

Experimental characterization, modelling and compensation of temperature effects in optotunable lenses.

Most tunable lenses (TLs) are affected by deviations in optical power induced by external temperature changes or due to internal heating while in use. This study proposes: (1) An experimental characterization method to evaluate the magnitude of the optical power deviations due to internal temperature shifts; (2) three different mathematical models (experimental, polynomial, and optimized) to describe the response of the lens with temperature; (3) predictions of the internal temperature shifts while using the lens in time frames of minutes, seconds, and milliseconds and; (4) a real time optical power compensation tool based on the implementation of the models on a custom voltage electronic driver. The compensation methods were successfully applied to two TL samples in static and dynamic experiments and in hysteresis cycles. After 40 min at a static nominal power of 5 diopters (dpt), the internal temperature exponentially increased by 17 °C, producing an optical power deviation of 1.0 dpt (1.5 dpt when the lens cools down), representing a 20% distortion for heating and 30% for cooling. Modelling and compensation reduced the deviations to 0.2 dpt when heating (0.35 dpt when cooling) and the distortions to 4% and 7%. Similar levels of improvement were obtained in dynamic and hysteresis experiments. Compensation reduced temperature effects by more than 75%, representing a significant improvement in the performance of the lens.

Visual simulations of presbyopic corrections through cataract opacification.

PURPOSE: To study the viability of visual simulation of presbyopic correction in patients with cataract and the effect and impact of the cataract on the perceived visual quality of the different simulated presbyopic corrections preoperatively and postoperatively. SETTING: San Carlos Clinical Hospital, Madrid, Spain. DESIGN: Observational, noninterventional, pilot study, early feasibility of the device being studied. METHODS: Cataract patients were tested preoperatively (n = 24) and postoperatively (n = 15) after bilateral implantation of monofocal intraocular lenses (IOLs). The degree of cataract was evaluated objectively with the objective scatter index (OSI). Visual acuity (VA) and perceived visual quality of natural scene images (Multifocal Acceptance Score) were measured before and after cataract surgery at far (4 m), intermediate (64 cm) and near distance (40 cm) with 4 binocular presbyopic corrections (single vision, bifocal, monovision and modified-monovision) simulated with a binocular Simultaneous Vision simulator based on temporal multiplexing. RESULTS: VA was significantly correlated with OSI ( r = -0.71, P < .0005), although the visual degradation at far for each correction was constant and not correlated with OSI. The visual benefit at near distance provided by the presbyopic correction was noticeable (23.3% ± 27.6% across corrections) for OSI <5. The individual perceptual scores were highly correlated preoperatively vs postoperatively ( r = 0.64, P < .0005) for all corrections and distances. CONCLUSIONS: Visual simulations of IOLs are an excellent tool to explore prospective postoperative vision. The high correlation in the perceptual scores pre- and post-cataract surgery demonstrates that SimVis Gekko can be used in cataractous patients to guide the selection of the optimal correction for a patient.

Closed-loop experimental optimization of tunable lenses.

Tunable lenses (TLs) are optical devices that can change their optical power in response to an electrical signal. In many applications, they are often pushed to or beyond their temporal limits. Fast periodic and/or abrupt variations of the optical power induce undesired distortions in their transient response and produce a decrease in their performance. A low-cost focimetry system, along with a custom closed-loop iterative optimization algorithm, was developed to (1) characterize a TL's response at high speed and (2) optimize their performance in realistic TL working conditions. A significant lens performance improvement was found in about 23 iterations with a decrease in the area under the error curve and an improved effective time. Applying the closed-loop optimization algorithm in a depth scanning experiment enhanced the image quality. Quantitatively, the image quality was evaluated using the structural similarity index metric that improves in individual frames, on average, from 0.345 to 0.895.

Multifocal contact lens vision simulated with a clinical binocular simulator.

PURPOSE: The purpose of this study is to compare the binocular visual perception of participants wearing multifocal contact lenses and these same lens designs viewed through a temporal multiplexing visual simulator. METHODS: Visual performance and perceived visual quality at various distances were obtained in 37 participants wearing soft M-CLs and through the SimVis Gekko programmed with the same lenses. In a pilot study (n = 10) visual performance was measured in terms of LogMAR visual acuity (VA) at far (4 m), intermediate (64 cm) and near (40 cm) distances and through-focus VA (TFVA) curves with the simulated M-CLs. In the follow-up study (n = 27), LogMAR VA at far, intermediate and near distances were measured both with the actual and simulated M-CLs. Perceived visual quality was measured in both studies using the Multifocal Acceptance Score (MAS-2EV), and a Participants Reported Outcomes Vision questionnaire. Differences between the metrics obtained with simulated and actual lenses were obtained. RESULTS: Both actual and simulated M-CLs increased depth-of-focus by a similar amount. Mean LogMAR VA differences with actual and simulated M-CLs ranged between 4 and 6 letters (0.08 ± 0.01, 0.12 ± 0.01 and 0.10 ± 0.01, for far, intermediate and near distances, respectively). MAS-2EV average score differences with actual and simulated M-CLs ranged between -1.00 and + 4.25. Average MAS-2EV scores were not correlated significantly with VA. However, MAS-2EV (average and individual scores) were highly correlated to visual quality questionnaire responses (p < 0.005). CONCLUSIONS: A simultaneous vision simulator accurately represented vision with M-CLs both VA at various distances and perceived visual quality, as measured in a clinical setting. The MAS-2EV metric accurately captured participant reported outcomes of standard vision questionnaires. The combination of SimVis Gekko and MAS-2EV has the potential to largely reduce chair time in M-CLs fitting.

Beyond traditional subjective refraction.

PURPOSE OF REVIEW: The evaluation of refractive error is probably the most important and common procedure in eye care. The gold standard method for evaluating refractive error is subjective refraction, a process that has not significantly changed in 200years. This article aims to review recent technologies and novel approaches attempting to improve this traditional procedure. RECENT FINDINGS: From laboratory prototypes to commercial instruments, the proposed methods aim to perform reliable and fast subjective refractions, following different approaches: using motorized phoropters in combination with automatic algorithms or even self-refraction, hybridizing objective and subjective measurements within the same instruments, or using new visual tasks beyond letter identification of blur estimation to obtain the refractive error subjectively. SUMMARY: The current trend in subjective refraction is to overcome the traditional manual blur reduction method, using automatic and self-refraction instruments, which can provide faster measurements with lower variability. Many of the technologies reported here are already in the market, and some have the potential of becoming the new standard in subjective refraction.

Optical and visual quality of real intraocular lenses physically projected on the patient's eye.

Visual simulators aim at evaluating vision with ophthalmic corrections prior to prescription or implantation of intraocular lenses (IOLs) in the patient's eye. In the present study, we present the design, implementation, and validation of a new IOL-in-cuvette channel in an Adaptive Optics visual simulator, which provides an alternative channel for pre-operative simulation of vision with IOLs. The IOL is projected on the pupil's plane of the subject by using a Rassow system. A second lens, the Rassow lens, compensates for an IOL of 20 D while other powers can be corrected with a Badal system within a 5 D range. The new channel was evaluated by through-focus (TF) optical quality in an artificial eye on bench, and by TF visual acuity in patients, with various IOL designs (monofocal, diffractive trifocal, and refractive extended depth of focus).

Simulating Outcomes of Cataract Surgery: Important Advances in Ophthalmology.

As the human eye ages, the crystalline lens stiffens (presbyopia) and opacifies (cataract), requiring its replacement with an artificial lens [intraocular lens (IOL)]. Cataract surgery is the most frequently performed surgical procedure in the world. The increase in IOL designs has not been paralleled in practice by a sophistication in IOL selection methods, which rely on limited anatomical measurements of the eye and the surgeon's interpretation of the patient's needs and expectations. We propose that the future of IOL selection will be guided by 3D quantitative imaging of the crystalline lens to map lens opacities, anticipate IOL position, and develop fully customized eye models for ray-tracing-based IOL selection. Conversely, visual simulators (in which IOL designs are programmed in active elements) allow patients to experience prospective vision before surgery and to make more informed decisions about which IOL to choose. Quantitative imaging and optical and visual simulations of postsurgery outcomes will allow optimal treatments to be selected for a patient undergoing modern cataract surgery.

Multifocal acceptance score to evaluate vision: MAS-2EV.

We present a new metric (Multifocal Acceptance Score, MAS-2EV) to evaluate vision with presbyopic corrections. The MAS-2EV is based on a set of images representing natural visual scenes at day and night conditions projected in far and near displays, and a near stereo target. Subjects view and score the images through different binocular corrections (monofocal corrections at far; bifocal corrections; monovision and modified monovision) administered with soft contact lenses (in cyclopleged young subjects) or with a binocular simultaneous vision simulator (in presbyopic and cyclopleged young subjects). MAS-2EV scores are visually represented in the form of polygons, and quantified using different metrics: overall visual quality, visual degradation at far, visual benefit at near, near stereo benefit, visual imbalance near-far, overall visual imbalance and a combined overall performance metric. We have found that the MAS-2EV has sufficient repeatability and sensitivity to allow differentiation across corrections with only two repetitions, and the duration of the psychophysical task (3 min for subject/condition/correction) makes it useable in the clinic. We found that in most subjects binocular bifocal corrections produce the lowest visual imbalance, and the highest near stereo benefit. 46.67% of the subjects ranked binocular bifocal corrections first, and 46.67% of the subjects ranked monovision first. MAS-2EV, particularly in combination with visual simulators, can be applied to select prospective presbyopic corrections in patients prior to contact lens fitting or intraocular lens implantation.

Vision is protected against blue defocus.

Due to chromatic aberration, blue images are defocused when the eye is focused to the middle of the visible spectrum, yet we normally are not aware of chromatic blur. The eye suffers from monochromatic aberrations which degrade the optical quality of all images projected on the retina. The combination of monochromatic and chromatic aberrations is not additive and these aberrations may interact to improve image quality. Using Adaptive Optics, we investigated the optical and visual effects of correcting monochromatic aberrations when viewing polychromatic grayscale, green, and blue images. Correcting the eye's monochromatic aberrations improved optical quality of the focused green images and degraded the optical quality of defocused blue images, particularly in eyes with higher amounts of monochromatic aberrations. Perceptual judgments of image quality tracked the optical findings, but the perceptual impact of the monochromatic aberrations correction was smaller than the optical predictions. The visual system appears to be adapted to the blur produced by the native monochromatic aberrations, and possibly to defocus in blue.

Longitudinal Chromatic Aberration in Patients Implanted With Trifocal Diffractive Hydrophobic IOLs.

PURPOSE: To measure the in vivo longitudinal chromatic aberration (LCA) from the chromatic difference of focus (480 to 700 nm) using psychophysical methods in patients bilaterally implanted with a hydrophobic trifocal intraocular lens (IOL). METHODS: Psychophysical best focus was measured in both eyes at different wavelengths (480 to 700 nm) and at three different viewing distances (0.00, +1.75, and +3.50 diopters [D]) using a custom-developed polychromatic adaptive optics set-up provided with a supercontinuum laser, a Hartmann-Shack wavefront sensor, a deformable mirror, a motorized Badal system, a pupil monitoring system, and a psychophysical channel with monochromatically illuminated stimuli. Measurements were performed on 10 patients (20 eyes) bilaterally implanted with hydrophobic trifocal diffractive IOLs (FineVisionHP POD F GF; PhysIOL). LCA was computed from the chromatic difference of focus curves as the difference between 480 and 700 nm at near, intermediate, and far. RESULTS: The LCA from psychophysical measurements was significantly higher for far vision (0.99 ± 0.06 diopters [D]), than for intermediate (0.67 ± 0.10 D) and near (0.23 ± 0.08 D) vision (one-way analysis of variance, P < .05). CONCLUSIONS: LCA for far vision was significantly higher than for intermediate and near vision in hydrophobic trifocal diffractive IOLs, in agreement with a previous study with the same optical design but hydrophilic material IOLs. The LCA for the hydro-phobic IOL is slightly higher than for the hydrophilic IOL at far. Different combinations of refractive and diffractive LCA will allow optimizing IOL designs to improve polychromatic image quality. [J Refract Surg. 2020;36(12):804-810.].

Optical and Visual Quality With Physical and Visually Simulated Presbyopic Multifocal Contact Lenses.

Purpose: As multifocal contact lenses (MCLs) expand as a solution for presbyopia correction, a better understanding of their optical and visual performance becomes essential. Also, providing subjects with the experience of multifocal vision before contact lens fitting becomes critical, both to systematically test different multifocal designs and to optimize selection in the clinic. In this study, we evaluated the ability of a simultaneous vision visual simulator (SimVis) to represent MCLs. Methods: Through focus (TF) optical and visual quality with a center-near aspheric MCL (low, medium and high near adds) were measured using a multichannel polychromatic Adaptive Optics visual simulator equipped with double-pass, SimVis (temporal multiplexing), and psychophysical channels to allow measurements on-bench and in vivo. On bench TF optical quality of SimVis-simulated MCLs was obtained from double-pass (DP) images and images of an E-stimulus using artificial eyes. Ten presbyopic subjects were fitted with the MCL. Visual acuity (VA) and DP retinal images were measured TF in a 4.00 D range with the MCL on eye, and through SimVis simulations of the same MCLs on the same subjects. Results: TF optical (on bench and in vivo) and visual (in vivo) quality measurements captured the expected broadening of the curves with increasing add. Root mean square difference between real and SimVis-simulated lens was 0.031/0.025 (low add), 0.025/0.015 (medium add), 0.019/0.011 (high add), for TF DP and TF LogMAR VA, respectively. A shape similarity metric shows high statistical values (lag κ = 0), rho = 0.811/0.895 (low add), 0.792/0.944 (medium add), and 0.861/0.915 (high add) for TF DP/LogMAR VA, respectively. Conclusions: MCLs theoretically and effectively expand the depth of focus. A novel simulator, SimVis, captured the through-focus optical and visual performance of the MCL in most of the subjects. Visual simulators allow subjects to experience vision with multifocal lenses prior to testing them on-eye. Translational Relevance: Simultaneous visual simulators allow subjects to experience multifocal vision non-invasively. We demonstrated equivalency between real multifocal contact lenses and SimVis-simulated lenses. The results suggest that SimVis is a suitable technique to aid selection of presbyopic corrections in the contactology practice.

Contact lenses, the reverse Pulfrich effect, and anti-Pulfrich monovision corrections.

Interocular differences in image blur can cause processing speed differences that lead to dramatic misperceptions of the distance and three-dimensional direction of moving objects. This recently discovered illusion-the reverse Pulfrich effect-is caused by optical conditions induced by monovision, a common correction for presbyopia. Fortunately, anti-Pulfrich monovision corrections, which darken the blurring lens, can eliminate the illusion for many viewing conditions. However, the reverse Pulfrich effect and the efficacy of anti-Pulfrich corrections have been demonstrated only with trial lenses. This situation should be addressed, for clinical and scientific reasons. First, it is important to replicate these effects with contact lenses, the most common method for delivering monovision. Second, trial lenses of different powers, unlike contacts, can cause large magnification differences between the eyes. To confidently attribute the reverse Pulfrich effect to interocular optical blur differences, and to ensure that previously reported effect sizes are reliable, one must control for magnification. Here, in a within-observer study with five separate experiments, we demonstrate that (1) contact lenses and trial lenses induce indistinguishable reverse Pulfrich effects, (2) anti-Pulfrich corrections are equally effective when induced by contact and trial lenses, and (3) magnification differences do not cause or impact the Pulfrich effect.

Testing the effect of ocular aberrations in the perceived transverse chromatic aberration.

We have measured the ocular transverse chromatic aberration (TCA) in 11 subjects using 2D-two-color Vernier alignment, for two pupil diameters, in a polychromatic adaptive optics (AO) system. TCA measurements were performed for two pupil diameters: for a small pupil (2-mm), referred to as 'optical TCA' (oTCA), and for a large pupil (6-mm), referred to 'perceived TCA' (pTCA). Also, the TCA was measured through both natural aberrations (HOAs) and AO-corrected aberrations. Computer simulations of pTCA incorporated longitudinal chromatic aberration (LCA), the patient's HOAs measured with Hartmann-Shack, and the Stiles-Crawford effect (SCE), measured objectively by laser ray tracing. The oTCA and the simulated pTCA (no aberrations) were shifted nasally 1.20 arcmin and 1.40 arcmin respectively. The experimental pTCA (-0.27 arcmin horizontally and -0.62 vertically) was well predicted (81%) by simulations when both the individual HOAs and SCE were considered. Both HOAs and SCE interact with oTCA, reducing it in magnitude and changing its orientation. The results indicate that estimations of polychromatic image quality should incorporate patient's specific data of HOAs, LCA, TCA & SCE.

Pre-operative simulation of post-operative multifocal vision.

While multifocal intraocular lenses (MIOLs) are increasingly implanted to correct for presbyopia, how one sees with a multifocal correction is hard to explain and imagine. The current study evaluates the quality of various visual simulating technologies by comparing vision with simulated MIOLs pre-operatively and the implanted MIOLs post-operatively in the same patients. Two simulation platforms were used: (1) a custom-developed adaptiveoptics (AO) system, with two visual simulator devices: a spatial light modulator (SLM) and an optotunable lens operating under temporal multiplexing (SimVis); and (2) a wearable, binocular, large field of view SimVis2Eyes clinical simulator (SimVis Gekko, 2Eyes Vision, Madrid, Spain). All devices were programmed to simulate a trifocal diffractive MIOL (POD F, FineVision, PhysIOL). Eight patients were measured pre-operatively simulating the trifocal lens and post-operatively with implantation of the same MIOL. Through-focus decimal visual acuity (TF VA) was measured (1) monocularly in monochromatic light using a four-alternative-forced-choice procedure in the AO system; and (2) binocularly using a clinical optotype in white light. Visual simulations pre-operatively predict well the TF VA performance found post-operatively in patients implanted with the real IOL. The average RMS difference between TF curves with the different visual simulators was 0.05 ± 0.01. The average RMS difference between the TF VA curves with the SimVis pre-operatively and the real MIOL post-operatively was 0.06 ± 0.01 in both platforms, and it was higher in cataract eyes (0.08 ± 0.01, on average across simulators) than in eyes with clear lens. In either group the shape of the TF curves is similar across simulators and pre- and post-operatively. TF curves cross-correlated significantly between simulators (lag k = 0, rho = 0.889), as well as with results with the real MIOL implanted (lag k = 0, rho = 0.853). Visual simulations are useful programmable tools to predict visual performance with MIOLs, both in an AO environment and in a clinical simulator. Pre-operative visual simulations and post-operative data are in good agreement.

Perceptual impact of astigmatism induction in presbyopes.

We investigated the effect of induced astigmatism on subjective best focus and on visual acuity in 28 subjects of different ages (pre-presbyopic and presbyopic) and with different refractive profiles (emmetropes and astigmats). Measurements were performed using a custom-developed Adaptive Optics system, which allowed correction of high order aberrations and induction of astigmatism (0.5, 1, 1.5 and 2.0 D; axis: 180°, 45° and 22.5°). Upon induction of astigmatism, best focus shifted towards negative values in pre-presbyopic emmetropic eyes (by -0.14 D for 0.5 D and by -0.33 D for 2.0 D), while it shifted towards positive values in presbyopes, both in emmetropic presbyopes (by +0.04 D for 0.50 D and by +0.16 D for 2.0 D) and in astigmatic presbyopes (by +0.23 D for 0.50 D and by +0.40 D for 2.0 D). Also, visual acuity was most sensitive to astigmatism induction in pre-presbyopic emmetropes and least sensitive in presbyopes, particularly when high order aberrations were corrected: visual acuity ratio with/without astigmatism was: 0.74/0.85/0.98 (for astigmatism induced at 180°) and 0.68/0.73/0.86 at 45°, for pre-presbyopic emmetropes/presbyopic emmetropes/presbyopic astigmats. These findings may be connected to long term exposure to astigmatism in astigmats and corrected presbyopes.