Early Detection of Refractive Errors by Photorefraction at School Age.

Early detection and treatment of refractive defects during school age are essential to avoid irreversible future vision loss and potential school problems. Previously, vision screening of preschool children used methods based on subjective visual acuity; however, technologies such as photorefraction have promoted the detection of refractive errors quickly and easily. In this study, 1347 children from 10 schools in Madrid aged 4 to 12 years participated in a program of early detection of visual problems, which consisted of visual screening composed of anamnesis and photorefraction with a PlusOptix A12R. The prevalence of refractive errors was analyzed in terms of spherical equivalent, cylinder and its orientation, and potential cases of development of high myopia or amblyopia. Hyperopia predominates in the early years, but the number of myopic subjects is higher than that of hyperopic subjects from the age of ten onwards. At all ages, the predominant orientation of astigmatism was with-the-rule. On average, 80% of the myopic subjects were uncorrected. Potential high myopia increased with age, from 4 to 21% of the measured population. Potential amblyopia cases decreased across age groups, from 19 to 13.7%. There is a need to raise awareness of the importance of vision screening at school age to address vision problems.

Visual performance with multifocal lenses in young adults and presbyopes.

A better understanding of visual performance with Multifocal Contact Lenses (MCLs) is essential, both in young eyes, where MCLs may be prescribed to control the progression of myopia wherein the MCLs optics interact with accommodation, and in presbyopes, where MCLs are increasingly used to compensate the lack of accommodation. In this study, we evaluated the through focus visual acuity (TFVA) with center-near MCLs of three additions (low, medium and high) and without an addition (NoLens) in 10 young adults and 5 presbyopes. We studied the effect of accommodation, age and pupil diameter (in cyclopleged subjects) on visual performance. The MCLs produced a small but consistent degradation at far (by 0.925 logMAR, averaged across eyes and conditions) and a consistent benefit at near in young subjects with paralyzed accommodation (by 1.025 logMAR), and in presbyopes with both paralyzed and natural accommodation (by 1.071 logMAR, on average). TFVA in young adults with NoLens and all MCLs showed statistically significant differences (Wilcoxan, p<0.01) between natural and paralyzed accommodation, but not in presbyopes with MCLs. In young adults, VA improved with increasing pupil diameter with the HighAdd MCL (0.08 logMAR shift from 3 to 5-mm pupil size). Visual imbalance (standard deviation of VA across distances) was reduced with MCLs, and decreased significantly with increasing near add. The lowest imbalance occurred in young adults under natural accommodation and was further reduced by 13.33% with MCLs with respect to the NoLens condition. Overall, the visual performance with MCLs in young adults exceeds that in presbyopes at all distances, and was better than 0.00 logMAR over the dioptric range tested. In conclusion, the center-near lenses do not degrade the near high contrast visual acuity significantly but maintains the far vision in young adults, and produce some visual benefit at near in presbyopes.

Matching convolved images to optically blurred images on the retina.

Convolved images are often used to simulate the effect of ocular aberrations on image quality, where the retinal image is simulated by convolving the stimulus with the point spread function derived from the subject's aberrations. However, some studies have shown that convolved images are perceived far more degraded than the same image blurred with optical defocus. We hypothesized that the positive interactions between the monochromatic and chromatic aberrations in the eye are lost in the convolution process. To test this hypothesis, we evaluated optical and visual quality with natural optics and with convolved images (on-bench, computer simulations, and visual acuity [VA] in subjects) using a polychromatic adaptive optics system with monochromatic (555 nm) and polychromatic light (WL) illumination. The subject's aberrations were measured using a Hartmann Shack system and were used to convolve the visual stimuli, using Fourier optics. The convolved images were seen through corrected optics. VA with convolved stimuli was lower than VA through natural aberrations, particularly in WL (by 26% in WL). Our results suggest that the systematic decrease in visual performance with visual acuity and retinal image quality by simulation with convolved stimuli appears to be primarily associated with a lack of favorable interaction between chromatic and monochromatic aberrations in the eye.

Evaluating the effect of ocular aberrations on the simulated performance of a new refractive IOL design using adaptive optics.

Adaptive optics (AO) visual simulators are excellent platforms for non-invasive simulation visual performance with new intraocular lens (IOL) designs, in combination with a subject own ocular aberrations and brain. We measured the through focus visual acuity in subjects through a new refractive IOL physically inserted in a cuvette and projected onto the eye's pupil, while aberrations were manipulated (corrected, or positive/negative spherical aberration added) using a deformable mirror (DM) in a custom-developed AO simulator. The IOL increased depth-of-focus (DOF) to 1.53 ± 0.21D, while maintaining high Visual Acuity (VA, -0.07 ± 0.05), averaged across subjects and conditions. Modifying the aberrations did not alter IOL performance on average.

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).

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.

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.

Interaction of Monochromatic and Chromatic Aberrations in Pseudophakic Patients.

PURPOSE: To measure monochromatic aberrations at various wavelengths in eyes implanted with the Clareon monofocal aspheric intraocular lens (IOL) (Alcon Laboratories, Inc., Fort Worth, TX). The authors estimated longitudinal chromatic aberration (LCA), modulation transfer functions (MTFs), and the impact of interactions between chromatic and monochromatic aberrations on retinal image quality. METHODS: Ten patients (age: 68.4 ± 3.21 years) were measured in two experiments: (1) Hartmann-Shack wave aberrations at five visible wavelengths (480 to 700 nm) and (2) best subjective focus at each wavelength. Objective and psychophysical LCAs were obtained from the Zernike defocus and psychophysical best focus, respectively. MTFs were calculated for the closest wavelengths to the peak sensitivity of the three cone classes (S [480 nm], M [555 nm], and L [564 nm]) using the measured aberrations and chromatic difference of focus. The degradation produced by LCA was estimated as the visual Strehl ratio for green divided by the visual Strehl ratio for blue and red. RESULTS: The root mean square for higher order aberrations (HOAs) ranged from 0.0622 to 0.2084 µm (700 nm, 4.3-mm pupil). Monochromatic visual Strehl ratio was above 0.35 in all patients. LCA was 1.23 ± 0.05 diopters (D) (psychophysical) and 0.90 ± 0.11 D (objective). Visual Strehl ratio decreased by a factor ranging from 1.38 to 3.82 on chromatic defocus from green to blue. There was a significant correlation between native visual Strehl ratio and the degradation produced by LCA (ie, visual Strehl555/visual Strehl480). CONCLUSIONS: The Clareon IOL compensates for spherical aberration, with postoperative wave aberrations dominated by astigmatism and other HOAs, being highly subject-dependent. The impact of LCA in blue is largely dependent on the magnitude of monochromatic aberrations. [J Refract Surg. 2020;36(4):230-238.].

VioBio lab adaptive optics: technology and applications by women vision scientists.

PURPOSE: Adaptive Optics allows measurement and manipulation of the optical aberrations of the eye. We review two Adaptive Optics set-ups implemented at the Visual Optics and Biophotonics Laboratory, and present examples of their use in better understanding of the role of optical aberrations on visual perception, in normal and treated eyes. RECENT FINDINGS: Two systems (AOI and AOII) are described that measure ocular aberrations with a Hartmann-Shack wavefront sensor, which operates in closed-loop with an electromagnetic deformable mirror, and visual stimuli are projected in a visual display for psychophysical measurements. AOI operates in infrared radiation (IR) light. AOII is provided with a supercontiniuum laser source (IR and visible wavelengths), additional elements for simulation (spatial light modulator, temporal multiplexing with optotunable lenses, phase plates, cuvette for intraocular lenses-IOLs), and a double-pass retinal camera. We review several studies undertaken with these AO systems, including the evaluation of the visual benefits of AO correction, vision with simulated multifocal IOLs (MIOLs), optical aberrations in pseudophakic eyes, chromatic aberrations and their visual impact, and neural adaptation to ocular aberrations. SUMMARY: Monochromatic and chromatic aberrations have been measured in normal and treated eyes. AO systems have allowed understanding the visual benefit of correcting aberrations in normal eyes and the adaptation of the visual system to the eye's native aberrations. Ocular corrections such as intraocular and contact lenses modify the wave aberrations. AO systems allow simulating vision with these corrections before they are implanted/fitted in the eye, or even before they are manufactured, revealing great potential for industry and the clinical practice. This review paper is part of a special issue of Ophthalmic & Physiological Optics on women in visual optics, and is co-authored by all women scientists of the research team.

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.

Visual simulators replicate vision with multifocal lenses.

Adaptive optics (AO) visual simulators based on deformable mirrors, spatial light modulators or optotunable lenses are increasingly used to simulate vision through different multifocal lens designs. However, the correspondence of this simulation with that obtained through real intraocular lenses (IOLs) tested on the same eyes has not been, to our knowledge, demonstrated. We compare through-focus (TF) optical and visual quality produced by real multifocal IOLs (M-IOLs) -bifocal refractive and trifocal diffractive- projected on the subiect's eye with those same designs simulated with a spatial light modulator (SLM) or an optotunable lens working in temporal multiplexing mode (SimVis technology). Measurements were performed on 7 cyclopleged subjects using a custom-made multichannel 3-active-optical-elements polychromatic AO Visual Simulator in monochromatic light. The same system was used to demonstrate performance of the real IOLs, SLM and SimVis technology simulations on bench using double-pass imaging on an artificial eye. Results show a general good correspondence between the TF performance with the real and simulated M-IOLs, both optically (on bench) and visually (measured visual acuity in patients). We demonstrate that visual simulations in an AO environment capture to a large extent the individual optical and visual performance obtained with real M-IOLs, both in absolute values and in the shape of through-focus curves.

Tunable lenses: dynamic characterization and fine-tuned control for high-speed applications.

Tunable lenses are becoming ubiquitous, in applications including microscopy, optical coherence tomography, computer vision, quality control, and presbyopic corrections. Many applications require an accurate control of the optical power of the lens in response to a time-dependent input waveform. We present a fast focimeter (3.8 KHz) to characterize the dynamic response of tunable lenses, which was demonstrated on different lens models. We found that the temporal response is repetitive and linear, which allowed the development of a robust compensation strategy based on the optimization of the input wave, using a linear time-invariant model. To our knowledge, this work presents the first procedure for a direct characterization of the transient response of tunable lenses and for compensation of their temporal distortions, and broadens the potential of tunable lenses also in high-speed applications.

Comparison of vision through surface modulated and spatial light modulated multifocal optics.

Spatial-light-modulators (SLM) are increasingly used as active elements in adaptive optics (AO) systems to simulate optical corrections, in particular multifocal presbyopic corrections. In this study, we compared vision with lathe-manufactured multi-zone (2-4) multifocal, angularly and radially, segmented surfaces and through the same corrections simulated with a SLM in a custom-developed two-active-element AO visual simulator. We found that perceived visual quality measured through real manufactured surfaces and SLM-simulated phase maps corresponded highly. Optical simulations predicted differences in perceived visual quality across different designs at Far distance, but showed some discrepancies at intermediate and near.