Visual Psychophysics / Physiological Optics - ARVO

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ARVO 2013 Annual Meeting Abstracts by Scientific Section/Group – Visual Psychophysics / Physiological OpticsCommercial Relationships: Yue Shi, None; Raymond A.Applegate, University of Houston (P); Ayeswarya Ravikumar,None; Harold E. Bedell, NoneSupport: NEI 5R01EY008520; NIH/NEI 5R01EY019105; NIH/NEIP30 EY 07551Program Number: 1280Presentation Time: 8:45 AM - 9:00 AMInfluence of aberration-induced blur on contrast sensitivity:comparison of different optotype sizesJens Buehren 1 , Hendrik Jungnickel 2, 3 , Wolfgang Raab 1 , DanielWeigel 3 , Michael Gebhardt 2 , Richard Kowarschik 3 , Thomas Kohnen 1 .1 Dept of Ophthalmology, Goethe University Frankfurt, Frankfurt amMain, Germany; 2 SciTec Department, Ernst Abbe University ofApplied Sciences, Jena, Germany; 3 Institute for Apllied Optics,Schiller University Jena, Jena, Germany.Purpose: To compare the decrease of contrast sensitivity (CS) due todefocus and higher-order aberration (HOA) blur measured withoptotypes of different size.Methods: Thirty-three emmetropic healty volunteers were included.In a first experiment (defocus blur), CS was measured in 31 eyes.Experimental fogging was performed with spherical trial lenses of 0,+0.25, +0.5 and +0.75 diopters (D). In a second experiment (HOAblur), CS was measured in 3 eyes at an adaptive optics (AO) visualsimulator. Besides the correction of lower-order aberrations (LOA)and full correction, subjects were presented 6 wavefront errors ofdifferent blur strength and characteristics (3 keratoconus eyes, 3 post-LASIK eyes). In total, 8 different wavefront errors with a VSOTF(visual Strehl ratio based on the optical transfer function) range of -0.05 to -1.70 log units were presented. In both experiments, CS wasmeasured with Landolt rings of 1.3 and 0.3 logMAR using FrACTsoftware. The impact of defocus blur (D) or HOA blur (VSOTF) onCS was assessed using linear regression analysis. The regressioncoefficient b and the coefficient of determination R 2 reflect thesensitivity of the CS contrast test to aberration-induced blur.Results: Experiment 1: Unfogged photopic CS was 1.93±0.06 logCS(1.3 logMAR) and 1.56±0.05 logCS (0.3 logMAR). Regressioncoefficients were higher for the 0.3 logMAR (b=-0.88, R 2 =0.70) thanfor the 1.3 logMAR Landolt ring (b=-0.39, R 2 =0.28). Experiment 2:CS was 1.98±0.17 (0.3 logMAR optotype: 0.95±0.14) log units withfull AO correction. Also in this experiment, CS was more sensitive tooptical blur if measured Landolt rings of 0.3 logMAR (b=0.63,R 2 =0.74) compared to those of 1.3 logMAR (b=0.34, R 2 =0.34).Conclusions: CS tests with large optotypes such as the Pelli-Robsontest may not pick up subtle, yet notable aberration-induced changes inretinal image quality. Therefore, for the assessment of effects ofoptical aberrations, CS testing should be performed at higher spatialfrequencies (e.g., 0.3 logMAR Landolt ring).Commercial Relationships: Jens Buehren, None; HendrikJungnickel, None; Wolfgang Raab, None; Daniel Weigel, None;Michael Gebhardt, None; Richard Kowarschik, None; ThomasKohnen, NoneSupport: Federal Ministry for Education and Research (BMBF)01EZ0608Program Number: 1281Presentation Time: 9:00 AM - 9:15 AMVisual performance under natural, corrected and AdaptiveOptics induced astigmatism: meridional and adaptational effectsMaria Vinas 1 , Pablo De Gracia 1 , Carlos Dorronsoro 1 , LucieSawides 1 , Gildas Marin 2 , Martha Hernandez 2 , Susana Marcos 1 .1 Visual Optics & Biophotonics Lab, Instituto de Optica, CSIC,Madrid, Spain; 2 R&D, Vision Science Department, EssilorInternational, Saint-Maur, France.Purpose: To study the extent to what prior adaptation to astigmatismaffects visual performance, whether this effect is axis-dependent, andthe time-scale effect of potential changes in visual performance in thepresence of astigmatism following its correction. To study whetherthe effect of possible positive interactions of aberrations (astigmatism& coma) on visual performance might be altered after long-termadaptation to correction of astigmatism.Methods: Measurements of visual acuity (VA) were performedunder induction of astigmatism and a combination of astigmatism andcoma, while controlling the low and high order aberrations (HOA) ofthe subject with an Adaptive Optics (AO) system, in 25 subjectsclassified in 3 groups: non-astigmats, habitually-corrected anduncorrected astigmats. Astigmatism (1.00D) was induced at 3different orientations: at the natural axis, at the perpendicularorientation, and at 45deg for astigmats, and at 0, 90 and 45deg fornon-astigmats. Experiments were also performed with coma (0.41µmat a relative angle of 45deg) combined with the mentionedamount/orientations of astigmatism. VA was measured in a total of14 different conditions, using an 8-Alternative Forced Choice(8AFC) procedure with tumbling E letters and a QUEST algorithm.Uncorrected astigmats were provided with proper astigmaticcorrection immediately after the first session. Measurements wereperformed during 6 months following correction.Results: In non-astigmats, inducing astigmatism at 90deg, under fullAO correction, produced a statistically (p
ARVO 2013 Annual Meeting Abstracts by Scientific Section/Group – Visual Psychophysics / Physiological Opticsneural plasticity in these eyes, improving their visual benefit.Methods: A large-stroke AO vision simulator was employed to trainthe worse eye of 2 KC subjects in a contrast detection test undercomplete aberration correction with AO. Prior to training, visualacuity (VA) and contrast sensitivity (CS) at 4, 8, 12, 16, 20, 24 and28 c/deg were measured in both eyes of subjects with AO correctionfor a 6mm pupil. The spatial frequency requiring 50% contrast fordetection with AO correction was picked as the training frequency.Subjects were required to train on a contrast threshold task with AOcorrection for 1 hour each for 5 consecutive days. During eachtraining session, 800 trials of threshold CS measurement at thetraining frequency with AO were conducted. The same pre-trainingmeasurements were repeated after the 5 training sessions.Results: Optical quality with AO was confirmed to be similar preand post-training and across training sessions. After training, CS withAO improved by a factor of 1.91 (range: 1.77-2.04) and 1.75 (range:1.22-2.34) on average over spatial frequencies in the two subjects. Inboth subjects, the benefit in CS was measured across a broad range ofspatial frequencies, i.e. at frequencies lower and higher than the oneemployed during training. In both subjects, this perceptual learningeffect with gratings transferred to letter VA, improving it by 1.5 lines(0.04 to -0.1 logMAR) and 1.3 lines (-0.02 to -0.15 logMAR)respectively. Inter-ocular transfer of training was also observed. Theuntrained eye’s CS was improved by a factor of 1.57 on averageacross spatial frequencies and VA by 0.8 lines (-0.01 to -0.09logMAR) in one of the two subjects with AO.Conclusions: The improvements in visual performance after trainingwith AO denote an improvement in neural sensitivity. Perceptuallearning with AO thus has the potential to enhance neural function inabnormal corneal patients leading to improved visual benefit after acustomized correction.Commercial Relationships: Ramkumar Sabesan, None;Geunyoung Yoon, Bausch & Lomb (F), Johnson & Johnson (F),Allergan (C), Staar Surgical (C), CIBA Vision (F), Acufocus (C)Support: NIH/NEI grant RO1EY 014999, Research to PreventBlindnessProgram Number: 1283Presentation Time: 9:30 AM - 9:45 AMWhat is the smallest change in visual acuity that is correlatedwith a change in image quality?Ayeswarya Ravikumar, Jason D. Marsack, Yue Shi, Raymond A.Applegate. College of Optometry, University of Houston, Houston,TX.Purpose: The 95% confidence interval for logMAR acuity testing is~ ±5 letters (±1 line)[ Optom Vis Sci, 1998. 75(5): 342]. Metrics ofimage quality (IQ) can quantify 6 just noticeable differences in blurbefore 1 line of acuity is lost [J Cataract Refract Surg, 2011. 37(8):1523] and visual acuity (VA) is highly correlated (R 2 > 0.8) to changein metrics of image quality when inducing several lines of change inacuity. However, the correlation between acuity and metric values isnot known as the change in acuity approaches the test re-testreliability of acuity. The purpose here is to determine how thecoefficient of determination (R 2 ) between change in VA and changein IQ metric/s value changes as the range is decreased from 8 lines tothe test re-test reliability of acuity measurement (1 line).Methods: The Thibos virtual eye generator [Opththalmic Physiolopt, 2009;29(3):288-291] was used to generate 60 WFEs whose logvisual Strehl ratio varied between 0.0 and -1.8 in approximately equalsteps. For each of the 60 WFEs, three unique logMAR acuity chartswere generated (0.8 to -0.3 logMAR). For each chart, VA wasmeasured up to the 5th letter missed for each of 3 normal subjects.Change in visual acuity was linearly regressed against change in 29IQ metrics to determine the coefficient of determination when thechange in visual acuity was decreased in 1 line steps from 8 lines to 1line.Results: See Figure. Extrapolation from the fitted line shows that R 2goes to zero at ~3 letters (0.6 of a line), which is below the test retestreliability for acuity measurement (1 line). With a 2 line loss (or oneline above the 95% confidence level for the measurement of acuity),42% of the variance in acuity is accounted for by the metrics. Thefunction begins to asymptote between 4 and 5 lines, and littleimprovement in correlation is seen with additional lines of acuitychange.Conclusions: Image quality metrics can detect blur prior to an acuityloss (prior work), begin to be correlated with acuity below the re-testreliability for acuity testing and reach a maximum R 2 > 0.8. Thesetwo experimental observations suggest that IQ metrics can serve asan objective tool for evaluating and designing therapy intended toimprove visual performance, and that correlations are primarilylimited by the acuity task and not by the IQ metrics.Commercial Relationships: Ayeswarya Ravikumar, None; JasonD. Marsack, University of Houston (P); Yue Shi, None; RaymondA. Applegate, University of Houston (P)Support: R01 EY08520 (RAA), R01 EY019105 (RAA), P30 EY07551 (Core Grant), N0025910 P1354 (RAA)Program Number: 1284Presentation Time: 9:45 AM - 10:00 AMDetermination of Customized Aberration ThresholdsCarmen Canovas 1, 2 , Patricia A. Piers 1 , Silvestre Manzanera 2 ,Christina Schwarz 2 , Pedro M. Prieto 2 , Henk A. Weeber 1 , PabloArtal 2 . 1 R&D, AMO Groningen B.V., Groningen, Netherlands;2 Laboratorio de Optica, Unversidad de Murcia, Murcia, Spain.Purpose: Different aberration terms may have lower or higherimpact on vision. This could be used to optimize correctionstrategies. We studied the customized level of spherical aberration(SA) and vertical coma (VC) that can be induced while maintainingacceptable high contrast visual acuity (VA) and to then determinewhether these levels of aberration affect subjects’ through focusvision.Methods: An adaptive optics visual simulator (Fernández, et al. Opt.Lett. 2001) was used to correct individual aberrations up to the fifthorder and to induce a common higher order aberration baseline (0.15µm RMS for a 5mm pupil) corresponding to that of an averagepseudophakic eye, in five normal subjects. High contrast VA wasmeasured with SLOAN letters at the best focus position with a 4mmphysical pupil. Letter size was then increased to correspond to adecrease in VA by 0.1LogMAR. Thresholds for SA (positive andnegative) and positive VC were then subjectively determined by©2013, Copyright by the Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Go to iovs.org to access the version of record. For permissionto reproduce any abstract, contact the ARVO Office at arvo@arvo.org.
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