Visual Psychophysics / Physiological Optics - ARVO

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ARVO 2013 Annual Meeting Abstracts by Scientific Section/Group – Visual Psychophysics / Physiological Opticsboth centrally and peripherally located stimuli using a standard 2-IFCtask.Results: We found a characteristic relationship that depended onmodulator disparity spatial frequency. At high modulator disparityspatial frequencies (>1 c/d), there is an optimal ratio of around 2.6,whereas at low modulator disparity spatial frequencies, there is anoptimal absolute carrier luminance spatial frequency (i.e., 3 c/d). Inthe periphery, vision is restricted to modulator disparity spatialfrequencies below 1 c/d and, as a consequence, follows the aboverule, there is an optimum absolute carrier luminance spatial frequencythat reduces in spatial frequency with increasing eccentricity.Conclusions: This finding is consistent with there being more thanone channel processing global stereo. This is subsequently confirmedusing a 2x2 AFC detection/discrimination paradigm. Furthermore,because of the different carrier/modulator relationships in central andperipheral vision, peripheral global stereo cannot be simply related tocentral global stereo by a scaling factor and thus cannot be simplydue to cortical magnification as previously proposed.Commercial Relationships: Robert F. Hess, None; Nirel Witz,NoneSupport: NSERC (#46528-11)Program Number: 2659Presentation Time: 8:45 AM - 9:00 AMEffect of inter-ocular differences in blur on spatial and stereoresolutionSowmya Ravikumar 1 , Bjorn Vlaskamp 2 , Martin S. Banks 1 . 1 VisionScience, University of California Berkeley, Berkeley, CA; 2 PhilipsResearch, Eindhoven, Netherlands.Purpose: Monovision—setting the refraction of one eye to adifferent value than the other—is a procedure for dealing withpresbyopia. The difference in refractions for the two eyes should bethe appropriate value for maximizing visual performance, but there islittle research on what the appropriate value is. We know that bothvisual acuity and stereoacuity worsen as blur increases. However,visual-acuity tasks can in principle be performed when one eye issuppressed, but stereo tasks cannot. Thus, visual acuity might belimited by image quality in the better eye while stereoacuity might belimited by the poorer eye. Some previous observations are consistentwith these expectations. Indeed, blur in one eye can be moredetrimental to stereoacuity than the same blur in both eyes (blurparadox).Methods: We compared visual acuity and stereoacuity in the sameobservers with the same blur manipulations. Stimuli were displayedbinocularly using a custom stereoscope. Accommodation wasparalyzed with cyclopentolate. An artificial pupil set the effectiveaperture to 4mm. Blur was introduced with ophthalmic lenses. Wemeasured visual acuity with a letter-identification task. We measuredstereoacuity using a random-dot stereogram that created sinusoidalcorrugations in depth oriented +/- 20 degrees about the horizontal;subjects indicated which of two corrugation orientations waspresented.Results: The results were consistent with our expectations. Forvarying amounts of blur in the two eyes, visual acuity closelyconformed to the better eye’s performance while stereoacuity waslargely limited by the worse eye’s blur. Monocular blur had almostno effect on visual acuity, with binocular visual acuity remainingclose to 20/20 with up to 1.5D blur in one eye. For the same amountof blur, stereoacuity decreased by a factor of almost two. When theblur was equal in the two eyes, stereoacuity was slightly better thanwhen the same blur was present in one eye only (e.g., In comparing1.5D in both eyes to 1.5D of blur in one eye only, in one subject,stereo-acuity was 1.98 cpd compared to 1.13 cpd and in anothersubject, stereoacuity was 1.54 cpd compared to 1.37 cpd).Conclusions: The results will help us design monovision protocols ina way that is the best compromise between visual acuity andstereoacuity for various viewing distances.Commercial Relationships: Sowmya Ravikumar, None; BjornVlaskamp, Philips (E); Martin S. Banks, NoneSupport: RO1-EY 12851 to MSBProgram Number: 2660Presentation Time: 9:00 AM - 9:15 AMBinocular combination of optically-induced asymmetricinterocular blurAixa Alarcon 1 , Len Zheleznyak 2, 1 , Martin S. Banks 3 , GeunyoungYoon 1, 2 . 1 Flaum Eye Institute, University of Rochester, Rochester,NY; 2 Institute of Optics, University of Rochester, Rochester, NY;3 Vision Science Program, University of California Berkeley,Berkeley, CA.Purpose: It has been reported that interocular mirror symmetry in theaberrations (or optical blur) is present in the normal population. Thegoal of this study was to investigate the effects of interoculardifferences of monocular blur orientation on binocular blurperception.Methods: Eight cyclopleged subjects were asked to binocularly viewa stimulus under 3 aberration conditions and to match the subjectiveblur by inducing defocus to an unaberrated stimulus in 0.05Dincrements. A binocular adaptive optics vision simulator was used tocorrect subjects’ native aberrations, induce the 3 aberrationconditions and to induce defocus for the blur matching task for a6mm pupil. A monochromatic (550nm) binary noise image withrandom edge orientation served as the stimulus. The aberrationconditions consisted of 0.5 and 1D astigmatism and 1μm coma. Theaberration orientation of the right eye was rotated 0 and 90 degrees(i.e. equivalent and orthogonal, respectively) in the case ofastigmatism and 0, 90 and 180 degrees in the case of coma while theleft eye’s aberration was held fixed at 0 degrees for all conditions. Inthe coma condition, right eye orientations of 0 and 180 degreescorrespond to a binocular mirror asymmetry and symmetry of blurorientation, respectively. Two subjects participated in the blurmatching experiment in the 0.5D astigmatism condition, and 8subjects participated in the remaining conditions.Results: Bilateral equivalent and orthogonal astigmatism of 0.5Dresulted in significantly different blur matches of 0.53±0.05 and0.36±0.09D, respectively (p
ARVO 2013 Annual Meeting Abstracts by Scientific Section/Group – Visual Psychophysics / Physiological OpticsProgram Number: 2661Presentation Time: 9:15 AM - 9:30 AMThe Effect of Unilateral Mean Luminance on BinocularCombination in normal and amblyopic visionChang-Bing Huang 1 , Jiawei Zhou 2 , Robert F. Hess 2 . 1 Key Laboratoryof Behavioral Science, Institute of Psychology, Chinese Academy ofSciences, Beijing, China; 2 Department of Ophthalmology, McGillVision Research, McGill University, Montreal, QC, Canada.Purpose: We investigated the role of interocular luminancedifference on supra-threshold binocular phase combination, fromwhich we wanted to derive the functional balance index between thetwo eyes, for both normals and amblyopes. We also attempted todetermine whether we can artificially simulate “amblyopic”behaviour in normal subjects and recover “normal” response patternin amblyopic subjects by inducing luminance difference in the twoeyes, and to understand the theoretical basis of such effects.Methods: Using a binocular combination paradigm developed by J.Ding and G. Sperling (2006) and neutral density (ND) filters ofvaried intensities, the effect of unilateral mean luminance onbinocular combination in 3 normal and 4 amblyopic observers werequantified.Results: In normal observers, attenuation of one eye’s stimulusluminance with ND filters produces binocular combination similar tothose of amblyopic subjects. Correspondingly, in amblyopicobservers, reduction of the fellow eye’s stimulus luminance producesbinocular combination similar to those of normal subjects. Theseresults can be well explained by a modified contrast gain-controlmodel, which suggests that decreasing the mean luminance in oneeye reduces the efficiency of gain-control from that eye to the othereye, thus lower its contribution in binocular combination.Conclusions: Our manipulation of interocular luminance differenceprovides a simple and effective way to modulate interocularimbalances in amblyopia by reducing the effectiveness of the signaloriginating from the fellow fixing eye, which might bear upon anyfuture binocular treatment of amblyopia.Commercial Relationships: Chang-Bing Huang, None; JiaweiZhou, None; Robert F. Hess, NoneSupport: CIHR (# MOP53346) to RFH, and the KnowledgeInnovation Program of the Chinese Academy of Sciences, Institute ofPsychology (Grant No. Y1CX201006 to CBH)Program Number: 2662Presentation Time: 9:30 AM - 9:45 AMThe Contribution of Perspective, Blur and Disparity to DepthPerception in Natural VisionGuido Maiello 1, 2 , Manuela Chessa 2 , Fabio Solari 2 , Peter Bex 1 .1 Department of Ophthalmology, Harvard Medical School, Boston,MA; 2 Department of Informatics, Bioengineering, Robotics andSystem Engineering, University of Genoa, Genoa, Italy.Purpose: Natural scenes contain multiple sources of depthinformation. However, the relative contribution of these alternativecues is not well understood under natural conditions. When thesecues are not accurately simulated in computer generated 3dimensional scenes, observers can experience visual fatigue, nauseaand diplopia. We examine depth perception in real images withnatural variation in perspective, blur and binocular disparity.Methods: Image patches subtending 8 degrees of visual angle wereextracted from light field photographs of natural scenes taken with aLytro camera that simultaneously captures up to 12 focal planes.When accommodation at any given plane was simulated, the correctdefocus blur and stereoscopic disparity at other depth planes wasextracted from the stack of focal plane images. Depth informationfrom geometric cues, relative blur and stereoscopic disparity wereindependently introduced into depth images. In a 2AFC paradigmwith feedback, four observers identified the closer of two stimulipresented concurrently.Results: Depth discrimination thresholds were lowest whengeometric and stereoscopic disparity cues were both present. Depthorder discrimination was not possible with defocus blur alone and theaddition of blur cues impaired geometric thresholds by reducing thecontrast of geometric information at high spatial frequencies. Whenblur cues were introduced along with geometric and disparity cues,they did not noticeably impair thresholds, and appeared tocompensate the perceptual bias towards the far plane previouslyinduced by disparity.Conclusions: Light field photographs are a useful tool to quantifyhow naturally-occurring cues contribute to depth perception. Correctdefocus blur diminishes visual fatigue while viewing stereoscopicstimuli (Hoffman, et al (2008) JoV 8(3), 33,1-33,30) and shouldtherefore not be discarded in 3D images. Here we show that defocuscues alone impair fine depth perception near the plane of fixation, butmight be beneficial if used in conjunction with stereoscopic disparity.Commercial Relationships: Guido Maiello, None; ManuelaChessa, None; Fabio Solari, None; Peter Bex, Adaptive SensoryTechnology, LLC (S), Rapid Assessment of Visual Sensitivity (P)Support: NIH Grant R01EY019281Program Number: 2663Presentation Time: 9:45 AM - 10:00 AMRapid assessment of core visual deficits in amblyopiaMiYoung Kwon 1 , Luis A. Lesmes 1 , Alexandra Miller 1 , MelanieKazlas 2 , Michael Dorr 1 , David G. Hunter 2, 1 , Zhong-Lin Lu 3 , PeterBex 1 . 1 Ophthalmology, Harvard Medical School, Boston, MA;2 Ophthalmology, Boston Children’s Hospital, Boston, MA;3 Psychology, Ohio State University, Columbus, OH.Purpose: Amblyopia is the most common cause of monocular visualloss in children, affecting approximately 3-5% of the population.Although amblyopia is associated with a wide range of visual deficitsthat include reduced visual acuity, loss of contrast sensitivity, spatialdistortion, and abnormal binocular interaction, outcomes foramblyopia treatment currently monitor only visual acuity. A majorobstacle to broad characterization of the deficits has been inefficiencyof psychophysical assessments such as long testing time. The presentstudy aims to develop novel methods for rapidly assessing correlationamong these core deficits in amblyopic vision.Methods: Contrast sensitivity, spatial distortion and binocularinteraction were assessed in subjects with strabismic amblyopia (5-46-yr-old; mean age =14.38 yrs; n=8), strabismus without amblyopia(6-84-yr-old; mean age =34.4 yrs; n=15) and normal vision (5-32-yrold;mean age =18.71 yrs; n=24). The contrast sensitivity function(CSF) was estimated in less than 30 trials with the quick CSF method(Lesmes et al., 2010) on a handheld device (iPad). Local and globalspatial distortion was measured with a dichoptic pointing task(Mcilreavy et al., 2010) in which subjects aligned a target dotpresented to their amblyopic eye with a cross-hair presented to theirfellow eye. Binocular interaction was measured with a dichopticmatching task (Ding & Sperling, 2006) in which subjects matched thephase of a binocular probe to the cyclopean percept of a dichopticpair of gratings whose ratios were systematically varied. Testing wasperformed in an ophthalmology clinic with a total testing time ofapproximately 20 minutes.Results: Compared to subjects with normal vision or strabismuswithout amblyopia, subjects with amblyopia had significantlyreduced contrast sensitivity (F(2,35) = 4.7, p = 0.015), significantlylarger spatial distortion (F(2,37) = 4.8, p = 0.014) and decreasedinterocular contrast summation.©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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