Visual Psychophysics / Physiological Optics - ARVO

ARVO 2013 Annual Meeting Abstracts by Scientific Section/Group – Visual Psychophysics / Physiological OpticsProgram Number: 4067Presentation Time: 9:30 AM - 9:45 AMComparability of Visual Performance of Individuals with LowVision in Real and Virtual Street IntersectionsLei Liu, Ellen L. Bowman. School of Optometry, University ofAlabama at Birmingham, Birmingham, AL.Purpose: Low Vision Orientation & Mobility (O&M) evaluation andtraining are typically performed in streets and street intersections.While effective, the efficiency of the practice can be greatlyimproved by employing computer-generated virtual street scenarios.To evaluate the feasibility of virtual O&M training, we comparedvisual performance of low vision patients in real and virtual streetintersections.Methods: A semi-CAVE virtual reality simulator was built. Itconsisted of a game computer, 3 digital projectors, three 2.4x1.9 mscreens (>180 o deg horizontal) and surrounding sound. Four virtualstreet intersections were built based on 4 real intersections in anurban environment. Google Street, Geographic Information Systemand on-site photos/videos were used to match the physical layout andsurrounding, traffic controls, and vehicle and pedestrian traffic of thereal and virtual intersections. Multiple crossing scenarios were set ateach intersection. Ten legally blind subjects with adequate priorO&M training performed 10 visual tasks in both real and virtualintersections. These tasks included identifying traffic elements,determining intersection layout and choosing the safest time to cross.The performance was rated pass or fail by two certified O&Mspecialists. Agreement between performance in corresponding realand virtual intersections was compared.Results: Data from corresponding real and virtual intersections wasorganized into a 2x2 contingency table. The overall, positive andnegative agreements were 83.3%, 89.4% and 68.6%, respectively,indicating that if a subject could perform a task in a real intersection,it was highly likely that she could also perform the same task in avirtual version of the intersection, and vice versa. The kappacoefficient was 0.59, bordering moderate and substantial agreement.A McNemar analysis of paired binary data showed an exactsignificance of 0.824, indicating no difference in performancebetween real and virtual intersections.Conclusions: Persons with low vision exhibited similar abilitieswhile performing visual tasks in real and virtual street intersections.The agreement suggested that computer-generated traffic scenesprovided sufficient visual and auditory information for low visionpatients to perform O&M tasks. Virtual reality has the potential tobecome a useful supplement to tradition low vision rehabilitationtraining.Commercial Relationships: Lei Liu, None; Ellen L. Bowman,NoneSupport: NIH Grant 1R21EY0195491.5s in random order, through adaptive optics to correct theaberrations of the eye. The PSV images (50/50 energy content) wereobtained from the combination of a focused image superimposed to adefocused version of the same image. At least 18 defocus conditions(0-3D) were subjectively ranked (10 repetitions). In addition, opticalquality was evaluated as a function of defocus, from the PSV and PDPoint Spread Functions (PSF), using the Modulation TransferFunction (MTF) at different frequencies as a metric.Results: As expected, images without defocus were perceived assharp (score s=5) in all subjects and conditions. The perceptualweighted rank systematically dropped for PD at a rate of 9.0±4.0 s/D,with the images perceived as completely blurred (s=0) from 0.6 Donwards. PSV images provided a similar decrease as their defocuscomponent increased, in the 0-0.3D range. However, in 3 subjects thescore reached a minimum at 0.5D (s=2.1±0.4) and then it waspartially recovered back towards sharpness (s=3.5 at 1.2D),remaining stable afterwards. The 4th subject showed a similar trendjudging PSV images but without a minimum. The objectivesimulations predicted the perceptual judgment trends, as well as thedifferences between judgments of PD and PSV images. MTF@20c/deg decreased sharply with defocus in PD, but reached a minimum(0.42 at 0.5 D) and recovered a stable level (0.50 from 1.5D) in PSV.Averaged MTFs (15-25 c/deg) provided the most accuratepredictions.Conclusions: As opposed to the common idea that simultaneousvision retinal images (as those found in multifocal contact orintraocular lenses) are severely optically degraded, but later restoredin neural processes, we have found a good correspondence betweenpure subjective perception experiments and pure optical simulations.Although our findings do not preclude for possible effects of neuraladaptation, neural effects seem to be secondary in the perceptualjudgment of sharpness in PSV.Program Number: 4068Presentation Time: 9:45 AM - 10:00 AMOptical quality and subjective judgments of blur under puresimultaneous visionCarlos Dorronsoro, Aiswaryah Radhakrishnan, Lucie Sawides,Susana Marcos. Instituto de Optica, CSIC, Madrid, Spain.Purpose: To compare retinal image quality and subjective imagesharpness under pure bifocal simultaneous vision (PSV) across awide range of addition values.Methods: Four subjects performed a weighted rank psychophysicalexperiment to grade (from totally blurred to totally sharp, 0 to 5) theperceptual quality of PSV images. As a control condition, theperceptual quality of purely defocused (PD) images was alsoassessed. Computer generated images of a face were observed, forCommercial Relationships: Carlos Dorronsoro, EssilorInternational (F); Aiswaryah Radhakrishnan, None; LucieSawides, None; Susana Marcos, Essilor (F), PCT/ES2012/070185(P)Support: FIS2011-25637; ERC-2011-AdG-294099; EU Marie CurieFP7-PEOPLE-2010-ITN #26405©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. 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