Visual Psychophysics / Physiological Optics - ARVO

ARVO 2013 Annual Meeting Abstracts by Scientific Section/Group – Visual Psychophysics / Physiological Opticsrange. The Farnsworth dichotomous test D-15 was taken twice foreach subject with 6 minutes in range.Results: 12.79% of subjects have color vision defect, 5 Males (8.7%)have Protan and 2 Females (3.5%) have Protan during the first test ofFarnsworth D-15; but only 2 Males (3.5%) have Protan during theretest of Farnsworth D-15.Conclusions: The prevalence of color vision defect among dentalpractitioners in this study is higher than the prevalence in a previousstudy (12.3% of 160 subjects). Color vision test should be applied todental practitioners in order to avoid any defect for shade matching ofteeth.Commercial Relationships: Hani Alarify, None; Nasser Aldossari,None; Ahmed Alharbi, None; Ali Masmali, None; TurkiAlmubrad, NoneProgram Number: 3021 Poster Board Number: C0184Presentation Time: 8:30 AM - 10:15 AMDependence of the color brown on the spatial configuration ofhigh luminance surroundsTanner DeLawyer, Ariel Frederick, Simon Kaplan, Tracy Lin, SophieShonka, Steven L. Buck. Psychology, University of Washington,Seattle, WA.Purpose: The same long-wavelength stimuli look brown when dimand yellow-orange when bright, relative to surrounding stimuli.Earlier research showed that the stimuli directly surrounding a brownstimulus were most important in the perception of brown. Weconfirmed these earlier results quantitatively and then tested thedependence of brown on brighter surrounding stimuli by varyingtheir spatial configuration, to assess necessary and sufficientconditions for perceiving brown.Methods: Observers, under room-light adaptation, adjusted theluminance of a constant-chromaticity 4°-diameter foveal test stimulusto set both upper and lower luminance thresholds for perceivingbrown under the four possible combinations of white and black near(4°x6° annulus) and far (6° and beyond) surrounds. The test stimulusappeared yellow-orange when at a high luminance and brown at alow luminance.Observers also completed a set of trials with an otherwise identical1°, 2°, 3°, 4°, 5°, 6°, or 7°-diameter foveal test stimulus with a 2°, 4°,6°, and 8° white near surround and black far surround.Results: Our results for the different combinations of near and farsurrounds indicated that the perception of brown occurred atsignificantly higher luminance thresholds in the presence of a whitenear surround regardless of far surround luminance. Subjects couldnot perceive brown with a black near and far surround.In our spatial configuration conditions we found a general trend thatas the size of the test stimulus increased, subjects had to adjust tolower luminance values in order to perceive brown. The size of theannulus did not have a significant effect on the subjects’ perceptionof brown.Conclusions: Our replication of earlier results establishedquantitative light levels that are necessary for the perception of brownunder normal lighting conditions both with and without the presenceof a high luminance near surround.Spatial results appear to indicate that as an object covers areas of theretina outside of the fovea the perception of brownness begins tofade, requiring a higher luminance contrast in order to perceive theobject as being brown. This agrees with observation that it is difficultto perceive a stimulus as brown when it is viewed extra-foveally evenin the presence of a high luminance surround. This suggests theneural mechanisms for perceiving a brown object are highlydependent on foveal input.Commercial Relationships: Tanner DeLawyer, None; ArielFrederick, None; Simon Kaplan, None; Tracy Lin, None; SophieShonka, None; Steven L. Buck, NoneProgram Number: 3022 Poster Board Number: C0185Presentation Time: 8:30 AM - 10:15 AMFrequency of atypical genotypes associated with normal anddefective color visionCandice Davidoff, Jay Neitz, Maureen Neitz. Ophthalmology,University of Washington, Seattle, WA.Purpose: The majority of red-green color vision deficiencies resultfrom gene rearrangements that cause the loss of normal L or M opsinexpression. This can be due to deletion of an L or M gene or insertionof an extra L gene between the normal L and M genes, displacing theM gene to a non-expressed position. Thus, characterizing the numberof L and M genes is a good predictor of the presence and type ofcongenital red-green color vision defects. However, two atypicaltypes of mutations, missense mutations and extra L opsin genesdownstream of the expressed positions, would result in misdiagnosesbased on L and M gene stoichiometry. This study aims to estimatethe frequency of these types of mutations in the population.Methods: For 803 males unselected for color vision deficiencies,PCR was performed to selectively amplify L or M opsin genes. Fromthese products exons 3 and 4 were sequenced. The number and typeof opsin genes on the X-chromosome were determined by SNPanalysis using Sequenom's MassARRAY system. For samples foundto have extra L genes, long range PCR was performed to amplify themost downstream gene and verify whether it encoded an L or Mopsin. For samples with missense mutations, parts of the last genewere sequenced to determine if the mutation was in a gene in anexpressed position.Results: 3 missense mutations were identified in L opsin genes:R151T, V171L and V232L. 8 mutations were found in M opsingenes: six C203R, one R163I and one synonymous mutation. NoC203R mutation was observed in any L opsin gene. 74 samples werefound to have extra L genes. Of these 25 were confirmed to have theextra L in an expressed position, 20 were confirmed to have L genesat the end of the array and thus are likely to have normal color vision,and 29 had arrays too long to determine the position of the extra Lgene.Conclusions: C203R mutations are unlikely to cause protan defects.Missense mutations that may cause protan defects were present in0.37% of the sample and those that may cause deutan defects weredetected in 1%. 9% of men in this sample have more than one L gene.Of those, at least a quarter had the genetic basis for normal colorvision despite the presence of an extra L gene. 3.1% of men could beconfirmed to have an L gene in the second position and are presumedto have deuteranomaly and another 3.6% may be deuteranomalousdepending on the location of the extra L gene(s) in arrays with > 3genes.Commercial Relationships: Candice Davidoff, None; Jay Neitz,Alcon (F), Alcon (P); Maureen Neitz, Genzyme (F), Alcon (F),Alcon (P)Program Number: 3023 Poster Board Number: C0186Presentation Time: 8:30 AM - 10:15 AMRod Hue Biases for Foveal Stimuli on CRT DisplaysKatharina G. Foote, Steven L. Buck. Psychology, University ofWashington, Seattle, WA.Purpose: Signals from rod photoreceptors bias (shift) the huesdetermined by cone photoreceptors for extrafoveal mesopic stimuli -creating green, blue, and red rod hue biases at long, middle, and shortwavelengths, respectively. The fovea contains far fewer rods and S©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.