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JM Renaud, C Habak, J Gresset, J Faubert; Effect of Target Size on Binocular Function in Age-Related Macular Degeneration . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3824.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Age-related macular degeneration (ARMD) induces asymmetrical function of the eyes. The purpose of this study was to assess the effect of target size on binocular function for static stimuli in older observers with and without ARMD. Previous studies (Faubert et al, ARVO, 2001; Faubert & Overbury, JAGS, 2000) have shown that some ARMD observers demonstrate binocular inhibition for contrast sensitivity. Binocular inhibition is defined as binocular performance being worse than the best monocular one. Methods: Thirteen older observers without ocular pathologies (ages 61-74) and twenty older observers with ARMD (ages 64-77) were tested. All observers were refracted for the viewing distance of 57 cm. Stimuli consisted of a red 0.5 cpd sine wave grating with a mean luminance of 9.5 cd/m2. Measures were made for three different grating dimensions: 5x5, 10x10 and 20x20 degrees, presented at fixation (central). Subjects were required to discriminate the orientation (vertical or horizontal) of the grating. Contrast thresholds (75% correct) were measured using a PEST procedure. Each condition was assessed binocularly and monocularly for each eye. Presentation time was 760 msec. Results: Observers (except for one) in the group without ocular pathologies showed binocular summation for all conditions, but the summation ratio was smaller for the largest stimulus size (20x20). Up to 50% of the ARMD observers showed binocular inhibition, the remainder showed either binocular summation or suppression. The percentage of ARMD observers demonstrating binocular inhibition decreased with increasing grating size. Conclusion: Some ARMD observers showed a pattern of binocular summation similar to that of older observers without ocular pathologies, whereas others showed binocular inhibition. An increase in target size affects binocular performance: the group without ocular pathologies showed less summation whereas the group of ARMD inhibitors showed less inhibition. Binocular inhibitors may benefit in using only one eye for small targets but using binocular vision does not seem detrimental when viewing large stimuli. CR: none. Support: MRC Grant MT-14777 to J.F.
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