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Chang-Bing Huang, Jiawei Zhou, Yifeng Zhou, Zhong-Lin Lu; Temporal Dynamics of Binocular Rivalry in Normal and Amblyopic Vision. Journal of Vision 2011;11(11):406. doi: 10.1167/11.11.406.
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Although the fellow eye dominates strongly in unilateral amblyopia, how the two eyes interact in binocular vision is largely unknown. Here we investigated the relative contributions of the amblyopic and fellow eyes in a binocular rivalry paradigm. We presented two orthogonal gratings of identical spatial profiles to the two eyes dichoptically, one to the fellow eye at fixed base contrast levels and the other to the amblyopic eye with proportional contrasts, and measured the time-course of binocular rivalry. The same procedure was applied to normal subjects. Five adults with unilateral anisometropic amblyopia and four normals participated. The phase-duration distributions were fitted with gamma functions (Mamassian & Goutcher, 2005). For normal subjects, images in the two eyes fused 17% of the time; increasing contrast in the right eye increased its dominance duration and decreased that of the left eye. The two eyes had approximately equal dominance time when the gratings in the two eyes were of equal contrast. For amblyopes, images in the two eyes fused 27% of the time; the amblyopic eye dominated about 31% of the total rivalry time when the amblyopic/fellow-eye contrast ratio was 1.0, about 50% when it was 3.0, and 68% when it was 5.6. Gamma functions with a single shape parameter but different scale parameters provided excellent descriptions of the phase duration distributions within each group. The shape parameter in the amblyopic group was about half that of the normal group, indicating a less variable switching dynamics in amblyopic vision, although the scale parameters of the two groups were comparable. In summary, the amblyopic eye needed much higher contrast to become dominant, was fused more with the fellow eye, and had comparable alternation rate but with less variance in phase duration. Possible models with interocular inhibition and stochastic processes will be discussed.
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