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Jian Ding, Dennis Levi; Binocular asymmetry in amblyopia. Journal of Vision 2014;14(10):957. doi: https://doi.org/10.1167/14.10.957.
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© ARVO (1962-2015); The Authors (2016-present)
Humans with amblyopia have an asymmetry in binocular vision: neural signals from the amblyopic eye (AE) are suppressed in the cortex by the fellow eye (FE). In order to balance their binocular vision, the signal (contrast and/or luminance) from the FE must be reduced until the two eyes contributions to binocular summation become equal (Ding, Klein & Levi, 2013b JOV, Ding & Levi, 2014 OPO, In Press). We define the binocular asymmetry to be the interocular contrast ratio AE/FE that results in balanced binocular vision. We used phase and contrast matching tasks to measure the perceived phase and contrast of a cyclopean sinewave, and fit the DSKL model, a binocular-combination model modified from Ding and Sperling (2006), to both the contrast and phase data. The binocular asymmetry was calculated from the best fit model. We found that binocular asymmetry in amblyopia depends on base contrast, mean luminance, and spatial frequency; the higher the stimulus contrast, luminance or spatial frequency, the higher binocular asymmetry. At a given spatial frequency, the binocular asymmetry can be described by a log-linear formula with two parameters, one for the maximum asymmetry and one for the rate at which the binocular system becomes asymmetric as contrast increases. We found that reducing the FEs luminance with a neutral density (ND) filter reduces its suppression of the AE, shifting the asymmetric line in parallel towards the symmetric line (AE/FE=1), thereby rebalancing the asymmetric binocular vision. However, because the binocular asymmetry varies with contrast, luminance, and spatial frequency, it is difficult or even impossible to rebalance the asymmetry for all visual conditions using a fixed ND filter. Nonetheless, wearing an ND filter before the FE (or increasing the luminance in the AE) may be more beneficial than the traditional method of patching the FE for treating amblyopia.
Meeting abstract presented at VSS 2014
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