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Alexandre Reynaud, Robert Hess; Suppression causes a complete breakdown in contrast constancy in amblyopes. Journal of Vision 2016;16(12):434. doi: https://doi.org/10.1167/16.12.434.
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Amblyopic patients have a deficit in visual acuity and contrast sensitivity in their amblyopic eye as well as suppression of the amblyopic eye input under binocular viewing conditions. In this study we wanted to assess, in normals and amblyopes, the contribution of the two eyes' input under binocular and monocular viewing. For this purpose, using a suprathreshold contrast matching task in which the eyes were stimulated either simultaneously or successively, we measured the binocular balance across spatial frequency and compared it with the contrast threshold sensitivity ratio measured with the same stimuli in both controls and amblyopes. First, we observed that the binocular matching became more imbalanced at high spatial frequency for amblyopes compared with controls. Second, this imbalance did not depend on whether the stimuli were presented simultaneously or successively in the two groups. Finally, for both modes of presentation, the matching balance correlates well with the interocular threshold sensitivity. To conclude, the form of the perceived suprathreshold contrast imbalance as a function of spatial frequency can be solely explained by the interocular threshold sensitivity ratio in amblyopia. This suggests a complete breakdown of contrast constancy previously reported (Hess & Bradley, Nature, 1980) under purely monocular conditions, adding weight to the argument that the reduced sensitivity at and above threshold has a common cause, namely binocular suppression.
Meeting abstract presented at VSS 2016
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