Adaptation to Interocular Differences in Blur
Adaptation to a blurred image causes a physically focused image to appear too sharp, and shifts the point of subjective focus toward the adapting blur, consistent with a renormalization of perceived focus. We examined whether and how this adaptation normalizes to differences in blur between the two eyes, which can routinely arise from differences in refractive errors. Observers adapted to images that were isotropically blurred or sharpened by varying the slope of the amplitude spectrum, or to oriented blur in images filtered to simulate different levels and axes of astigmatism. Adaptation to both types of blur produced strong aftereffects that showed strong transfer across the eyes. Greater transfer was found for the isotropic blur than for the oriented blur, both in a monocular adaptation task and in a contingent adaptation task in which the two eyes were simultaneously exposed to different blur levels. These contingent aftereffects were more robust for the astigmatic blur. When one eye was exposed to a sharper image than the other, the aftereffects instead showed little interocular difference and were strongly dominated by the sharper image. Our results suggest that while short term adaptation can rapidly recalibrate the perception of blur, it cannot do so independently for the two eyes, and that the binocular adaptation of blur is determined largely by the sharper of the two eye's retinal images.
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