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 filtered to simulate optical defocus or different axes of astigmatism, as well as to images that were isotropically blurred or sharpened by varying the slope of the amplitude spectrum. Adaptation to the different types of blur produced strong aftereffects that showed strong transfer across the eyes, as assessed both in a monocular adaptation task and in a contingent adaptation task in which the two eyes were simultaneously exposed to different blur levels. Selectivity for the adapting eye was thus generally weak. When one eye was exposed to a sharper image than the other, the aftereffects also tended to be 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 biased by the sharper of the two eyes' retinal images.