Adaptation to interocular differences in blur

Abstract

Adaptation to blurred or sharpened images alters the physical blur level that is perceived to be in focus. These adjustments can be selective for different aberrations of the eye's optics, and could play a role in compensating neural responses for retinal image blur. We asked how adaptation adjusts to differences in blur between the eyes, which can arise from interocular differences in refractive errors. Separate left and right eye images were shown in a fused 4-deg field on a monitor viewed through a stereoscope. The images consisted of Mondrians with edges sharpened or blurred by varying the slope of the amplitude spectrum, or noise filtered to simulate different axes and magnitudes of astigmatism with constant total blur. Observers adapted for 120 sec to a blurred or sharpened image presented to one eye, or to images with different blur in each eye, with stimuli spatially jittered to avoid local light adaptation. Interleaved 2AFC staircases were then used to estimate for each eye the slope that appeared best focused or the level of astigmatic blur that appeared isotropic. Adaptation to images filtered by varying the spectral slope showed almost complete transfer between the eyes, and when different stimuli were shown in the two eyes aftereffects were dominated by the sharper image. In contrast, astigmatic blur showed significant selectivity for the presented eye, and simultaneous opposite aftereffects could be induced in each eye when adapted to blur along orthogonal meridia. The differences in selectivity could depend on whether the form of blur maintained the same (isotropic slope changes) or different (astigmatic or oriented blur) contours in the two eyes' images. Our results suggest that adaptation could selectively adjust to some but not all refractive differences between the eyes, and that the adaptation may tend to be dominated by the sharper retinal image.

EY-10834.