Perceived blur and higher-order aberrations

Abstract

Several studies have demonstrated short- and long-term aftereffects in the perception of blur after adaptation to sharpened or blurred images, either optically or by computational filtering. Moreover, Adaptive Optics (AO) has proved to be an effective tool for testing visual perception under controlled ocular aberrations.

A series of psychophysical experiments were performed to (1) explore short-term adaptation to the blur produced by high order aberrations (HOA) from real patients (and scaled versions) by measuring the shift of the best-perceived focus following adaptation to those different levels of blur; (2) investigate whether subjects are naturally adapted to the level of blur produced by their HOA and (3) extract the orientation features of the internally coded blur, by searching the oriented blur producing best perceived image quality in each subject using a “Classification Image” inspired method. To guarantee that all subjects were exposed to a controlled blur, images were projected through a custom AO system combined with a psychophysical channel. All measurements were performed under AO-corrected aberrations, and the projected images blurred by convolution with known aberrations.

The shifts in the best-perceived focus following adaptation to scaled HOA are proportional to the amount of blur in the adapting image. The results strongly suggest that vision is adapted to the overall amount of blur produced by the ocular high order aberrations of an individual's eye and that calibration mechanisms for normalizing blur also operate using orientation cues.