Abstract
In everyday life, the brain deals with various visual impairments, including astigmatism, which damages the perception of a particular orientation due to its meridian-specific blurring characteristics. We tend to suffer less from the optical distortion after being exposed to astigmatism chronically, but little is known about the neural mechanisms. Therefore, the current study investigated how the brain recovered orientation information from distorted retinal input under astigmatism. We asked participants with normal vision to report the perceived orientation of the briefly presented tilted Gabor stimuli when astigmatism was transiently induced. In comparison, the participants with chronic astigmatism performed the identical task with their astigmatism. Then, we estimated the neural orientation tuning responses from the simultaneously recorded EEG activity across the two groups of people. Under the induced astigmatism, orientation tuning responses were severely skewed according to the meridian-specific astigmatic optical blur. In contrast, the skew of the neural orientation responses was far less severe under chronic astigmatism, even if the eye’s refractive errors were similar. When the eye’s refractive error was fully corrected, participants with chronic astigmatism showed an inverse bias in orientation perception, suggesting sustained neural mechanisms that automatically compensate for the retinal distortion. Consistently, neural orientation responses were enhanced at the optically blurred axis but reduced at the orthogonal to the blurred axis after long-term exposure. This automatically counteracts to the distortion that weakens the orientation information at the blurred axis caused by astigmatism. Our computational model further confirmed that the amount of compensation in chronic astigmatism was well correlated with the push-pull gain modulation of neural orientation responses. Our novel evidence suggests the involvement of mechanical neural compensation counteracting orientation-specific retinal aberration in astigmatism, which provides a practical guide in clinical situations.