Automatic compensation enhances the orientation perception in chronic astigmatism

Abstract

Astigmatism is a prevalent optical problem in which two or more focal points blur the retinal image at a particular meridian. Although many features of astigmatic vision, including orientation perception, are impaired at the retinal image level, the visual system appears to partly restore perceptual impairment after an extended period of astigmatism. However, the mechanism of orientation perception restoration in chronic astigmatism has not yet been clarified. We investigated the notable reduction of perceptual error in chronic astigmatism by comparing the orientation perception of a chronic astigmatism group with the perception of a normal-vision group, in which astigmatism was transiently induced. We found that orientation perception in the chronic group was more accurate than in the normal vision group. Interestingly, the reduction of perceptual errors was automatic; it remained even after the optical refractive errors were fully corrected, and the orientation perception was much more stable across different orientations, despite the uneven noise levels of the retinal images across meridians. We provide here a mechanistic explanation for how the compensation of astigmatic orientation perception occurred, using neural adaptation to the biased distribution of orientations.

Assessment of a Clinical Test for Detection of Alteration in Visual Perception Due to Astigmatism

“…This may be due to the fact that the cohort of normal participants is not accustomed to blurred perception, as opposed to astigmatic and keratoconic participants who may experience blurred vision more frequently and who adapt to their residual uncorrected astigmatism. 31 , 32 …”

“…This may be due to the fact that the cohort of normal participants is not accustomed to blurred perception, as opposed to astigmatic and keratoconic participants who may experience blurred vision more frequently and who adapt to their residual uncorrected astigmatism. 31,32 This point could be addressed in a future experiment comparing the results of the test in two cohorts with similar magnitudes of astigmatism and with similar ocular wavefronts. The two cohorts being newly diagnosed vs long-standing astigmatism.…”