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Ramkumar Sabesan, Geunyoung Yoon; Neural compensation to asymmetric optical blur to enhance visual performance in keratoconic eyes. Journal of Vision 2008;8(17):78. doi: https://doi.org/10.1167/8.17.78.
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Spatial vision is governed by both ocular aberrations and neural factors. Adaptive optics (AO) facilitates investigation of the neural factors affecting visual performance in isolation by eliminating optical aberrations almost perfectly. In our previous study, we observed poorer visual performance in highly aberrated keratoconic (KC) eyes compared to normals1 after correcting optical aberrations using AO. In the absence of optical imperfections, the poorer visual performance in KC eyes might be attributed to a neural insensitivity arising from chronic exposure to asymmetric optical blur. In this study, we tested the hypothesis that long-term visual experience with irregular optical blur might lead to enhanced visual performance in KC eyes. High contrast tumbling E visual acuity (HCVA) was measured in 2 KC eyes, wearing their prescription soft contact lenses, and 3 normal eyes viewing through each of the 2 KC eye's aberrations. The KC eyes had 4.5 times more optical aberrations than normal eyes on average over a 6-mm pupil with their corrective optics. KC eye's aberrations were induced and maintained dynamically with closed-loop AO during vision testing in normal eyes, with root-mean-square error of around 0.1 µm for a 6-mm pupil. Both KC eyes demonstrated better visual performance than normals. HCVA in logMAR for KC#1 and normals was 0.02 ±0.01 and 0.25 ±0.04, respectively, over a 6-mm pupil and was statistically different (p=1.5e-6). A similar result was obtained for KC#2 also. This might suggest that the neural visual system compensates for asymmetrically blurred retinal image quality to enhance visual performance in KC eyes
SabesanR.YoonG. (2008). Short-Term Visual Benefit of Correcting Higher Order Aberrations in Keratoconic Eyes. Invest Ophthalmol Vis Sci., 49, ARVO E-Abstract 2842.
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