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Ramkumar Sabesan, Geunyoung Yoon; Perceptual learning after correcting the eye’s aberration with adaptive optics. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1282.
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© ARVO (1962-2015); The Authors (2016-present)
Highly aberrated keratoconic (KC) eyes do not elicit the maximum visual advantage immediately after a customized correction. This is attributed to the neural insensitivity arising from chronic visual experience with poor retinal image quality, dominated by low spatial frequencies. The goal of this study was to investigate if targeted perceptual learning with adaptive optics (AO) can stimulate neural plasticity in these eyes, improving their visual benefit.
A large-stroke AO vision simulator was employed to train the worse eye of 2 KC subjects in a contrast detection test under complete aberration correction with AO. Prior to training, visual acuity (VA) and contrast sensitivity (CS) at 4, 8, 12, 16, 20, 24 and 28 c/deg were measured in both eyes of subjects with AO correction for a 6mm pupil. The spatial frequency requiring 50% contrast for detection with AO correction was picked as the training frequency. Subjects were required to train on a contrast threshold task with AO correction for 1 hour each for 5 consecutive days. During each training session, 800 trials of threshold CS measurement at the training frequency with AO were conducted. The same pre-training measurements were repeated after the 5 training sessions.
Optical quality with AO was confirmed to be similar pre and post-training and across training sessions. After training, CS with AO improved by a factor of 1.91 (range: 1.77-2.04) and 1.75 (range: 1.22-2.34) on average over spatial frequencies in the two subjects. In both subjects, the benefit in CS was measured across a broad range of spatial frequencies, i.e. at frequencies lower and higher than the one employed during training. In both subjects, this perceptual learning effect with gratings transferred to letter VA, improving it by 1.5 lines (0.04 to -0.1 logMAR) and 1.3 lines (-0.02 to -0.15 logMAR) respectively. Inter-ocular transfer of training was also observed. The untrained eye’s CS was improved by a factor of 1.57 on average across spatial frequencies and VA by 0.8 lines (-0.01 to -0.09 logMAR) in one of the two subjects with AO.
The improvements in visual performance after training with AO denote an improvement in neural sensitivity. Perceptual learning with AO thus has the potential to enhance neural function in abnormal corneal patients leading to improved visual benefit after a customized correction.
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