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Liu Zitian, Zidong Chen, Daming Deng, Minbin Yu; Refractive Adaptation Selectively Changes Magnocellular Pathway in Anisometropic Amblyopia. Invest. Ophthalmol. Vis. Sci. 2019;60(9):227.
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© ARVO (1962-2015); The Authors (2016-present)
Sustained refractive correction could improve visual function in anisometropic amblyopia, often referred to as refractive adaptation, but the underlying physiological changes in the central visual pathways is unknown. The purposes of this study were to characterize functional loss in magnocellular and parvocellular pathways and to assess the effect of refractive adaptation on the two pathways in patients with anisometropic amblyopia using visual-evoked potentials.
14 anisometropic amblyopes with a history of refractive correction, 19 ones without such a history and 14 normal controls participated in this study. Magnocellular and parvocellular visual function were assessed in each eye by recording steady-state visual-evoked potential responses to stimuli composed of isolated checks that sinusoidally modulated around standing contrast (pedestal) in 6 levels of depth of modulation. The pedestal was either equal to the DOM to favor magnocellular pathway or fixed at 48% Weber contrast to favor parvocellular pathway. Signal-to-noise at the stimulus frequency were derived from Fourier analysis, and the contrast-response functions were compared among these three groups.
In normal controls, the contrast response function for magnocellular-biased condition increased steeply at low contrast levels and saturated quickly, while that for parvocellular-biased condition increased linearly. All anisometropic amblyopes showed reduced SNR for both conditions in the amblyopic eyes, with decreased initial gain and lower maximal SNR for magnocellular pathway and lower slope for parvocellular pathway. When compared with uncorrected amblyopic eyes, corrected amblyopic eyes exhibited significantly stronger response in magnocellular-biased condition, with better initial gain and higher maximal SNR. However, this was not the case for parvocellular -biased condition. After fully refractive corrected for two months, the previously uncorrected amblyopes exhibited improved magnocellular signal rather than parvocellular, which further suggesting the selective effect of refractive adaptation on magnocellular pathway.
Anisometropic amblyopia produces deficits in both magnocellular and parvocellular pathways in the amblyopic eyes. Refractive adaptation may selectively change magnocellular pathway in anisometropic amblyopia rather than parvocellular pathway.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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