Immediate cortical adaptation in visual and non-visual areas functions induced by monovision

Abstract

A common and often successful option to correct presbyopia with contact lenses (CLs) is monovision. This is an unbalanced correction across the two eyes where one eye is corrected for far vision and the other eye is corrected for near vision. Monovision is therefore a form of acquired anisometropia that causes a superimposition of an in-focus image with a blurred image. In spite of this visual anisometropia, monovision has been successfully used for many decades, however the brain mechanism supporting monovision is not well understood. The aim of this study was to measure the visual evoked potentials (VEPs) with a high-density electrode array (64-channel) in a group of presbyopes and to provide a detailed spatiotemporal analysis of the cortical activity after a short period of adaptation to monovision with contact lenses. When compared to a balanced eye near correction, monovision produced both a clear reduction of the earliest VEP components, the C1 and the N1, and an amplitude increase of the P1 and pP1. These results indicate that the unilateral blurring induced by wearing monovision CLs reduces feed-forward activity in primary visual area and feedback activity in extrastriate areas (C1 and N1 reduction). Interestingly, other brain activities in both extrastriate visual areas (the P1 component) and in the anterior insula (the pP1 component) seem to compensate this dysfunction, increasing their activity during monovision. These changes confirm the presence of fluid brain adaptation in visual and non-visual areas during monocular interferences.

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