Neural and Perceptual Adaptations in Bilateral Macular Degeneration: An Integrative Review.

Abstract

Bilateral age-related macular degeneration (AMD) results in central vision loss, affecting the fovea-associated cortical regions. This review examines neuroimaging and psychophysical evidence of spontaneous neural adaptation in acquired bilateral central scotoma. Early visual brain areas show reduced cortical thickness and axonal integrity due to postsynaptic (anterograde) degeneration. Contrary to animal models, evidence for spontaneous adaptation in the primary visual cortex (V1) is limited. Activity in the lesion projection zone (LPZ), previously seen as extensive cortical remapping, may result from non-retinotopic peripheral-to-foveal feedback, sharing substrates with healthy retinal feedforward processes. Preferred retinal loci (PRLs) are influenced more by location and task than by residual vision quality. Reduced lateral masking in the PRL may reflect decreased contrast sensitivity from retinal damage, rather than genuine adaptive mechanisms. Weakened crowding in the PRL is explained by transient adaptation in healthy subjects to artificial scotomas, not by long-term plasticity. Higher visual areas may show compensatory mechanisms enhancing complex tasks like symmetry, face, and motion discrimination. Leveraging spontaneous adaptation through perceptual learning-based treatments can preserve residual visual abilities. Because of limited evidence for spontaneous reorganization in AMD, behavioural training and emerging techniques are crucial for optimal treatment efficacy.