Visual impairment in multiple sclerosis involving post-geniculate gray and white matter: above and beyond.

Visual impairment is one of the most common and disabling manifestations of multiple sclerosis (MS). While visual dysfunction related to optic neuritis and brainstem involvement is well recognized, visual impairment associated with post-geniculate visual pathways-including the optic radiations and visual cortex-remains comparatively under-studied and under-recognized in clinical practice. Increasing evidence from advanced neuroimaging, optical coherence tomography, and neuropsychological testing has demonstrated that lesions affecting post-geniculate white and gray matter contribute to both symptomatic and subclinical visual dysfunction in people with multiple sclerosis (PwMS). These abnormalities include homonymous visual field defects, visuoperceptual dysfunction, visual cognitive impairment, and higher-order ocular motor abnormalities. Cortical lesions and cortical thinning correlate with deficits in visual memory, visuospatial processing, and processing speed, while optic radiation damage contributes to retrograde transsynaptic degeneration and impaired visual information processing. Emerging eye-movement paradigms further suggest that higher-order ocular motor dysfunction reflects widespread gray matter involvement and may serve as a sensitive biomarker of disease burden. This review summarizes current histopathological and imaging evidence for post-geniculate pathway involvement in MS and discusses its clinical relevance for diagnosis, monitoring, and functional assessment.