Detection of post-stroke visual field loss by quantification of the retrogeniculate visual pathway

Visual field loss is associated with poor post-stroke functional outcomes. However, early detection of visual field loss is often challenging in patients with disabling stroke. This study explored the association between the microstructural integrity of the retrogeniculate pathway and visual field loss in disabling stroke patients undergoing inpatient rehabilitation. Thirty patients with stroke lesions involving the retrogeniculate visual pathway were included. The degree of visual field loss was determined by the visual field index and mean deviation using automated perimetry. The fractional anisotropy (FA) values were obtained for the lateral geniculate nucleus and optic radiation; the FA laterality indices, representing the degree of degeneration, were calculated. The FA values were compared between the affected and unaffected hemispheres. The patients were categorized into complete and incomplete hemianopia groups, and their FA values were compared. The relationship between the FA laterality index and the degree of visual field loss was assessed. FA values of the lateral geniculate nucleus and optic radiation were lower on the affected side than on the unaffected side (P < 0.001 and P < 0.001, respectively). The affected optic radiation in the complete hemianopia group showed a lower FA value than in the incomplete group (P = 0.006). The FA laterality index of the optic radiation was positively correlated with the degree of visual field loss (visual field index, ρ = 0.629; mean deviation, ρ = 0.568). The quantification of the retrogeniculate visual pathway may aid in detecting post-stroke visual field loss. The microstructural integrity of the optic radiation is associated with the severity of visual field loss.