25th December 2023

Anatomical considerations

The optic chiasm permits the hemi-decussation of the visual field information, such that the information from the left visual field (left temporal and right nasal field) and right visual field (right temporal and left nasal field) is processed in the contralateral visual cortex. Lesions at the optic chiasm produce bi-temporal hemianopia. Retro-chiasmal lesions produce homonymous hemianopia. Congruity describes the degree of similarity between the visual field defects in both eyes. The more posterior the lesion in retro-chiasmal visual pathway, the more congruous the visual field defect is.