A patient has a right homonymous hemianopia with macular sparing. Where is the most likely site of the lesion?

• A Left optic tract
• B Left lateral geniculate nucleus
• C Right internal capsule (posterior limb)
• D Left occipital (calcarine) cortex, with dual blood supply to the macular cortex from PCA and MCA ✓

Explanation

A contralateral (right) homonymous hemianopia with macular sparing indicates a lesion in the left occipital lobe (primary visual cortex, area V1). Macular sparing is explained by the dual blood supply to the posterior occipital cortex (macular representation): both the posterior cerebral artery (PCA) and middle cerebral artery (MCA) contribute to macular cortex supply. When a PCA infarct causes the hemianopia, the MCA collateral supply preserves the macular cortex. Optic tract lesions produce incongruent hemianopia without macular sparing.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.