A 62-year-old hypertensive man has a complete right homonymous hemianopia in which the central 5 degrees of vision on both sides are preserved. The lesion is most likely in which location, and why is the macula spared?

• A Left optic tract; macula has double representation in the tract
• B Left temporal lobe radiations; macular fibres do not pass through Meyer's loop
• C Left parietal lobe; macular fibres synapse in the cuneus only
• D Left occipital pole; the macular cortex receives collateral supply from the middle cerebral artery ✓

Explanation

Macular sparing localises the lesion to the occipital cortex. The macular representation lies at the occipital pole, which sits in the border zone between posterior and middle cerebral arterial territories, so middle cerebral artery collaterals maintain macular perfusion when the posterior cerebral artery is occluded. Optic tract and radiation lesions typically split fixation because they lack this dual arterial supply. Temporal lobe lesions classically give a superior quadrantanopia rather than a complete hemianopia.

Reference: Gray's Anatomy, 42nd ed.

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Written and medically reviewed by the StethoPrep medical team.