Fundoscopy of a patient with long-standing bitemporal hemianopia from a pituitary macroadenoma shows horizontal band-shaped pallor of both optic discs. This appearance is called bow-tie optic atrophy and occurs because:

• A Temporal retinal fibres are compressed at the orbital apex
• B Crossing nasal retinal fibres degenerate after chiasmal compression ✓
• C Papilloedema from raised intracranial pressure damages all fibres equally
• D The uncrossed temporal fibres atrophy first from direct tumour invasion

Explanation

In chiasmal compression, the decussating fibres from each nasal retina (carrying the temporal visual fields) are selectively damaged. Their loss produces pallor in two wedge-shaped sectors of nasal retina corresponding to the upper and lower arcuate bands, separated by the spared papillomacular bundle, giving the characteristic bow-tie pattern. Uncrossed temporal fibres subserving the nasal fields are preserved, which rules out options A and D.

Reference: Kanski's Clinical Ophthalmology, 9th ed.

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Written and medically reviewed by the StethoPrep medical team.