A 58-year-old hypertensive man wakes with painless superior altitudinal visual loss in the left eye. Fundoscopy shows diffuse pale disc swelling. The right disc appears flat with a tiny cup-to-disc ratio of 0.05. ESR and CRP are normal. The most likely diagnosis is:

• A Arteritic anterior ischaemic optic neuropathy from giant cell arteritis
• B Non-arteritic anterior ischaemic optic neuropathy ✓
• C Optic neuritis
• D Compressive optic neuropathy

Explanation

Non-arteritic anterior ischaemic optic neuropathy (NAION) presents as sudden painless monocular visual loss, typically noticed on waking, with segmental disc oedema. B structurally small, crowded disc with a cup-to-disc ratio under 0.2 is the key predisposing anatomy, seen here in the fellow eye. Giant cell arteritis is excluded by normal ESR and CRP and by absence of systemic symptoms, killing option A. Pain on eye movement and young age favour optic neuritis, which is absent here.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.