• Optic nerve
• immunology
• neoplasia

A 54-year-old gentleman presented to our Eye Unit following an optician referral with a 4-month history of gradual visual deterioration. Other significant symptoms included problems with his mobility and balance consistent with an ataxic sensory neuropathy for which he had not sought medical advice. History revealed a significant amount of cigarette smoking and alcohol intake with poor dietary habits. On examination, he had a best-corrected visual acuity of 2/60 in both eyes. Pupil reaction was sluggish, but there was no relative afferent pupil defect and ocular motility and anterior segment examinations were all normal. Due to the severity of visual loss, he was unable to perform formal colour vision tests.

Fundus examination revealed bilateral pale optic discs with atrophy more prominent on the temporal side. A provisional diagnosis of bilateral optic atrophy secondary to nutritional/toxic cause was assumed. The patient then had blood tests, which included serum vitamin levels. Visual field testing revealed peripheral constriction in both eyes. His blood mean corpuscular volume was 110.9 fL (normal=75–95) and ferritin …