Vitamin B12 deficiency optic neuropathy detected by asymptomatic screening.

Asymptomatic bilateral optic disc swelling was detected in a 19-year-old man with type 1 diabetes through routine photographic screening for retinopathy. He was found to have significant vitamin B(12) deficiency which the authors believe was the cause for the optic neuropathy. After B(12) replacement, visual function and optic disc appearances returned to normal.