Clinical Reasoning: A 22-year-old man with progressive bilateral visual loss.

A 22-year-old man complained of progressive bilateral blurred vision that had developed 6 years ago. He also noted dispersed scotomas and graying of vison in both eyes, without photopsia, orbital pain, or double vision. He had not seen an ophthalmologist until he could hardly recognize people by appearance 1 week previously. Bilateral optic atrophy (figure, A) was recorded with best-corrected visual acuities of counting fingers OD and 20/400 OS. Perimetry revealed global visual field loss OD and tunnel vision OS (figure, B). He was referred to our neurology clinic, where he reported recurrent mild dull headache from age 10.