Uhthoff and his symptom.

At the turn of the last century, Wilhelm Uhthoff was a renowned clinical neuro-ophthalmologist, and probably the first clinician whose entire career was devoted to this discipline. His achievements are among those that mark the commencement of contemporary neuro-ophthalmology. Uhthoff's symptom of visual loss with exercise is most frequently associated with optic neuritis. The symptom carries a major risk for recurrence of optic neuritis and development of multiple sclerosis. This study and its companion in the publication show that, independently, a metabolic byproduct of exercise or increases in body temperature cause a reversible conduction block in demyelinated optic nerves and result in temporary loss of vision [corrected].