Objective: To assess visual function more than 10 years after an episode of optic neuritis in patients enrolled in the Optic Neuritis Treatment Trial.

Methods: Longitudinal follow-up of a randomized clinical trial. Methods: Vision testing included measures of visual acuity, contrast sensitivity, and visual field. Quality of life was assessed with the National Eye Institute Visual Function Questionnaire.

Results: Examinations were completed on 319 patients. In most patients, visual function test results in the eyes that experienced optic neuritis at study entry ("affected eyes") were normal or only slightly abnormal after 9.9 to 13.7 years. Visual acuity in the affected eyes was >or=20/20 in 74%, 20/25 to 20/40 in 18%, <20/40 to 20/200 in 5%, and <20/200 in 3%. On average, visual function was worse in patients with multiple sclerosis (MS) than in those without MS. Recurrent optic neuritis in either eye occurred in 35% of patients. Such attacks were more frequent in patients with MS (P <.001). The National Eye Institute Visual Function Questionnaire scores were lower when visual acuity was abnormal and when MS was present.

Conclusions: Most patients retained good to excellent vision more than 10 years after an attack of optic neuritis. Recurrences were more frequent in patients with MS.