Background: Participants enrolled in the Optic Neuritis Treatment Trial have been observed for more than a decade to assess the relationship between optic neuritis and the development of clinically definite multiple sclerosis.
Objective: To assess neurologic disability 10 to 12 years after an initial episode of optic neuritis.
Design: Longitudinal follow-up of a clinical trial.
Setting: Fourteen Optic Neuritis Treatment Trial clinical centers performed standardized neurologic examinations, including an assessment of neurologic disability.
Participants: One hundred twenty-seven patients who had developed clinically definite multiple sclerosis.
Main outcome measures: Functional Systems Scale and Expanded Disability Status Scale.
Results: The disability of most patients was mild, with 65% of patients having an Expanded Disability Status Scale score lower than 3.0. The degree of disability appeared to be unrelated to whether the baseline magnetic resonance imaging scan was lesion-free or showed lesions (P =.51). Among patients with baseline lesions, the degree of disability was unrelated to the number of lesions that were present on the scan (P =.14). Two patients died owing to severe multiple sclerosis, one of whom had no lesions revealed on the baseline scan.
Conclusion: Most patients who develop clinically definite multiple sclerosis following an initial episode of optic neuritis will have a relatively benign course for at least 10 years.