Optic neuritis and multiple sclerosis.

T HE INVESTMENT of the National Eye Institute in the Optic Neuritis Treatment Trial continues to pay dividends. In this issue of the ARCHIVES, the Optic Neuritis Study Group reports on the risk of developing multiple sclerosis (MS) after an attack of isolated optic neuritis. This issue is of great importance to patients and physicians and, as the authors acknowledge, has been addressed in prior studies, some of which yielded similar results. However, with its impressive number of subjects, high retention rate, prospective design, standardized procedures, and well-defined criteria, the Optic Neuritis Treatment Trial has produced results that will likely be influential. The Optic Neuritis Study Group provides 10to 13year follow-up on a cohort of patients who had experienced an attack of acute optic neuritis unaccompanied by other clinical evidence of MS. Follow-up was available on 87% of the original 388 patients, a remarkable achievement in itself. The risk of developing MS by clinical criteria was 38% at 10 years and 40% at 12 years. Magnetic resonance imaging (MRI) findings at the time of the acute optic neuritis episode correlated with the risk. Patients with at least 1 brain lesion had a 10-year risk of 56%, whereas 22% of those with normal brain MRI results developed clinical MS during that interval.