Multiple sclerosis following optic neuritis in Chile.

Twenty three unselected cases of optic neuritis were re-examined between 2 and 18 years after the onset of the disease, with a mean of 9.7 years. Only 8/23 (35%) had unilateral non-recurrent disease. One patient only (4.3%) went on to develop multiple sclerosis. These findings support the impression that demyelinating disease varies considerably in Latin America compared with northern industrialised countries.