Optic neuritis is a demyelinating inflammatory disease of the optic nerve that presents with an abrupt loss of vision. The majority of patients are between the ages of 20 and 50 years, with a mean age ranging from 30 to 35 years. It occurs more commonly in women than in men. The onset is usually with pain on eye movement in one eye and subacute visual loss. One-third of patients have a mildly edematous optic disc. The visual disturbance resolves in 95% of cases. Many cases of optic neuritis are associated with multiple sclerosis or neuromyelitis optica or can occur in isolation. Occasionally, optic neuritis can result from infectious processes involving the paranasal sinuses or occur in the course of a systemic viral infection. High-dosed intravenous methylprednisolone therapy speeds recovery but does not improve the final outcome. For patients judged to be at high risk of developing multiple sclerosis, immune prophylaxis with beta-interferon or glatiramer acetate is recommended.