Multiple sclerosis is a common demyelinating disorder of the central nervous system, and neuro-ophthalmologic manifestations occur in the majority of patients. This article provides a review of the pathogenesis, epidemiology, and classification of multiple sclerosis. Neuro-ophthalmologic abnormalities associated with multiple sclerosis, including acute demyelinating optic neuritis and internuclear ophthalmoplegia, are described in detail. Current and emerging technologies designed to assess visual function in multiple sclerosis are discussed. A summary presents the appropriate evaluation and management of patients with optic neuritis and other first demyelinating events (also referred to as clinically isolated syndromes).