New directions in optic neuritis and multiple sclerosis.

Optic neuritis (ON) is the initial presentation in 15% to 20% of cases of multiple sclerosis (MS). Thirty-eight percent to 50% of patients with MS develop ON at some point during the course of their disease. The Optic Neuritis Treatment Trial (ONTT) provided much prospective data about the clinical presentation, clinical course with respect to treatment, and development of MS in patients with ON. The clinical course of MS initially involves episodes of demyelination followed by full recovery; however, later attacks often leave persistent deficits that lead to secondary progression of the disease. The risk of developing progressive neurologic deficits can be reduced by starting therapy with immunomodulating drugs early in the course of the disease. Optical coherence tomography is a noninvasive way to monitor patients with ON to determine if they are undergoing subclinical axonal loss of ganglion cells. Progression of axonal loss on optical coherence tomography may prompt a change in therapy or further imaging.