Optic neuritis (ON) is an inflammatory disorder of the optic nerve. Most cases are idiopathic or associated with MS. ON can be associated with a variety of systemic or ocular disorders and is the most common acute optic neuropathy in adults younger than 46 years. Among high-risk populations for MS, the incidence of ON is about 3 per 100,000 population per year, whereas in other areas the incidence is about 1 per 100,000 population per year.1-13 Acute ON often presents as an isolated clinical event without contributory systemic abnormalities (monosymptomatic ON). Clinical features include periocular pain, abnormal visual acuity and fields, reduced color vision, a relative afferent pupillary defect, and abnormal visual evoked potentials. The fundus may appear normal or demonstrate edema of the optic nerve head (papillitis).12-18 MRI white matter abnormalities identical to those seen in MS are found in 50 to 70% of monosymptomatic ON cases.19-22 The visual deficit of ON may worsen over 1 to 2 weeks and usually begins improving over the next month. Lack of improvement in visual function by 30 days is unusual.23 However, most patients have some residual visual function deficit, even if visual acuity improves to 20/20.1-18 Differential diagnosis includes compressive, ischemic, hereditary, toxic, or other inflammatory optic neuropathies (e.g., sarcoid). These conditions usually do not exhibit the same clinical pattern (table 1) or rate of recovery as monosymptomatic ON.1-13 View this table: Table 1. Features of acute demyelinating monosymptomatic optic neuritis Treatment of monosymptomatic ON has included oral, retrobulbar, and IV steroids, immunoglobulin, and acupuncture.23-77 Monosymptomatic acute ON is not rare and because the usefulness of oral prednisone in this disorder has recently been questioned,23,78-82 this practice parameter was developed to provide …