Natural History of Optic Neuritis

Background: \- Optic neuritis often is a symptom of multiple sclerosis (MS). Many people who experience optic neuritis are later diagnosed with MS. MS disease activity seen on magnetic resonance imaging (MRI) scans is often greater than that seen in tests given during regular doctor's visits. Even though MRI is a helpful tool for studying optic neuritis and MS, more information is needed on how MS symptoms show up on MRI scans. Researchers want to use MRI scans to track changes in the optic nerve after an optic neuritis episode. This approach will help them study the relationship between optic neuritis and MS. Objectives: \- To collect more information about the relationship between optic neuritis and multiple sclerosis. Eligibility: * Individuals between 18 and 50 years of age who have new optic neuritis. * Individuals between 18 and 50 years of age who have new symptoms of MS other than optic neuritis. * Healthy volunteers between 18 and 50 years of age. Design: * Participants will be screened with a physical exam and medical history. They may provide blood or urine samples. * Participants with optic neuritis or other MS symptoms will have a baseline study visit. They will have a physical exam and full eye exam. To look for signs of MS, they will have evoked potential tests to see how the body responds to stimulation. They will also have an MRI scan to study any changes in the brain and optic nerves. * After the first visit, participants will have steroid treatment for 5 days for the optic neuritis. * Additional study visits will be given 1, 3, 6, 9, and 12 months after the baseline visit. The tests from the first visit, including the MRI scans, will be repeated at these visits. * Healthy volunteers will have a baseline study visit. They will have a physical exam and full eye exam. They will have evoked potential tests to see how the body responds to stimulation. They will also have an MRI scan to study any changes in the brain and optic nerves. * Healthy v