This will be a prospective cross-sectional, non-interventional study; total recruitment will be 200 subjects. Recruitment will be stratified to enroll at least 50 subjects currently taking Lemtrada and 50 subjects with a documented diagnosis of ON. The study will enroll subjects primarily from practices in the Tampa Bay Area and adjacent counties. It is a planned non-interventional study; subjects will be followed by their neurologist and the study ophthalmologist and will receive standard of care. All subjects will have the ophthalmological examination and diagnostic measures, by the Principal Investigator, Dr. Grace Levy-Clarke, at Tampa Bay Uveitis Center.