This is a 3-year, pharmacologically non-interventional study to evaluate OCT as an outcome measure in patients with relapsing remitting multiple sclerosis (RRMS). Approximately 350 RRMS patients, either untreated or treated with an approved MS disease-modifying therapy and approximately 70 reference subjects without ophthalmologic or neurologic disease are enrolled. No study medications are provided. Patients on disease-modifying therapy are treated according to the local prescribing information. For each MS patient and each reference subject, the study consists of Screening (up to 1 month), Baseline, and a 36-month longitudinal data collection phase. Eligibility will be confirmed during Screening.