For the OCT study, 31 African American and 61 Caucasian American healthy controls (1:2 age and sex matched cohorts; n = 92) and 116 African Americans and 116 Caucasian Americans with multiple sclerosis (age and sex matched cohorts; n = 232) were enrolled. All the patients from the MRI cohorts were also included in the OCT component of the study. For the longitudinal OCT analyses, rates of change in 17 of 31 African American healthy controls (55%) and 33 of 61 Caucasian American healthy controls (54%) could be analysed longitudinally based on at least 1 year of follow-up. In the multiple sclerosis cohorts, all recruited participants were included in the longitudinal OCT analyses (116 in the African Americans and Caucasian Americans cohorts). The summary of demographics, baseline characteristics, and differences therein, stratified by African and Caucasian American race, are provided in Table 1. The baseline demographics of the healthy control cohorts stratified by race are given in Supplementary Table 2.