APOE and Schnyder corneal dystrophy: The multiple linear regression analysis exploring the association of age, sex, education, APOE ε4 status, A status, and syndromic diagnosis (SCD vs MCI) with each regional macular VD measure showed that age had a significant effect on macular VD in the nasal, temporal, and inferior quadrants (all, p < 0.027), sex had a significant effect on macular VD in the temporal quadrant (p = 0.033), and syndromic diagnosis had a significant effect on macular VD in the temporal and superior quadrants (p < 0.043), so those were included as adjusting factors in all following analyses (Additional file 1).