APOE and Schnyder corneal dystrophy: The lack of difference between the SCD groups might also be due to the fact that the SCD-clinic tended to be younger (about 68.3 years old in SCD-clinic against 71.70 in SCD-community and 72.25 in controls), and the proportion of APOE ε4 carriers was relatively small in the SCD-clinic (15%) compared to the SCD-community (26%) or the controls (18%); when the analyses were corrected for age, level of education, and APOE ε4 status, a general trend appeared in the between-group comparison of amyloid SUVr (p = 0.096, Additional file 6).