GSTM1 and Schnyder corneal dystrophy: This finding contrasts with the prevalence of peripheral SCR in SCD, which is reportedly associated with male sex.1,19 Higher hemoglobin levels in male patients and a protective effect of estrogen on endothelial function in female patients are hypothesized to explain the lower prevalence of retinopathy in female patients.19,20 Although our female patients did not differ from male patients in distribution of Hb genotype or SCR severity, they did differ in age.