GSTM1 and Schnyder corneal dystrophy: The expected proportions of high-risk genotypes associated with SCD (Hb SS and Hb SC) in the cohort are 0.085 (8.5%). A binomial test indicates a statistically significant difference (p = 0.017) between the observed frequency of high-risk genotypes (Hb SS and Hb SC) (5.2%; 95% CI: 3.2-7.9%) and the expected frequency (8.5%) under HWE.