Analysing the results according to Hb phenotype (Kruskal- Wallis test), within the SCD group, the HJB and AI red cell counts tended to be higher in the HbSS population compared to the other compound heterozygotes, however, the results were not statistically significant either for the HJB (P = 0.883) or AI counts (P = 0.534). Here, GSTM1 is linked to Schnyder corneal dystrophy.