NOS3 and Schnyder corneal dystrophy: Comparison of genotype and allele frequencies between SCD late menarche and SCD early menarche group (Table 2) revealed higher incidence of homozygous wild type genotypes in SCD early menarche whereas higher incidence of heterozygous genotypes along with higher prevalence of mutant alleles of eNOS gene polymorphisms were observed in SCD late menarche group.