The results showed that both MTHFR C677T genotype (TT vs. CT and CC) and vitamin B12 deficiency were positively correlated with SCD (OR = 2.882, 95% CI 1.189 to 6.986, P = 0.019 and OR = 2.742, 95% CI 1.129 to 6.662, P = 0.026, respectively). The gene discussed is MTHFR; the disease is Schnyder corneal dystrophy.