In the additive model, genotypes 422CC, 422TT, 422CT, 976GG, 976TT, and 2685AA in COL4A3 and 1444CT, 3979AA, 3979GG, 4548AG, 4932CC, and 4932CT in COL4A4 were significantly different between KC patients and the control group (Table 6). Here, COL4A4 is linked to keratoconus.