P141L, D326Y, and G895G in COL4A3 and P482S, M1327V, V1516V, and F1644F in COL4A4 polymorphisms were associated with KC patients, either as genotypes or alleles, with calculated p values less than 0.05 (Fisher’s exact test; Table 4, Table 5, and Table 6). Here, COL4A4 is linked to keratoconus.