Significantly represented alleles in KC patients are 976G (D326Y, COL4A3) with OR= 15.017, 3979G (M1327V, COL4A4) with OR= 2.497, and 4932C (F1644F, COL4A4) with OR= 1.750 (Table 4). This evidence concerns the gene COL4A4 and keratoconus.