Specific genes that have been associated with KC through candidate gene analysis include Visual System Homebox 1 (VSX1), Superoxide Dismutase 1 (SOD1), Zinc Finger Protein 469 (ZNF469), and collagen genes such as COL4A1/2/3/4 and COL8A1/2 [19,20,21,22,23,24,25,26,27,28,29,30,31]. This evidence concerns the gene SOD1 and keratoconus.