Correlation of clinical and keratometric parameters with COL4A4 (rs2228557) and TIMP-1 (rs4898) in keratoconus patients.KC, keratoconus; OD, right eye; OS, left eye; OU, both eyes; CXL, cross-linking surgeryKK1, 2, 3 are phenotyping classification and show the level progress of keratoconus disease in patients. Here, COL4A4 is linked to keratoconus.