COL4A4 and keratoconus: Results in the distribution of genotypes (CC, CT, TT) in rs2228557 of the COL4A4 gene between KC patients and controls in the Stabuc-Silih et al's study were different from our results.[14] Similar to our findings, Kokolakis et al demonstrated that the TT genotype was significantly over-represented in healthy individuals and suggested a protective role for this genotype in the KC development.[31]