<b>Conclusions</b>: This study supports the hypothesis of a functional role for <i>COL4A3</i> (rs55703767, G/T), <i>MMP-9</i> (rs17576, A/G) and <i>TIMP-1</i> (rs6609533, A/G) SNPs in the pathogenesis of keratoconus.
Our findings showed that the rs55703767G/T polymorphism decreased the risk of KC (OR = 0.26, 95% CI = 0.08-0.82, P = 0.022). rs17576A/G, associated with KC and the A allele, was significantly overrepresented in healthy individuals. rs6609533A/G (X-chromosome) increased the risk of KC in females (OR = 2.27, 95% CI = 1.06-4.76, P = 0.036).