In addition, we studied the gene of an auxiliary BER factor, XRCC1. We aimed to explore the association of 5 single nucleotide polymorphisms (SNPs): the g.46438521G>C (rs4462560) polymorphism of the NEIL1 gene, the c.2285T>C (rs1136410) polymorphism of the PARP-1 gene, the c.–1370T>A (rs1054875) polymorphism of the POLG gene, the c.580C>T (rs1799782) and c.1196A>G (rs25487) polymorphisms of the XRCC1 gene with KC occurrence. The gene discussed is NEIL1; the disease is keratoconus.