XRCC1 and pterygium: Because there is evidence that genetic factors and UV-induced damage play a role in the development of pterygium [1,22,23]—genetic predisposition to pterygium was recently discovered using the single nucleotide polymorphism (SNP) method—and the polymorphisms of DNA repair genes have an effect on host capacity of removing DNA damage, it is logical to assume the correlation between pterygium and the genetic polymorphisms of DNA repair enzymes XRCC1, XPA, and XPD.