OGG1 and pterygium: XRCC1 and human 8-oxoguanine DNA glycosylase 1 (hOGG1) are BER system genes and XRCC1, in our series, and hOGG1, in the report of Kau et al. [22] , are found to be associated with pterygium formation; therefore, the BER system indeed plays an important role in pterygium formation.