XRCC1 and pterygium: The analysis of the polymorphisms located at XRCC1 codon 399 in pterygium showed that 31 (37.3%) were homozygous for the A/A genotype, 17 (20.5%) were homozygous for the G/G genotype, and 35 (42.2%) were heterozygous for the A/G genotype.