CYP1A1 and pterygium: The analysis of the CYP1A1 MSPI polymorphisms in pterygium showed that 34 (33.0%) were homozygous for the m1/m1 genotype, 15 (14.6%) were homozygous for the m2/m2 genotype, and 54 (52.4%) were heterozygous for the m1/m2 genotype.