GSTM1 and pterygium: In this study, we try to analyze the CYP1A1 and GSTM1 gene polymorphisms using PCR-RFLP (Polymorphism Chain Reaction-Restriction Fragment Length Polymorphism) and PCR (Polymorphism Chain Reaction) methods in 205 pterygium specimens and 206 controls to understand how CYP1A1 and GSTM1 polymorphisms increase the risk of pterygium.