['The objective of this study was to determine the relationship between APOE polymorphism and the severity of retinal hard exudates in Mexican patients with type 2 diabetes.', 'We studied 36 patients with diabetic retinopathy and 22 unrelated and apparently healthy age-matched individuals. Blood samples for DNA genotyping and lipid profile were taken. Genotyping of polymorphic APOE alleles was done after polymerase chain reaction amplification of genomic DNA, digestion with HhaI, and agarose gel electrophoresis. Stereoscopic 35 degrees color fundus photographs were taken of seven standard fields. Diabetic retinopathy, macular edema and hard exudates were graded according to a standardized procedure.', 'The results showed that the lipid profile was higher but not statistically significant (p > 0.05) in e4 allele carriers, with the exception of total lipids (p > 0.05). The frequency of severe retinal hard exudates was higher in those epsilon4 allele carriers (p < 0.05). The higher frequency of visual impairment (VA < 0.5 Log MAR) in epsilon4 carriers showed a tendency towards statistical significance (p = 0.057).'] Is the epsilon4 allele of apolipoprotein E gene a potential risk factor for the severity of macular edema in type 2 diabetic Mexican patients?