Apolipoprotein E polymorphisms and primary glaucoma in Saudis

PURPOSE The frequencies of apolipoprotein E (APOE) alleles and genotypes were examined in 230 Saudi subjects including primary open-angle glaucoma (POAG; n=60) and primary angle-closure glaucoma (PACG; n=40) patients as well as 130 control subjects. METHODS The presence of glaucoma in patients was based on clinical examination and/or ophthalmic records. The APOE allele frequency (epsilon2, epsilon3, and epsilon4) was studied by polymerase chain reaction (PCR) followed by reverse-hybridization and restriction fragment length polymorphism techniques. RESULTS Analysis of data showed a complete absence of epsilon2 allele and a significantly lower frequency of the epsilon3 allele in primary glaucoma patients (90.5%) compared to the control subjects (95.7%, p=0.034, relative risk [RR]=0.473, protective fraction [PF]=0.318). The frequency of the epsilon4 allele was significantly higher in the glaucoma patients (9.5%) compared to the control subjects (4.2%, p=0.034, RR=2.169, etiological fraction [EF]=0.329). The epsilon3/epsilon3 genotype was more common in controls than patients (p=0.060, RR=0.465, PF=0.322). The difference in genotype (epsilon3/epsilon4) was not statistically significant between the two groups (p=0.283). Genotype epsilon4/epsilon4 was found only in 3% of patients while being completely absent in the controls (p=0.080). The genotypes, epsilon2/epsilon2, epsilon2/epsilon3, and epsilon2/epsilon4, were absent in both the test and control groups. When patients were divided on the basis of types of glaucoma, POAG patients had a significantly higher frequency of epsilon4 allele and epsilon4/epsilon4 genotype than controls whereas there was no significant difference between PACG patient and control groups in frequencies of APOE alleles and genotypes. CONCLUSIONS This study indicates that the epsilon4 allele may be associated with POAG and could be a risk factor while epsilon3 may be protective for POAG, and APOE polymorphisms may not be associated at all with PACG in Saudis.