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 (ε2, ε3, and ε4) 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 ε2 allele and a significantly lower frequency of the ε3 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 ε4 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 ε3/ε3 genotype was more common in controls than patients (p=0.060, RR=0.465, PF=0.322). The difference in genotype (ε3/ε4) was not statistically significant between the two groups (p=0.283). Genotype ε4/ε4 was found only in 3% of patients while being completely absent in the controls (p=0.080). The genotypes, ε2/ε2, ε2/ε3, and ε2/ε4, 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 ε4 allele and ε4/ε4 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 ε4 allele may be associated with POAG and could be a risk factor while ε3 may be protective for POAG, and APOE polymorphisms may not be associated at all with PACG in Saudis.