Endothelial nitric oxide synthase polymorphism (G894T) and nonarteritic anterior ischemic optic neuropathy

Nonarteritic anterior ischemic optic neuropathy (NAION) is associated with vascular risk factors and a genetic predisposition for NAION. In this study, we examined the potential association of endothelial nitric oxide synthase (eNOS) G894T polymorphism with NAION. For this, 45 patients (29 men and 16 women) and 193 controls (122 men and 71 women) were enrolled prospectively and genotyped for eNOS genes. Genotypes were determined by polymerase chain reaction and restriction enzyme analysis. The prevalence of eNOS polymorphisms was estimated in NAION patients and controls. Genotype frequencies were estimated with chi-square test, and odds ratios were calculated. We found that eNOS G894T polymorphism is not associated with NAION occurrence as the genotype and allele frequencies were not significantly different between the control and patient groups (TT vs. GG + GT: P = 0.646 and T vs. G: P = 0.86). The precise mechanism of NAION occurrence has not been elucidated yet; since NAION may occur when a compromised watershed microcirculation is combined with insufficient autoregulation of systematic circulation, other alterations in the eNOS gene or polymorphism of genes involved in systematic circulation may be associated with NAION occurrence.