Nonarteritic Anterior Ischemic Optic Neuropathy Is Associated with a Specific Platelet Polymorphism Located on the Glycoprotein Ibα Gene

Objective: To evaluate the association between platelet glycoprotein polymorphisms and the risks of single and second eye involvement with nonarteritic anterior ischemic optic neuropathy (NAION). Design: Case-control study. Participants: Ninety-two consecutive patients with NAION, 26 of whom had second eye involvement, and 145 controls who attended the eye clinic for nonvascular entities. Methods: Polymerase chain reactions and restriction enzyme analyses were performed for genotyping 5 platelet glycoprotein polymorphisms on DNA extracted from whole blood. Main Outcome Measures: Frequencies of the various platelet polymorphisms. Results: One of the 5 platelet glycoprotein polymorphisms analyzed, the B allele of the glycoprotein Ibα variable number of tandem repeats (VNTR), was a significant independent risk factor for NAION, with an odds ratio of 4.25 and a 95% confidence interval of 1.67 to 10.82 (P = 0.0026). All other platelet glycoprotein polymorphisms were similarly distributed in patients and controls. In addition, 9 of 16 patients who bore the VNTR B allele (56.3%) had second eye involvement, whereas among patients not harboring the VNTR B allele only 17 of 72 patients (23.6%) had second eye involvement (P = 0.009). Moreover, second eye involvement occurred earlier in patients who bore the specific polymorphism. Conclusions: The presence of the VNTR B allele of glycoprotein Ibα confers a significant risk for NAION and predisposes affected patients to second eye involvement.