Ischaemic optic neuropathy is caused by ischaemia of the anterior part of the optic nerve which is supplied by the short posterior ciliary arteries [
9] although there was a suggestion that the origin of ischaemia may be distal to the short posterior ciliary arteries [
10]. There are two types- arteritic optic neuropathy, caused by giant cell arteritis [
7] and non-arteritic ischaemic optic neuropathy. The pathogenesis of the latter is unclear [
8], however, a few risk factors have been identified such as hypertension, nocturnal arterial hypotension, diabetes mellitus, ischaemic heart disease, hyperlipidaemia and atherosclerosis [
3‐
8].
Platelets play an important role in the coagulation in the event of an endothelial injury. This is mediated by platelet glycoprotein which also provides the binding site for von Willebrand factor. A study by Salomon, et al suggested that the presence of the VNTR B allele of GPIbα increases the risk of NAION with an odds ratio of 4.25 (95% CI = 1.67–10.82) and also second eye involvement [
21]. Nine out of 16 patients with the allele (56.3%) had the second eye involvement whereas for those without, only 17 out of 72 patients (23.6%) had second eye involvement (
P = 0.009) [
20]. Polymorphisms in platelet glycoprotein have already been shown to increase the risk of thrombotic conditions such as ischaemic strokes [
13,
14] and ischaemic heart disease [
15,
16].
The platelet surface glycoproteins are divided into three groups I, II and III. The group I which is further divided into groups Ia, Ib Ic and GPIbα which is a surface membrane heterodimer with a larger α chain [
22]. When there is an endothelial damage, platelets interact with the exposed subendothelial matrix via GP Ib-IX-V complex and the vWF factor [
23]. The complex consists of one GPIbα subunit bonded to two molecules of GPIbβ via disulphide bonding which is then non-covalently bonded to GPIX and GPV [
24]. The GPIbα of the complex provides the binding site to the immobilised vWF [
24]. This interaction supports slow rolling of platelets and continuous adhesion [
24] [
25] under high shear stress [
26]. It eventually leads to thrombus formation [
27]. There are four variants of GPIbα which result from different numbers of VNTR. They are named A, B, C and D in the order of reducing number of repeats (4, 3, 2 or 1 repeat) and molecular mass [
28]. There is little known in the literature regarding the VNTRs of GPIbα and its effect in thromboembolic disease. One study by Salomon et al suggested that the presence of the VNTR B allele of GPIbα was likely to increase platelet interaction with the endothelium hence leading to the occlusion of posterior ciliary arteries [
21]. Here we report the first case of bilateral NAION in the presence of both VNTR B alleles of GPIbα. This case further supports the evidence that the VNTR B allele of GPIbα increases the risk of NAION including the second eye involvement. This may have further implications for the function of platelet glycoproteins.