Optic disc parameters and choroidal vascular index as potential risk indicators in non-arteritic anterior ischaemic optic neuropathy: a retrospective study.

Background: Although previous research has explored the involvement of the choroid in the pathogenesis of non- arteritic anterior ischaemic optic neuropathy (NAION), the relationship between optical coherence tomography angiography (OCTA) findings and choroidal features remains unclear. An understanding of this relationship may help clarify the vascular mechanisms underlying this disease. The aim of this study was to investigate the relationships between OCTA and choroidal parameters in patients with NAION during the post-acute phase, after the resolution of optic disc oedema. Methods: This retrospective analysis included the affected eyes of patients with unilateral NAION, their unaffected fellow eyes, and the eyes of age- and sex-matched healthy controls. The three groups were compared with regard to OCTA and choroidal parameters. Retinal imaging was conducted approximately 2 months after NAION occurrence to allow for the spontaneous resolution of characteristic optic disc oedema. Results: A total of 75 eyes were included in the final analysis: 25 NAION-affected eyes, 25 fellow eyes, and 25 control eyes (13 women and 12 men). Age and sex distributions were similar across groups. The peripapillary vessel density (pVD), flow area (FA), retinal nerve fibre layer (RNFL) thickness, and choroidal vascularity index (CVI) in all quadrants were significantly lower in NAION eyes than in unaffected and control eyes. Unaffected eyes also demonstrated significantly lower radial peripapillary capillary (RPC) mean, RPC temporal, and RPC FA values than did the healthy controls. A moderate correlation was observed between RPC pVD and the mean RNFL thickness in NAION eyes and between RPC FA and the mean RNFL thickness in both NAION and unaffected eyes. The strong relationship between RPC perfusion and RNFL thinning could not be statistically confirmed after false discovery rate correction; thus, a direct cause-and-effect relationship could not be validated. Conclusions: There were no significant correlations between OCTA and choroidal parameters across all groups. These findings suggest that the retina and choroid are affected through distinct mechanisms in NAION. However, reductions in OCTA parameters, including CVI, were evident in NAION eyes. Overall, the study findings underscore the potential of OCTA as a non-invasive tool for identifying risk factors and monitoring disease progression in NAION.