Optic disc characteristics evaluated with swept source optical coherence tomography angiography (SS-OCTA) in nonarteritic anterior ischemic optic neuropathy (NAION): a cross-sectional study

Background Nonarteritic anterior ischemic optic neuropathy (NAION) is one of common optic neuropathies affect optic disc. But the structure of optic disc in NAION remains poorly understood. Our aim was to identify optic disc characteristics of NAION. Methods This cross-sectional study included chronic-stage affected eyes and unaffected eyes from NAION patients and normal eyes from age-matched individuals. Measurements of optic disc and macula from swept source optical coherence tomography angiography (SS-OCTA) were recorded. Besides conventional OCTA parameters, we also manually measured circumpapillary retinal nerve fiber layer (cRNFL) thickness, lamina cribrosa depth (LCD) and prelaminar tissue thickness (PLTT). Additionally, we introduced a new parameter, retinal nerve fiber layer density (RNFLD). Results This study finally included 53 NAION-fellow eyes, 26 chronic-stage NAION eyes and 50 normal eyes. NAION-fellow eyes and NAION eyes showed significantly thicker PLTT compared to normal eyes (p < 0.001). NAION fellow eyes showed similar peripapillary retinal nerve fiber layer (pRNFL) thickness but significantly thicker cRNFL (p < 0.001) compared to normal eyes. And NAION eyes showed significantly thinner pRNFL (p < 0.001) but similar cRNFL compared to normal eyes. RNFLD was higher in NAION-fellow eyes compared to the other two groups (p < 0.01). Logistic analyses showed PLTT was independently associated with NAION susceptibility (OR = 1.017, 95% CI: 1.009-1.025, p < 0.001). ROC curve of PLTT showed that the area under the curve (AUC) was 0.905 (95% CI: 0.846-0.964, p < 0.001). Conclusions Both affected and unaffected eyes of NAION patients exhibited an increase in non-nerve fiber components within the retinal nerve fiber layer at optic disc. These increased components might be glial tissue or the remnants of the primitive vitreous. Additionally, PLTT was an independent susceptibility factor for NAION.