The authors present a cross-sectional, non-interventional study of healthy volunteers and those with non-arteritic anterior ischaemic optic neuropathy (NAION) recruited over a six-month period at a single site. NAION is the most common cause of acute optic neuropathy over the age of 50, but the exact pathophysiology of the condition is still unclear, with the exact level of vascular compromise being undefined. In order to investigate the choroidal vasculature in NAION, the study aimed to analyse the peripapillary choroidal vascularity index (CVI) in NAION eyes, contralateral normal eyes and compare to the CVI in the healthy population. The peripapillary CVI is a new tool of measurement and was calculated using horizontal swept-source optical coherence tomography scans. A total of 20 eyes of patients with acute unilateral NAION, 20 healthy fellow eyes and 40 eyes of 40 healthy patients were included in the study. Results showed that NAION eyes had a significantly lower CVI than age-matched controls in both nasal and temporal areas. In addition, temporal CVI in NAION eyes was significantly lower than counterpart fellow eyes. The authors concluded that NAION eyes have significantly reduced vascularity in the peripapillary area. This may suggest those with smaller CVI are more prone to ischaemia from reduced vascularity resulting in NAION.