To assess the characteristics of optic nerve head drusen vasculature in comparison to acute nonarteritic anterior ischemic optic neuropathy (NAION) and normal eyes as determined by optical coherence tomography angiography (OCT-A).

In this prospective observational study, 10 well-documented cases of ONHD, 10 patients with acute unilateral NAION, and 10 age-matched normal eyes were enrolled. OCT-A imaging was performed using a RTVue-XR Avanti scanner in all cases. Standard AngioVue software was used for automatic calculation of vessel density in the area defined as a 750-μm-wide oval ring extending from the optic disc margin.

Vessel density measurements were statistically significantly different in nerve head (NH) measurements between the three groups. There were significant differences between ONHD and NAION groups and between NAION and normal eyes in all regions. There was no significant difference between normal eyes and eyes with ONHD in all regions of optic nerve head except for inferior nasal peripapillary region (p=0.044). Vessel density measurements were statistically significantly different in all radial peripapillary capillary (RPC) flow density measurements between the three groups except for nasal peripapillary region (p=0.08). In normal eyes, the mean total peripapillary optic nerve head and RPC flow densities was 60.96 ± 2.37% and 62.75 ± 2.76% with the highest average density in the inferior tempo peripapillary sector (64.57 ± 3.73% and 66.54 ± 3.70, respectively). In eyes with NAION, the same parameter decreased (45.68 ± 5.70% and 49.47 ± 5.42%) by 19% and 17%, compared with normal control eyes (p<0.001).

We found a significant decrease in optic nerve head flow density parameters in eyes with acute NAION compared with ONHD and normal eyes. Quantitative OCT-A evaluation could differentiate optic disc edema due to NAION from pseudo disc edema due to ONHD.