To assess the characteristics of optic nerve head drusen (ONHD) vasculature in comparison to acute non-arteritic 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 normal eyes were enrolled. OCT-A imaging was performed using a RTVue-XR Avanti instrument in all cases. Qualitative grading was performed for dilation and tortuosity of the peripapillary vessels by 3 graders. Quantitative comparison was performed for peripapillary and inside disc vessel densities.

The inter-grader agreement regarding dilation and tortuosity of the peripapillary vessels was poor in three groups. Vessel density measurements were statistically significantly different in nerve head (NH) measurements among 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).

We found a significant decrease in optic nerve head flow density parameters in eyes with acute NAION compared with ONHD and normal eyes. Despite poor inter-grader agreement in qualitative analysis, it seems that quantitative OCT-A evaluation could differentiate optic disc edema due to NAION from pseudo disc edema due to ONHD.