Structural and Functional Analyses in Nonarteritic Anterior Ischemic Optic Neuropathy: Optical Coherence Tomography Angiography Study

Background: Retinal and optic disc perfusion in nonarteritic anterior ischemic optic neuropathy (NAION) is incompletely understood. Our aim was to investigate the characteristics of the microvascular structures at the peripapillary area and optic disc, and their associations with retinal structure and function in patients with NAION. Methods: We conducted a prospective, observational case series study. Thirty-four eyes, consisting of 15 NAION eyes and 19 normal eyes, were included. Optical coherence tomography (OCT) angiography was used to measure the vessel densities in the peripapillary superficial retina and whole-depth mode inside the optic disc. Measurement of circumpapillary retinal nerve fiber layer (cpRNFL) thickness was performed using OCT. Sectorial division analysis of cpRNFL was performed by eliminating the influences of the difference in disc rotation between OCT images and OCT angiography images. Results: The vessel densities of peripapillary retina and inside the optic disc were significantly reduced in the NAION compared to the normal (both P < 0.001). Both the severity of visual field defect and cpRNFL thinning were significantly associated with the peripapillary vessel density ( P = 0.006, P = 0.046), but not with the optic disc vessel density ( P = 0.981, P = 0.856). cpRNFL and peripapillary vessel density showed reduction predominantly in the superior sectors, corresponding to the visual field defect. However, the correlations showed discrepancy of the sectors. Conclusions: The microvascular structures in the peripapillary retina and optic disc were reduced, but the cpRNFL thinning was associated with vessel density only in the peripapillary retina, indicating that the vessel densities in the peripapillary retina and optic disc may be differently affected in the pathological process of NAION.