Peripapillary Microvascular and Structural Parameters in Atrophic Nonarteritic Anterior Ischemic Optic Neuropathy, Unaffected Fellow Eyes and Controls in an Indian Population

Nonarteritic ischemic optic neuropathy (NAION) is believed to be an ischemic insult to the optic nerve head and is one of the most common acute optic neuropathies of adulthood. Prevention of NAION in the fellow eye has not yet been accomplished. Optical coherence tomography angiography (OCTA) is a new and emerging non-invasive technology that provides microvascular information that complements the structural data. This prospective study is aimed to fill the lacunae in data that is available in the Indian population. We included 36 patients with NAION, their 36 fellow eyes and 37 healthy controls. The peripapillary perfusion index, peripapillary flux, peripapillary retinal nerve fibre layer (RNFL) thickness values and disc volumes of eyes were evaluated. The NAION eyes had lower peripapillary perfusion index, flux and RNFL thickness values in all sectors compared with both the fellow and the healthy control eyes (p = < .05). A statistically significant difference was found in disc volume between control eyes and fellow eyes, which included eyes with disc at risk configuration as well as normal disc configuration. Eyes with disc at risk configuration had a numerically lower disc volume than eyes with normal disc configuration. Fellow eyes overall had numerically lower perfusion index, higher RNFL thickness, and similar flux which was statistically non-significant compared with the healthy eyes. Correlation between the localization of visual field defects and the quadrants showing impairments of perfusion index and peripapillary RNFL were also assessed. These findings may indicate the potential vascular risk factors for the development of NAION in fellow eyes.