Morphological and Vascular Features of the Optic Nerve in Healthy Asians

Abstract

Abstract Title: Morphological and Vascular Features of the Optic Nerve in Healthy Asians Background: Glaucoma is the second leading cause of blindness worldwide, impacting nearly 3 million patients in the US and 80 million globally. Glaucoma is characterized by progressive optic neuropathy, which leads to structural and vascular damage to the optic nerve (ON) and retina. A novel technology, known as optical coherence tomography angiography (OCTA), captures both the structure and vascular features of the retina and ON. Previous studies have indicated that blacks with large optic discs (ODs) experience a more severe form of glaucoma. Information about OD size and glaucoma in Asians is not well documented. Therefore, the aim of our study was to evaluate morphological and vascular features of the OD in healthy South Asian (SA India), East Asian (EA- China), and Southeast Asian (SEA- Vietnam) patients using OCTA scans. Methods: In this IRB approved, retrospective, age-matched study conducted at an academic center, we reviewed OCTA scans from 76 healthy subjects who were self-identified as SA, SEA, or EA. Exclusion criteria included high myopia/hyperopia, poor scan quality and vitreoretinal disorders. We measured mean disc area, rim area, cup/disc ratio, and vessel densities on the ON. Data was analyzed with pairwise Student’s two-tailed t-tests. Results: After exclusions, 46 patients [33 (62 eyes) SA, 4 (8 eyes) EA, 9 (16 eyes) SEA] were included. The mean disc vertical size of SEA was higher than SA (1.84mm vs. 1.73mm, p=0.016). The mean disc area in SEA was higher than that in SA (2.49mm² vs. 2.25mm², p=0.024). There were no differences in measurements between SA and EA or EA and SEA. Peripapillary vessel density was significantly higher in SA than in EA (52.2% vs. 50.2%, p=0.036). All other measurements were not significant. Conclusion: Our pilot study has shown that disc area and disc vertical size are greater in SEA than SA, potentially making them more prone to glaucomatous damage. We believe that these OD ethnic differences, if further investigated, could serve as early markers of glaucoma in healthy Asian eyes.