Comparison of Optic Nerve Head Morphology and Microvasculature in the Fellow Eye of Patients with NAION to Small Optic Discs: An Assessment by OCTA
Kaveh Abri Aghdam1 *, Faezeh Hashemi Rahbarian1 , Pasha Anvari1 , Khalil Ghasemi Falavarjani1
- Eye Research Center, Eye Department, The Five Senses Health Institute, Rassoul Akram Hospital, School of Medicine, Iran University of Medical Sciences, Tehran, Iran.
Abstract: To compare the morphology and microvasculature of the optic nerve head in the fellow eye of patients with non-arteritic anterior ischemic optic neuropathy (NAION) to those of individuals with small optic discs, using optical coherence tomography angiography (OCTA).
Methods: This cross-sectional study included 45 patients (58 eyes): fellow eyes of patients with previous NAION (18 patients, 18 eyes), eyes with a small disc (14 patients, 21 eyes, vertical disc diameter < 1.5 mm), and control eyes (13 patients, 19 eyes, 1.5 mm < vertical disc diameter < 2.2 mm).
Results: There was a significant difference in the inside disc vessel densities across the three groups (p=0.03). The vessel density in the fellow eye with NAION was significantly higher compared to eyes with a small disc (p=0.009). There was no significant statistical difference between the three groups in terms of peripapillary retinal nerve fiber thickness. Both the cup-to-disc ratio and the vertical and horizontal cup-to-disc ratios showed a significant difference among the three groups (p<0.001). These ratios were significantly lower in the unaffected fellow eyes of NAION patients compared to both eyes with a small disc and healthy eyes (p<0.01). The rim area in the small disc group was significantly lower than that in the unaffected fellow eyes of NAION patients (p<0.001). The disc area in the unaffected fellow eyes of NAION patients was significantly lower than that in normal eyes (p=0.02). The cup volume in the unaffected fellow eyes of NAION patients was significantly less than that in the small disc group, and also less than that in the normal eye group (p<0.001).
Conclusion: The vessel density within the disc in unaffected fellow eyes of NAION was significantly higher compared to eyes with a small disc. While disc size does not pose a risk factor for NAION, crowding of the optic disc does. The likelihood of NAION can be predicted by analyzing the vessel density within the disc using OCTA.
