Optical Coherence Tomography–Based Differentiation of Nonarteritic Anterior Ischemic Optic Neuropathy and Central Retinal Artery Occlusion: Longitudinal Analysis of Inner Retinal Layer Thinning

BACKGROUND: Nonarteritic anterior ischemic optic neuropathy (NAION) and central retinal artery occlusion (CRAO) are both causes of acute vision loss. When patients present within the first several weeks of symptom onset, clinical signs such as optic disc or inner retinal edema often allow differentiation. However, as time progresses and edema resolves, both diseases lead to optic atrophy and retinal thinning, sometimes making them difficult to distinguish. Clinical experience suggests that CRAO results in more significant thinning of the inner retinal layers, particularly the ganglion cell layer (GCL), compared with NAION. This study seeks to investigate whether these differences remain detectable months after symptom onset and whether optical coherence tomography (OCT) imaging can reliably distinguish these entities in the chronic phase. METHODS: This is a retrospective single-center cohort study comparing OCT-derived ganglion cell thickness, total retinal thickness, and asymmetry of inferior/superior hemiretinas in patients with NAION and CRAO who presented early after vision loss and underwent follow-up imaging at approximately 3, 6, or 12 months. RESULTS: At all time points, GCL and retina thinning were more severe in the CRAO group. The ratio of GCL to total retina was significantly lower in the CRAO group. More asymmetry was observed in the NAION group, with the superior hemiretina more frequently affected. CONCLUSIONS: OCT average GCL thickness determined by automatic segmentation is an excellent discriminator between prior CRAO and prior NAION eyes at 3, 6, and 12 months.