BACKGROUND: Anterior ischemic optic neuropathy (AION) is the most common cause of acute optic neuropathy in older patients. Distinguishing between arteritic AION (A-AION) and nonarteritic (NA-AION) is paramount for improved patient management. PURPOSE: The aim of this study was to evaluate 3-dimensional high-resolution vessel wall (HR-VW) magnetic resonance imaging (MRI) at 3 T to discriminate A-AION from NA-AION. MATERIALS AND METHODS: This prospective single-center study was approved by a national research ethics board and included 27 patients (17 A-AION and 10 NA-AION) with 36 AIONs from December 2014 to August 2017 who underwent 3 T HR-VW MRI. Two radiologists blinded to clinical data individually analyzed the imaging separately and in random order. Discrepancies were resolved by consensus with a third neuroradiologist. The primary diagnostic criterion was the presence of inflammatory changes of the ophthalmic artery. Secondary diagnostic criteria included the presence of an enhancement of the optic nerve or its sheath, the optic disc, or inflammatory changes of posterior ciliary or extracranial arteries. A Fisher exact test was used to compare A-AION from NA-AION patients. RESULTS: Inflammatory changes of the ophthalmic artery were present in all patients with A-AION but in none of NA-AION (P < 0.0001). Its sensitivity, specificity, positive predictive value, and negative predictive value were 100%. Inflammatory changes of posterior ciliary arteries were significantly more likely in A-AOIN (82% vs 0%, P < 0.0001). Interreader and intrareader agreements were almost perfect (κ = 0.82-1). CONCLUSIONS: High-resolution vessel wall MRI seems highly accurate when distinguishing A-AION from NA-AION and might be useful to improve patient management.