Non-Arteritic Anterior Ischemic Optic Neuropathy (AION)

A 65-year-old man with type 2 diabetes, hypertension, and obstructive sleep apnea on CPAP presents with sudden painless vision loss in the right eye on waking. Visual acuity is counting fingers at 2 meters. Fundoscopy reveals the structure marked **A** in the diagram—pale segmental optic disc edema in an altitudinal pattern—with splinter hemorrhages at the disc margin. ESR is 22 mm/hr and CRP is 4 mg/L. The contralateral disc is small and crowded. Which of the following best explains the pathophysiology of this presentation?