Non-Arteritic Anterior Ischemic Optic Neuropathy (NAION)

A 62-year-old man with hypertension, type 2 diabetes, and obstructive sleep apnea awakens with sudden painless vision loss in the left eye. On examination, visual acuity is 6/36 in the affected eye with an inferior altitudinal visual field defect. Dilated fundoscopy shows the finding marked **A** in the diagram—a pale, diffusely swollen optic disc with blurred margins and splinter hemorrhages at the disc edge. The contralateral disc is small and crowded (disc-at-risk). Fluorescein angiography shows segmental delayed filling of the optic disc without choroidal delay. ESR is 12 mm/hr and CRP is 3 mg/L. Which of the following best explains the pathophysiology of this presentation?