Central retinal artery occlusion

A 68-year-old man with atrial fibrillation (off anticoagulation due to prior GI bleed) presents to the emergency department with sudden painless complete loss of vision in the right eye occurring 90 minutes ago. Visual acuity is no light perception with a relative afferent pupillary defect. Fundus examination of the right eye reveals the findings marked **A** in the diagram: a diffusely pale edematous retina with a striking cherry-red spot at the fovea and markedly attenuated arterioles with segmentation of blood column (cattle-trucking). ESR and CRP are normal. Which of the following is the MOST LIKELY DIAGNOSIS?

A 72-year-old woman with hypertension and atrial fibrillation on subtherapeutic warfarin presents with sudden painless loss of vision in the right eye 90 minutes earlier. Visual acuity is hand motions with a dense relative afferent pupillary defect. Dilated fundoscopy reveals the acute findings of central retinal artery occlusion. The structure marked **A** in the diagram appears as a bright red spot at the fovea against a surrounding pale, milky-white retina. Which of the following best explains the pathophysiology of this finding?