Review Question - QID 216735

A 71-year-old man presents to the emergency department with a 1-hour history of vision loss in his right eye. He says that he was watching television when he suddenly was unable to see out of his right eye. He did not note any pain or other associated symptoms when this visual loss occurred. As he sits in the emergency department, his vision slowly returns. His temperature is 98.3°F (36.8°C), blood pressure is 166/92 mmHg, pulse is 89/min, respirations are 16/min, and oxygen saturation is 99% on room air. Physical exam reveals 20/20 vision in both eyes with the patient wearing glasses which is his baseline. He walks with a steady gait and has normal strength and sensation in the upper and lower extremities. His cranial nerves are grossly intact. Which of the following is the most likely cause of this patient's symptoms?