A young man presented to the emergency department with a 1-day history of vision loss in the left eye. He had experienced eye redness for 1 week, which resolved with use of artificial tears; a mild posterior headache; and paresthesias of the left thumb and index and middle fingers.
His medical history was significant for epilepsy as a child, although he had been seizure free for more than 10 years without medication. He had no ocular history, was not taking any medications, and had no known drug allergies. He smoked 2 to 4 packs of cigarettes per day, consumed 1 to 3 alcoholic drinks per day, and denied illicit drug use. He denied recent travel, vaccinations, systemic illnesses, or influenza-like symptoms.