Review Question - QID 109681

A 27-year-old man presents to the emergency department with pain in his right eye. The patient states that his eye hurts and that he cannot see well. He cannot remember when his symptoms started or what caused them. The patient has a past medical history of schizophrenia and IV drug abuse. His current medications include intramuscular haloperidol and nicotine patches. The patient has a 20-pack-year smoking history. His temperature is 99.5°F (37.5°C), blood pressure is 120/68 mmHg, pulse is 100/min, respirations are 15/min, and oxygen saturation is 98% on room air. On physical exam, you note a poorly kempt man as well as the findings shown in Figure A. Pain is elicited upon examination of cranial nerve 3 in the right eye. The patient is unable to read a chart on the wall of the exam room and complains of double vision. Which of the following is the most likely diagnosis?