Review Question - QID 214780

A 43-year-old man presents with decreased vision in his left eye. The patient is homeless and is unaware of his medical history. He has progressive difficulty reading signs and words, especially in the left eye, for the past 3 months. He endorses “black flies” in his vision and some generalized blurriness but denies any pain, recent trauma, discharge, flashing lights, or current eyeglasses or contact lens use. On review of systems, he endorses watery diarrhea, which he claims is normal for him. On examination, the patient is thin appearing and has areas of white patches on his tongue that can be scraped away. His temperature is 98.6°F (37.0°C), blood pressure is 115/70 mmHg, pulse is 70/min, and respirations are 12/min. Visual acuity is hand motion in the left eye and 20/25 in the right eye. There is a relative afferent pupillary defect in the left eye but not the right eye. The anterior chamber is deep and quiet with no cell or flare bilaterally. A dilated fundus examination demonstrates the findings shown in Figure A. Which of the following is the most appropriate treatment?