A 44-year-old woman presents to the emergency department with a 24-hour history of painless, gradual loss of vision in her left eye. She describes her vision as “dark and blurry.” The patient’s medical history is significant for pulmonary embolism, renal failure (treated with dialysis), and diabetes. Her vital signs are normal, and physical examination was unremarkable except for an afferent pupillary defect and low visual acuity on the counting fingers test in the left eye. The patient currently has a dialysis shunt in her arm.

Can you diagnose this condition? What is the next best step in testing and treatment?

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