Clinical reasoning: acute-onset homonymous hemianopia with hyperglycemia: seeing is believing.

A 32-year-old woman with a history of bipolar disorder, polycystic ovarian syndrome, and hypertension and a 4-year history of uncontrolled type 2 diabetes mellitus (DM) presented with bifrontal headache, elevated blood sugars (>500 mg/dL), and abrupt-onset left homonymous hemianopia upon awakening. Vital signs included temperature 98.0 degrees F, blood pressure 160/89 mm Hg, and heart rate 67 bpm. Neurologic examination showed dense left homonymous hemianopia with macular sparing and without other focal findings.