Clinical Reasoning: A 64-year-old man with visual distortions

A 64-year-old right-handed man presented to the emergency department with a 4-week history of bilateral blurred and distorted vision. He reported that objects in his central visual field appeared to change shape and were disproportionately large or small. He also reported intermittent flashes of light with altered color perception. His medical history was notable for prostate cancer treated with prostatectomy, Bell palsy at age 25, gastroesophageal reflux disease, and bilateral refractive errors. His family had also noted intermittent episodes of confusion and anger over the preceding weeks along with difficulty recognizing family members. He endorsed minimal right-sided periorbital headache but reported no diplopia, weakness, paresthesiae, numbness, speech changes, or history of similar symptoms. He had no recent history of fever, illness, or infectious exposures. He had no history of seizures or migraine. He was taking omeprazole and did not smoke or use alcohol or illicit drugs.