Cortical blindness

A 67-year-old man presents to the emergency department for evaluation of visual impairment. The patient has not had headache, trauma, or difficulty with speech, swallowing, or walking. Past medical history is significant for coronary artery disease, hypertension and hyperlipidemia. Temperature is 37°C (98.6°F), pulse is 120/min (irregularly irregular), respirations are 17/min and blood pressure is 160/90 mm Hg. On neurological examination, the patient is alert and oriented to person, place, and time. Speech is fluent, and the patient follows all commands. Visual field examination findings are shown below.  The remainder of the neurological examination is within normal limits. Perfusion of which of the following regions of the brain is most likely impaired in this patient?