Correct! These constricted visual fields contain powerful localizing features--the “step-offs” in the visual field defects along the vertical meridian that are identical in the corresponding hemifields. In other words, these are BILATERAL CONGRUOUS HOMONYMOUS HEMIANOPIAS. Although the responsible lesions could lie anywhere in the retrochiasmal portion of the visual pathway on both sides, the most common location would be in visual cortex, where a single event—occlusion of the basilar artery or its two branches, the posterior cerebral arteries, could infarct both sides.

Do not be surprised if the profound visual field loss is the patient’s only new deficit—that happens if the proximal posterior arterial circulation opens up quickly. Echocardiography showed an aortic valve vegetation, which could have been the source of emboli. Were the optic chiasm the site of damage, visual fields would have been variants of bitemporal hemianopia, not homonymous hemianopia. Bilateral optic nerve damage would cause visual field defect “step-offs” along the horizontal meridian, not seen here. Bilateral simultaneous retinal events—detachments or infarctions—are exceedingly rare and would not cause such symmetrical visual field defects with borders aligned to the vertical meridian. By the way, the patient need not have infarcted both sides of visual cortex at the same time. He could have had an old unilateral homonymous hemianopia about which he was unaware and now experienced a second event affecting only one cerebral hemisphere.

Incorrect

Incorrect

Incorrect