A tumor compresses the center of a patient's optic chiasm, selectively damaging the axons that cross there. Which visual deficit is most likely to result?
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Answer: D (Loss of the peripheral visual fields of both eyes)
At the optic chiasm, axons from the nasal half of each retina cross to the opposite side. These retinal regions receive information from the peripheral, or temporal, visual fields. Compression of the center of the optic chiasm therefore disrupts peripheral vision in both eyes. Loss of vision in only one eye would result from damage to an optic nerve before the chiasm, whereas loss of the same visual field in both eyes would result from damage posterior to the chiasm.