What does the term homonymous hemianopsia describe?

• A. Loss of color vision in both eyes
• B. Loss of central vision in one eye
• C. Loss of the same visual field in both eyes
• D. Loss of peripheral vision only in one eye

Answer: (C)

Homonymous hemianopsia describes losing the same half of the visual field in both eyes. This pattern appears when a lesion lies after the optic chiasm—in the contralateral post-chiasmal pathways (optic tract, optic radiations, or occipital cortex). Because the nasal retinal fibers cross at the chiasm and the temporal fibers stay on the same side, a right-sided post-chiasmal lesion causes left field loss in both eyes, and a left-sided lesion causes right field loss in both eyes. This is distinct from monocular losses (which involve only one eye) or from color or central vision problems.