Which visual field defect is most common after severe traumatic brain injury?

• A. Nasal step
• B. Bitemporal VF defect
• C. Homonymous hemianopsia
• D. Central scotoma

Answer: (C)

When trauma damages the visual pathways behind the optic chiasm, the most common outcome is a homonymous hemianopsia—the same half of the visual field is lost in both eyes. This occurs because the fibers after the chiasm carry information from the opposite side of space, so a lesion in the left occipital lobe or left optic radiations produces a right homonymous hemianopia, and a right-side injury produces a left one. In severe brain injury, contusions or diffuse axonal injury often involve the posterior cerebral structures where these post-chiasmal fibers reside, making this defect the typical post-injury pattern. By contrast, a bitemporal defect would imply chiasmal involvement, a central scotoma points to macular or retinal/optic nerve issues, and a nasal step aligns more with glaucoma or anterior pathway damage rather than post-chiasmal injury.