What visual field defect results from damage to the optic chiasm?

What visual field defect results from damage to the optic chiasm?

• A. Homonymous hemianopsia
• B. Central scotoma
• C. Monocular blindness
• D. Bitemporal Hemianopsia

Answer: (D)

The key idea is that the optic chiasm is where the nasal-retinal fibers cross to the opposite side, so it carries information about the temporal (outer) visual fields from both eyes. When the crossing fibers are damaged at the chiasm, the temporal fields from both eyes are lost, producing bitemporal hemianopsia. This pattern is classically seen with lesions compressing the chiasm, such as pituitary tumors. In contrast, a lesion after the chiasm causes a homonymous hemianopsia (loss of the same side of the field in both eyes), central scotoma involves central vision, and monocular blindness results from damage to one optic nerve before the chiasm.

The key idea is that the optic chiasm is where the nasal-retinal fibers cross to the opposite side, so it carries information about the temporal (outer) visual fields from both eyes. When the crossing fibers are damaged at the chiasm, the temporal fields from both eyes are lost, producing bitemporal hemianopsia. This pattern is classically seen with lesions compressing the chiasm, such as pituitary tumors. In contrast, a lesion after the chiasm causes a homonymous hemianopsia (loss of the same side of the field in both eyes), central scotoma involves central vision, and monocular blindness results from damage to one optic nerve before the chiasm.