Bitemporal hemianopia is seen in lesion of
**Core Concept**
Bitemporal hemianopia is a type of visual field defect characterized by the loss of vision in the outer half of each visual field. It occurs due to a lesion affecting the optic chiasm, specifically the fibers carrying information from the nasal halves of each retina.
**Why the Correct Answer is Right**
The optic chiasm is a critical structure where the optic nerves from each eye cross over partially. The nasal fibers from each eye cross over to the opposite side, while the temporal fibers remain on the same side. A lesion in the optic chiasm, such as a pituitary tumor, can compress the crossing nasal fibers, leading to bitemporal hemianopia. This type of defect is typically seen in conditions affecting the pituitary gland, such as pituitary adenomas or other space-occupying lesions.
**Why Each Wrong Option is Incorrect**
**Option A:** Lesion of the optic nerve would result in unilateral visual loss, not bitemporal hemianopia.
**Option B:** Lesion of the occipital lobe would result in homonymous hemianopia, not bitemporal hemianopia.
**Option C:** Lesion of the optic tract would result in homonymous hemianopia, not bitemporal hemianopia.
**Clinical Pearl / High-Yield Fact**
The optic chiasm is a common site for lesions causing bitemporal hemianopia, but it's essential to remember that other conditions, like optic neuritis or optic nerve sheath meningiomas, can also cause visual field defects.
**Correct Answer:** C. Lesion of the optic chiasm.