Lesion at which pa of visual pathway causes homonymous hemianopia?
**Core Concept**
The visual pathway is a complex system that transmits visual information from the eyes to the brain. A lesion in this pathway can cause various visual field defects, including **homonymous hemianopia**, which is a loss of vision in the same half of the visual field in both eyes. This occurs due to damage to the **optic tract** or further back in the visual pathway.
**Why the Correct Answer is Right**
A lesion in the **optic tract** or **lateral geniculate body** can cause homonymous hemianopia because these structures carry visual information from the opposite half of the visual field in both eyes. Damage to these areas results in the loss of visual input from the affected half of the visual field, leading to homonymous hemianopia.
**Why Each Wrong Option is Incorrect**
**Option A:** A lesion in the optic nerve causes monocular blindness, not homonymous hemianopia.
**Option B:** A lesion in the optic chiasm causes bitemporal or binasal hemianopia, depending on the location.
**Option D:** A lesion in the visual cortex can cause various visual field defects, but homonymous hemianopia typically results from lesions before the visual cortex.
**Clinical Pearl / High-Yield Fact**
Homonymous hemianopia is often associated with **contralateral hemisphere lesions**, and it's essential to identify the location of the lesion to determine the underlying cause.
**Correct Answer:** C. Optic Tract.