**Core Concept**
The optic radiation is a bundle of nerve fibers that carries visual information from the lateral geniculate nucleus to the primary visual cortex. A lesion in this area, specifically in Meyer's loop, can cause visual field defects. **Meyer's loop** is a portion of the optic radiation that carries fibers from the lower part of the visual field.

**Why the Correct Answer is Right**
A lesion in Meyer's loop would specifically affect the fibers carrying information from the lower part of the visual field, leading to a **contralateral upper quadrantanopia**. This is because the fibers in Meyer's loop are responsible for transmitting visual information from the contralateral lower visual field to the ipsilateral visual cortex.

**Why Each Wrong Option is Incorrect**
**Option A:**
**Option B:**
**Option C:**
**Option D:**

**Clinical Pearl / High-Yield Fact**
A key point to remember is that lesions in different parts of the visual pathway can cause distinct visual field defects, making it crucial to understand the anatomy of the visual pathway for accurate diagnosis.

**Correct Answer:** D. Contralateral upper quadrantanopia.