**Core Concept**
Homer's syndrome is a rare disorder characterized by a combination of ptosis, miosis, and anhidrosis (absence of sweating) on the same side of the face as the lesion. It is caused by a disruption in the sympathetic nerves supplying the eye and face.

**Why the Correct Answer is Right**
The sympathetic nerves that control the eye and face originate from the hypothalamus and pass through the superior cervical ganglion. The fibers then synapse in the ciliary ganglion, which is responsible for regulating the diameter of the pupil and the amount of sweat produced. Homer's syndrome occurs when there is a lesion in the sympathetic pathway, resulting in a loss of sympathetic tone to the eye and face. This leads to the characteristic symptoms of ptosis, miosis, and anhidrosis.

**Why Each Wrong Option is Incorrect**
**Option A:** Ptosis is a feature of Homer's syndrome, so this is not the correct answer.
**Option B:** Miosis is also a feature of Homer's syndrome, so this is not the correct answer.
**Option C:** Anhidrosis is a feature of Homer's syndrome, so this is not the correct answer.

**Clinical Pearl / High-Yield Fact**
It's worth noting that Homer's syndrome is often associated with other conditions such as Horner's syndrome, which is a similar disorder that affects the same side of the face but does not involve anhidrosis.

**Correct Answer: D.**