**Core Concept**
Horner's syndrome is a clinical disorder characterized by a disruption in the sympathetic innervation to the eye, resulting in a constellation of symptoms including ptosis, miosis, and anhidrosis. This condition arises from lesions affecting the sympathetic pathway from the hypothalamus to the eye, often due to trauma, cancer, or vascular events.

**Why the Correct Answer is Right**
The characteristic features of Horner's syndrome include:
- Ptosis (drooping eyelid) due to the loss of sympathetic innervation to the superior tarsal muscle.
- Miosis (constricted pupil) resulting from the absence of sympathetic activity on the dilator pupillae muscle.
- Anhidrosis (reduced sweating) on the affected side of the face.
These symptoms arise from the disruption of the sympathetic pathway, which is mediated by the enzyme dopamine beta-hydroxylase and the neurotransmitter norepinephrine.

**Why Each Wrong Option is Incorrect**
**Option A:** Miosis is a key feature of Horner's syndrome, so this option is incorrect.
**Option B:** Ptosis is also a hallmark of Horner's syndrome, making this option incorrect.
**Option C:** Anhidrosis is a common symptom of Horner's syndrome, particularly on the affected side of the face.

**Clinical Pearl / High-Yield Fact**
A useful mnemonic to remember the symptoms of Horner's syndrome is the acronym "PTA": Ptosis (drooping eyelid), Miosis (constricted pupil), and Anhidrosis (reduced sweating).

**Correct Answer: C. Anisocoria is typically seen in Horner’s syndrome, not anhidrosis.