**Core Concept**
Angle closure glaucoma is a medical emergency characterized by a sudden increase in intraocular pressure (IOP) due to the closure of the iridocorneal angle. This condition can lead to optic nerve damage and vision loss if not promptly treated.

**Why the Correct Answer is Right**
The first line of treatment for angle closure glaucoma involves reducing the IOP to prevent further damage to the optic nerve. **Pilocarpine**, a muscarinic receptor agonist, is the drug of choice for initial management. Pilocarpine works by constricting the pupil (miosis) and increasing the outflow of aqueous humor through the trabecular meshwork, thereby reducing IOP. Additionally, pilocarpine helps to open the iridocorneal angle, allowing more aqueous humor to drain.

**Why Each Wrong Option is Incorrect**
**Option A:** **Atropine** is an anticholinergic agent that would worsen angle closure glaucoma by dilating the pupil, increasing the obstruction of the iridocorneal angle.
**Option B:** **Timolol** is a beta-blocker that reduces aqueous humor production but may not be effective in the acute setting of angle closure glaucoma.
**Option C:** **Acetazolamide** is a carbonic anhydrase inhibitor that reduces aqueous humor production but is not the first line of treatment for angle closure glaucoma.

**Clinical Pearl / High-Yield Fact**
In the setting of angle closure glaucoma, prompt treatment with pilocarpine and subsequent iridotomy (laser peripheral iridotomy) is essential to prevent long-term vision loss.

**Correct Answer: C. Pilocarpine**