## Core Concept
Acute angle-closure glaucoma is a medical emergency characterized by a sudden increase in intraocular pressure (IOP) due to obstruction of the pupillary aperture and subsequent iris blocking the trabecular meshwork. Management involves reducing IOP and improving aqueous outflow. Certain medications can exacerbate this condition by causing pupillary dilation or increasing IOP.

## Why the Correct Answer is Right
Pilocarpine is a muscarinic receptor agonist that causes miosis (pupillary constriction). In the context of acute angle-closure glaucoma, **pilocarpine** can help alleviate the condition by increasing the outflow of aqueous humor through the trabecular meshwork, thereby reducing intraocular pressure. It is used as part of the treatment regimen to manage acute angle-closure glaucoma.

## Why Each Wrong Option is Incorrect
* **Option A:** Atropine is an anticholinergic agent that causes mydriasis (pupillary dilation). This can worsen acute angle-closure glaucoma by further dilating the pupil, which can increase the obstruction of the trabecular meshwork and exacerbate the condition.
* **Option B:** Antihistamines can also cause pupillary dilation and dryness, potentially worsening the condition.
* **Option C:** Anticholinergic and sympathomimetic agents can cause mydriasis, which is contraindicated in acute angle-closure glaucoma.

## Clinical Pearl / High-Yield Fact
A key point to remember is that in acute angle-closure glaucoma, the goal is to decrease intraocular pressure and improve aqueous outflow. Medications that cause mydriasis (pupillary dilation) should be avoided, while those that cause miosis (pupillary constriction) can be therapeutic.

## Correct Answer: D. Pilocarpine