**Core Concept:** Brimonidine is a topical alpha-2 agonist used as a medication for the treatment of glaucoma and ocular hypertension. It acts on ocular alpha-2 receptors to reduce intraocular pressure (IOP) by decreasing aqueous humor production and increasing aqueous humor outflow.

**Why the Correct Answer is Right:** Brimonidine acts as a selective alpha-2 agonist, specifically binding to ocular alpha-2 receptors. This binding leads to the following:

1. Reduced production of aqueous humor in the anterior chamber of the eye due to inhibition of the sympathetic activity.
2. Increased outflow of aqueous humor through the uveoscleral pathway, which is the less common outflow pathway in the eye.

**Why Each Wrong Option is Incorrect:**

A. **Option A (Agonism of alpha-1 receptors):** Brimonidine is a selective alpha-2 agonist, not alpha-1. Alpha-1 receptors are involved in vasoconstriction, which is not the desired effect for lowering IOP in glaucoma treatment.

B. **Option B (Inhibition of carbonic anhydrase):** Brimonidine does not inhibit carbonic anhydrase. Carbonic anhydrase inhibitors, such as timolol, are beta-blockers used for glaucoma treatment, but they work through a different mechanism than brimonidine.

C. **Option C (Increased aqueous humor production):** As explained earlier, brimonidine decreases aqueous humor production, not increases it.

D. **Option D (Inhibition of prostaglandin synthesis):** Brimonidine does not inhibit prostaglandin synthesis. Prostaglandin analogues, like latanoprost, are used in the treatment of glaucoma and work through a different mechanism than brimonidine.

**Clinical Pearl:** Alpha-2 agonists like brimonidine are part of a larger group of medications called alpha-blockers, which are used to lower IOP in glaucoma patients by targeting ocular alpha-2 receptors. Selecting the correct option (A) helps ensure effective treatment and minimize potential side effects associated with other mechanisms (B-D).