Okay, let's tackle this question step by step. The question is about a patient with acute congestive glaucoma in the right eye and asks for the prophylactic measure for the fellow eye. First, I need to recall what acute congestive glaucoma is. That's another term for acute angle-closure glaucoma, right? It's a medical emergency where the intraocular pressure (IOP) rises rapidly because the drainage angle of the eye becomes blocked. This can lead to vision loss if not treated promptly.

Now, the key here is the prophylactic measure for the fellow eye. Since the patient already has an acute attack in one eye, the other eye is at risk because angle-closure glaucoma often affects both eyes, especially if the underlying cause is anatomical, like a shallow anterior chamber or a small eye. So the fellow eye might have a similar anatomical predisposition.

The options weren't provided, but common prophylactic measures might include laser peripheral iridotomy, which creates a small hole in the iris to allow fluid to drain and prevent angle closure. Other options could be incorrect treatments like using beta-blockers, which are for chronic management, or other procedures like trabeculectomy, which is more for chronic cases. Another possible wrong option might be a different type of laser treatment, like YAG, which is used for posterior capsule opacification, not for angle closure.

So the correct answer is likely laser peripheral iridotomy. The reasoning is that this procedure prevents the acute attack in the fellow eye by creating an alternative pathway for aqueous humor to flow from the posterior to the anterior chamber, thus preventing the pupillary block that leads to angle closure. Other options don't address the anatomical issue or are used for different conditions. The clinical pearl here is to remember that for patients with acute angle-closure in one eye, the fellow eye should undergo prophylactic iridotomy to prevent a similar attack.

**Core Concept**
Acute angle-closure glaucoma (AACG) occurs due to sudden blockage of the trabecular meshwork by the iris, causing rapid intraocular pressure (IOP) elevation. Prophylaxis in the fellow eye targets anatomical predispositions like pupillary block or narrow angles.

**Why the Correct Answer is Right**
The prophylactic measure is **laser peripheral iridotomy (LPI)**. This creates a small hole in the iris, allowing aqueous humor to bypass the pupillary block and equalize pressure between anterior and posterior chambers. It prevents angle closure in the fellow eye by addressing the root anatomical cause. LPI is first-line for high-risk eyes with narrow angles or a history of AACG in one eye.

**Why Each Wrong Option is Incorrect**
**Option A:** *Medical therapy (e.g., beta-blockers)* reduces IOP but does not address anatomical risk factors for angle closure.
**Option B:** *Trabeculectomy* is a surgical intervention for chronic glaucoma, not prophylaxis.
**Option C:** *YAG laser capsulotomy* treats posterior capsule opacification, unrelated to angle closure.

**Clinical Pearl / High-Yield Fact**
Never miss prophylactic LPI in the fellow eye of AACG patients. The mnemonic **"One eye, two eyes—iridotomy, not

✓ Correct Answer: D. Laser iridotomy