**Core Concept**
Glaucoma is a group of eye conditions that damage the optic nerve, often due to abnormally high pressure in the eye (intraocular pressure, IOP). The primary goal of glaucoma treatment is to reduce IOP to prevent further damage.

**Why the Correct Answer is Right**
The treatment of glaucoma often involves the use of medications that lower IOP. These medications can be divided into several classes, including prostaglandin analogs, beta-blockers, alpha agonists, and carbonic anhydrase inhibitors. However, some medications are not used in the treatment of glaucoma.

* **Option A:** Timolol is a beta-blocker that is commonly used in the treatment of glaucoma to reduce IOP. It works by decreasing the production of aqueous humor in the eye. Therefore, this option is incorrect.
* **Option B:** Latanoprost is a prostaglandin analog that is used to treat glaucoma by increasing the outflow of aqueous humor from the eye. This option is incorrect because it is actually used in the treatment of glaucoma.
* **Option C:** Acetazolamide is a carbonic anhydrase inhibitor that is used in the treatment of glaucoma to reduce IOP. It works by decreasing the production of aqueous humor in the eye. This option is incorrect.
* **Option D:** Digoxin is a cardiac glycoside that is used to treat conditions such as atrial fibrillation and congestive heart failure. It is not used in the treatment of glaucoma because it does not have a significant effect on intraocular pressure.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the treatment of glaucoma often involves a combination of medications and surgical interventions to reduce IOP and prevent further damage to the optic nerve.

**Correct Answer:** D. Digoxin.