**Question:** The most common cause of glaucoma with elevated IOP and optic nerve damage present in only ONE eye is

A. Angle-closure glaucoma
B. Primary open-angle glaucoma
C. Normal-tension glaucoma
D. Secondary glaucoma

**Correct Answer:** **A. Angle-closure glaucoma**

**Core Concept:** Glaucoma is a group of eye diseases characterized by optic nerve damage and associated with elevated intraocular pressure (IOP). Two main types exist: angle-closure and open-angle glaucoma.

**Why the Correct Answer is Right:** Angle-closure glaucoma is caused by a partial or complete closure of the drainage angle between the cornea and the iris, leading to an increased IOP. When the damage is limited to only one eye, it is called unilateral angle-closure glaucoma. This clinical presentation is distinct from other types of glaucoma, which typically involve both eyes.

**Why Each Wrong Option is Incorrect:**

**A. Primary open-angle glaucoma**: This type of glaucoma has a normal or slightly elevated IOP, making it an unlikely choice for the given scenario.

**B. Normal-tension glaucoma**: Although normal tension, it typically affects both eyes, not just one.

**C. Normal-tension glaucoma**: Similar to B, this type usually involves both eyes.

**D. Secondary glaucoma**: Secondary glaucoma is caused by an underlying condition, such as an infection or injury. The question specifies that the glaucoma is primary, making this option incorrect.

**Clinical Pearl:** Unilateral angle-closure glaucoma should prompt a thorough examination for the affected individual, as it may indicate a potential impending bilateral angle-closure attack. Early treatment can prevent further vision loss in the unaffected eye.