## **Core Concept**
Primary glaucoma refers to a group of eye conditions characterized by progressive optic neuropathy associated with visual field defects, where the intraocular pressure (IOP) is elevated. It is termed "primary" when there is no underlying cause or secondary condition leading to the increased IOP. The two main types are primary open-angle glaucoma (POAG) and primary angle-closure glaucoma (PACG).

## **Why the Correct Answer is Right**
The correct answer, **D. Primary Open-Angle Glaucoma (POAG)**, is a type of primary glaucoma. POAG is the most common form of glaucoma and is characterized by the slow clogging of the drainage canals, resulting in increased eye pressure. This condition progresses gradually and is often asymptomatic until significant vision loss occurs. The mechanism involves impaired trabecular meshwork outflow, leading to elevated IOP.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not specify a known type of primary glaucoma. Without specific details, it's hard to assess its accuracy directly.
- **Option B:** This option is incorrect as it refers to secondary glaucoma, which results from identifiable causes such as trauma, surgery, or other eye diseases.
- **Option C:** This option is incorrect because it is not a recognized classification of glaucoma.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that **Primary Open-Angle Glaucoma (POAG)** often presents bilaterally and asymmetrically, with patients typically being asymptomatic until late in the disease. Early detection through screening and regular eye exams is crucial for preventing irreversible vision loss.

## **Correct Answer:** D. Primary Open-Angle Glaucoma.