## **Core Concept**
Primary Open-Angle Glaucoma (POAG) is a chronic condition characterized by the progressive loss of retinal ganglion cells and their axons, leading to optic nerve damage. This damage is often associated with increased intraocular pressure (IOP) and specific changes in the optic disc.

## **Why the Correct Answer is Right**
In POAG, several characteristic changes occur in the optic disc due to increased IOP. These include:
- **Horizontal cupping**: The optic cup typically enlarges horizontally due to the loss of nerve tissue and displacement of the lamina cribrosa.
- **Bayoneting sign**: This refers to the posterior displacement of the vessels as they cross over the edge of the cup, giving the appearance of a bayonet.
- **Dot sign**: Also known as the "dot-and-pencil" sign, it represents a small vessel that remains in the lamina cribrosa and appears as a dot.

## **Why Each Wrong Option is Incorrect**
- **Option C: Macular oedema** is not typically seen in POAG. POAG primarily involves progressive damage to the optic nerve head without directly causing macular edema. Macular edema is more commonly associated with conditions like diabetic retinopathy, retinal vein occlusion, or uveitis.

## **Clinical Pearl / High-Yield Fact**
A key clinical feature to remember in POAG is the **asymptomatic progression** of the disease until significant vision loss occurs. Early detection through regular eye exams and IOP checks is crucial. A classic exam trap is underestimating the importance of optic disc evaluation in glaucoma diagnosis.

## **Correct Answer:** C. Macular oedema