**Core Concept**
Papilloedema is a condition characterized by swelling of the optic disc due to increased intracranial pressure (ICP). This swelling is caused by the pressure exerted on the optic nerve head, leading to the displacement and distortion of the retinal vessels.

**Why the Correct Answer is Right**
Papilloedema occurs when there is a rise in ICP, which can be due to various causes such as tumors, hemorrhages, or hydrocephalus. The increased pressure causes the optic disc to become edematous and swollen, which can lead to visual disturbances and even blindness if left untreated. The optic disc edema is typically bilateral and can be accompanied by other signs such as retinal hemorrhages and cotton-wool spots.

**Why Each Wrong Option is Incorrect**
**Option A:** Visual field defects are not a primary feature of papilloedema, although they can occur in advanced cases.
**Option B:** Papilledema is not typically associated with a decrease in visual acuity, as the swelling of the optic disc does not directly affect the retina's ability to transmit visual information.
**Option C:** Enlargement of the blind spot is a common feature of papilloedema, as the swelling of the optic disc can cause the displacement of the retina and the optic nerve fibers.

**Clinical Pearl / High-Yield Fact**
A key clinical feature of papilloedema is the presence of a "cotton-wool spot," which is a small, white, fluffy area of retinal edema that can be seen on fundoscopic examination.

**Correct Answer: C. Enlargement of the blind spot**