**Core Concept**
Papilloedema is a condition characterized by swelling of the optic disc due to increased intracranial pressure. The earliest sign of papilloedema is a subtle change in the optic disc appearance, often detected through ophthalmoscopy.

**Why the Correct Answer is Right**
The correct answer is related to the visual field defect that occurs in papilloedema. The earliest sign of papilloedema is a small, blind spot in the visual field, usually in the upper quadrants. This is due to the compression of the optic nerve fibers, which can be detected before any visible changes in the optic disc. The blind spot is caused by the compression of the papillomacular bundle, a group of nerve fibers that are responsible for central vision.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the first visible sign of papilloedema is not the disc pallor, which occurs later in the course of the disease.
**Option B:** This option is incorrect because the venous engorgement is a sign of increased intracranial pressure, but it is not the earliest sign of papilloedema.
**Option C:** This option is incorrect because the retinal hemorrhages are a sign of advanced papilloedema, not the earliest sign.

**Clinical Pearl / High-Yield Fact**
The earliest sign of papilloedema can be subtle and may require careful observation to detect. It is essential to perform a thorough visual field examination to detect the blind spot, which is often the first sign of papilloedema.

**Correct Answer: C. Visual field defect (blind spot)**