Field defect seen in papilloedema
**Core Concept**
Papilloedema is a condition characterized by swelling of the optic disc, often due to increased intracranial pressure. The primary field defect seen in papilloedema is related to the compression of the optic nerve and its surrounding structures.
**Why the Correct Answer is Right**
The characteristic field defect in papilloedema is a bitemporal hemianopia. This occurs due to the compression of the optic chiasm, which is the location where the optic nerves from each eye cross over. As the optic chiasm is compressed, the crossing fibers are affected, leading to a loss of vision in the temporal fields of both eyes. The optic chiasm is a critical structure where the optic nerves from each eye cross over, and its compression can lead to bitemporal hemianopia.
**Why Each Wrong Option is Incorrect**
**Option A:** Central scotoma - This type of field defect is typically seen in conditions affecting the macula, such as macular degeneration, and is not characteristic of papilloedema.
**Option B:** Homonymous hemianopia - This type of field defect occurs when there is damage to the optic tract or higher, and is not typically seen in papilloedema.
**Option C:** Quadrantanopia - This type of field defect occurs when there is damage to a portion of the visual pathway, but is not characteristic of papilloedema.
**Clinical Pearl / High-Yield Fact**
Papilloedema can be a sign of increased intracranial pressure, and its presence should prompt further investigation to rule out underlying causes such as tumors, hemorrhages, or other conditions that may be causing the increased pressure.
**Correct Answer: D. Bitemporal hemianopia.**