## **Core Concept**
Amaurosis fugax, also known as transient monocular vision loss, is a condition characterized by temporary loss of vision in one eye. It is often described as a curtain or shade descending over the eye. This condition is typically caused by a temporary reduction in blood flow to the retina.

## **Why the Correct Answer is Right**
The correct answer, **D. Central retinal artery**, is right because amaurosis fugax is most commonly caused by embolic occlusion of the central retinal artery or its branches. The central retinal artery is a branch of the ophthalmic artery, which itself is a branch of the internal carotid artery. Emboli that temporarily occlude this artery can lead to transient ischemia of the retina, manifesting as amaurosis fugax.

## **Why Each Wrong Option is Incorrect**
- **Option A:** The posterior cerebral artery primarily supplies the occipital lobe and is involved in the visual pathway but not directly responsible for amaurosis fugax.
- **Option B:** The internal carotid artery is the parent artery for the ophthalmic artery and subsequently the central retinal artery, but occlusion of the internal carotid artery would more likely lead to broader cerebral or ocular ischemic symptoms rather than transient monocular vision loss.
- **Option C:** The ophthalmic artery does give rise to the central retinal artery, but amaurosis fugax is more specifically related to occlusion of the central retinal artery itself rather than the ophthalmic artery.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that amaurosis fugax is a transient and reversible condition but often serves as a warning sign for future ischemic strokes. Patients with amaurosis fugax are at increased risk of stroke, and thus, it is crucial to investigate the cause, often involving imaging of the carotid arteries to look for stenosis or sources of emboli.

## **Correct Answer:** **D.** Central retinal artery.