**Core Concept:** Central retinal artery occlusion (CRAO) is a medical emergency characterized by complete blockage of the central retinal artery, leading to sudden loss of vision in one eye due to compromised blood supply to the retina.

**Why the Correct Answer is Right:** CRAO is typically caused by embolism, arterial dissection, or arterial spasm. However, the correct answer (D) refers to "arterial occlusion by cholesterol plaque" which is not a common cause of CRAO. In contrast, embolism, dissection, and spasm are more likely mechanisms leading to arterial blockage.

**Why Each Wrong Option is Incorrect:**

A. "Arterial occlusion by cholesterol plaque" is incorrect because it is not a common cause of CRAO.
B. "Increased intraocular pressure" is incorrect as it is unrelated to arterial blockage and does not explain the sudden onset of vision loss in CRAO.
C. "Retinal artery dissection" is incorrect because retinal artery dissection, which itself is a rare cause of CRAO, is characterized by arterial wall involvement, not occlusion by a plaque.
D. "Arterial occlusion by cholesterol plaque" is incorrect as explained above.

**Clinical Pearl / High-Yield Fact:**

Understanding the various causes of CRAO (e.g., embolism, arterial dissection, spasm) is essential for early recognition and appropriate management. Timely intervention is crucial as CRAO results in irreversible vision loss if not treated promptly.