**Question:** Painless sudden loss of vision occurs in all EXCEPT

A. Central retinal artery occlusion
B. Uveitis
C. Migraine
D. Carotid artery occlusion

**Correct Answer:** **Option C: Migraine**

**Core Concept:** Sudden loss of vision can result from various causes involving different anatomical structures and physiological processes. These include arterial occlusions, inflammatory conditions, and neurological disorders.

**Why the Correct Answer is Right:** Migraine is a neurological disorder characterized by recurrent, severe headaches typically associated with nausea, vomiting, and sensitivity to light and sound. In migraines, blood vessels in the brain undergo vasospasm (constriction), which does not result in a complete blockage or occlusion of blood vessels supplying the retina or optic nerve.

**Why Each Wrong Option is Incorrect:**

**A. Central retinal artery occlusion (CRAO)**: This occurs due to occlusion of the central retinal artery, leading to sudden, severe vision loss. Causes may include embolism, atherosclerosis, or trauma.

**B. Uveitis:** Uveitis is an inflammation of the uvea, a layer of the eye containing blood vessels, iris, and choroid. It can lead to vision loss due to inflammation, edema, and blockage of blood vessels or optic nerve compression.

**C. Migraine**: As explained above, migraines involve vasospasm, not occlusion, of blood vessels. Migraine-induced vision loss is usually intermittent and not sudden.

**D. Carotid artery occlusion:** This occurs due to occlusion of the major blood vessels supplying the brain, resulting in stroke and neurological deficits, not sudden vision loss.

**Clinical Pearl:** Sudden vision loss can be a concerning symptom, and prompt medical attention is essential in evaluating and managing these cases. In contrast to migraine, other causes of sudden vision loss (CRAO, uveitis, and carotid artery occlusion) typically manifest with specific clinical features and risk factors.