Okay, let's tackle this question. The patient has sudden onset blindness without pain. The options aren't listed, but the correct answer is missing. Hmm. I need to figure out what the possible causes are for sudden painless vision loss.

First, I recall that sudden vision loss can be due to various conditions. The key here is the absence of pain. Painful vision loss might be something like optic neuritis or uveitis. But without pain, the possibilities are different. Common causes include arterial occlusions, like central retinal artery occlusion (CRAO) or amaurosis fugax. Also, maybe a retinal detachment, but that usually has other symptoms like floaters or flashes. Another possibility is a stroke affecting the visual pathways, such as a posterior cerebral artery (PCA) stroke. Macular degeneration is usually gradual, so probably not that. Diabetic retinopathy can cause sudden loss if there's a hemorrhage, but that's less common.

Wait, the question says "sudden onset," so I should focus on acute causes. CRAO is a classic example of painless, sudden vision loss. The patient might have a history of atherosclerosis or carotid artery disease. Amaurosis fugax is transient and due to an embolus from the carotid artery. But if it's persistent, it's more likely CRAO. PCA stroke can also cause homonymous hemianopia, but that's usually in both eyes. Retinal detachment might present with painless loss, but usually with other symptoms like floaters or a curtain effect.

So the correct answer is likely CRAO. Now, let's structure the explanation. The core concept is understanding the differential diagnosis for sudden painless vision loss. The correct answer is CRAO because it's caused by occlusion of the central retinal artery, leading to ischemia. The other options need to be addressed. For example, if an option was optic neuritis, that's painful. Retinal detachment has other symptoms. Stroke might be a distractor but presents differently. The clinical pearl here is that painless sudden vision loss is often due to vascular occlusion, and CRAO is a medical emergency requiring immediate treatment like ocular massage or thrombolysis. The correct answer should be the one referring to CRAO.

**Core Concept**
Sudden painless vision loss typically indicates an ocular or neurological vascular emergency. Central retinal artery occlusion (CRAO) is a classic cause due to embolic occlusion of the retinal artery, leading to ischemic injury without pain.

**Why the Correct Answer is Right**
Central retinal artery occlusion (CRAO) occurs when the central retinal artery is blocked, often by an embolus from the carotid artery or heart. This results in abrupt, painless vision loss due to retinal ischemia. The retina lacks pain receptors, so pain is absent. Immediate intervention (e.g., ocular massage, paracentesis) is critical to restore blood flow and prevent permanent vision loss.

**Why Each Wrong Option is Incorrect**
**Option A:** *Optic neuritis* typically causes painful vision loss, often with optic nerve inflammation and demyelination (e.g., multiple sclerosis).
**Option B:** *Retinal detachment* usually presents with floaters, flashes, or a "curtain

✓ Correct Answer: C. Vitreous haemorrhage