**Core Concept**
Sudden loss of vision is typically due to acute ocular pathologies affecting the retina, anterior chamber, or optic nerve. The mechanism often involves obstruction of visual pathways, inflammation, or ischemia, whereas chronic or gradual conditions do not present with abrupt onset.

**Why the Correct Answer is Right**
Central serous retinopathy (CSR) is a condition where subretinal fluid accumulates, causing a sudden, often unilateral, loss of vision due to retinal dysfunction. Endophthalmitis involves acute inflammation of the eye, leading to rapid vision loss. Angle closure glaucoma results in sudden vision loss due to elevated intraocular pressure from blocked aqueous humor outflow. Corneal ulceration, while painful and potentially sight-threatening, usually causes **gradual** vision loss due to corneal opacity or opacity progression, not sudden onset. It may cause pain and photophobia, but not abrupt, immediate vision loss like the others.

**Why Each Wrong Option is Incorrect**
Option A: Angle closure glaucoma causes sudden vision loss due to acute optic nerve compression from iris blockage.
Option B: Endophthalmitis causes rapid, severe vision loss due to inflammation and retinal damage.
Option C: Central serous retinopathy presents with sudden, often unilateral, blurred vision due to retinal fluid accumulation.

**Clinical Pearl / High-Yield Fact**
Sudden vision loss is a red flag for acute conditions like glaucoma or retinal detachment. Always consider **acute uveitis, glaucoma, or retinal detachment** in such cases — corneal ulcers are typically **chronic**, painful, and associated with infection, not sudden visual loss.

✓ Correct Answer: D. Corneal ulceration