Which of the following best describes central retinal venous occlusion?

• A. Sudden or gradual vision loss, floaters, 'blood and thunder' fundus appearance.
• B. Severe eye pain with photophobia and corneal edema.
• C. Progressive peripheral vision loss with normal retina.
• D. Acute onset diplopia with normal fundus.

Answer: (A)

Central retinal venous occlusion causes sudden painless vision loss in one eye because the main retinal vein becomes blocked, leading to impaired drainage and retinal hemorrhages. The hallmark fundus finding is congested, dilated and tortuous veins with widespread retinal hemorrhages and optic disc edema, producing the classic "blood and thunder" appearance. Floaters can occur with hemorrhages, but the key feature is the sudden vision loss paired with that distinctive fundus picture, which fits CRVO best.

The other scenarios point to different problems: severe eye pain with photophobia and corneal edema suggests an acute angle-closure crisis or corneal edema from another cause rather than a retinal vein occlusion; progressive peripheral vision loss with a normal retina implies a vitreoretinal or optic neuropathy different from CRVO; acute onset diplopia with a normal fundus indicates a misalignment or cranial nerve palsy rather than retinal vascular occlusion.