This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anaesthesia
Most common cause of ruheosis iridis ? 
Select and explain. 
A. Tumor, B. CRAO, C. Radiation retinopathy, D. Diabetic retinopathy
D: Diabetic retinopathy
Answer: D: Diabetic retinopathy 
Explanation: Ans. is 'd' i.e., Diabetic retinopathy Causes of rubeosis iridis (neovascularization of iris) Common :- Diabetic retinopathy (most common cause), central retinal vein occlusion, Eale's disease, sickle-cell retinopathy. Rare causes :- Long standing retinal detachment, central retinal aery occlusion, intraocular inflammation (uveitis), intraocular tumors (choroidal melanoma, retinoblastoma), radiation retinopathy, ocular ischemic syndrome (carotid aery disease, carotid-cavernous fistula).