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: Ophthalmology
[{'content': 'All of the following may be used to differentiate Central Retinal Venous Occlusion (CRVO) from ocular Ischemic syndrome due to carotid artery stenosis, Except – \nSelect and explain. \nA. Dilated retinal vein, B. Tortuous retinal vein, C. Retinal artery pressure, D. Opthalmodynamometry', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Dilated retinal vein is seen both in CRVO and ocular ischemic syndrome; therefore, this feature cannot differentiate these two. However, in CRVO vein is tortuous while in ocular ischemic syndrome it is non-tortuous.\nRetinal artery perfusion pressure is decreased in ocular ischemic syndrome and is normal in CRVO.\nOphthalmodynamometry shows low ophthalmic artery pressure in ocular ischemic syndrome and normal to high pressure in CRVO.', 'role': 'assistant'}]