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
An elderly male with hea disease presents with sudden loss of vision in one eye; examination reveals cherry red spot; diagnosis is: 
Select and explain. 
A. Central retinal vein occlusion, B. Central retinal aery occlusion, C. Amaurosis fugax, D. Acute ischemic optic neuritis
B: Central retinal aery occlusion
Answer: B: Central retinal aery occlusion 
Explanation: B i.e. Central Retinal Aery Occlusion Central retinal aery occlusion characteristically presents with sudden painless loss of vision, cherry red spot & cattle-truck appearanceQ (of retinal veins usually). Source of emboli from carotid aery & hea disease, and thrombus from aeriosclerosis along with hypeension & aeritis are predisposing factors.