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': 'A young patient presented with sudden painless loss of vision with systolic murmur over chest, ocular examination reveals – cherry red spot in macula with clear AC, with perception of light, diagnosis – \nSelect and explain. \nA. Central retinal artery occlusion, B. Central retinal vein occlusion, C. Macular choroiditis with infective endocarditis, D. Central serous retinopathy', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Amongst the given options CRVO, CRAO and central serous retinopathy can cause sudden painless loss of vision. However following features favour the diagnosis of CRAO :-\n\n\nCherry red spot\nSystolic murmur (suggests cardiac lesion which may be the source of emboli)', 'role': 'assistant'}]