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: Unknown
[{'content': 'Amaurosisfugax is due to - \nSelect and explain. \nA. TIA, B. Tobacco, C. Optic neuritis, D. Papilloedema', 'role': 'user'}, {'content': "Answer: A \nExplanation: Amaurosis fugax is sudden temporary and painless loss of vison due to transient failure of retinal circulation.\nIt may occur in carotid transient ischemic attack (TIA)\nAmaurosis is complete loss of sight in one or both eyes, in the absence of ophthalmoscopic or other marked objective signs.\n\xa0\nAmaurosis fugax\nIt refers to sudden, temporary and painless monocular visual loss occurring due to a transient failure of retinal circulation.\nCommon causes are :-\nCarotid transient ischaemic attacks (TIA)\nEmbolization of retinal circulation\nPapilledema\nGiant cell arteritis\nRaynaud's disease\nMigraine\nAs a prodromal symptom of central retinal artery or carotid artery occlusion\nHypertensive retinopathy\nVenous stasis retinopathy\n\xa0\nTypically described by the patients as a curtain that descends from above or ascends from below to occupy the upper or lower halves of their visual fields. The attack lasts for two to five minutes and resolves in the reverse pattern of progression, leaving no residual deficit.\n\xa0\nUraemic amaurosis\n\xa0\nIt is sudden, bilateral, complete loss of sight occuring probably due to the effect of certain toxic materials upon the cells of the visual centre in patients suffering from acute nephritis, eclampsia of pregnancy and renal failure.It is associated with dilated pupils which generally react to light. Usually, the vision recovers in 12-48 hours.", 'role': 'assistant'}]