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': "Keratoconus is associated with all except – \nSelect and explain. \nA. Down's syndrome, B. Ehlers–Danlo's syndrome, C. Marfan's syndrome, D. Usher's syndrome", 'role': 'user'}, {'content': "Answer: D \nExplanation: Systemic conditions associated with keratoconus are a marfan syndrome, osteogenesis- imperfecta, EDS, Down's syndrome, MVP, atophy (asthma, eczema, atopic keratoconjunctivitis, hay fever).", 'role': 'assistant'}]