This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cornea and sclera, Subject name: Ophthalmology
[{'content': "Keratoconus is associated with all except- \nSelect and explain. \nA. Down's syndrome, B. Ehlers-Danlos' syndrome, C. Marfan's syndrome, D. Usher's syndrome", 'role': 'user'}, {'content': "Answer: D \nExplanation: Keratoconus may be associated with : Ocular conditions e.g. ectopia lentis, congenital cataract, aniridia, retinitis pigmentosa, and vernal keratoconjunctivitis (VKC).Systemic conditions e.g., Marfan's sysndrome, atopy, Down's syndrome, Ehlers-Danlos syndrome, osteogenesis imperfecta and mitral valve prolapse. Reference:Comprehensive ophthalmology,AK Khurana,4th edition,page no.120", 'role': 'assistant'}]