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 patient using a contact lens develops a corneal infection. Laboratory diagnosis of acanthamoeba keratitis was established. The following is the best drug for treatment – \nSelect and explain. \nA. Propamidine, B. Neosporine, C. Ketoconazole, D. Polyhexamethylene biguanide', 'role': 'user'}, {'content': 'Answer: D \nExplanation: PHMD is the drug of choice. Chlorhexidene is an alternative\n\n"Treatment with PHMB or chlorhexidene is often combined with propamidine and neomycine". — Infections of eye', 'role': 'assistant'}]