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
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 – 
Select and explain. 
A. Propamidine, B. Neosporine, C. Ketoconazole, D. Polyhexamethylene biguanide
D: Polyhexamethylene biguanide
Answer: D: Polyhexamethylene biguanide 
Explanation: PHMD is the drug of choice. Chlorhexidene is an alternative

"Treatment with PHMB or chlorhexidene is often combined with propamidine and neomycine". — Infections of eye