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': 'Which of the following method is used to make a diagnosis of corneal ulcer caused by acanthamoeba? \nSelect and explain. \nA. KOH mount, B. Calcofluor white stain, C. Lactophenol cotton blue stain, D. All of the above', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Acanthamoeba keratitis is caused by a free lying amoeba found in soil, fresh water, well water, sewage and air. Corneal infection occur from direct contact with water contaminated with this organism. Diagnosis of acanthamoeba can be made by any of the following methods: KOH mount is useful for recognition of acanthamoeba cysts. Calcofluor white stain: stains cysts of acanthamoeba bright apple green under fluorescence microscope. Lactophenol cotton blue stain can demonstrate acanthamoeba cysts. Culture on non nutrient agar may show trophozoites within 48 hours. Ref: Ophthalmology By A. K. Khurana page 129.', 'role': 'assistant'}]