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': 'The central nebular corneal opacity is easily treated with: \nSelect and explain. \nA. Lamellar keratoplasty, B. Penetrating keratoplasty, C. Gas permeable contact lens, D. Soft contact lens', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. Lamellar keratoplasty', 'role': 'assistant'}]