This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Diseases of Cornea, Subject name: Ophthalmology
[{'content': 'Which is therapeutic indication of keratoplasty: \nSelect and explain. \nA. Keratoconus, B. Perforated corneal ulcer, C. Myopia, D. hypermetropia', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Perforated corneal ulcer Indication of penetrating keratoplasty Therapeutic - replaces inflamed cornea and maintains structural integrity of the eye ball Perforated corneal ulcer Optical - improve vision, opacity, bullous keratopathy ,advanced keratoconus', 'role': 'assistant'}]