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
Which is therapeutic indication of keratoplasty: 
Select and explain. 
A. Keratoconus, B. Perforated corneal ulcer, C. Myopia, D. hypermetropia
B: Perforated corneal ulcer
Answer: B: Perforated corneal ulcer 
Explanation: 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