This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cornea and sclera, Subject name: Ophthalmology
[{'content': 'Safe size of corneal graft with less chances of failure is - \nSelect and explain. \nA. 7.5 mm, B. 5.5 mm, C. 6.5 mm, D. 4.5 mm', 'role': 'user'}, {'content': 'Answer: A \nExplanation: With the help of a corneal trephine (7.5 mm to 8 mm in size)a paial thickness incision is made in the hostcornea . Then, anterior chamber isentered with the help of a razor blade knife andexcision is completed using corneo-scleral scissors. REF:Comprehensive ophthalmology,AK Khurana,4th edition,pg no.125.', 'role': 'assistant'}]