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 is the most important factor in the prevention of the endophthalmitis in cataract surgery? \nSelect and explain. \nA. Preoperative preparation with povidone iodine, B. One week antibiotic therapy prior to surgery, C. Trimming of eyelashes, D. Use of intravitreal antibiotics', 'role': 'user'}, {'content': 'Answer: A \nExplanation: "The only proven method of prophylaxis against postoperative endophthalmitis is sterile ophthalmic preparation using the povidone - iodine solution on the skin (5-10%) and in the conjunctival sac (5%)".\n—\xa0F. Steinest.', 'role': 'assistant'}]