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
Which of the following is the MOST impoant factor in the prevention of the endophthalmitis due to cataract surgery? 
Select and explain. 
A. Preoperative preparation with povidone iodine, B. One week antibiotic therapy prior to surgery, C. Trimming of eyelashes, D. Use of intravitreal antibiotics
A: Preoperative preparation with povidone iodine
Answer: A: Preoperative preparation with povidone iodine 
Explanation: Clinical studies have proven that use of 5% povidone iodine cream to clean conjunctiva and eyelids before cataract surgery has significant benefits in reducing the rate of endophthalmitis. Therefore it should be applied to eyes before surgery to reduce the incidence of endophthalmitis. Studies have shown some efficacy of intracameral antibiotics in prevention of postoperative endophthalmitis. The addition of gentamicin and vancomycin to the irrigating fluid during phacoemulsification may result in significant reduction in the microbial contamination of anterior chamber aspirates. Ref: Modern Ophthalmology: The Highlights By Benjamin F. Boyd, page 273-4.