We thank van Rooij and associates for their favorable evaluation of our study. For periocular disinfection before surgery, 10% povidone–iodine commonly is used in Japan, whereas 5% povidone–iodine usually is used in America and Europe. Although bactericidal activity of povidone–iodine is observed over a very wide concentration range of 0.0005% to 10%, the concentration range that is nontoxic to ocular tissues and at the same time has a high bactericidal effect has been reported to be 0.05 to 0.5%. The reason is that a dilute solution favors free iodine formation and consequently is more potent in bactericidal activity. Therefore, a 1% solution would be more bactericidal that a 5% solution. Moreover, povidone–iodine can cause corneal damage from 2.5%. For periocular and ocular surface disinfection, instead of a 5% solution, 1% povidone–iodine can be expected to be safe and highly bactericidal. This may be reflected in the apparent reduction in endophthalmitis rate in the series of van Rooij and associates.

Povidone–iodine has the advantages of being low cost, having no drug resistance, being rapidly bactericidal, and being in widespread use worldwide. A broad bactericidal spectrum against microorganisms, including methicillin-resistant Staphylococcus aureus , multidrug-resistant bacteria, Candida virus, and Acanthamoeba has been demonstrated. With increasing concern about multidrug-resistant bacteria, instead of adding antibiotics into the infusion fluid during cataract surgery, repeated application of 0.25% povidone–iodine to the ocular surface is recommended. We have used this ocular surface irrigation method during cataract surgery in more than 3000 eyes and have not observed any association with corneal injury or postoperative inflammation.

Although the bactericidal effect of povidone–iodine peaks at a concentration of 0.1%, such diluted solution in an open container at room temperature in the operation room setting is unstable. The color fades and bactericidal activity drops after 8 hours. Even with 0.25% povidone–iodine, the bactericidal effect also decreases to approximately 0.1% after 8 hours. Therefore, in our operating room, we prepare fresh 0.25% povidone–iodine twice daily, once in the morning and once in the afternoon.