To the Editor:
We appreciate the interest of Drs. Carifi and Kopsachalis in our manuscript and study.
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It is most important to recognize that our rabbit model is a model that evaluates the ability of the topically administrated antibacterial drugs to penetrate the cornea and prevent endophthalmitis. The addition of intracameral injection or systemic administration was not within the focus of this study. Our intention was not a model of endophthalmitis treatment and not a model to mimic ocular surgery. Our design was to test (not prove) our hypothesis that fluoroquinolone antibiotics are superior to the nonfluoroquinolone antibiotics. To prove indicates a bias, and our design was to accept or reject the hypothesis that fluoroquinolone anti-infectives are better than nonfluoroquinolones. Like all animal models, consistency is the utmost importance. We needed to challenge all animals equally with an anterior chamber injection of bacteria. We recognize that this does not represent ocular surgery. The inclusion of povidone-iodine is not a weakness in our study and design. It strengthens our study. We wanted to demonstrate the proof of principle that povidone-iodine did not penetrate pass the cornea into the anterior chamber to consistently prevent endophthalmitis, and should not be relied upon for this purpose. In addition, povidone-iodine is considered the standard of care for eradicating surface contamination, and many may wonder how povidone-iodine would do in this anterior chamber contamination study.
Another goal of our study was to provide information to the ophthalmic surgeon for making decisions in regard to surgical prophylaxis. If topical antibacterial prophylaxis is favored by the surgeon, our data suggest that topical fluoroquinolone anti-infectives appear to penetrate better into the anterior chamber than topical nonfluoroquinolone antibacterial drugs to prevent the postsurgical infections. If costs are an issue, our data also suggest that the less-expensive off-patent topical anti-infective ofloxacin (a second-generation fluoroquinolone) was as effective as moxifloxacin (a fourth-generation fluoroquinolone). However, our study did not test the prevention of endophthalmitis using fluoroquinolone-resistant Staphylococcus aureus. We previously demonstrated that, using the same model, topical moxifloxacin was more effective than topical levofloxacin (purified ofloxacin) in preventing endophthalmitis due fluoroquinolone-resistant S. aureus as interpreted using the serum standards of susceptibility.
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