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Antibiotic use in ophthalmic surgery still debated
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The ideal regimen for infection prophylaxis in penetrating ocular surgery seems to begin before surgery and to include betadine prep, according to two leading surgeons. Intraoperative antibiotic prophylactic regimens are sometimes advocated, but there is debate over their efficacy, the surgeons said.
“The ideal regimen seems to be starting the antibiotics 3 days prior to surgery at a dose of four times daily or a three dose pulse 30 to 60 minutes preop,” say William J. Lahners, MD, and Richard L. Lindstrom, MD, in the April 1 print edition of Ocular Surgery News U.S. Edition. “It clearly provides reduction of conjunctival bacterial flora and high aqueous levels, while avoiding many of the disadvantages of other regimens.”
Studies have shown that the incidence of culture positive anterior chamber taps taken during surgery is significantly reduced in patients receiving preop antibiotics, the surgeons said. Convenience is a factor as well, as the patient administers the antibiotic. Topical antibiotics are also relatively safe and minimally toxic, with no risk of macular toxicity, endothelial toxicity, ocular perforation, idiosyncratic reaction or potential for intraocular injection complications.
Preop oral and intravenous antibiotics have been “hampered by poorly reproducible aqueous levels, short duration of effective killing levels and cost,” the surgeons said. Perioperative subconjunctival administration runs the risks of all periocular injections, including macular infarction and ocular perforation. Administering antibiotics postop may be too late, considering peak levels in the aqueous humor can occur up to 2 to 3 hours after administration, they add.
Adding antibiotics to the irrigating fluid in phacoemulsification surgery is another controversial issue, the surgeons note. There have been reports of decreased colony-forming units in anterior chamber samples following surgery, but other reports show no significant differences. In addition, the levels are so low they are quickly diluted postop and have a half-life of only 51 minutes.
Some physicians advocate placement of intracameral antibiotics immediately following the surgical procedure, but studies supporting the effectiveness of the technique are lacking.