An expert discusses how to ensure optimal administration.
Reviewed by Steve Arshinoff, MD, FRCSC
Moxifloxacin is superior to vancomycin as prophylaxis for endophthalmitis after cataract surgery, and its optimal delivery—to ensure a sufficient amount reaches the anterior chamber—is intracameral, according to Steve Arshinoff, MD, FRCSC.
Arshinoff holds academic appointments at the University of Toronto and McMaster University (Hamilton, Ontario); Ben Gurion University of the Negev, in Beer Sheba, Israel; and Airlangga University, in Indonesia, and recently authored a textbook on bilateral cataract surgery.
Discussing different agents for postoperative endophthalmitis (POE) prophylaxis at the Toronto Cataract Course earlier this year, Arshinoff noted that there has been an evolution in this area.
After results of the European Ssociety of Cataract and Refractive Surgeons (ESCRS) study were published in 2007, IC cefuroxime had been regarded as the gold standard until an increase in the incidence of cefuroxime-resistant Enterococcus isolates was observed.1 Vancomycin had also been used to minimize the risk of POE, but associated cases of hemorrhagic occlusive retinal vasculitis resulted in its falling out of favor, Arshinoff said.2 Moxifloxacin, on the other hand, when administered in larger volume but at a lower concentration, has never been linked to toxic effects.3
Arshinoff also pointed to the efficacy of moxifloxacin against bacteria, citing the study of Libre and Matthews on endophthalmitis isolates from Bascom Palmer, which demonstrated that among IC antibiotics, only moxifloxacin at doses of 0.5 mg or greater was adequate to kill all isolates.4
“Vancomycin and cefuroxime were not effective against Pseudomonas aeruginosa or the more resistant strains of Staphylococcus,”he observed.“We know that the injection of small volumes does not work. The injection of 0.1 cc is not particularly good, as there is a huge amount of variability by loss from the syringe due to bubbles or other injection problems associated with very small volume injections.”
According to Arshinoff, sideport administration of 0.5 to 0.6 mL of diluted antibiotic (3 cc moxifloxacin 0.5% in 7 cc balanced salt solution, yielding a concentration of 150 μg/0.1 mL) should be the final step of cataract surgery after the main incision has been sealed and hydrated. This volume is necessary, he stressed, due to the continuous dilution of the antibiotic as it is injected and exchanged with the aqueous humor.5 “The injection of only 500 μg results in the amount remaining in the anterior chamber being inadequate due to washout,” he explained, whereas his approach offers advantages with minimum risk.
When antibiotic resistance has been reported with IC moxifloxacin, he added, it has invariably been because an insufficient quantity of moxifloxacin had been injected into the anterior chamber, never reaching the 500-μg level.
Antibiotics can also be injected into the corneal stroma to help seal the incision, but the amount of antibiotic that remains there cannot be calculated, he said: “It is hard to do the math if you inject into the corneal stroma. It is easier to quantify if you inject directly into the anterior chamber.”
Given that no hemorrhagic occlusive retinal vasculitis due to IC moxifloxacin has been reported, Arshinoff recommended against vancomycin and for moxifloxacin as POE prophylaxis. “Why take a risk when there is no significant risk with moxifloxacin, and the injection protocol and dose have been well worked out?” he said.