Soaking acrylic IOLs in a fourth-generation fluoroquinolone for 60 seconds resulted in antimicrobial activity. If confirmed during in vivo studies, this finding could give clinicians another means of preventing endophthalmitis following cataract surgery.
After being soaked in either gatifloxacin (Zymar, Allergan) or moxifloxacin (Vigamox, Alcon Laboratories) for 1 minute, acrylic IOLs (SA 60, Alcon) had kill zones, and those soaked in normal saline did not, said Edward F. Smith, MD, clinical assistant professor at State University of New York Downstate, Brooklyn. Ten lenses were soaked in gatifloxacin, 10 in moxifloxacin, and 10 in saline. The lenses then were dried and plated on Mueller Hinton agar with quality-controlled ATCC 25923 Staphylococcus aureus overlay.
Each Petri dish contained one gatifloxacin-, one moxifloxacin-, and one saline-soaked lens, as well as one antibiotic disk for a control. This was done on a sterile field to simulate operating-room conditions. All the Petri dishes were incubated for 24 hours. Kill zones surrounding the IOLs and the antibiotic disk then were analyzed and compared.
"We wanted to determine whether we could deliver antibiotic levels to the eye by soaking the IOL in commercially available antibiotic. We wanted to see if we could achieve any kind of depot effect on the part of the lens," Dr. Smith said.
To study this question, Dr. Smith, SUNY Downstate resident Abdel-Rahman Elbash, MD, and others first assessed the antimicrobial properties of the IOLs soaked in fourth-generation fluoroquinolones for an hour. Nine IOLs were soaked in gatifloxacin, moxifloxacin, or saline. All lenses soaked in the antibiotics had significant (>32 mm) kill zones, and those soaked in saline had none. A comparison of condition means performed using repeated measures ANOVA was highly significant (p < 0.002). No statistical difference was seen between the IOLs soaked in moxifloxacin or gatifloxacin in this study.
Despite the discovery in the initial study of antimicrobial activity from the fluoroquinolone-soaked lenses, Drs. Smith and Elbash realized that the finding might not be clinically relevant because medical personnel were unlikely to soak IOLs for an hour before surgery.
The second study
This perception prompted the subsequent study, in which the lenses were soaked for a much shorter period.
"We find again that we get significant kill zones around the lens. One minute seems like something that potentially could be clinically relevant," Dr. Smith said. "What we're looking for is to see, in fact, if we do go ahead and use this in some fashion, that antibiotic could be delivered to the eye at the time of implanting the IOL. That potentially could be very protective because of the devastating complications of endophthalmitis.
"These levels appear to be significant, but we do not yet have any in vivo studies," Dr. Smith continued. "We're in the process of looking into doing that now to see what levels could be achieved in the anterior chamber."