OAKLAND, Calif. — Intracameral antibiotic injections were associated with a 22-fold reduction in the risk of postoperative infection following cataract surgery when compared with the standard post-operative treatment of antibiotic eyedrops, according to a Kaiser Permanente study.
The study, published in the current online version of the Journal of Cataract and Refractive Surgery, looked at the incidence of endophthalmitis, a rare but serious complication of cataract surgery. The researchers studied over 16,000 surgeries performed in the Diablo Service Area of Kaiser Permanente in Northern California between 2007 and 2011.
Standard practice for post-operative care after cataract surgery is treatment with antibiotic eyedrops; the study examined the injection of intracameral antibiotics directly into the front chamber of the eye at the end of surgery.
“Antibiotic eyedrops applied to the surface of the eye must penetrate inside eye to reach the site where pathogens can take hold and cause infection,” explained lead author Neal Shorstein, MD, of the Kaiser Permanente Department of Ophthalmology in Walnut Creek. “This study examined whether injecting antibiotics directly inside the eye at the end of surgery would be more effective to prevent endophthalmitis infection.”
The study found that:
- In 2007, when cataract patients received antibiotic eyedrops only, the rate of endophthalmitis infection was 3.1 per 1,000 surgeries.
- In 2008 and 2009, when eye surgeons added injection of the commonly used antibiotic cefuroxime to their post-operative eyedrop regimen (unless contraindicated by allergy to penicillin or posterior capsular rupture, a surgical complication), the rate of infection fell to 1.43 per 1,000 surgeries.
- In 2010 and 2011, when 100% of cataract surgery patients received injections of one of three antibiotics (cefuroxime, moxifloxacin or vancomycin, depending on the patient’s allergies to medicines), the infection rate dropped to 0.14 per 1,000 surgeries; the resulting infection rate during this period was 22 times lower than the 2007 rate. In this same time period (2010-2011), patients with surgical complications were for the first time also injected, so the further fall in infection rate may indicate that antibiotic injection is particularly beneficial in patients with surgical complications.
“The cataract surgeons at Kaiser Permanente used different approaches to prevent infection, making for a natural experiment. Because surgeons changed their practices over time, we were able to analyze whether infection rates changed, too,” said Lisa J. Herrinton, PhD, a research scientist with the Kaiser Permanente Division of Research and a co-author on the study.
At the same time that intracameral injection was being added to cataract surgery in 2007 and 2008, the Kaiser Permanente eye surgeons were replacing tobramycin eyedrops, an older agent, with a newer one, gatifloxacin. The percentage use of gatifloxacin remained the same throughout the remainder of the study period. “This change could have confounded the research,” Herrinton noted, “but because the infection rate declined 10 fold from 2009 to 2011, the surgeons’ switch to gatifloxacin was probably not the reason for the overall decrease in infection rate during the study period.”
Throughout the study period, three of the surgeons in the Diablo Service Area used intracameral injection alone (without eyedrops) in patients with no surgical complications, and the rate of endophthalmitis infection among their patients was similar to the rate when antibiotic eyedrops were used in conjunction with injections.
“This may indicate that antibiotic eyedrops are unnecessary in patients who have had uncomplicated cataract surgery,” Shorstein said. “Another research study is needed to assess the benefits of eyedrops in patients who receive antibiotic injection.”
Antibiotic injections have since been adopted throughout the Kaiser Permanente Northern California Region.
Dr. Shorstein was motivated to initiate injections of intracameral antibiotics in Kaiser Permanente’s Diablo Service Area in 2007 after a randomized study by the European Society of Cataract and Refractive Surgeons showed that cefuroxime injections helped to prevent infection after cataract surgery. The European study was published in the same journal as the current paper.
“The ability to improve the safety and outcome of cataract surgery with such a simple technique as an injection is very exciting,” Shorstein said. “Patients feel more secure undergoing the operation knowing that we’re able to significantly lower the risk of a devastating complication that can even lead to blindness in some cases.”
Kevin L. Winthrop, MD, with the Division of Infectious Diseases, Ophthalmology, and Public Health, Oregon Health and ScienceUniversity, was also a co-author of the study.