Risk factors for post-cataract surgery endophthalmitis among representative sample of Medicare patients

Fort Lauderdale, FL-A study examining potentially modifiable risk factors to reduce post-cataract surgery endophthalmitis found that antibiotic injections during surgery could reduce the risk, however, it was questionable whether the preoperative or postoperative use of antibiotic drops or ointments was beneficial, said Emily W. Gower, PhD, assistant professor of ophthalmology, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore. She also is director of the Wilmer Clinical Research Unit and holds a joint appointment in epidemiology in the Bloomberg School of Public Health.

She and her colleagues conducted a case-control study of a nationally representative sample of Medicare beneficiaries. Cases of post-cataract surgery endophthalmitis during 2003-2004 were identified using Medicare claims data. From the national database of several million records, the group selected five states based on a large volume of surgery and having an endophthalmitis rate similar to the overall U.S. population. Cases from California, Florida, Illinois, Michigan, and Texas were included in the sample. Each case was matched with five controls.

Physicians’ offices were contacted for data, and retinal specialists also were approached to provide confirmatory data on identified cases of endophthalmitis. Factors for analysis were collected in five categories: surgical, antibiotic use, postoperative regimen, patient characteristics, and surgeon characteristics.

The team identified 1,268 cases of presumed endophthalmitis and obtained data on 582 cases. For controls, they requested information on approximately 4,600 individuals and received data on 1,845 individuals. They had surgical data on 544 patients; using retinal data, they excluded 81 cases that did not have endophthalmitis and are waiting for additional data on 53 cases. The analysis presented by Dr. Gower included 410 cases of endophthalmitis and 1,780 controls.

Results of the univariate analysis showed that use of clear-corneal incisions increased the risk for endophthalmitis by about 40%. Having a suture was considered a risk, but this may be an indirect factor resulting from the surgical complication that required the suture, Dr. Gower said. Antibiotic drops at the end of surgery also were a risk factor, as were postoperative antibiotic drops and ointment in the days following surgery.

Protective factors included three types of antibiotic use: in the irrigating solution, subconjunctival, and intracameral injection at the close of surgery. Antibiotic ointment at the end of surgery also was protective.

In the multivariate analysis, clear-corneal incisions no longer were a significant risk factor. Surgical volume, which was a risk factor in the univariate analysis, remained borderline significant, whereas surgical complications were a substantial risk factor.

Dr. Gower strongly recommended that a clinical trial of antibiotic use during surgery be conducted in the United States to obtain more definitive data. A trial using moxifloxacin (Vigamox, Alcon Laboratories) has been proposed. Trials in Europe have shown a benefit of intracameral cefuroxime.