Increase in endophthalmitis cases being studied

August 1, 2007

Endophthalmitis remains one of the most dreaded of post-cataract surgical complications, and its incidence has been increasing in recent years. Researchers at the Wilmer Eye Institute at Johns Hopkins University School of Medicine, Baltimore, are trying to determine what patient- and surgery-related factors are associated with endophthalmitis after cataract surgery.

Key Points

Endophthalmitis remains one of the most dreaded of surgical complications after cataract surgery. Three to 12 days after what both patient and surgeon hoped was successful cataract surgery, certain patients suddenly notice progressively worsening vision, sharp pain, and a red eye. Those patients must be treated with intravitreal injections and sometimes vitrectomy, and long-term vision can be severely compromised. On top of that, lawsuits sometimes follow.

Despite careful pre-surgical efforts to clean the eye area of bacteria, surgeons are reporting an increase in the number of endophthalmitis cases in recent years. That increase has been observed at the same time researchers abroad are reporting far fewer cases than are seen domestically. A team of researchers at the Wilmer Eye Institute at Johns Hopkins University School of Medicine, Baltimore, is working to determine an accurate figure for the number of endophthalmitis cases that occur in the United States and to identify common risk factors.

In the 1990s, the infection occurred once in 1,000 cases. However, by 2000, that rate had increased to be about one in 400 cases, said Emily W. Gower, PhD, assistant professor, Department of Ophthalmology, Wilmer Eye Institute, and director, Wilmer Clinical Research Unit, with a joint appointment in epidemiology, Bloomberg School of Public Health, Johns Hopkins. Dr. Gower is lead investigator on the survey, which is being conducted in five states-California, Florida, Illinois, Michigan, and Texas-to try to find common risk factors linking these cases. Assisting with the study are Johns Hopkins' Ashley Behrens, MD, Peter J. McDonnell, MD, Oliver Schein, MD, and James M. Tielsch, PhD.

Cataract surgeons take many precautions in an effort to avoid endophthalmitis, from the use of topical antibiotics and antiseptics before surgery, to carefully draping the eye to keep the lids and lashes out of the operative field, to making wounds that are "elegant and secure," he said.

"Frankly, we don't know what works and what doesn't work, but we do all these things at tremendous cost to prevent something that is relatively rare but very important," Dr. Schein said.

Dr. Gower said she wonders whether one risk factor might be a change in surgical technique from a larger incision that required stitches to today's more common clear-cornea incision, for which, often, no stitches are needed to close the smaller, self-healing incision that may leave the eye vulnerable to bacterial infection.

"Following that change, we started seeing an increased rate of endophthalmitis," Dr. Gower said.

"Within the first day or two after surgery is when, if the eye hasn't healed enough, you can have leakage," she said.

That leakage could allow common bacteria present on the ocular surface to enter the wound, she explained.

Patient base

Researchers obtained from the Centers for Medicare and Medicaid Services (CMS) a sample list of all cataract surgeries performed on Medicare patients in 2003 and 2004. Patients were identified only by their Medicare identification numbers. Surgeons who had cases of endophthalmitis develop during those 2 years will be asked to complete a questionnaire about each case. The questionnaire asks about patient characteristics, other diseases present, and surgical techniques-such as what type of incision was used and where, which antibiotics and steroids were given before and during surgery, and other perioperative factors.

The study intends to look at 700 endophthalmitis cases, plus five controls for each case. "There's a fairly good chance that if someone was doing cataract surgery during that year, [he or she] will be on our list," Dr. Gower said.

Although information for the Endophthalmitis Post-Cataract Surgery Study (EPCS) was obtained from Medicare, Dr. Gower gave assurance that CMS would not have access to the study particulars.