July 2009

 

CATARACT/ IOL

 

Higher rates of endophthalmitis


by Michelle Dalton EyeWorld Contributing Editor

   

A population-based study confirms overall rates of endophthalmitis remain low, but risk factors can be identified

Example of endophthalmitis; here possibly started with an infection of the incision line Source: Daljit Singh, M.D.

Certain patient groups, including those who have undergone complicated cataract surgery, have a higher rate of acute endophthalmitis than those in whom surgery is uneventful, according to a large, population-based study. Age also plays a role, researchers said.1 Wendy V. Hatch, O.D., M.Sc., and colleagues at the University of Toronto, Toronto, retrospectively analyzed administrative data from 440,000 consecutive cataract surgeries in Ontario. All the surgeries took place between April 1, 2002, and March 31, 2006.

In this analysis, acute endophthalmitis “was defined using surrogate markers for intraocular infection, including vitrectomy, vitreous injection, or aspiration procedures not in combination with air/fluid exchange or dislocated lens extraction, performed 1 to 14 days after surgery.” On the day of surgery, anterior vitrectomy was used as a surrogate marker for capsular rupture. During the time frame of the analysis, there were 617 suspected acute endophthalmitis cases of 442,177 cataract surgeries. This means that unadjusted and adjusted rates of suspected acute endophthalmitis were both 1.4 per 1,000 cataract surgeries. The researchers did find men had higher rates than women, that the oldest patients (those older than 85) had a rate of 2.18 per 1,000 surgeries, and the youngest age group (those between 20 and 64 years old) had the second highest rate of 1.76 per 1,000 surgeries. “Articles like this one are important contributors to the literature,” said Nick Mamalis, M.D., professor of ophthalmology, John A. Moran Eye Center, Department of Ophthalmology & Visual Sciences, University of Utah, Salt Lake City. “One of the problems we have in quantifying endophthalmitis is that the overall incidence is so low. Most often, it’s on the level of 1 in 1,000 or close. So in order to really determine endophthalmitis rates, you need to study hundreds of thousands of patients.”

Although this study is a valuable addition to the literature in that it supports other retrospective study conclusions, there are not any “significant new clinical implications from this study,” said Brian Little, F.R.C.Ophth., consultant ophthalmologist, Royal Free Hospital, London. “It cannot address any specific clinical issues as it’s simply an observational outcome analysis of insurance data.”

Dr. Little noted the Royal College of Ophthalmologists in the United Kingdom. recently audited more than 55,000 cataract surgeries to identify higher risk cases and also found one significant risk factor for posterior capsule rupture or vitreous loss was an older age.2

Study details

The current Canadian study “seems to largely confirm what has already been published and established in the cited studies regarding the quantified risks for endophthalmitis,” he said. The Canadian study does confirm that the increase in endophthalmitis most ophthalmologists feared when converting to clear corneal incisions does not appear to have remained, Dr. Mamalis said. “This study showed that, after four years, the levels of endophthalmitis returned to reasonable levels,” he said. Drs. Hatch et al. noted intraoperative complications, particularly an anterior vitrectomy in tandem with the cataract surgery, led to a 10-fold increase in acute endophthalmitis compared with patients in whom there were no intraoperative complications.

The Canadian study “once again confirms the importance of keeping the lens capsule intact. Once that capsule is ruptured, any bacteria can get into the vitreous. That alone will increase the risk of endophthalmitis significantly,” Dr. Mamalis said.

The study also found a 40% higher odd ratio for men compared to women, although other studies have not found gender-specific rates. The Canadian researchers said the differences warranted further analysis, but could be the result of age distributions or general populations.

Study limitations

Dr. Mamalis said the researchers did a good job of identifying the study’s limitations, including lacking “the clinical information that is required for a more definitive diagnosis of endophthalmitis.”1 Because the information gleaned was from administrative data only, surgical techniques were not evaluated, the researchers acknowledged.

“In terms of some of the specifics, there is no information on the treatments these patients had, such as antibiotic A or antibiotic B,” Dr. Mamalis said. “You can’t get more detailed information in a study like this, so we don’t know why older patients had the complications. We can’t tell specifically in each case why the endophthalmitis occurred.”

For instance, Dr. Little said, the United Kingdom data found a combination of a surgical trainee and a patient older than 90 years would carry a much higher composite odds ratio for vitreous loss (about a 5% probability, which is three times the normal rate, he said). Such details are not available in the Canadian analysis.

Dr. Mamalis added that the researchers only focused on the two-week post-op time frame, “so we don’t have any data on those who might present later.”

Dr. Hatch wrote using anterior vitrectomy as the surrogate marker could potentially underestimate the risk rates if some surgeons opted not to perform an anterior vitrectomy. The authors suggest the findings be incorporated into patient education before surgery to indicate the overall low incidence of serious complications. “These authors have nicely outlined their limitations,” Dr. Mamalis said. “This study does help to highlight that the incidence of endophthalmitis is not increasing in this broad-based analysis.”

References:

1. Hatch WV, Cernat G, Wong D, Devenyi R, Bell CM. Risk factors for acute endophthalmitis after cataract surgery: A population-based study. Ophthalmology. 2009;116:425-430.

2 Narendran N, Jaycock P, Johnston RL, et al. The Cataract National Dataset electronic multicenter audit of 55,567 operations: risk stratification for posterior capsule rupture and vitreous loss. Eye. 2009;23:31-37.

Editors’ note: Drs. Mamalis and Little have no financial interests related to their comments.

Contact information

Little: brianlittle@blueyonder.co.uk
Mamalis: 801-581-6586, nick.mamalis@hsc.utah.edu

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