Management strategies may reduce risk of endophthalmitis after 25-gauge vitrectomy

Japanese population-based study is first to find no difference in risk between 20- and 25-gauge vitrectomy.

Surgical strategies identified in a retrospective, population-based cohort study may suggest preventive measures surgeons can take to reduce the risk of endophthalmitis after 25-gauge vitrectomy.

The study, led by Hiroyuki Shimada, MD, PhD, was the first to find no difference in risk between 20- and 25-gauge vitrectomy. Previous studies in the United States found a significantly higher risk of postsurgical endophthalmitis after 25-gauge vitrectomy.

The study looked at 6,935 consecutive patients in Japan undergoing either 20- or 25-gauge surgery. Of the 3,592 eyes in the 20-gauge cohort, postoperative endophthalmitis developed in one eye (0.0278%), caused by methicillin-resistant Staphylococcus aureus. There was one case of endophthalmitis from Enterococcus faecalis in the 3,343 eyes that underwent 25-gauge vitrectomy (0.0299%); intraoperative triamcinolone was not used during the case. There was no statistically significant difference in risk of endophthalmitis between the two cohorts.

Microbial contamination was found in five of 85 (5.9%) irrigation fluid samples and one of 85 (1.2%) vitreous samples after 20-gauge vitrectomy; microbial contamination was found in seven of 128 (5.5%) irrigation samples and three of 128 (2.3%) vitreous samples after 25-gauge surgery. There were no significant differences between the groups.

The results contrast findings published by Scott et al that found a significantly higher rate of endophthalmitis after 25-gauge vitrectomy compared with 20-gauge vitrectomy. A 2007 study by Kunimoto et al identified a 12-fold higher incidence of endophthalmitis after 25-gauge vitrectomy in their study population.

Dr. Shimada attributed the difference in risk between these studies to the way the surgeries were performed. Namely, Dr. Shimada said, all of the surgeons in his study employed irrigation, used an angled incision and performed a peripheral vitrectomy as part of the procedure.

Study differences

Although the three studies differ in reporting risk of endophthalmitis, methodological differences do not appear to be a contributing factor, Dr. Shimada said. All three studies were retrospective, interventional, comparative cohort studies, and the study populations were all identified through computerized database searches.

In addition, although Shimada et al and Scott et al collected samples from cases positive for endophthalmitis, Kunimoto et al did not, meaning that cases of noninfectious endophthalmitis might have skewed results in the Kunimoto study. However, Dr. Shimada said, “the number is unlikely to be high enough to affect the final result.”

Another difference is that in Japan, it is standard protocol to perform ocular surgery on hospital-admitted patients, but that fact alone should not account for the lower risk in Dr. Shimada’s study. The risk of endophthalmitis from other inpatient ocular surgery procedures, such as cataract surgery, may be telling in this regard. – by Bryan Bechtel

References:

Kunimoto DY, Kaiser RS, for the Wills Eye Retina Service. Incidence of endophthalmitis after 20- and 25-gauge vitrectomy. Ophthalmology. 2007;114(12):2133-2137.
Scott IU, Flynn HW Jr, Dev S, et al. Endophthalmitis after 25-gauge and 20-gauge pars plana vitrectomy: incidence and outcomes. Retina. 2008;28(1):138-142.
Shimada H, Nakashizuka H, Hattori T, Mori R, Mizutani Y, Yuzawa M. Incidence of endophthalmitis after 20- and 25-gauge vitrectomy: causes and prevention [published online ahead of print Oct. 17, 2008]. Ophthalmology.

Hiroyuki Shimada, MD, PhD, can be reached at Surugadai Hospital of Nihon University, Department of Ophthalmology, 1-8-13 Surugadai, Kanda, Chiyodaku, Tokyo 101-8309, Japan; e-mail: sshimada@olive.ocn.ne.jp.