February 2009




Tracking infection trends

by Matt Young EyeWorld Contributing Editor



Two views of post-op endophthalmitis Source: Nick Mamalis, M.D.

Could sutureless 25-gauge vitrectomy pose an increased risk of endophthalmitis over the older 20-gauge technique? New research suggests that yes, this is a distinct possibility. A study, published online in June 2008 in Eye, compared the two procedures and found the rate of endophthalmitis after 25-gauge vitrectomy is higher, but not statistically significantly so—at least not in that study. However, combined with other new research, it does suggest a concerning infection trend among this newer 25-gauge technique. Also of note: The emerging endophthalmitis case related the 25-gauge vitrectomy technique that resulted to the combined phacoemulsification procedure. The authors wondered whether there might therefore be a special infection concern in performing 25-gauge vitrectomy during a combined procedure.

Comparing cases

Diana V. Do, M.D., Johns Hopkins University School of Medicine, Baltimore, and colleagues, analyzed 3,477 consecutive vitrectomy patients. Of these, 3,046 patients underwent 20-gauge vitrectomy, and 431 underwent 25-gauge vitrectomy. Both groups had one case of endophthalmitis each, which meant the rate of endophthalmitis was higher in the 25-gauge group. To be specific, it was 0.03% in the 20-gauge group and 0.23% in the 25-gauge group. Further analysis revealed an even more interesting insight. For combined procedures (cataract surgery and vitrectomy), the 20-gauge group experienced no endophthalmitis (0%, 0 of 170 cases). But the 25-gauge group experienced a higher rate of endophthalmitis: 2.17% (1 of 46 cases). “It is possible that the reported case of endophthalmitis after combined 25-gauge vitrectomy and cataract surgery occurred secondary to the cataract surgery rather than the vitrectomy portion of the procedure even though the corneal incision was sutured and did not leak,” Dr. Do reported. “Cataract surgery is associated with a higher risk of postoperative endophthalmitis than is vitrectomy, with cited rates ranging from 0.1 to 0.2%. Alternatively, combining the surgeries may have increased the risk of endophthalmitis.”

Further, phacoemulsification combined with 20-gauge vitrectomy has been performed extensively and, reportedly, without increased infection risk. “There is limited evidence addressing the safety of 25-gauge vitrectomy in combination with cataract surgery,” Dr. Do reported. No reports of endophthalmitis were made in relation to a combined procedure with 25-gauge vitrectomy, but there were less than 200 patients combined in such reports. “None of these studies, however, were adequately powered to assess an increased risk for endophthalmitis,” Dr. Do reported.

Even Dr. Do’s study of 3,477 cases could not say for sure whether there was an increased risk for endophthalmitis in 25-gauge vitrectomy overall. But along with other studies, it suggests that 25-gauge vitrectomy should cause some concern. “Kunimoto and Kaiser retrospectively analysed 8601 consecutive cases of vitrectomy and found that 25-gauge vitrectomy had a statistically significant 12-fold higher incidence of endophthalmitis (culture results not recorded) compared with 20-gauge vitrectomy (0.23 vs 0.018%),” Dr. Do noted. “In another study, Scott et al. recently retrospectively examined 6375 patients who underwent 20-gauge PPV [pars plana vitrectomy] and 1307 patients who underwent 25-gauge PPV. The incidence of endophthalmitis was 0.03% for 20-gauge PPV compared to 0.84% for 25-gauge PPV (P<0.0001), which represents a 24 times increased risk with the sutureless 25-gauge system.”

The 25-gauge technique isn’t meant to cause more headaches. It was intended to decrease iatrogenic trauma to the eye, reduce post-op astigmatism, and decrease operation time, Dr. Do noted. But she also suggests that its non-sutured wounds could allow pathogens to pass more easily into the eye. “Hypotony, observed after 25-gauge vitrectomy with an incidence of 3.8–20%, may serve as conduit for infection,” Dr. Do concluded.

“For instance, in human cadaveric eyes, fluctuations of IOP following sutureless clear cornea surgery may allow entry of surface fluid into the anterior chamber during the initial postoperative period when the wound has not healed. Furthermore, with the 25-gauge vitrectomy system, the infusion flow rate is reduced sixfold, potentially decreasing the amount of fluid that dilutes or flushes out organisms within the eye.”

John D. Sheppard, M.D., professor of ophthalmology, microbiology, and immunology, Eastern Virginia Medical School, Norfolk, Va., agreed that the lack of sutures with 25-gauge vitrectomy could be a reason for any potential increased infection risk. “Certain precautions can be taken to stagger the incision and protect the patient from endophthalmitis,” Dr. Sheppard said. “Vitrectomy still is a remarkably safe procedure.”

Editors’ note: Dr. Do has no financial interests related to this study. Dr. Sheppard has no financial interests related to his comments.

Contact information

Do: 410-955-3518, ddo@jhmi.edu
Sheppard: 757-622-2200, docshep@hotmail.com

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