Retina Today - Improving the Safety of Small-gauge Vitrectomy (January 2011)

摘要

The use of small-gauge vitrectomy (25-gauge and 23-gauge) has increased rapidly since 2002 due to its advantages of decreased surgical time, less postoperative inflammation, and faster visual recovery.1-5 The 2009 Preferences and Trends (PAT) Survey of the American Society of Retina Specialists reported that nearly 80% of respondents commonly employ small-gauge systems. Recently, however, concerns have arisen that use of small-gauge systems may increase the risk of endophthalmitis.6-9 Proper preoperative sterilization techniques along with improved methods of entry, exit, and surgical technique should decrease these risks. POTENTIAL RISKS OF SMALL-GAUGE SYSTEMSThe risk of endophthalmitis with 20-gauge vitrectomy has been previously reported to be 0.03% to 0.05%.10-13 Retrospective reviews of 25-gauge endophthalmitis data have reported conflicting information. As compared with 20-gauge studies, Kunimoto et al7 reported a 12-fold increased risk, Scott et al8 reported a 28-fold increased risk, but Hu et al14 reported no statistically significant difference (a 0.07% [1/1424] rate for 25-gauge cases). Several hypotheses have been proposed to explain why 25-gauge vitrectomy may lead to a higher rate of postoperative endophthalmitis, including the following: a?￠ wound closure may be incomplete;15 a?￠ unsutured wounds that lead to early postoperative hypotony may allow intraocular influx of extraocular fluid and microorganisms;1-4,10,16,17 a?￠ lower infusion rates with reduced influx and efflux of fluid may allow a greater bacterial inoculum to remain in the eye;1-3 a?￠ residual vitreous skirt may facilitate bacterial adherence adherence and sequester bacteria from normal immunologic factors and extraocular antibiotics;18 and a?￠ vitreous wick prolapse through the sclerotomy site may create a potentially open conduit through the conjunctival and scleral wound, facilitating entry of bacteria into the eye.19 IMPROVEMENTS IN ENTRY TECHNIQUESuccessful outcomes in small-gauge vitrectomy are highly dependent upon the preoperative preparation and entry technique. Preoperatively, the use of povidone- iodine along the lid margins and perioperative area significantly reduces the bacterial flora, thus decreasing the risks of endophthalmitis. Furthermore, placing povidone-iodine for a few seconds near entry sites may further lower the risk as direct application has been demonstrated in well-controlled studies to decrease the microbiologic flora before intraocular surgery. 20,21 Modifications in entry technique have also decreased complication risk. Original 25-gauge surgical systems employed a direct perpendicular entry through intact conjunctiva without displacement,1-3 allowing a direct opening to the vitreous cavity and thus increasing the risks of endophthalmitis, hypotony, and choroidal detachment in early studies. My colleagues and I3 reported no cases of endophthalmitis but did report an incidence of 4% of hypotony and persistent choroidal detachments associated with small blebs. Gupta et al22 also reported hypotony within the first 24-hour period in numerous eyes. Such complications necessitated the following improvements in entry technique (Figure 1). First, the conjunctiva and sclera should be flattened in order to allow entry more parallel to the limbus. Second, the conjunctiva should be displaced laterally to prevent communication between this incision and the scleral incision. Third, rather than a perpendicular incision, a two-step incision was developed in which an oblique, beveled incision parallel to the limbus through the conjunctiva and sclera is followed by a perpendicular tunnel entry, thus creating a self-sealing wound.23 In one study, angled incisions were associated with a significantly lower risk for external communication as opposed to straight incisions (Figure 2).24 Flattening and displacing the conjunctiva to create a self-sealing incision was an