SURGICAL UPDATES: Improvements in Small-gauge Vitrectomy May Reduce Potential Complications

By Rohit Ross Lakhanpal, MD
 

The Vit-Buckle Society (VBS) was originally formed by a group of vitreoretinal surgical fellows at the annual Fellow’s Forum in Chicago in January 2006. The group, Derek Y. Kunimoto, MD, Rohit Ross Lakhanpal, MD, Thomas A. Albini, MD, Charles Mango, MD, and R.V. Paul Chan, MD, had become friends during the interview process 2 years earlier. At that time, they decided to form a new vitreoretinal society for emerging surgeons focusing on surgical innovation and technique while also fostering an atmosphere of discussion and camaraderie. Thus, the VBS mission statement is to provide an open forum for innovative vitreoretinal surgeons to share best practices, to foster the development and use of novel surgical technologies and strategies for retinal diseases, and to demonstrate the value of mentorship of emerging vitreoretinal surgeons. This includes mentoring upcoming vitreoretinal fellows. Subsequently, new members joined the Steering Committee, which includes the original members along with Audina Berrocal, MD, John Kitchens, MD, and Andrew Moshfeghi, MD. Recently, in association with the American Society of Retina Specialists, VBS has conducted three annual meetings in which surgical challenges, techniques, and new innovations are openly discussed among 50 to 60 participating attendees. Timothy G. Murray, MD, MBA, has been the VBS mentor and has been invaluable in terms of his enthusiasm and expertise.

NEW COLUMN IN RETINA TODAY
Beginning with this issue of Retina Today, the VBS will participate in a regular column featuring articles authored by VBS members to highlight topics of interest to the membership.Many of these articles will be cross-referenced to surgical videos on EYETUBE.NET , the ophthalmic video resource produced by Bryn Mawr Communications, publishers of Retina Today.

-Rohit Ross Lakhanpal, MD; and Thomas Albini, MD

Small-gauge vitrectomy system (25-gauge and 23-gauge) use has increased rapidly since 2002 due to its advantages of decreased surgical time, reduced postoperative inflammation, and faster visual recovery compared with 20-gauge vitrectomy.1-5 The 2009 Preferences and Trends (PAT) Survey from the American Society of Retina Specialists reported that nearly 80% of respondents commonly employ smallgauge 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 in entry, exit and surgical technique should decrease these risks. This article highlights some of these methods.

POTENTIAL RISKS OF
SMALL-GAUGE SYSTEMS
The risk of endophthalmitis in 20-gauge systems 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 the 25-gauge cases).

Several hypotheses have been proposed to explain why 25-gauge vitrectomy may lead to a higher rate of postoperative endophthalmitis: Complete wound closure may not be achieved;15 unsutured wounds may lead to early postoperative hypotony, allowing an intraocular influx of extraocular fluid and microorganisms;1-4,10,16,17 lower infusion rates with reduced influx and efflux of fluid may allow a greater bacterial inoculum to remain in the eye;1-3 residual vitreous skirt may facilitate bacterial adherence and sequester bacteria from normal immunologic factors and extraocular antibiotics;18 vitreous wick prolapse through the sclerotomy site may create a potentially open conduit through the conjunctival and scleral wound that may facilitate entry of bacteria into the eye.19

IMPROVEMENTS IN ENTRY TECHNIQUE
Successful outcomes in small-gauge vitrectomy are highly dependent upon preoperative preparation and entry technique. Preoperatively, the use of povidoneiodine along the lid margin and/or perioperative area significantly reduces bacterial flora, thus decreasing the risk of endophthalmitis. Furthermore, placing povidoneiodine 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 This allowed a direct opening to the vitreous cavity, thus increasing the risks of endophthalmitis, hypotony, and choroidal detachment in early studies. Lakhanpal et al3 reported no cases of endophthalmitis, but did report incidence of 4% of hypotony and persistent choroidal detachments associated with small blebs. Gupta et al22 reported hypotony within the first 24-hour period in numerous eyes as well.

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; next, the conjunctiva should be displaced laterally in order to prevent communication between this incision and the scleral incision; third, rather than a perpendicular incision, a two-step incision should be used, 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 significantly lower risk for external communication as opposed to straight incisions (Figure 2).24

Flattening and displacing the conjunctiva in order to create a self-sealing incision was an important development. This may be performed with a variety of instruments, such as a cotton-tip applicator, 0.3 forceps, or plug-pulling forceps. Another option is the Dugel End Plate (Peregrine Surgical, New Britain, PA): This instrument simultaneously flattens and displaces the conjunctiva, then designates the angle of entry, and finally aids in trocar removal (Figures 3 and 4).

IMPROVEMENTS IN SURGICAL PROCEDURE AND CANNULA REMOVAL
A variety of techniques may be employed during smallgauge vitrectomy in order to decrease the risks of hypotony and endophthalmitis. Previous studies have postulated that insufficient vitreous removal during 25-gauge vitrectomy may provide an area for bacterial adherence.25 Thus, performing a more complete vitrectomy, particularly with triamcinolone staining near the sclerotomy sites, is a simple way to correct this problem. Another potential issue is that prolapse of a vitreous wick through the sclerotomy site may create a potentially open conduit through the conjunctival and scleral wound that may facilitate entry of bacteria into the eye.19 Once again, more complete vitrectomy at or near the sclerotomy sites decreases this risk. Also, the use of air tamponade at the conclusion of surgery may act as both a barrier to bacterial inoculation and a way to prevent hypotony.

Improvements in cannula removal and appropriate use of subconjunctival antibiotics near the sclerotomy sites may reduce potential complication risks. Vitreous wick prolapse may be prevented19 during closure by simply placing the light pipe through the microcannula during removal (Figure 5). This prevents the suction-like effect that can occur during cannula removal. This mechanism of cannula removal with air tamponade may allow air rather than vitreous to seal the sclerotomy site wound. Finally, injection of subconjunctival antibiotics adjacent to the sclerotomy sites may decrease bacterial entry through sclerotomy sites. Some authors have recently proposed that there is a correlation between relative hypotony at the conclusion of surgery and the influx of bacteria through sclerotomy sites, increasing the risk of endophthalmitis.26, 27 Air tamponade and relatively higher intraocular pressure may be a deterrent to bacterial influx.27 Extra insufflation of air may also be necessary if the intraocular pressure is deemed to be too low. Many of these recommendations for small-gauge surgery improvements have been proposed by the Microsurgical Safety Task Force at the most recent meeting of the American Society of Retina Specialists.28

CONCLUSIONS
Small-gauge vitrectomy systems have been in widespread use since 2002. For experienced surgeons, there has been a steep learning curve in terms of entry techniques, surgical technique and instrumentation, and microcannula removal. These improvements have decreased the relative risk of endophthalmitis, but longer-term study must be done. Hu et al14 determined that there is no statistically significant difference in endophthalmitis rates between 20— gauge and 25-gauge systems, directly contradicting two previous studies.7,8

Currently, the prevailing evidence emphasizes the importance of the following measures to reduce endophthalmitis risk: Infection prevention measures, including lid scrubbing and direct povidone-iodine application; conjunctival displacement and angled/beveled incision; more complete vitreous removal adjacent to the sclerotomies; air tamponade; repositing potential extraconjunctival vitreous wick with light-pipe assisted cannula removal and subconjunctival antibiotic injection; and extra insufflation of air/gas, if necessary, to stabilize intraocular pressure.

Having performed thousands of small gauge vitrectomies since 2002 without a case of endophthalmitis, I believe that the increased risk is largely techniquedependent. The documented risk modifications described above should decrease the endophthalmitis risk dramatically.

Rohit Ross Lakhanpal, MD is a Partner at Eye Consultants of Maryland and a Clinical Assistant Professor of Ophthalmology at The University of Maryland School of Medicine. He reports no financial or proprietary interest in any of the products or techniques mentioned in this article. He has been a Consultant in the past for both Bausch & Lomb and Alcon Surgical. He is currently the Vice-president of the Vit-Buckle Society (VBS). Dr. Lakhanpal is Section Co-Editor of the VBS page in Retina Today and on EYETUBE.NET. He can be reached at +1 410 581 2020 or via e-mail at retinaross@yahoo.com.

Thomas Albini, MD is Assistant Professor of Clinical Ophthalmology at the Bascom Palmer Eye Institute in Miami, FL. He specializes in vitreoretinal diseases and surgery and uveitis. He has served as a speaker for both Bausch & Lomb and Alcon Surgical, as well as consultant for Alcon Surgical. He is currently the Membership Chair of the Vit-Buckle Society (VBS). Dr. Albini is Section Co-Editor of the VBS page in Retina Today and on EYETUBE.NET. He can be reached at +1 305 482 5006; or via e-mail at talbini@med.miami.edu.

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Retina Today is a publication that delivers the latest research and clinical developments from areas such as medical retina, retinal surgery, vitreous, diabetes, retinal imaging, posterior segment oncology and ocular trauma. Each issue provides insight from well-respected specialists on cutting-edge therapies and surgical techniques that are currently in use and on the horizon.