Eyeworld

MAR 2012

EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.

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22 EW NEWS & OPINION March 2012 Tools & techniques Minimally invasive EX-PRESS Glaucoma Filtration Device implantation without by Richard S. Hoffman, M.D. N ew tools and techniques continue to be evaluated and refined with the goal of further reducing the complications and improving the results of glaucoma surgical procedures. One such tool, the EX-PRESS Glaucoma Filtration Device (Alcon, Fort Worth, Texas), is a miniature, non-valved, stainless-steel stent developed as an alternative to trabeculectomy filtration surgery. The mini shunt is approximately 3 mm long with an external diameter of 400 microns and is available with two central lumen diameters of 50 or 200 microns. The original technique for im- plantation of the EX-PRESS device was as a subconjunctival implant. Numerous complications of this unguarded tech- nique, including hypotony, conjunctival erosion, extrusion, suprachoroidal hem- orrhage, and endophthalmitis, ultimately resulted in the institution of the current implantation method, which is per- formed under a guarded partial thick- ness scleral flap. The current method necessitates a conjunctival peritomy and construction of a rectangular scleral flap, similar to those created during a standard trabeculectomy. At the 2011 ASCRS Film Festival, we demonstrated a new approach for implanting the EX-PRESS device that utilizes a scleral tunnel starting from a clear corneal incision. The technique al- lows for shunt implantation without the need for conjunctival incisions and may offer a faster and safer method for glaucoma surgery. Richard Hoffman, M.D., Tools & techniques editor Watch this video on your smartphone or iPad using your QR code reader. (Scanner available for free at your app store.) Or view the video of Dr. Hoffman's procedure at www.eyeworld.org/replay.php. Technique Prior to beginning the surgical dis- section, the location for the shunt placement should be determined. A region with minimal episcleral vas- cularization with small caliber ves- sels should be chosen, and areas that have undergone previous scleral in- cisions for cataract surgery should be avoided. The superior bulbar con- junctival vessels can be constricted with a circular Merocel sponge soaked in phenylephrine 2.5% and placed for 10-15 minutes. In addi- tion, a superior subconjunctival injection of lidocaine 1% with epi- nephrine may help constrict the episcleral vessels and reduce the severity of subconjunctival bleeding when the scleral dissection is opened into the subconjunctival space. The first step of the procedure involves a clear corneal incision placed just anterior to the conjuncti- val insertion. This incision can be created with a diamond or steel step knife and should be approximately 350 microns in depth and 4 mm in length (Figure 1). A scleral pocket is then dissected posteriorly with a beveled crescent blade for approxi- mately 3 mm (Figure 2). The scleral pocket is opened into the subcon- junctival space with either the crescent knife or a sharp tipped dia- mond or metal keratome to create a scleral tunnel (Figure 3). An alterna- tive method that has been used suc- cessfully by David Crandall, M.D., utilizes a Sharpoint paracentesis knife (Angiotech Pharmaceuticals, Vancouver, British Columbia) with a small 90-degree bend at the tip. This knife enters the scleral pocket with the bent sharp tip parallel to the plane of the pocket, and with rota- tion of the knife handle, the tip pen- etrates the roof of the pocket and is used to cut the posterior opening for the full width of the pocket (Figure 4). Following completion of the scleral tunnel, the wound is then opened by placing a small skin hook or Kuglen hook under the roof of the scleral tunnel and a Sinskey hook within the corneal stroma of the anterior aspect of the grooved clear corneal incision. An assistant would hold the Sinskey hook while the surgeon holds the skin hook in the non-dominant hand. With gen- tle opposing traction, the Sinskey hook will pull the external anatomic structures overlying the trabecular meshwork anteriorly as the skin hook retracts the roof of the scleral tunnel, thus exposing the site for the mini shunt placement (Figure 5). A 27-gauge needle with a bent tip is then inserted into the anterior chamber, just anterior to the poste- rior aspect of the blue zone, which overlies the region of the trabecular meshwork (Figure 6). The needle tip should be bent and inserted so that the resulting micro-incision is paral- lel to the plane of the iris. The EX- PRESS device is then inserted into the incision, initially rotated 90 de- grees from its ultimate final position (Figure 7). Once it is seated with the external flange against the sclera, it is rotated 90 degrees into the proper orientation and the injector is squeezed to release the shunt. Al- though it is not possible to orient the shunt insertion in the iris plane due to the current limitations in the injector design and the limited anatomic exposure, a properly con- structed perforating micro-incision and the overlying scleral tunnel roof apposed against the shunt's external flange will ultimately orient the shunt tip parallel with the iris. Once the shunt is in position, the hooks are removed and a single tangential 10-0 nylon suture is placed at the limbus to close the an- terior aspect of the scleral tunnel. Beginning the suture placement in Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

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