Eyeworld

NOV 2012

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

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November 2012 EW RESIDENTS 71 Scleral tunnel incisions The scleral tunnel incision requires more steps and can be more chal- lenging to the beginning surgeon. The first step in this type of incision is to perform a 5 mm conjunctival peritomy at the limbus where the in- cision will be made. Blunt dissection of Tenon's is performed followed by hemostasis with electrocautery. The scleral tunnel incision is then started by stabilizing the eye with .12 for- ceps and making an approximately ½ thickness groove with the blade perpendicular to the surface of the sclera 1-2 mm posterior to the lim- bus. This groove should be approxi- mately 3 mm in width (enough to easily accommodate the metal ker- atome). The sharp edge of the cres- cent blade (#66 blade) is typically used to make this groove, but a #74 or #64 blade can be utilized for this purpose. The tip of the crescent blade is then placed in the groove and with the blade heel down, tunneled forward into the sclera by gentle circular movements. Once the blade has advanced to clear cornea, the heel of the blade remains down but the tip is elevated to tunnel slightly forward into clear cornea. The crescent blade is removed. The metal microkeratome is then placed into the tunnel and up into clear cornea, with the heel down. As with the clear corneal incision, after the keratome is tunneled 1 mm into clear cornea the heel of the ker- atome is raised and the tip pointed down until wrinkling around the tip is seen. The anterior chamber is en- tered with the blade to its full width and then removed. The end result is a watertight triplanar incision. Pitfalls encountered while mak- ing this incision include: a thin scle- ral flap that may tear and interfere with being watertight during phaco, cutting too deep into sclera, which could lead to injury, disinsertion, or bleeding from the ciliary body, globe perforation and difficulty during phaco, entering straight into the anterior chamber too close to the iris root causing issues with iris prolapse from the wound, bleeding from scleral or episceral vessels, which can interfere with visualization during the case, and a poorly closed scleral incision, which can lead to bleb formation or potential infection. I encourage all the residents to get bovine or pig eyes from the Figures 1a and 1b. The clear corneal wound (1a) and scleral tunnel (1b) are essentially constructed the same way, but the incision is longer and more involved for a scleral tunnel Source: Son Ho, M.D. butcher or eyes not suitable for transplantation from the local eye bank and practice making these inci- sions many times before performing their first surgery. Hopefully with practice and using the techniques I have described, they will avoid the pitfalls above. perfect substitute for the human eye, the corneal similarities make them ideal for learning wound construc- tion. The tactile feedback provided allows residents to get comfortable with the "feel" of the instruments and tissues. Our residents are re- quired to practice wound construc- tion in supervised wet labs prior to starting cataract surgery. Several principles apply when Jessica Ciralsky, M.D. Assistant professor of ophthalmology Weill Cornell Medical School New York Dr. Ciralsky: In cataract surgery, every step builds upon the previous step. Since clear corneal and scleral tunnel incisions are initial steps, it is essential to have proper wound con- struction for successful cataract sur- gery. A poorly constructed wound may lead to wound leakage, shallowing of the anterior chamber, and ultimately, complications. Most wet labs use porcine eyes to practice cataract surgery. Although porcine eyes are not a teaching wound construction both in the wet lab and operating room. 1) Prepare the eye: The eye must be firm, from generous viscoelastic ap- plication through the paracentesis site, prior to making the main inci- sion. A firm eye is more stable, less prone to distortion, and allows more predictable wound construction. 2) Stabilize the eye: Using a second instrument in the sideport incision is my preferred method for securing the eye. This technique is easy to teach and easy to master. 3) Use familiar instruments: Disposable stainless steel blades are my favorite because they provide better tissue resistance feedback and can be used in practice wet labs. For clear corneal incisions, inci- sion location, shape, and size are all important. I place incisions at the anterior limbus to incorporate vascular tissue to help with wound healing. I prefer a biplanar incision. Start with the heel of the blade flush against the sclera and then advance 2 mm within the plane of the cornea before lifting the heel of the blade and entering the anterior chamber. If possible, obtain keratomes with 2 mm depth marks for beginning cases. I prefer 2.2 mm keratome incisions, if available, as square incisions have been shown to be the most stable. For scleral tunnel incisions, incision site preparation and incision architecture are critical. Adequately prepare for the incision by making peritomies larger than the planned incisions and achieving good hemostasis. Correct incision configuration is accomplished by consistently creating partial thick- ness scleral grooves and tunnels and by avoiding second planes with the introduction of the keratome. Novice surgeons frequently create scleral grooves that are too deep or tunnels that are too shallow. Practice makes perfect. A good wound sets the stage for successful surgery. EW Editors' note: Dr. de la Cruz has financial interests with Alcon (Fort Worth, Texas). Drs. Ciralsky and Metzinger have no financial interests related to this article. Contact information Ciralsky: jessciralsky@gmail.com de la Cruz: 312-996-2020, josedlc@uic.edu Metzinger: Rebecca.Metzinger@va.gov

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