Eyeworld

NOV 2012

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

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70 EW RESIDENTS November 2012 Cataract tips from the teachers The first cut is the deepest When we teach architecture to Sherleen Chen, M.D. Assistant professor of ophthalmology Harvard Medical School Director of Cataract and Comprehensive Ophthalmology Massachusetts Eye and Ear Infirmary Jose de la Cruz, M.D. Assistant professor, Department of Ophthalmology Director, Millennium Park Eye Center University of Illinois Eye and Ear Infirmary, Chicago Roberto Pineda, M.D. Assistant professor of ophthalmology Harvard Medical School Director of Refractive Surgery Massachusetts Eye and Ear Infirmary Dr. de la Cruz: In order to be suc- cessful at wound construction, we need to understand the three goals in corneal incisions: adequate size, shape, and architecture. This is true for both types of cataract wounds, clear corneal as well as scleral tunnel incisions. I will focus on the clear corneal incision, since it is currently favored for phacoemulsification. The size of the wound will be ll phaco surgeons have at some point directly experienced the veracity of the statement, "Each step of phaco builds upon the preceding step." As the initial step of phaco, the importance of wound construction cannot be overemphasized. Successfully performed, its relevance can fade into the background as the ensuing steps of phaco more dramatically unfold. But when poorly constructed, cataract incisions can become a source of continued struggle and, unfortunately, complication. Whether too tight or wide, long or short, anterior or posterior, each compromise has its own surgical consequence. In this column, three expert teachers share their techniques for teaching, learning, and troubleshooting cataract wound construction. A Sherleen Chen, M.D., and Roberto Pineda, M.D. dictated by the instruments used during surgery, as well as the type and size of intraocular lens to be implanted. I teach our residents to construct their wounds with a 2.4 mm keratome blade. This size allows for a snug fit of the phacoemulsifica- tion probe and sleeve, allowing for optimal fluidics. This same size wound is appropriate for most one-piece IOLs without having to expand the wound or inducing any significant amount of astigmatism. Ideally, I like to see a clear corneal wound tunnel that is as long as the width of the wound. Too short of a tunnel increases the risk of iris pro- lapse. Too long and the entry is too anterior, increasing the possibility of distorting the wound and affecting visibility. Our preferred shape for clear corneal incisions is a square or trape- zoid. With the recent availability of a femtosecond cataract system in our institution, we are now more accurately constructing trapezoidal wounds that keep our entry in the anterior chamber at 2.4 mm and 2.7 mm at the corneal limbal end, allowing a greater angle of move- ment without wound distortion. our residents, we all have different preferences ranging from uniplanar to triplanar wound construction. Attempting multiplanar wounds is where I see the inadvertent nicking of the capsule entering the anterior chamber with the keratome vertical. To avoid this, I teach our residents to first have counter pressure diametrically opposite to where the wound is being constructed. I prefer using .12 forceps wide open resting on the conjunctiva. This gives me confidence that it will be a controlled entry into the anterior chamber. In addition to this, I ask the resident to enter the cornea from the edge of the limbus with a slight "push down, move forward, push down movement" without pointing the tip of the keratome vertically. This allows a more controlled entry, eliminating the possibility of nicking the anterior capsule and still having a wound that's multiplanar and of adequate length. (Figure 1b) are essentially con- structed the same way, but the incision is simply longer (and a bit more involved) for a scleral tunnel. Many different blades and com- binations of blades are available to the beginning surgeon. I suggest using only the metal keratome blade with the addition of a crescent blade for cutting the sclera in scleral tunnel incisions. Once the basic principles of wound making have been learned and achieved, residents can then try other types and combi- nation of blades. Clear corneal incisions Rebecca C. Metzinger, M.D. Associate professor of ophthalmology Tulane University Health Sciences Center Department of Ophthalmology Chief of ophthalmology Southeast Louisiana Veterans Healthcare System, New Orleans Dr. Metzinger: In teaching cataract surgery to novice surgeons, I start by having them think about basic wound construction. In order to be self-sealing, watertight incisions, the incisions are typically made in a tri- planar fashion. It is important that the beginning surgeon understands that this means there are three sepa- rate parts or "planes" of the incision, and he or she needs to concentrate on how each part of this incision is made. The clear corneal wound (Figure 1a) and the scleral tunnel The clear corneal incision (once the eye is filled with viscoelastic) is started by stabilizing the globe with .12 forceps and then making an approximately ½ thickness groove with the blade perpendicular to the surface of the cornea on or just ante- rior to the limbus. For the beginning surgeon, it is typically easiest to do this with one side of the keratome blade. This groove should be roughly 1-2 mm in length. The tip of the keratome is then placed in the groove with the heel of the blade down. The blade is tunneled upward into the clear cornea for approxi- mately 1 millimeter. I highly recommend that the novice utilize a keratome blade that has a horizontal mark on the surface to indicate the correct distance of this tunnel (Figure 1a, upper left corner). Once the tunnel is made in clear cornea, the heel of the keratome is raised and the tip pointed down until wrinkling around the tip is seen. The anterior chamber is entered with the blade to its full width and then removed. The end result will be a watertight triplanar clear corneal incision. Pitfalls encountered while mak- ing this incision include: entering straight into the anterior chamber, thus not being a self-sealing inci- sion, forcing the blade forward or out too fast, which makes the incision too wide and thus not watertight during phaco, poor stabilization of the globe with ripping of the tunnel with the blade, thus having issues of not being watertight, and an entrance into the anterior chamber too close to iris root, thus causing issues with iris prolapsing out of the wound.

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