EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
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22 EW NEWS & OPINION June 2012 Tools & techniques Using the Wong incision to improve the seal of a clear corneal incision by Michael Y. Wong, M.D. Stromal hydration of a supraincisional pocket helps prevent bacterial endophthalmitis ometimes the most useful and innovative ideas are the simplest. These "duh" ideas, as in "Duh, why didn't I think of that?" I find to be the most exciting and practical. How many times in a surgical session have we fought with a clear corneal incision that won't self seal, only to surrender to a 10-0 nylon suture that ensures a watertight inci- sion? Wouldn't it be nice if there were a simple method of sealing the incision with- out having to resort to sutures or glue? Now, with a simple addition to the clear corneal incision, we can stromally hydrate the roof of the incision, in addition to the sides, and improve the ability of the clear corneal incision to seal on the table. In this month's column, Michael Y. S Wong, M.D., describes his ingenious incision that allows for improved stromal hydration. Both the technique and explana- tion for how the method improves self seal- ability are intriguing. The alteration can be made at the start of the procedure or added when the surgeon realizes that the incision won't seal without some help. It's wonderful to be able to add this little trick to our surgical armamentarium, and as far as I'm concerned, there's nothing "wong" with having a few extra tricks. Richard Hoffman, M.D., tools & techniques editor T he increasing popularity of clear corneal incisions in cataract surgery has been accompanied by a worri- some suggestion that the incidence of bacterial endoph- thalmitis1 and toxic anterior seg- ment syndrome are on the rise.2 This article describes a simple, quick, and inexpensive technique to tightly ap- pose the lips of the incision, making for a more secure and prolonged seal. Technique Prior to creating the clear corneal in- cision, I make a supraincisional stro- mal pocket 0.5 mm anterior to the intended entrance. With a simple stab of a diamond or metal ker- atome, I create a 2 mm pocket that resembles an equilateral triangle, its base toward the limbus. The pocket's depth can be anywhere from one- third to two-thirds stromal thick- ness. I hydrate the stroma through this pocket with balanced salt solu- tion at the end of the case, thus cre- ating a bulge that exerts an inward pressure on the external lip of the clear corneal incision. The internal lip is pressed outward by the IOP. The combined pressure makes for a tight apposition of both lips of the incision and thus prevents the egress or ingress of fluid through the wound for a period of 24 hours. By that time, the ciliary body is produc- ing aqueous, and the endothelial pump has brought the lamellae of the stroma tightly together. The seal is firm enough to withstand fluctua- tions in IOP, whether high or low. We can create two pockets in- Watch this video on your smartphone or iPad using your QR code reader. (Scanner available for free at your app store.) stead of one if desired, and I have found that there is tremendous latitude in the dimensions of the pocket(s) without impairing the ef- fect (Figures 1 and 2). There are no significant complications of this technique. Formally described as stromal hydration of a suprainci- sional pocket, the technique is collo- quially called the Wong incision or "Wong way." Increased margin of safety A perfectly constructed, square, or nearly square clear corneal incision created with a diamond knife is safe and secure.3,4 The outward forces of the IOP press up on the internal as- pect of the corneal lip to provide a sufficient seal until the endothelial pump dries the internal channel of the incision. In practice, however, conditions are less than perfect. The incision's edges may not be as clean or long as desired, may be distorted by heat from the phaco tip, may be stretched by the IOL's insertion, or may be weakened by a limbal relax- ing incision. The Wong incision can provide a margin of safety in these instances. Effective seal through vulnerable period of hypotony The structural weakness of a stan- dard clear corneal incision can be exposed in the post-op period when additional biomechanical stress oc- curs with blinking, rubbing of the eye, ocular movement, and hy- potony from a relative shutdown of the ciliary body. In vitro, hypotony in a cadaveric eye results in an in- flow of India ink placed on the ocu- lar surface.5 In vivo, the release of aqueous through a clear corneal in- cision to manage a post-op pressure spike can result in temporary hy- potony with a subsequent superficial inflow of fluorescein placed in the tear film.6 causes the globe to expand from a relatively collapsed state in hy- potony to produce a vacuum action. This situation may be one of the causes of toxic anterior segment syndrome. In contrast, the Wong incision remains watertight in the presence of hypotony, as evident upon hy- drating the pocket at the end of a cataract operation without reform- ing the anterior chamber and exert- ing external pressure with a cellulose sponge. The IOP is low, and the inci- sion does not leak. In the estimated 20% of patients who experience post-op hypotony,7 the eye would thus be protected from a superficial Figure 1. The surgeon begins by creating a stromal pocket that is 1.5-2 mm wide. If using two stab incisions, he places them side by side so that the incision resembles an upside down W. A side view shows the pocket to be just anterior to and above the usual entry into the anterior chamber Figure 2. At the conclusion of the case, the surgeon uses a 30-gauge cannula to hydrate the tip and edges of the supraincisional stromal pocket with balanced salt solution. The reformed anterior chamber pushes upward on the internal aspect of the corneal lip, while the stromal hydration pushes downward on the wound Source (all): Michael Y. Wong, M.D. The resilience of the sclera