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Preventing endophthalmitis with stable incisions
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Ophthalmologists must be familiar with the elements necessary for creating stable clear corneal incisions to provide the best care for patients after cataract and refractive surgery. Studies have shown that creating stable clear corneal incisions is important in preventing endophthalmitis.1-3
Creating clear corneal incisions
I introduced clear corneal cataract incisions in 1992 and have used them exclusively since that time. Clear corneal incisions are made in the plane of the cornea, not iris parallel, and have an arc length of greater than the cord length of 2 mm, as observed from above, and are less than or equal to 3.5 mm wide (if they are not sutured).4,5 Historically, artists’ interpretations of clear corneal incisions showed them to be straight single-plane incisions in which one surface could easily slide over the other, creating instability. Charles Williamson, MD, and David Langerman, MD, developed techniques to prevent this instability. Williamson introduced a shallow, perpendicular groove to be made before incising the cornea into the anterior chamber. Langerman then deepened this groove to increase stability. However, the grooved incision resulted in foreign body sensation, pooling of mucus and debris, and a disruption in the fluid barrier created by an intact epithelium. The fluid barrier enhances endothelial pumping to the upper reaches of the cornea, facilitating the seal in the immediate postoperative period. In addition, the gaping of the groove was associated with a gaping of the internal lips of the incision (Figure 1a). We now create paracentesis-style incisions to avoid these complications.
Clear corneal incisions are curvilinear rather than straight, as indicated by artists’ interpretations. Their architecture allows for a fit similar to tongue-in-groove paneling, reducing the likelihood of one surface sliding over the other, which improves stability (Figure 1b).
Stromal hydration is recommended to enhance stability. Stromal hydration thickens the incision, forcing the floor up against the roof, enhancing endothelial pumping. A Seidel test performed with fluorescein documents that the incision is sealed. If it is unclear if the incision is sealed, then it should be rehydrated. If rehydrating the incision is ineffective, then a suture should be placed. Although many ophthalmologists report that stromal hydration lasts only 1 or 2 hours, the resulting swelling lasts longer than 24 hours and helps seal the incision, as documented by optical coherence tomography (OCT) (Figure 1b). OCT offered ophthalmologists the first view of corneal incisions in the living eye in the early postoperative period (all previous views of corneal incisions were of autopsied human eyes).
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Blades to create optimum wound architecture
Clear corneal incisions can be created using a variety of blades. In the past, blades with straight sides were used. These blades were problematic because if the incision needed to be enlarged by cutting to the sides, then the architecture was violated, resulting in less self-sealability. Since then, trapezoid-shaped blades have been developed, which allow for preservation of the incision architecture when enlarging for IOL implantation by reinserting the blade and advancing it further into the incision. A learning curve is associated with new incision techniques. In the past decade, 8% to 10% of surgeons, each year, have been in the learning curve of the transition to clear corneal incisions, which may increase the incidence of endophthalmitis.
Many blade designs have been shown to be effective in creating proper architecture, including metal blades. The Kojo Slit blade (Becton-Dickinson Medical-Ophthalmic Systems, Franklin Lakes, NJ) is curved in the direction of the incision width, which allows ophthalmologists to create an arcuate incision parallel to the curvature of the peripheral cornea. The incision has a cord length with a width that is narrower than the width of the arcuate incision in the dimension tangential to the limbus (Figure 1c). This length may improve stability.
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Endophthalmitis prophylaxis
Corneal incision construction and architecture are of primary importance in preventing endophthalmitis. Proper length, width and profile of the incision facilitate the ability to self-seal and add safety. Other key elements of endophthalmitis prophylaxis include a proper preoperative antibiotic regimen, preparation of the surgical field, surgical technique, incision closure, testing the incision for leakage and postoperative antibiotics. The results of this study indicate that an incision in the plane of the cornea with a cord length of at least 2 mm appears to give uniquely advantageous architecture for adequate self- sealability. Richard S. Hoffman, MD, Mark Packer, MD, FACS, and I have performed surgery for more than 10 years on more than 10,000 patients without a single incidence of endophthalmitis. This is not due to “good luck,” but rather to maintaining concerted attention to detail.
References
- Eifrig CW, Flynn HW, Scott IU, Newton J. Acute-onset postoperative endophthalmitis: Review of incidence and visual outcomes (1995-2001). Ophthalmic Surg Lasers. 2002;33:373-378.
- Miller JJ, Scott IU, Flynn HW Jr, Smiddy WE, Newton J, Miller D. Acute-onset endophthalmitis after cataract surgery (2000-2004): Incidence, clinical settings and visual acuity outcomes after treatment. Am J Ophthalmol. 2005;139:983-987.
- Monica ML, Long DA. Nine-year safety with self-sealing corneal tunnel incision in clear cornea cataract surgery. Ophthalmology. 2005;112:985-986.
- Fine IH. Self-sealing corneal tunnel incision for small-incision cataract surgery. Ocular Surgery News. 1992;10:38-39.
- Fine IH. Clear corneal incisions. Int Ophthalmol Clin. 1994; 34:59-72.