Glaucoma drainage devices fall into two major categories, valved and nonvalved. The former were designed to alleviate both extremely high and low IOP during the early postoperative period. Although valved implants are excellent for early postoperative IOP control, they often provide worse long-term pressure control than do nonvalved devices. Ophthalmologists have developed a number of methods to block the free flow of aqueous through a nonvalved drainage tube, including two-stage implantation,3 occlusive ligatures,4 and internal blockage with a stent.5-8
The first method of aqueous blockage involves suturing the drainage plate to the sclera without inserting the tube into the anterior chamber. After the capsule forms over the plate a few weeks later, the surgeon can insert the tube into the anterior chamber without the fear of profound hypotony. With the occlusive ligature technique, the surgeon ties a biodegradable suture around the tube just anterior to the drainage plate and places tube fenestrations anterior to the ligature, or he incorporates what is termed a ripcord in the ligature for release as needed. The internal blockage with a stent technique involves threading a suture into the tube lumen and releasing the stent once the capsule forms postoperatively.
This author prefers the technique of occlusive ligature and standardized fenestration of the drainage tube.9 Tying a ligature around the drainage tube can be technically challenging, particularly without the help of an assistant. I favor this technique over others, because early postoperative IOP control is often adequate, and there is no risk of profound hypotony associated with the early release of the ripcord or internal stent. This article describes a novel technique for tying an occlusive ligature around the tube of a Baerveldt drainage device (Pfizer Inc., New York, NY).
BACKGROUND
The nonvalved Baerveldt drainage device is constructed entirely of medical grade silicone. Its episcleral plate is available in different surface areas of between 200 and 500 mm2. The Baerveldt implant contains a silicone tube that is 32 mm in length and attaches to the anterior surface of the plate.
TECHNIQUE
Step 1. Inspect the glaucoma drainage device under the microscope to confirm that no manufacturing defects are present. Inject BSS (Alcon Laboratories, Inc., Fort Worth, TX) from the cannula of an irrigating syringe through the tip of the tube in order to confirm its patency (Figure 1).
Figure 1. Injecting BSS from an irrigating syringe through the tip of the Baerveldt tube confirms the tube's patency. (All illustrations by Matthew Holt.)
Step 2. Cut a relatively straight piece (approximately 6 cm in length) of 7–0 biodegradable suture without the needle attached.
Step 3. Thread one end of the suture under the tube and tuck it beneath the manufacturer's 9–0 anchoring platform suture (Figure 2).
Figure 2. The surgeon threads one end of a 7–0 biodegradable suture behind the Baerveldt tube and under the 9–0 anchoring platform suture (magnified in inset).
Step 4. Loop the first three passes of a 3-1-1 knot loosely around the tube as shown in Figure 3.
Figure 3. The surgeon loosely ties the first three loops of a 3-1-1 knot around the Baerveldt tube.
Step 5. Cut the anchoring platform suture with microscissors and remove it.
Step 6. Tie the first throw of the 3-1-1 knot snugly around the tube, approximately 2 mm anterior to the surface of the plate, so that no further flow of fluid is detectable through the posterior aperture of the Baerveldt plate (Figure 4).
Figure 4. The surgeon completes the 3-1-1 knot after removing the 9–0 anchoring platform suture so that the knot is approximately 2 mm anterior to the Baerveldt plate.
Step 7. Complete the 3-1-1 knot (Figure 5).
Figure 5. The 3-1-1 knot is tied securely until no further flow of BSS is detectable at the posterior aperture.
Step 8. Insert the Baerveldt glaucoma drainage device into the patient's eye per your preferred technique.
CONCLUSION
Tying off a nonvalved glaucoma drainage implant can be a cumbersome and daunting task for the surgeon and may lead to unnecessarily increased OR time. This article describes a simple and effective technique for the occlusive ligation of a Baerveldt drainage tube.
Leon W. Herndon, MD, is Associate Professor of Ophthalmology at the Duke University Eye Center in Durham, North Carolina. He does not hold a financial interest in any of the products or companies mentioned herein. Dr. Herndon may be reached at (919) 684-6622; hernd012@mc.duke.edu.
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