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Two techniques may help manage tubal retraction associated with glaucoma drainage implants
A surgeon explains how to use a Tube Extender and a 22-gauge angiocatheter tubing segment.
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Glaucoma is the most common cause of irreversible blindness worldwide, affecting about 70 million people. It is characterized by progressive loss of optic nerve axons and resultant visual field damage. Unfortunately, due to its insidious course, it is often diagnosed only when the individual has advanced, irreversible visual field loss.
Globally, primary open-angle glaucoma is the most common type of glaucoma. Elevated IOP has been implicated as the major risk factor, and hence, the main goal of glaucoma therapy is to lower IOP to prevent continued retinal ganglion cell loss and expansion of visual field loss. In an attempt to lower IOP, the clinician’s therapeutic armamentarium includes the use of topical ophthalmic glaucoma medications, trabecular meshwork laser treatment, filtering glaucoma surgery, which can be penetrating, nonpenetrating or limited penetration, allogenic implants and ciliary body cyclophotocoagulation.
One of the complications related to glaucoma drainage devices is tube retraction. Moving the glaucoma drainage device anteriorly or replacing it with a new device requires extensive surgical undertaking. An alternative method to deal with tubal retraction would be to extend the existing tube of the glaucoma drainage device.
In this column, Dr. Aref describes the two surgical techniques that may be useful in the management of tubal retraction associated with glaucoma drainage implants.
Thomas “TJ” John, MD
OSN Surgical Maneuvers Editor
Glaucoma drainage implant (GDI) surgery involves the placement of an extraocular artificial filtering device to lower IOP. All drainage implants consist of a silicone rubber tube connected to an end plate. In several instances, lengthening of the silicone tube may be required. Tube retraction with continued growth of an eye in pediatric patients, inadvertent tube amputation, or tube revision surgery involving re-direction of the tube all may require lengthening of the silicone tubing of a pre-existing drainage implant. There are several strategies for lengthening a GDI tube. This article will describe two techniques to accomplish this goal: use of a Tube Extender (New World Medical) and use of a 22-gauge angiocatheter tubing segment.
Ahmad A. Aref
Tube Extender
The Tube Extender consists of silicone tubing (inner diameter: 0.305 mm; outer diameter: 0.635 mm) connected to an accessory plate. The accessory plate houses an opening designed for insertion of the pre-existing tubing to allow for effective lengthening. Because various GDIs all contain similar silicone tubing, the Tube Extender may be used to lengthen any GDI type. The device may be stored at room temperature.
Figure 1. The pre-existing drainage implant tubing is inserted into the larger opening of the Tube Extender accessory plate using non-toothed forceps.
Figure 2. The Tube Extender accessory plate is sutured to the sclera with non-absorbable sutures passed through the device’s anchoring holes.
Images: Aref AA
Once conjunctival dissection has exposed the pre-existing GDI, the proximal portion of the tubing should be trimmed to create an anterior bevel. Using non-toothed forceps, the beveled tip of the tubing is placed into the accessory plate opening of the Tube Extender (Figure 1). Non-absorbable sutures may be used to secure the two pieces of tubing together. The accessory plate is then sutured to the sclera with non-absorbable sutures passed through the device’s anchoring holes (Figure 2). The distal portion of the Tube Extender tubing is then trimmed to an adequate length and inserted into the eye through a standard sclerotomy. The accessory plate and anterior portion of the tubing should be covered with a tissue patch graft to decrease the risk of exposure. Conjunctiva may then be reapproximated to the limbus and closed using the surgeon’s preferred technique.
Angiocatheter tubing
Angiocatheters are typically used to connect the venous blood supply to intravenous tubing. Various gauges of angiocatheter tubing are available for this purpose. A section of 22-gauge angiocatheter may be used to extend GDI silicone tubing when necessary.
After conjunctival dissection has been performed to expose the pre-existing GDI, the proximal portion of the tubing should be trimmed to create an anterior bevel. A 4-mm segment of 22-gauge angiocatheter tubing may be sectioned with a blade or sharp surgical scissors (Figure 3). The pre-existing silicone tubing is inserted into the angiocatheter tubing with non-toothed forceps (Figure 4). A separate piece of silicone tubing, which may be acquired from a Crawford nasolacrimal duct set (FCI Ophthalmics), is inserted into the distal portion of the angiocatheter tubing segment (Figure 5). The proximal and distal portions of silicone tubing should be sutured to the angiocatheter tubing segment with non-absorbable sutures (Figure 6). The distal portion of silicone tubing may be trimmed to an adequate length. After the distal portion is inserted into the eye, the entire length of tubing may be secured to the sclera using non-absorbable sutures. The anterior portion of the tubing and the portion containing the angiocatheter tubing segment should be covered with a tissue patch graft to decrease the risk of exposure. Conjunctiva may then be reapproximated to the limbus and closed using the surgeon’s preferred technique.
Figure 3. A 4-mm segment of a 22-gauge angiocatheter tubing is cut using sharp surgical scissors.
Figure 4. The pre-existing drainage implant tubing is inserted into the proximal portion of the angiocatheter tubing segment using non-toothed forceps.
Figure 5. A piece of silicone tubing is inserted into the distal portion of the angiocatheter tubing using non-toothed forceps.
Figure 6. The angiocatheter and silicone tubing segments are sutured together using non-absorbable sutures.
Conclusion
All surgeons who perform GDI surgery should be prepared to lengthen a silicone tube if necessary. The Tube Extender and 22-gauge angiocatheter tubing are two available devices to perform successful tube extension. The Tube Extender’s accessory plate makes the entire device more bulky compared with angiocatheter tubing. However, the Tube Extender is available off the shelf and does not require further manipulation by the operating surgeon.