An 86-year-old black female with hemorrhagic glaucoma secondary to wound vascularization following extracapsular cataract extraction underwent the implantation of a 350-mm2 Baerveldt glaucoma implant (Pfizer Inc., New York, NY) . During surgery, Dr. Lama trimmed the tube so that the bevel faced the corneal endothelium and then implanted the device so that approximately 2 mm of the tube was visible in the anterior chamber. Next, he stented and ligated the tube.
During the first 2 postoperative weeks, the patient's IOP ranged between 25 and 32 mm Hg with medical therapy that included acetazolamide 500 mg b.i.d. Three weeks following surgery, however, her IOP rose into the 50s. An anterior chamber paracentesis resulted in only a transient decrease in IOP, which again rose into the 50s after a little over 1 hour.
Dr. Lama then pulled the 4–0 nylon stent suture, and the patient's IOP immediately decreased to 4 mm Hg, upon which the eye suddenly developed a 2-mm layering hyphema and mild shallowing of the anterior chamber that resulted in peripheral iridocorneal apposition. An exuberant fibrinoid reaction ensued that caused envelopment of both the tube and iris, with lost visibility of the tube. Even after the anterior chamber spontaneously deepened and both the hyphema and inflammatory reaction resolved, Dr. Lama could not visualize the tube.
Since the tube appeared to be functioning reasonably well, as evidenced by a visible bleb over the plate and control of the IOP to between 16 and 20 mm Hg on timolol 0.5% b.i.d., we elected not to intervene and followed the patient conservatively. Her visual fields and disc appearance remained stable. Nineteen months later, however, the eye's IOP increased to the low 30s and could not be controlled medically.
We used a 30-gauge needle to penetrate the subcapsular space over the plate but observed no aqueous flow into the adjacent subconjunctival space, nor could we recover any flow via aspiration. Because B-scan ultrasonography failed to disclose a bleb overlying the plate, we diagnosed distal tube failure.
HOW WOULD YOU PROCEED?
1. How would you revise the tube?
2. Is repositioning a viable option?
3. Would you implant a second tube?
SURGICAL COURSE
Dr. Lama performed a limbal conjunctival peritomy and carefully dissected the subconjunctival tissue in order to allow visualization of the tube on the episcleral surface. A paracentesis incision followed by the injection of fluorescein-stained saline into the anterior chamber confirmed the presence of anterior tube obstruction.
Dr. Lama's attempt to reposition the tube into the anterior chamber was unsuccessful as a result of broad anterior synechiae and the relative shortness of the tube. He therefore elected to proceed with a tube-lengthening procedure. Dr. Lama then selected an adult lacrimal silicone intubation set (StenTube; Atrion Medical, Birmingham, AL) (Figure 1) because it features a variable diameter across its length (outer diameters of 0.86 mm and 1.32 mm). He could fit the Baerveldt glaucoma drainage tube, which has an outer diameter of 0.64 mm, through the lumen of the 1.32-mm segment but not through the 0.86-mm segment. (Although upon direct inspection the lumen of the 1.32-mm end appears to be wider, the manufacturer-reported internal diameter is uniformly 0.41 mm ± 0.05 mm.)
Figure 1. The authors compare the external and internal diameters of the glaucoma tube (narrower) and extender (wider).
Dr. Lama cut an approximately 20-mm piece of tubing, which included both segment dimensions, from the StenTube set. He then trimmed the wider segment to 4 mm with the bevel facing upward. Next, he explanted the Baerveldt tube from the anterior chamber and further shortened it so that the distal end lay approximately 1 mm proximal to the fistula entry site.
Dr. Lama passed a 4–0 PROLENE Polypropylene Suture (ETHICON, Somerville, NJ) through the lumen of the extension and the glaucoma tube to serve as a guide wire and stent. He then internally “threaded” the glaucoma tube into the lumen of the extension for approximately 3 mm until the extension's wider end rested completely on the episcleral surface proximal to the fistula site. After removing the PROLENE guide wire, Dr. Lama used two 10–0 PROLENE sutures to secure the anastomosis. He trimmed, beveled, and then implanted the narrower distal end (0.86 mm) of the extension so that it reached beyond the peripheral synechiae. To create a tighter fit, Dr. Lama enlarged the fistula slightly to 0.80 mm with a 21-gauge needle and stretched the tissue to allow implantation of the tube. After securing the anastomosed tubes to the globe with two 10–0 nylon sutures, Dr. Lama placed a 6 X 6-mm scleral patch graft in order to cover the tube and extender located over the fistula site.
OUTCOME
Twenty months after the extension procedure, the patient's IOP was stable in the low teens on timolol 0.5% b.i.d. The anterior chamber was quiet, and the tube was in an excellent position (Figures 2 and 3).
Figure 2. The two ends (glaucoma tube and extender) have been anastomosed with 10–0 PROLENE.
Figure 3. The tube extension procedure yielded this clinical appearance 3 months postoperatively.
DISCUSSION
Glaucoma drainage devices have been used successfully to manage complicated glaucomas when standard filtration procedures with antimetabolites are unsuccessful. Nevertheless, shunts may fail for a number of reasons, including (1) tube obstruction by iris, blood, or vitreous, (2) tube retraction out of the eye, or (3) exuberant encapsulation and scarring over the plate.
Tube failure due to retraction is an uncommon but frustrating complication of glaucoma drainage device implantation. It may occur because the tube was too short initially or due to subsequent retraction that results from scarring or plate migration. The latter occurs as a result of contraction of the fibrous capsule around the plate, and a loosely anchored plate is often a predisposing factor.
Physicians may successfully manage tube retraction by surgical methods involving tube lengthening or plate repositioning. The second option, however, involves extensive dissection into the capsule in order to mobilize the plate, so it is the less favored technique. Tube lengthening is a simpler option.
In addition to tube retraction, inadvertent damage to or amputation of the tube during the course of surgical revision are also indications for a tube lengthening procedure. To date, there have been few published descriptions of surgical tube-lengthening techniques for the management of retracted or inadvertently amputated tubes. One method involved a silastic sleeve.1 With this technique, the surgeon divides the tube and splices the silastic sleeve in between the ends of the divided tube. The ends are then anastomosed with 10–0 nylon sutures. Another recently described method involves splicing an angiocath from a 23-gauge intravenous tube set in between ends of the tube.2
Figure 4. The above sequence illustrates the method used intraoperatively to extend the tube (A-I).
No single technique of tube lengthening has become the gold standard. The technique detailed in this article is relatively simple to perform and offers the advantage of a stable, watertight seal (Figure 4). Furthermore, owing to its tapered end, the extension itself can be safely implanted into the anterior chamber without the risk of dislocation into the anterior chamber, because the 1.32-mm end of the segment will not fit through the fistula site, which rests on the episcleral surface.
Paul J. Lama, MD, is Assistant Professor of Ophthalmology at the New Jersey Medical School in Newark, New Jersey. He holds no financial interest in any of the products or companies mentioned herein. Dr. Lama may be reached at (973) 972-9467; lamapj@umdnj.edu.
Robert D. Fechtner, MD, is Professor of Ophthalmology at the New Jersey Medical School in Newark, New Jersey. He holds no financial interest in any of the products or companies mentioned herein. Dr. Fechtner may be reached at (973) 972-2030; fechtner@umdnj.edu.
1. Kooner KJ. Repair of Molteno implant during surgery. Am J Ophthalmol. 1994;117:673.
2. Smith MF, Doyle JW. Results of another modality for extending glaucoma drainage tubes. J Glaucoma. 1999;8:5:310-314.
