Placement and Extension of Glaucoma Drainage Devices Using Polypropylene Suture in Pediatric Patients

Introduction

Tube insertion of glaucoma drainage devices in pediatric cases may be challenging due to abnormal anterior segment anatomy complicating placement, and corneal opacities limiting visualization.1 These complexities may lead to complications such as poorly placed tubes2 and leakage from inadvertent tract expansion.3,4 Postoperative tube-related complications include clogs, kinks, identification of inadvertent cuts, or retraction.5 In the context of pediatric glaucoma, where patients may undergo initial glaucoma drainage device placement early in life, ocular growth and aggressive scarring may also cause tube retraction outside of the anterior chamber necessitating tube replacement or extension.6,7 Similar to initial glaucoma drainage device tube placement, tube extension in pediatric cases may be complicated by complex anatomy and limited visualization. In this article, we discuss surgical techniques for initial non-valved glaucoma drainage device tube placement and a glaucoma drainage device tube extension using polypropylene suture as a guidewire and stabilizer in pediatric patient populations.

Technique

Tube Placement

Materials for this technique include a nonvalved glaucoma drainage device implant and a blue 3-0 polypropylene (Ethicon) suture. After dissecting the Tenon capsule and conjunctiva, the glaucoma drainage device reservoir is sutured to the sclera in a standard manner. Estimating the length of the desired tract, the tube is cut accordingly. Starting from the endplate side, a blue 3-0 polypropylene suture is threaded through the glaucoma drainage device tube's lumen until it passes through completely to the tube's open end (Figure 1A). A 23-gauge needle is used to create a sclerostomy tract approximately 3 to 4 mm posterior to the limbus to the tube's desired end position in the anterior segment (Figure 1B). In some circumstances, this may require passing through high iris insertion or synechiae adhesions. The polypropylene tip protruding from the free end of the glaucoma drainage device tube is passed through the previously made sclerostomy tract (Figure 1C). The blue color of the polypropylene material allows for easier visualization in the anterior chamber. The rigid polypropylene filament passes with ease through fibrinous obstacles and the iris. If the polypropylene suture encounters resistance while being passed through the sclerostomy tract, the suture can be removed and cut at an angle to create a beveled tip. Once the tip of the polypropylene filament can be visualized in the desired area in the anterior chamber, the tube is then advanced along the polypropylene until its end position in the anterior chamber is reached. Once tube placement is appropriate, the guidewire suture is removed from the tube's lumen closest to the endplate (Figure 1D). Alternatively, according to the surgeon's discretion, a paracentesis can be created and the polypropylene can be removed from the tube's distal end using intraocular forceps. The remainder of the surgery (verification of tube patency, ligation and confirmation of ligation, and tube attachment to episcleral tissue) can be performed following surgeon preference.

Open multimedia modal

Results

The use of a 3-0 polypropylene suture facilitates efficient placement and extension of glaucoma drainage device tubes using the two methods above. The method described for glaucoma drainage device tube placement is especially useful for pediatric cases with obscure or distorted anatomy and/or limited visualization of the anterior chamber. As opposed to the flexible nature of the silicone tube alone, the polypropylene's rigidity and small diameter allows passage of the suture through the tract without interference from obstructing anatomy such as the iris or fibrous membrane. Furthermore, if using blue polypropylene, the color allows visualization in the anterior chamber despite poor corneal clarity. For tube extension, the rigid structure of the polypropylene suture stabilizes both the extending and existing tubes when sliding one on top of the other. Without the stability of the suture, forceps-assisted guidance of one flexible tube over another flexible tube is difficult.

Discussion

These techniques may solve difficulties with ideal tube placement and simplify tube extension in complex pediatric cases. Wright et al3 described a similar procedure to the aforementioned glaucoma drainage device tube placement technique but did not emphasize its utility in pediatric patients with complex anterior segment anatomy. Additionally, Andrew et al9 described a technique for inserting a 3-0 Supramid (S. Jackson, Inc) suture inside the glaucoma drainage device tube's lumen to increase tube rigidity. However, they opted to keep the suture inserted and only remove it postoperatively during a minor procedure if further intraocular pressure lowering was desired. We believe removal of the suture intraoperatively is preferred to optimize the functionality of the glaucoma drainage device and prevent complications, such as endophthalmitis, associated with stent exposure if the suture is removed postoperatively.10

The second technique, polypropylene-assisted tube extension, is an alternative approach to a solution for some postoperative glaucoma drainage device tube complications, such as a cut tube or tube retraction. In these cases, the decision to replace or move the entire glaucoma drainage device requires extensive tissue dissection, which runs a risk of impinging on proximal anatomy such as the limbus.5 By opting to extend the tube rather than replace the glaucoma drainage device implant, the endplate and surrounding capsule can be preserved, maintaining aqueous flow.11 Although many authors have discussed methods of tube extension, none have used polypropylene to assist with attachment and placement. A previously described technique for tube extension is tube-intube, which can be achieved using materials such as a 22-gauge angiocatheter, additional glaucoma drainage device tube, or alternative tubes such as a nasolacrimal stent.5,6,8,11–13 Alternatively, a Tube Extender (New World Medical, Inc), which includes an additional silicone plate and tube with an opening to insert the shortened tube, has also been described by Sarkisian and Netland5 but can be too long or bulky in a child's eye. Although these previously described extension techniques have been successful in extending the utility of glaucoma drainage device tubes, they do not include the use of a polypropylene suture to facilitate and guide attachment as described here.

Limitations of the use of polypropylene for placement and extension of the glaucoma drainage device tube must be considered. Ligating the tube after placement using polypropylene prevents the surgeon from checking for watertight ligation by flushing.14 In terms of cost, polypropylene sutures are inexpensive and thus do not add significantly to the cost of placement or extension of glaucoma drainage device tubes.

Overall, using polypropylene as a guidewire and/or stabilizer can facilitate glaucoma drainage device tube placement and extension operations in complex pediatric cases with obscure anatomy, poor visualization, or tube retraction. Future studies may be conducted to confirm the advantages of the described techniques by evaluating procedure times, postoperative intraocular pressures, and postoperative complications.