CLINICAL TECHNIQUE |
https://doi.org/10.5005/jp-journals-10078-1430 |
A New “Tube-in-tube” Method to Extend Glaucoma Drainage Devices Using Paul Glaucoma Implant
1,2Department of Ophthalmology, Manchester Royal Eye Hospital, Manchester, England, United Kingdom
Corresponding Author: Tasmin Berman, Department of Ophthalmology, Manchester Royal Eye Hospital, Manchester, England, United Kingdom, Phone: +44 0161 2761234, e-mail: Tasminberman@nhs.net
Received: 21 February 2024; Accepted: 18 March 2024; Published on: 29 October 2024
ABSTRACT
Aim and background: To describe a novel and uncomplicated technique of elongating the tubing of a glaucoma drainage device (GDD) sourced from a segment of the tube from a Paul® Glaucoma Implant (PGI).
Surgical technique: Conjunctival and Tenon’s peritomy are performed with relaxing incisions to expose the original tube. The original tube is then removed from the anterior chamber, and the original entry site is closed. The tip of the original Baerveldt/Ahmed tubing is shortened to near the plate, and the lumen is stretched open using Burke’s forceps (nontoothed to avoid damage to the tubing) while the appropriate length of the Paul tube was being pushed inside and is secure without the need for any suturing. The new smaller Paul tube is then inserted back into the anterior chamber using a 26-gauge tract. An 8-0 Ethilon® was then used to secure the tube to the sclera, and TISSEL® was used to secure it (Baxter, United States). Depending on the positioning, either the original Tutoplast® pericardium or new double-layered Tutoplast® can be placed over the tube to prevent erosion. The Tenon’s and conjunctiva were then closed to secure the conjunctival and Tenon’s back in their original position at the limbus, and the radial conjunctival incisions can be closed using TISSEL® fibrin glue or further sutures if required.
Conclusion: This method offers several benefits over previously documented techniques; it avoids significant bulkiness, and the elongated tube conforms to the curvature of the globe owing to the suitable rigidity of the extended section. The additional tubing segment fits securely without the need for sutures. Introducing a smaller diameter tube into the anterior chamber in comparison to other GDDs minimizes the surface area between the tube and corneal endothelium, therefore decreasing the rate of potential endothelium cell loss.
Clinical significance: This novel “tube-in-tube” technique is efficient, safe, and straightforward to perform. It eliminates the need for alterations in glaucoma medication since the PGI is not thought to offer any flow resistance.
Keywords: Case series, Glaucoma, Glaucoma drainage device complications, Glaucoma drainage devices, Paul® Glaucoma implant, Surgical technique, Tube extension
How to cite this article: Berman T, Au L. A New “Tube-in-tube” Method to Extend Glaucoma Drainage Devices Using Paul Glaucoma Implant. J Curr Glaucoma Pract 2024;18(3):130–133.
Source of support: Nil
Conflict of interest: None
INTRODUCTION
The utilization of glaucoma drainage devices (GDDs) has increased in recent years due to the tube versus trabeculectomy (TVT) study1,2 and post-COVID-19, where service demand is stretched more than ever.3,4 Despite advancements in surgical techniques, postoperative complications are not uncommon, irrespective of the surgical implant used. These include corneal decompensation, hypotony, tube retraction, and tube exposure.
The main reasons for needing to reposition or extend a GDD are tube retraction due to implant movement, corneal decompensation or a tube being cut too short at the time of primary surgery.
Postoperative movement of the implant can lead to tube retraction. This leads to inadequate anterior chamber tube length and failure of drainage due to blockage.
Corneal decompensation can occur when the tube in the anterior chamber is positioned either too long or has been placed too anteriorly, causing endothelial loss.5 One possibility is to surgically reposition the tube into the ciliary sulcus. This is sometimes used as a primary surgery for patients who already have a corneal graft or are at high-risk of corneal decompensation.6,7 However, in order to position a tube in the sulcus and avoid iris blockage, it is necessary for the tube to have sufficient length for the tube to be visible near the edge of the patient’s pupil. Consequently, the existing tube might require extension when moved from the anterior chamber to the sulcus position.
There are several published solutions to extend and reposition a GDD tube. These include repositioning the tube within the anterior chamber and securing it to the limbus, repositioning the plate of the tube to a more anterior position,8 using a tube extender, which is readily available commercially to purchase,9-11 using 22-gauge intravenous angiocatheter,12-14 Crawford tubing15 or implanting a new GDD.16
The Paul Glaucoma Implant (PGI) (PGI; Advanced Ophthalmic Innovations, Singapore, Republic of Singapore) is a relatively new aqueous shunt device. It is a GDD made of medical-grade silicone, which does not have a valve. Compared to the Molteno 3® (MOLTENO Ophthalmic Ltd), Ahmed (New World Medical, Rancho Cucamonga, California) and Baerveldt® tube (Johnson & Johnson Vision, Santa Ana, California), the tube diameter is significantly smaller with an external diameter of 467 µm and an internal diameter of 127 µm. This compares to the Baerveldt tube (BVT), which has an external diameter of 635 µm and an internal diameter of 305 µm and the Ahmed valve, which has an external diameter of 630 µm and an internal diameter of 300 µm (Fig. 1).
Fig. 1: Image showing GDD tube diameters for PGI, BVT and Ahmed valve. Showing from left to right—PGI: ID = 127 µm; ED = 467 µm; BVT: ID = 305 µm; ED = 635 µm; Ahmed valve: ID = 300 µm; ED = 630 µm
This smaller diameter reduces the size of the tube within the anterior chamber, minimizing the area of contact between the tube and the endothelium and, therefore, theoretically, the rate of endothelium loss.
We describe a novel and practical surgical method using a portion of the PGI tube to reposition and extend a GDD tube in three cases where they were causing corneal decompensation due to positioning in the anterior chamber (Table 1).
| Glaucoma type | Previous treatment | Visual acuity preprocedure (LogMAR) | Visual acuity postprocedure (LogMAR) | IOP preprocedure (mm HG) | IOP postprocedure (mm HG) | Change in IOP (mm HG) | Medication preprocedure | Medication postprocedure | Change in medication |
|---|---|---|---|---|---|---|---|---|---|
| Secondary glaucoma | Phakic lens implantation, DSEAK and phacoemulsification plus IOL, redo DSAEK, BVT | HM due to failed corneal graft | HM is awaiting a corneal graft | 10 | 11 | 1 (10%) | No treatment | No treatment | 0 |
| Primary angle closure glaucoma | BVT, penetrating keratoplasty secondary to bullous keratopathy | 0.98 imp 0.4 PH | 1.06–0.82 PH | 18 | 16 | 2 (11%) | Latanoprost and dorzolamide/timolol combination | Latanoprost and dorzolamide/timolol combination | 0 |
| Secondary glaucoma (uveitis) | Ileuven 2019, 2021, ozurdex, PPV, DSEAK 2017 | 1.0 | 0.74 | 14 | 12 | 2 (14%) | Latanoprost and dorzolamide/timolol combination | Latanoprost and dorzolamide/timolol combination | 0 |
BVT, Baerveldt tube; DSEAK, Descemet’s stripping endothelial automated keratoplasty; IOL, intraocular lens; IOP, intraocular pressure, PH, pinhole
SURGICAL TECHNIQUE
The procedure can be performed under local anesthetic using sub-Tenon’s injection (2% lidocaine and 0.5% bupivacaine) or, if required, under general anesthetic. The eye is rotated to gain exposure and access using a 7-0 Novofil® or 7-0 silk corneal traction suture. Conjunctival and Tenon’s peritomy is performed with relaxing incisions over 3 o’clock hours to expose the original tube, removing the overlying tutoplast/scleral patch graft cover. The original tube is then removed from the anterior chamber, and the original entry site is plugged with a small triangular piece of Tutoplast® and sutured with 9-0 Ethilon® to ensure a watertight closure. An appropriate length of Paul tube was cut. The tip of the original BVT/Ahmed tubing is shortened to near the plate, and the lumen is stretched open using burkes forceps (nontoothed to avoid damage to the tubing) while the Paul tube was being pushed inside (Fig. 2). The internal lumen of a BVT/Ahmed offers a snug secured pressure fit for the Paul tubing without the need for any suturing. The new smaller Paul tube is then inserted back into the anterior chamber using a 26-gauge tract. An 8-0 Ethilon® was then used to secure the tube to the sclera, and TISSEL® was used to secure it (Baxter, United States). Depending on the positioning, either the original Tutoplast® pericardium or new layered Tutoplast® can cover the segment of the tube to prevent erosion. The Tenon’s and conjunctiva were then closed using 10-0 Ethilon® sutures to secure the conjunctival and Tenon’s back in their original position at the limbus, and the radial conjunctival incisions can be closed with either TISSEL® fibrin glue or sutures depending on surgical preference.
Fig. 2: Image showing PGI tube placed inside existing BVT
Case 1
A 52-year-old female developed secondary glaucoma after phakic lens implantation at age 32, requiring a Descemet’s stripping endothelial automated keratoplasty (DSEAK) for corneal decompensation. The patient then developed secondary glaucoma, requiring a BVT. The cornea decompensated postoperatively, requiring a second DSEAK. The cornea then decompensated again in 2022, and a decision was made to adjust the position of the tube using the technique documented prior to further corneal procedures, which are still awaited. Preoperative intraocular pressure (IOP) was 10 mm Hg, and postprocedure was 11 mm HG (10% change). They were on no glaucoma drops needed preoperatively and did not require any drops postprocedure.
Case 2
A 57-year-old female with primary angle closure glaucoma. She had a primary trabeculectomy and underwent a previous BVT in 2016 and subsequently developed bullous keratopathy requiring a penetrating keratoplasty. She underwent surgery to reposition the tube by the technique documented prior to penetrating keratoplasty, which was performed in 2022. Preoperative IOP was 18 mm HG on three medications. Postprocedure IOP was 16 mm Hg (11% change), and they were still on the same three medications.
Case 3
A 44-year-old male with glaucoma secondary to sarcoid uveitis. He had an extensive ophthalmic surgery history, including BVT in 2010, which was subsequently trimmed in 2016, DSEAK in 2017, pars plana vitrectomy to treat an epiretinal membrane in 2021 and intravitreal steroids in 2019 and 2021 to treat his uveitis. Due to decompensation of the cornea, he then underwent surgery to reposition the tube by the technique documented in 2022 while he was awaiting further corneal procedure. Preoperative IOP was 14 mm Hg on three medications, and postprocedure IOP was 12 mm HG (14% change) on the same three medications.
DISCUSSION
Several methods have been described for extending GDDs, all with good success. The most described techniques involve using a 22-gauge angiocatheter and tube extenders.
The use of a 22-gauge angiocatheter was first described by Smith and Doyle17 and then by Bansal and Fenerty.14 They describe using the angiocatheter between two cut ends of the GDD tube. This method requires suturing to secure the expanded portion of tubing and tying of the tube to prevent early hypotony. There was also quite a lot of variation in the rigidity of brands of angiocatheters, therefore making surgical techniques difficult.
Commercial tube extenders, which are readily available, have previously been used to extend GDD tubes.9-11 The main disadvantage is that it is very bulky, making it suboptimal to use near the limbus.
Moving the plate of the GDD to a more anterior position has been described for tube retraction.8 There is an increased risk of postoperative scarring due to the extensive dissection required of both the conjunctiva and Tenon’s capsule. Subsequently, this may lead to potential postoperative failure or erosion of the device.
Implantation of a new GDD16 involves significant surgical time. If a new GDD is placed at the same position as the initial surgery, it carries a risk of significant scarring response and potential risk of erosion due to reopening of the conjunctiva. If the new device is implanted in an alternative quadrant, this potentially affects surgical options for the future if the new device fails. More importantly, if the device itself is functioning well, as in all of our cases, it is purely because the tube needs repositioning; therefore, implantation of a new device should be reserved after less invasive procedures have failed.
Chiang et al.18describe a similar tube-in-tube technique with the tubing from an Ahmed tube and their method of placing the tube inside the original tube using Kelman–McPherson forceps. This method, however, requires suturing the two tubes together using a 10-0 nylon nonabsorbable suture. By using our described technique, not only do you not have to suture the inserted tube extension, but you also have the advantage of the other practical advantages of the PGI over other GDDs. No suturing of the extended tube is required. There is also no need for ligation or stenting of the tube because there is no disruption to the original tube plate, and it is already encapsulated. In addition, with an external diameter of 467 µm and an internal diameter of 127 µm, the tube diameter is smaller than that of the Molteno 3®, Ahmed and Baerveldt®; this should not offer extra resistance, meaning that the IOP should remain stable compared to preoperative values which have been shown in all three of our cases (mean change in IOP 11% ± 2% with no change in medication with any case). This smaller tube also theoretically reduces the rate at which endothelium cell loss occurs because it minimizes the surface area between the tube within the anterior chamber and corneal endothelium.
A PGI can be cut to provide any length of tubing segment required; because it has a smaller external diameter than other GDDs or commercial tube extenders, it does not add significant bulk to the eye, and the lengthened tube follows the curvature of the globe owing to appropriate rigidity of the extended segment. The new segment of tubing has a secure fit to the original tube without leaks or the need for additional sutures. By placing a smaller diameter tube in the anterior chamber compared to other GDDs, the surface area between the tube and corneal endothelium is decreased, which reduces the rate of endothelium loss. In addition, due to the procedure not affecting the drainage, no alteration is required for the glaucoma medication either immediately or in the subsequent postoperative follow-up. This is superior to the use of alternative methods to extend the tube, such as extending the tube with a Xen stent,19 which creates outflow resistance and does not fit snugly into the tube.20 In addition, as the Xen implant has a lumen of 45 µm, it is theoretically more prone to blockage and, as it is more fragile, therefore more likely to break. As far as we are aware, currently, there are no publications describing using a PreserFlo Microshunt to extend a tube; however, Fritsche et al., 202221 have published the use of a PreserFlo Microshunt to treat late postoperative hypotony after a BVT suggesting that despite the PreserFlo Microshunt external diameter being almost identical to the BVTs internal diameter the effect on IOP makes it unsuitable for this use.
In our opinion, using a Paul tube offers an effective and viable surgical option for extending a segment of GDD tubing. When used with the surgical method outlined above, it should be considered a practical primary option to extend retracted or damaged Ahmed, Baerveldt, and Molteno GDDs.
The only disadvantage is the expense of using a new Paul tube implant. This, however, can be counteracted by good theater utilization and case scheduling by having a second patient attend for a complete Paul tube, therefore not wasting the plate and connected tube length and improving health economics.
CONCLUSION
This surgical technique has many advantages over previously published methods; due to the size and rigidity of the PGI tubing, no significant bulkiness is added to the sclera, and the elongated tube conforms to the curvature of the globe well. The additional segment of tubing fits securely within the current tube without leaking or the need for sutures. Introducing a smaller diameter tube into the anterior chamber in comparison to other GDDs minimizes the surface area between the tube and corneal endothelium, therefore decreasing the rate of potential endothelium cell loss. Finally, as it has no effect on the IOP, no change in medication postoperatively is required.
Clinical Significance
This surgical approach offers a simple and effective way to extend an existing GDD. It does not influence the IOP. This technique may be used to treat various complications encountered with GDDs.
ORCID
Tasmin Berman https://orcid.org/0000-0002-6251-2103
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