|Year : 2020 | Volume
| Issue : 1 | Page : 40-42
Innovative usage of the remaining portion of ahmed glaucoma valve tube as an implant in nonpenetrating glaucoma surgery
Saeed Shokoohi-Rad, Mohammad Yaser Kiarudi, Mohammad-Reza Ansari-Astaneh
Eye Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
|Date of Submission||06-Jan-2019|
|Date of Decision||23-Apr-2019|
|Date of Acceptance||16-Dec-2019|
|Date of Web Publication||17-Feb-2020|
Dr. Saeed Shokoohi-Rad
Department of Ophthalmology, Eye Research Center, Mashhad University of Medical Sciences, Mashhad
Source of Support: None, Conflict of Interest: None
| Abstract|| |
With the advent of nonpenetrating glaucoma surgeries (NPGS), these techniques are noticed more considerably by glaucoma surgeons due to lower complications in comparison to penetrating surgeries with comparable outcomes. One of the main objectives in these surgeries is the creation of an intrascleral filtering space as an alternative for subconjunctival filtering bleb. Intrascleral fibrosis in the long term reduces the volume of intrascleral bleb, so the use of implants as a space holder for preventing the collapse of scleral flaps and continued aqueous humor drainage is recommended. A lot of materials with diverse designs have been used as implants in NPGS. In this study, the remaining of Ahmed valve's tube was used as an implant in four eyes of four patients. The technique for the implant we introduced, offers significant advantages over previously reported implants. The material is biocompatible, low cost, and easily accessible in all the centers performing glaucoma surgeries.
Keywords: Ahmed valve's tube, implant, nonpenetrating glaucoma surgery
|How to cite this article:|
Shokoohi-Rad S, Kiarudi MY, Ansari-Astaneh MR. Innovative usage of the remaining portion of ahmed glaucoma valve tube as an implant in nonpenetrating glaucoma surgery. Oman J Ophthalmol 2020;13:40-2
|How to cite this URL:|
Shokoohi-Rad S, Kiarudi MY, Ansari-Astaneh MR. Innovative usage of the remaining portion of ahmed glaucoma valve tube as an implant in nonpenetrating glaucoma surgery. Oman J Ophthalmol [serial online] 2020 [cited 2020 Jul 6];13:40-2. Available from: http://www.ojoonline.org/text.asp?2020/13/1/40/278545
| Introduction|| |
With the advent of nonpenetrating glaucoma surgeries (NPGS), they are noticed more considerably by glaucoma surgeons due to lower complications in comparison to penetrating surgeries with comparable outcomes. The widely accepted procedures in NPGS consist of deep sclerectomy (DS), viscocanalostomy, and canaloplasty. In DS, the substantial drainage occurs at the level of the anterior trabeculum, and four mechanisms for decreasing intraocular pressure (IOP) have been proposed, including subconjunctival bleb, intrascleral bleb, suprachoroidal, and episcleral vein outflow.
One of the main objectives in the DS is the creation of an intrascleral filtering space as an alternative for subconjunctival filtering bleb. However, intrascleral fibrosis in the long term reduces the volume of intrascleral bleb, so the use of implants as a space holder for preventing the collapse of scleral flaps and continued aqueous humor drainage is recommended.
The intrascleral implants used in NPGS can be classified into two major categories: absorbable and nonabsorbable. Yet, these implants are costly, are not always readily accessible, and may not available in all the centers.
In this study, for the first time, we introduced a novel technique for the creation of an implant by the remaining of the tube cut during the shunting procedure, with the advantages of being biocompatible, easily available, and nonabsorbable with low cost.
| Case Report|| |
Our technique, in fact, is the creation of an intrascleral implant by unused Ahmed valve's tube from the previous Ahmed glaucoma valve (AGV) surgery. The steps of surgery are as usual viscocanalostomy. First, corneal traction suture with silk 7.0 is inserted. A fornix-based peritomy is performed, and then, superficial scleral flap (5 mm × 5 mm) is created with crescent blade and approximate depth of 20%–30% of scleral thickness. This superficial flap is fixed under corneal traction suture. After that, a deep scleral flap (4 mm × 4 mm) is created with attention to observe dark choroidal reflex at the bottom of the flap. A meticulous dissection is performed forward until the Schlemm's canal is reached and deroofed. Then, dissection of trabeculo-Descemet's membrane (TDM) with sponge and secondary instrument is done, and inner scleral flap is excised with Vannas scissors.
Cannulation of Schlemm's canal and injection with Amvisc Plus Viscoelastic gel (1.6% sodium hyaluronate, Bausch + Lomb) is done. At this stage, a piece of Ahmed valve's tube from the previous AGV surgery is sterilized in plasma after washing with balanced salt solution (BSS). Then, (for two patients) the tube is incised with a stab blade 15° into two halves and about 4 mm of its length is cut [Figure 1].
After that, two parallel incisions (2 mm) are made in scleral bed with a distance of 1.5 mm from each other that yields a band-shaped scleral flap. For prophylaxis of the choroidal damage, after the first incision, gel is injected into the suprachoroidal space. The tube is placed in the suprachoroidal space underneath the band-shaped scleral flap [Figure 2]a and [Figure 2]b. Moreover, in two patients, a section of the tube measuring about 10 mm is first incised into two halves, and then, 5 mm of one side of the tube is again cut into two one-fourth segments using Vannas scissors. Then, as shown in the picture, it is placed under the scleral flap, and each of the one-fourth segments is advanced 1–2 mm into the Schlemm's canal, so that M shape may be produced [Figure 2]c and [Figure 2]d. After securing the implant, superficial scleral flap is sutured with 10.0 nylon over the implant, and then, conjunctiva is sutured.
|Figure 2: U-shaped tube in the suprachoroidal space (a) and its schematic illustration (b) The arrows show aqueous flow to suprachoroidal space. M-shaped tube in the suprachoroidal space under scleral flap and one-fourth segments advanced into the Schlemm's canal (c) and its schematic illustration (d)|
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Four patients with advanced primary open-angle glaucoma with cup-to-disc ratio ≥0.8 who were not controlled with full antiglaucoma medication (preoperative intraocular pressure at the range of 22–30 mmHg with four drops) underwent viscocanalostomy surgery with implant by this technique. With 9-month follow-up, the intraocular pressures were significantly reduced and maintained within the normal limit (9–13 mmHg) without antiglaucoma medication in all cases. There was no visual loss because of the procedure. The TDM rupture did not occur in any patients.
| Discussion|| |
A lot of materials with diverse designs have been used as implants in NPGS. In general, they are classified into absorbable and nonabsorbable groups. The first implant introduced in NPGS was AquaFlow (collagen implant) which is absorbable and expands when exposed to aqueous and is finally absorbed after 6–9 months. A randomized clinical trial by Shaarawy and associated showed that complete success rate in patients with DS and collagen implant was twice the patients without collagen implant. Another implant from the absorbable category is the reticulated hyaluronic implant. T-flux and Esnoper are two examples of nonabsorbable implants. T-flux was introduced by Gonzalo which is fixed beneath the scleral flap without sutures. Mansouri et al. used the PMMA implant which is rigid and nonabsorbable. Autologous scleral implant has also been introduced, which involves suturing of 4 mm × 1 mm segments of the deep scleral flap excised from the patient.
In this study, the remaining of Ahmad valve's tube was used as an implant in four eyes of four patients. During the 9-month follow-up, the intraocular pressure of the four patients was at the range of 9–13 mmHg without the use of medications. The potential complications of NPGS consist of intraoperative suprachoroidal hemorrhage, displacement of implant, uncontrolled IOP, corneal hematoma, TDM rupture, and persistent hyphema. In our series, no intraoperative or postoperative complications occurred. The incision of the tube creates a U-shape which probably improves the flow of aqueous into the suprachoroidal space. Furthermore, placing the one-fourth segment of the tube in the Schlemm's canal in an M-shape fashion hinders the collapse of part of it and promotes the performance of intrascleral bleb.
One concern of intrascleral implants is migration or displacement of the implant. In our introduced technique, two mechanisms make migration of the implant unlikely. First, the external diameter of the tube of Ahmed shunt is 635 μ, and the average diameter of Schlemm's canal is 121 μ. By creating one-fourth segment with an outer diameter of 158 μ and entering 1.5 mm tube segment into Schlemm's canal, it will be stable without movement. Second, the suturing of the superficial scleral flap over the implant will cover the implant and prevents its migration. The second concern of this technique may be the reuse of AGV tube, so we can use tube extender.
Despite the external bleb in trabeculectomy procedure, the features of the intrascleral bleb in DS cannot be evaluated precisely by slit lamp examinations. The anatomic characteristics of bleb in DS such as bleb height and position of the implant have been studied by the AS-OCT.,
To study the features of the intrascleral bleb, we used AS-OCT (TOMEY SS-1000 CASIA OCT) to evaluate the intrascleral blebs. Two patients undergoing viscocanalostomy with and without implant 6 months after the surgery were evaluated of similar views at 2 mm distance from the posterior of limbus [Figure 3]. At the maximal size on the vertical view, the bleb area was obviously greater using an implant.
|Figure 3: Anterior segment optical coherence tomography of the intrascleral bleb. Vertical section in patients with (a) and without implant (b)|
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In summary, the technique for implant we introduced, offers significant advantages over the previously reported implants. The material is biocompatible, low cost, and easily accessible in all centers performing glaucoma surgeries. It efficiently promotes the aqueous flow not only by preventing the collapse of the intrascleral bleb but also aids improvement of the aqueous flow into the suprachoroidal space. In addition, when fashioned as M shaped, it prevents the collapse of part of the Schlemm's canal. This is a preliminary report of fashioning a new implant by the unused rest of an Ahmad valve's tube, and a randomized clinical study is going on to compare the long-term efficacy of this kind of implant.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]