Prolene Canalostenting in Deep Sclerectomy: A Pilot Study.

PURPOSE: To study the effect of implantation of a 5/0 prolene suture segment inside Schlemm's canal as an adjunct to deep sclerectomy.
MATERIALS AND METHODS: This was a prospective, interventional case series of nine eyes of six patients with open angle glaucoma. Patients underwent deep sclerectomy with insertion of a segment of 5/0 prolene into Schlemm's canal at the filtration site without suturing. The main outcome measures were: Intraocular pressure (IOP), postoperative interventions, and complications. Ultrasound biomicroscopy of the filtration area as well as the prolene suture was performed at 6 months postoperatively.
RESULTS: Patients were followed for a mean of 8.1 ± 4.5 months. Mean IOP decreased statistically significant from 19 ± 4.2 mmHg preoperatively to 12 mmHg at 15 months postoperatively (P < 0.0001). The number of glaucoma medications was reduced from 3.7 ± 0.7 preoperatively to 0 postoperatively. No postoperative complications were noted. IOP remained in the low teens in all patients out to the last postoperative visit. Yttrium-aluminum-garnet laser goniopuncture was not required in any case.
CONCLUSION: Implantation of a 5/0 prolene suture in Schlemm's canal during deep sclerectomy was a safe, cost-effective adjunct to maintain the patency of the intrascleral space and Schlemm's canal thus controlling IOP for 6 months postoperatively.

INTRODUCTION

The penetrating nature of trabeculectomy makes it prone to several complications, many of which are vision-threatening.1 Deep sclerectomy was introduced by Fyodorov in 1989 as a nonpenetrating alternative to trabeculectomy.2 The advantage of deep sclerectomy is the progressive filtration of aqueous humor through the thin trabeculo-Descemet's membrane (TDM) thus avoiding the sudden hypotony encountered with trabeculectomy. In deep sclerectomy, an intrascleral filtering space is created and aqueous drains from the anterior chamber through the TDM into newly created transcleral aqueous humor veins ending in the episcleral drainage system.3

Several modifications have been introduced to improve the outcome of deep sclerectomy, including the insertion of a space maintainer to preserve the patency of the intrascleral bed. Examples of these maintainers have included viscoelastics, polymethylmethacrylate,4 hydroxymethyl methacrylate and high reticulated hyaluronic implant.5 Other modifications include the introduction of viscocanalostomy by Stegman in 1999 and later, canaloplasty.6 Although the results of canaloplasty have been promising, the added cost of the microcatheter is a disadvantage in some settings.

In this study, we present the 6-month outcomes following a cost-effective technique to maintain the patency of the intrascleral bed and Schlemm's canal in deep sclerectomy using 5/0 prolene.

MATERIALS AND METHODS

This study adhered to the tenets of the declaration of Helsinki. A written informed consent was obtained from all patients.

In this prospective clinical study, we included eyes with uncontrolled open-angle glaucoma, despite maximal tolerated medical therapy. We excluded patients who had a contraindication for deep sclerectomy (e.g., angle closure glaucoma and uveitic glaucoma) and eyes with previous ocular surgery other than cataract surgery. The medical history was recorded, and all patients underwent a comprehensive ophthalmic examination.

A superior corneal traction suture was taken using a 7/0 or 8/0 polyglactin (Vicryl, Ethicon, Somerville, NJ, USA) on a spatulated needle, and the eye was rotated inferiorly. A fornix-based conjunctival flap was created, and blunt dissection was extended toward the superior conjunctival fornix. A superficial triangular half thickness scleral flap was fashioned with its base measuring 4 mm and its apex located 4 mm from the limbus. The dissection was completed using a crescent blade into clear cornea. Cellulose sponges soaked in mitomycin-C (MMC) were applied under the scleral flap, as well as under the dissected area of conjunctiva superiorly. A sponge soaked with MMC (0.4 mg/ml) was applied for duration of 2 min, and then the area irrigated copiously with balanced saline solution. A temporal paracentesis was then performed followed by dissection of a deep scleral flap, 0.5 mm within the edge of the superficial flap. Dissection was carried forward, deroofing Schlemm's canal. Dissection then proceeded between the corneal stroma and Descemet's membrane, creating a corneal “window.” At this point, seeping of the aqueous humor through peripheral Descemet's membrane was usually observed. A 10 mm long segment of polypropylene 5/0 (Ethicon, Somerville, NJ, USA) was then introduced inside Schlemm's canal through one of its ends, then threaded into the other end [Figure 1]. Hence, the suture was centered on the exposed TDM. The deep flap was excised with microscissors, and the superficial flap sutured a single 10/0 nylon suture at its apex. Healon GV was injected under the flap. The conjunctival layer was sutured using two separate 10/0 nylon sutures. Subsequently, a subconjunctival injection of vancomycin and dexamethasone was delivered.

Figure 1

(a) Insertion of one side of prolene suture into Schlemm's canal. (b) Insertion of the other side of the prolene suture

Statistical analysis

Data were statistically described in terms of mean ± standard deviation and range when appropriate. All statistical calculations were done using Statistical Package for the Social Science (SPSS) (SPSS Inc., Chicago, IL, USA) version 15 for Microsoft Windows. A P < 0.05 was considered as statistically significant.

RESULTS

This study included nine eyes of 6 patients aged 39.7 ± 20.4 years (range, 20 years to 72 years). The mean follow-up was 8.1 ± 4.5 months. There was a statistically significant reduction of intraocular pressure (IOP), from a mean of 19 mmHg preoperatively to 12 mmHg at 15 months postoperatively (P < 0.0001) [Figure 2]. None of the patients required medical therapy or yttrium-aluminum-garnet (YAG) laser goniopuncture to control IOP out to last postoperative follow-up.

Figure 2

Reduction of intraocular pressure during the postoperative period

DISCUSSION

In this pilot study, we describe our experience using 5/0 prolene suture as a Schlemm's canal stent and space maintainer in deep sclerectomy. There was a significant reduction in IOP in all cases with no intraoperative or postoperative complications. None of the eyes required YAG goniopuncture and the IOP consistently remained in the low teens in all cases until the last follow-up (8.1 ± 4.5 months postoperatively). The suture remained stable and could be seen by gonioscopic examination as well as ultrasound biomicroscopy (UBM) examination. UBM also revealed an elevated bleb, indicating the presence of subconjunctival and intrascleral aqueous reservoirs.

Several space-maintainers have been studied for preserving the patency of the intrascleral space in deep sclerectomy such as the reticulated hyaluronic acid implant, SK-GEL,7 and the T-flux implant.8 The biocompatible9 nature of the polypropylene material would allow prolonged maintenance of the patency of the intrascleral space as well as the adjacent Schlemm's canal. Maintaining the patency of Schlemm's canal in the area of the scleral flap by the prolene suture would ensure continuous percolation of aqueous from Schlemm's canal into the intrascleral space, thus maintaining the patency of the latter. Gonioscopic examination demonstrated the suture, seen clearly as a blue line in the anterior chamber angle. This has the added benefit of helping to demarcate the site of the trabeculo-Descemet window in cases requiring YAG goniopuncture following deep sclerectomy.

Our study showed that 5/0 prolene can be used as a safe, cost-effective (<10 US$ per suture) space maintainer in deep sclerectomy, aiding in long-term IOP control. Controlled studies involving a larger number of patients and over a longer follow-up period are warranted to evaluate the outcomes of the current study. Additionally, comparative studies with currently available space maintainers (e.g., SK-GEL and T-Flux implant), and canaloplasty and the technique described in the current study with regards to IOP control and the cost of surgery.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.