XEN45 Gel Stent Implantation in Glaucoma Surgery

Introduction

Glaucoma is a group of eye diseases that results in damage to the optic nerve and permanent visual loss; more than 60 million people around the world are affected by glaucoma. Increased intraocular pressure (IOP) is the most important risk factor for the development of optic nerve damage and changes in the visual field. Therefore, the most effective treatment modality is the reduction of IOP, in order to prevent glaucoma progression and optic nerve atrophy. Trabeculectomy and episcleral aqueous drainage implants are currently the most widely used surgical methods for reducing IOP and treating glaucoma. Unfortunately, these procedures have potentially destructive intraoperative and postoperative complications, such as hypotony, choroidal effusion, blebitis, and endophthalmitis. Therefore, there is a trend of developing new surgical procedures to avoid the complications arising from conventional surgical procedures. These new surgical methods, called "minimally invasive glaucoma surgery" (MIGS), have some advantages over the conventional glaucoma surgical procedures, such as ab interno applicability, the elimination of external intervention requirements, and the ease of performance alongside cataract surgery. These advantages allow MIGS methods to be safer and less invasive than other surgical methods.

The XEN gel stent (Allergan, Dublin, Ireland) is a recently developed, permanent, ab interno collagen implant that reduces IOP by draining aqueous fluid from the anterior chamber into the subconjunctival space. The stent is a hydrophilic tube that is 6 mm long and composed of porcine gelatin crosslinked with glutaraldehyde. There are three sizes of this stent: 45 μm, 63 μm, and 140 μm, all with different inner diameters. The XEN45 gel stent is CE-marked in the European Union, and it is indicated for the treatment of refractory glaucoma that has proven resistant to previous surgical treatment and for patients with primary open angle glaucoma (POAG), pseudoexfoliative glaucoma, or pigmentary glaucoma that cannot be controlled with the maximum tolerated medical therapy. It is also licensed for use in Canada, Switzerland, and Turkey. The XEN45 gel stent was recently approved by the U.S. Food and Drug Administration (FDA). Because it is a new device, there are still unknown aspects of its efficacy and safety and of the proper surgical technique for its use. This study aimed to report the follow-up data after XEN45 gel stent implantation surgery in patients with different types of glaucoma.

Methods

This was a retrospective, consecutive case series study. Patients who had an XEN45 gel stent implantation surgery between January 2015 and March 2016 were enrolled in the study. Patients were included whose refractory glaucoma was resistant to previous surgical treatment. Patients were also included who had POAG, pseudoexfoliative glaucoma, or pigmentary glaucoma, with uncontrolled IOP and progressive visual field damage despite using the maximum tolerated dose of topical antiglaucomatous medications. Patients who had previous glaucoma surgery were included as well. The exclusion criteria included primary closed-angle glaucoma, a history of uveitis, and the presence of corneal disease. Patients who did not attend follow-up visits were also excluded. All patients were informed about the treatment and the potential complications. Informed patient consents were obtained preoperatively. The procedures of the study were approved by the institutional review board of the hospital and adhered to the tenets of the Declaration of Helsinki. The study protocol was approved by the local ethics committee (approval code: TUTF-BAEK 2016/213).