An Innovation in Glaucoma Surgery: XEN45 Gel Stent Implantation
Condition: Glaucoma Eye
MeSH terms: Glaucoma
Study type: Observational

Summary: 
      Purpose: To report the follow-up data for patients who had XEN45 gel stent implantation, a
      new method of minimally invasive glaucoma surgery (MIGS).

      Material and Methods: Fifteen eyes of fifteen patients who had XEN45 gel stent implantation
      surgery were investigated in the study. All the patients were examined preoperatively and at
      the following postoperative time points: 1 day; 1 and 2 weeks; and 1, 2, 3, 6, and 12 months.
      Intraocular pressure (IOP) was measured by Goldmann applanation tonometry. Combined surgical
      procedures (XEN 45 + phacoemulsification + intraocular lens) were performed in the cases that
      had cataracts in addition to glaucoma.
    

Detailed description: 
      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).

      Before the XEN45 implantation, slit-lamp biomicroscopy and gonioscopic examination were
      performed. Intraocular pressure was measured by Goldmann applanation tonometry (AT 900, Haag
      Strait, Bern, Germany). A detailed fundus examination was done using a 78-dioptre non-contact
      lens after pupil dilatation by 1% tropicamide gutt.

      All of the surgical procedures were performed under sterile conditions by the same surgeon
      (OK). Irrigation of the eyelashes, eyelids, and periorbicular tissues was performed with
      antiseptic 10% povidone iodine. While using an eye speculum, 5% povidone iodine was flushed
      onto the conjunctiva and fornix for two minutes; conjunctival irrigation was then completed
      with saline. The surgery was performed under peribulbar anaesthesia with 5 mL prilocaine and
      5 mL bupivacaine. After peribulbar anaesthesia, the superonasal quadrant of the conjunctiva
      was marked by blue surgical dye 3 mm posterior to the limbus. Clear corneal incisions (main
      and side-port) were created in the inferotemporal and superotemporal quadrants; a highly
      cohesive viscoelastic was used to stabilise the anterior chamber during surgery. A 27-gauge
      pre-loaded injector was placed into the eye through the main clear corneal incision at the
      inferotemporal quadrant. The needle was directed toward the superonasal quadrant (Figure 3).
      One hand was used to manipulate the injector, and the other hand was used to fix and rotate
      the eye. The needle was pushed into the sclera and carried forward into the subconjunctival
      space. The surgery was performed under gonioscopic control. A 6-mm-long implant was created
      to be positioned 2 mm into the subconjunctival space, 3 mm into the sclera, and 1 mm into the
      anterior chamber. Therefore, visualization of the tip of the needle exiting from the sclera
      indicated that an optimal 3-mm intrascleral tunnel had been formed. The XEN45 implant was
      deployed by rotating a dial on the inserter. Once bleb formation was seen, the needle was
      withdrawn. The viscoelastic material was aspirated, and then 0.1 ml of 1% cefuroxime was
      injected into the anterior chamber. Finally, the clear corneal incisions were hydrated with a
      balanced salt solution. Mitomycin C was not injected into the conjunctiva at any stage of the
      surgery. Topical steroid and antibiotic treatments were applied after the surgery. A topical
      steroid (prednisolone acetate 1%) was applied six or more times daily to control
      postoperative intraocular inflammation. The topical steroid treatment was stopped after the
      first month postoperative. Ocular massage for one minute four times daily was recommended
      during the postoperative period. Needling was not performed at any of the postoperative
      visits. Topical antiglaucomatous medications were added as needed according to the
      postoperative IOP levels. Follow-up visits were planned for 1 day, 1 and 2 weeks, and 1, 2,
      3, 6, and 12 months.

      Combined surgery (XEN45 + phacoemulsification + intraocular lens) was performed in the cases
      that had cataracts in addition to glaucoma. In combined surgery, the XEN45 implantation was
      performed after the phacoemulsification. After the intraocular lens implantation in the
      capsular sac, the anterior chamber was filled with a highly cohesive viscoelastic material.
      Then, the same procedures as were described previously were carried out.

      All the data were compiled into a computer file for statistical analysis, and Statistical
      Package for Social Sciences for Windows 17.0 was used to perform the Wilcoxon signed ranks
      test. A p value less than 0.05 was considered statistically significant.
    

Intervention name(s): XEN45 gel stent implantation in glaucoma surgery
Intervention type(s): Device
Intervention description(s): 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
Observational model: Case-Only
Time perspective: Retrospective
Sampling method: Probability Sample
Study population: 
        Fifteen patients who had an XEN45 gel stent implantation surgery between January 2015 and
        March 2016 were enrolled in the study.
      
Keywords: glaucoma; trabeculectomy; minimally invasive glaucoma surgery; XEN45 gel stent