Eyeworld

EW GLAUCOMA 34 January 2019 nasal quadrant for implantation, creating a connection between the anterior chamber and the subcon- junctival space via a scleral tunnel. XEN insertion does not come into contact with the iris or the corneal endothelium. Outcomes Dr. Elkarmouty presented his 6- and 12-month outcomes. The average IOP 1 year after the surgery was about 10 mm Hg, ranging from 5 mm Hg to 17 mm Hg. Following the IOP development over time showed that at 2 weeks, 25 patients had a mean IOP reduction of 9.4 mm Hg (95% CI 5.6–13.3, P=.0001). At 3 months, seven patients showed mean IOP reductions of 9.3 mm Hg (95% CI 5.8–12.7, P=.0006), and at 6 months, four patients showed mean IOP reductions of 9.8 mm Hg (95% CI0.8–18.7, P=.040). He performed needling in five patients and in one patient who had undergone implantation combined with phaco. He noted a shallow anterior chamber in three patients postoperatively, which resolved on their own within a few days. Two patients underwent second XEN implantations, both of which were successful. No choroidals or macu- lopathy was observed in any of the study patients. Dr. Elkarmouty is aggressive in his postoperative anti-inflammatory regimen. Patients receive triamcin- olone via a sub-Tenon's injection at the end of the procedure and get 0.1% dexamethasone every 2 hours for up to 3 months after the surgery, which he then tapers. He explained that the implementation of bleb needling is not driven by evidence of high IOP but by the healing response. "During the postoperative phase, we have a very low threshold for performing bleb needling," he said. "We do not wait for an IOP spike to occur before performing this procedure. Any signs of an aggressive healing response such as early encapsulation or a fibrot- ic band causing bending of the subconjunctival portion of the XEN implant is considered an indication for bleb needling. This is carried out under topical anesthesia on a slit lamp using a 30-gauge needle and is followed by a subconjunctival injection of dexamethasone," Dr. Elkarmouty said. Complications of using the XEN can include subconjunctival or ante- rior chamber bleeding, XEN expo- sure in the anterior chamber in eyes in which the subconjunctival space is small, and the opposite situation in eyes in which the subconjuncti- val space is too large. Postoperative complications can include hypot- ony (physiological or numerical), scarring and failure, ischemic bleb, or XEN in the iris. Corroboration The FDA XEN investigation demon- strated at 12 months that 75% of patients achieved the target of greater than or equal to 20% IOP re- duction from baseline on the same or fewer medications. The mean IOP decrease was 9 mm Hg, and the mean decrease in medications was 1.6. These eyes all underwent con- junctival dissection which, when Practical continued from page 33 XEN completely outside the AC in the subconjunctival space OCT showing well-positioned XEN Source: Ahmed Elkarmouty, FRCS omitted, could result in improved surgical outcomes. 1 Another multicenter, interna- tional, interventional study that evaluated the XEN versus trabe- culectomy revealed no significant difference in safety or efficacy be- tween the two surgeries and showed 43% of the XEN eyes required needling. 2 "Surgeons should keep in mind that needling may be required and need to be comfortable with this procedure when implanting the XEN microstent," Dr. Elkarmouty said. "Also, be prepared to do your homework in terms of the aftercare for your patients. They require a careful follow-up. Revision may be necessary, however, a second stent implantation is a feasible option if the first stent fails." Surgical tips Dr. Elkarmouty advised surgeons to plan the implant location before making their incision and to make sure the area is marked at 3 mm from the limbus. It is important to ensure that the Tenon's is not adherent to the episclera and to prevent perforation by the needle when entering the subconjunctival space. He also marks an area where there are no conjunctival vessels to minimize risk of hemorrhage, which may obscure the needle entry into the subconjunctival space. He explained that sleeve resis- tance could present a problem when entering the anterior chamber and to exercise caution in phakic eyes to avoid any damage to the lens. He uses pilocarpine drops before surgery in phakic eyes to minimize this risk. When inserting the needle into the angle, he aims high and slightly anteriorly. Since viscoelastic deepens the anterior chamber considerably, it may interfere with the surgeon's judgment of the angle anatomy, particularly if the procedure is not carried out under direct visualiza- tion by a gonioscopy lens. Finally, if injected too posteriorly in the angle, the XEN may enter the iris root or be too close to the iris, which may occlude its tip. He advised surgeons to use traction while advancing the needle through the sclera until the full bev- el can be seen and to remove trac- tion and maintain a slight forward pressure with the injector while de- livering the implant through gentle actuation of the slider. EW References 1. Grover DS, et al. Performance and safety of a new ab interno gelatin stent in refractory glaucoma at 12 months. Am J Ophthalmol. 2017;183:25–36. 2. Schlenker MB, et al. Efficacy, safety, and risk factors for failure of standalone ab interno gelatin microstent implantation versus standalone trabeculectomy. Ophthalmology. 2017;124:1579–1588. Editors' note: Dr. Elkarmouty has no financial interests related to his comments. Contact information Elkarmouty: ahmed.elkarmouty@moorfields.nhs.uk

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