Efficacy of Needling Revision After XEN Gel Stent Implantation: A Prospective Study

Abstract

The XEN gel stent is currently the only minimally invasive glaucoma surgical device that targets the subconjunctival outflow pathway through an ab interno placement. It has demonstrated a significant intraocular pressure (IOP)-lowering potential and a favorable safety profile compared with traditional filtering surgery. However, despite a less invasive approach, the presence of a filtering bleb inevitably implies some risk of complications. The most commonly reported bleb-related complication, with rates as high as 45%, is bleb fibrosis associated with raised IOP. To restore filtration in those failing blebs, needling revision is considered the procedure of choice. In this study, we present the results of mitomycin C-augmented needling after XEN implantation. This was a prospective, interventional study, conducted at a single tertiary glaucoma center. Fifty-one eyes of 51 patients with raised IOP associated with either a fibrotic or shallow bleb or increased vascularity following XEN gel stent implantation at the investigation site between January 2015 and June 2016 were enrolled in this study. Patients with other identified causes of filtration failure (stent malposition, internal ostium obstruction, retained viscoelastic) were excluded. Included patients who underwent mitomycin C-augmented needling revision, and follow-up examinations were conducted at 1 day, 1 week, and 1, 3, 6, 12, 18, and 24 months. The primary outcome was the magnitude of IOP reduction following needling revision at the last follow-up visit. Secondary outcome measures were the number of needling procedures carried out in all patients, the rate of patients requiring further filtering surgery following needling revision, and the rate of intraoperative and postoperative complications associated with needling revisions. The average age was 74.4±9.6 years; 66.7% (n=34) were female individuals. Primary open-angle glaucoma was the most common diagnosis (n=21, 41.2%). A total of 78 needling procedures were performed over the 24-month follow-up. Overall 20 of 51 eyes (39.2%) required >1 needling revision, and 14 eyes (24.5%) eventually required reoperation to maintain IOP within their desired target range. Before XEN implantation, mean preoperative IOP was 22.3±8.2 mm Hg and decreased to 14.1±8.0 mm Hg at day 1 postoperatively (-36.8%). The last measured IOP before the first needling revision was on average 23.6±8.9 mm Hg, which reduced to a mean 12.1±4.2 mm Hg at the first postrevision appointment (-48.7%). At the last follow-up appointment, on average 17.0±7.0 months after the first needling, the mean IOP was 14.3±4.1 mm Hg (-35.9% and -39.4% from preoperative and prerevision baselines, respectively). Complications associated with needling revisions were partial amputation of the XEN implant during needling (n=2, 3.9%), hypotony with choroidal detachment (n=1, 2%), and failure to achieve target IOP requiring subsequent surgery (n=14, 27.5%). No association was found between any of the recorded characteristics and the number of needling revisions performed or their outcomes. The present study shows that needling revision following XEN gel stent implantation is a relatively safe and efficient intervention to restore filtration in failing blebs, with a significant and durable IOP-reduction potential.