A New Expander for Schlemm Canal Surgery in Primary Open-angle Glaucoma—Interim Clinical Results

Purpose: To evaluate a new canal expander in circumferential viscocanalostomy (canaloplasty) for whites with primary open-angle glaucoma (POAG). Design: Prospective, single-center, noncomparative study. Participants: Twenty-two eyes of 22 consecutive patients with medically uncontrolled POAG underwent primary viscocanalostomy and implantation of the Stegmann Canal Expander into Schlemm canal with a follow-up time of at least 1 year. Materials and Methods: Schlemm canal was unroofed ab externo, and dilated with viscoelastic material and microcatheter. The Stegmann Canal Expander is a flexible, fenestrated hollow implant of 9 mm in length. One expander was implanted into either side of the surgically created of ostium to keep the Schlemm canal permanently open. The superficial scleral flap was closed watertight. Laser goniopuncture of the trabeculo-Descemet membrane window was performed if postoperative intraocular pressure (IOP) exceeded 16 mm Hg. Main Outcome Measures: Complete successes were defined as a confirmed IOP≤21, ≤18, and ≤16 mm Hg without medications, respectively, combined with a 30% IOP reduction. Number of antiglaucomatous medications, best-corrected visual acuity, and intraoperative and postoperative complications were recorded. Results: The mean IOP dropped from 27.1±5.3 mm Hg preoperatively to 13.6±1.6 mm Hg at 6 months, 13.0±1.5 mm Hg at 9 months, and 13.1±2.2 mm Hg at 12 months (P<0.001). The complete success rates for an IOP≤21, ≤18, and ≤16 mm Hg combined with a 30% IOP reduction were 91% [95% confidence interval (CI), 0.80-1.0], 91% (95% CI, 0.80-1.0), and 91.0% (95% CI, 0.80-1.0) at 6 months, and 86% (95% CI, 0.73-1.0), 82% (95% CI, 0.67-1.0), and 82.0% (95% CI, 0.67-1.0) at 12 months. The success rate of an IOP≤16 mm Hg without medications did not depend on age [hazard ratios (HR) 1.02; 95% CI, 0.85-1.12; P=0.74], preoperative IOP (HR 0.97; 95% CI, 0.83-1.23; P=0.89), and mean visual defect (HR 1.05; 95% CI, 0.72-1.27; P=0.76). Laser goniopuncture was performed on 2 eyes (9%) 4.1 months postoperatively; the mean IOP was 19.5 mm Hg before and 13.6 mm Hg after goniopuncture. The number of medications dropped from 2.9±0.6 before surgery to 0.05±0.2 after surgery (P<0.001). The postoperative best-corrected visual acuity at last visit (0.12±0.09; range, 0 to 0.39) was comparable to preoperative values (mean±SD, 0.16±0.10; range, 0 to 0.39) (P=0.35). Minor intraoperative or postoperative complications included microhyphema (8 eyes) and transient elevated IOP (steroid responder; 2 eyes). Conclusions: Implantation of the Stegmann Canal Expander in canaloplasty lowered IOP significantly in POAG without complications related to the device in this 1-year observation period.