Comparing two tensioning suture sizes for 360° viscocanalostomy (canaloplasty): a randomised controlled trial

Abstract

To compare the safety and efficacy of two polypropylene (Prolene) sutures for tensioning of the inner wall of Schlemm's canal (SC) in black African patients with primary open-angle glaucoma (POAG) undergoing canaloplasty. In a prospective randomised trial of 90 patients, canaloplasty was performed with a flexible microcatheter (iTrack-250A) and sodium hyaluronidate 1.4% (Healon GV). After complete circumferential dilatation of the SC, a Prolene suture, either 6-0 Prolene (group 1) or 10-0 Prolene (group 2), was retracted through the SC and tightened leaving tension on the canal and trabecular meshwork. Nd:YAG laser goniopuncture was not performed postoperatively. The mean preoperative intraocular pressure (IOP) was 42.7 mm Hg+/-12.5 (SD) in group 1 and 45.0 mm Hg+/-12.1 (SD) in group 2 (P=0.70). The mean postoperative IOP without medications was 18.4 mm Hg+/-7.1 (SD) in group 1 and 16.4 mm Hg+/-6.6 (SD) in group 2 at 1 month (P=0.10), 19.2 mm Hg+/-6.4 (SD) in group 1 and 16.4 mm Hg+/-4.9 (SD) at 15 months (P=0.04). Pressures equal or less than 21, 18, and 16 mm Hg without medications (complete success) at 12 months were 51.0% (95% confidence interval (CI) 0.35-0.73), 34.1% (95% CI 0.21-0.56), and 21.2% (95% CI 0.11-0.42) in group 1, and 76.9% (95% CI 0.62-0.96), 68.8% (95% CI 0.54-0.89), and 53.6% (95% CI 0.38-0.76) in group 2, respectively. In the Cox regression analysis, IOP<18 mm Hg without medications depended significantly on the type of Prolene (hazard ratio (HR) 2.60, 95% CI 1.24-5.46, P=0.01) and age (HR 1.3, 95% CI 1.03-1.86, P=0.03), but not on preoperative IOP (HR 1.01, 95% CI 0.99-1.04, P=0.16) and gender (HR 0.67, 95% CI 0.34-1.33, P=0.26). No filtering bleb was observed. Intra- and postoperative complications were similarly rare in the two groups and included partial 'cheese-wiring' (2), Descemet's rupture (2), and hyphaema (3). In this clinical trial, IOP reduction was substantial in canaloplasty and slightly greater in combination with 10-0 Prolene than 6-0 Prolene sutures at an equally low complication rate. Younger age, but not the level of IOP at surgery, had a positive effect on the amount of IOP reduction, thus suggesting that an early surgical intervention to re-establish physiological outflow offers the best prognosis.