Time course of induced astigmatism after canaloplasty

To study the changes in astigmatism after canaloplasty and to analyze its correlation with long-term intraocular pressure (IOP) results.

Twenty-six eyes of 26 consecutive patients with primary open-angle glaucoma (n=14) and pseudoexfoliative glaucoma (n=12) undergoing canaloplasty were included in this retrospective study. Canaloplasty comprised of 360-degree catheterisation of Schlemm canal by means of a flexible microcatheter with distension of the canal by 2 tensioning 10-0 polypropylene sutures. Primary outcome measures included IOP, glaucoma medication usage, astigmatism, and adverse events at 2, 4, 12, and 24 weeks postoperatively.

The mean preoperative IOP was 21.1±5.8 mm Hg. The mean IOP decreased to 14.25 ±4.3 mm Hg at 6 months. Mean astigmatism preoperatively was 0.77±0.5 D, which increased to 3.3±1.7 D at 2 weeks postoperatively (P≤0.05; Wilcoxon-test). Thereafter, the astigmatism underwent a spontaneous decline, reaching 1.9±0.8 D at 4 weeks and 1.2±0.74 D at 12 weeks postoperatively. Best-corrected visual acuity did not change significantly. Six months after canaloplasty, mean astigmatism reached the preoperative range of 0.86±0.52 D. Astigmatism at 2 weeks correlated significantly and inversely with IOP at 6 months (r=0.59, P=0.005; Spearman).

The change of astigmatism after canaloplasty follows a clear time course with a maximum at 2 weeks reaching preoperative values at 6 months. The amount of surgically induced astigmatism might be helpful to predict outcome of canaloplasty in terms of IOP reduction.