Ab externo canaloplasty results and efficacy: a retrospective cohort study with a 12-month follow-up

BACKGROUND: The aim of this study is to review the outcomes of canaloplasty versus canaloplasty combined with phacoemulsification in a retrospective cohort study and to evaluate the efficacy of these methods in terms of intraocular pressure (IOP) lowering effect, postoperative complications and additional glaucoma surgery or reintroduction of medical therapy over a 12-month follow-up. METHODS: In a retrospective cohort study, 602 eyes with primary open angle glaucoma (POAG) were treated with canaloplasty or canaloplasty combined with phacoemulsification. The results were evaluated separately in two main groups; group A canaloplasty (262 eyes) and group B canaloplasty combined with phaco (322 eyes). Each group was then subdivided into three additional groups according to the severity of glaucoma. The criteria for successful treatment were evaluated between three IOP ranges; IOP ≤ 16 mmHg, 18 mmHg and 21 mmHg. Complete success was considered the percentage of eyes reaching target IOP with no medication and partial success with medication. Groups A and B subgroups were compared using the Kaplan Meier test. Mean IOP, reduction of antiglaucoma agents and additional IOP lowering methods were also evaluated. The follow-up time was 12 months. Statistical significance was set at p < 0.05. RESULTS: An incomplete intraoperative cannulation of Schlemm’s canal resulting in conversion to other glaucoma surgery occurred in 18 eyes (2.99%). In both of the main groups, postoperative hyphema, descemet membrane detachment and transient IOP rise were the most common postoperative complications. The mean IOP in group A and subgroups at 12 months was 13.26 ± 4.5 mmHg, 15.19 ± 3.97 mmHg and 18.09 ± 3.75 mmHg. Respectively in group B mean IOP was 14.51 ± 4.69 mmHg, 14.40 ± 4.11 mmHg and 14.25 ± 2.76 mmHg. Complete success was achieved in group A in 69.19, 74.51 and 74.31% of eyes. In group B complete success was achieved in 81.60, 77.33 and 83.33% of eyes respectively. Kaplan Meier between groups A and B was statistically significant for IOP ≤ 16 mmHg and IOP ≤ 21 mmHg (p = 0.0041 and p = 0.0312), but not for IOP ≤ 18 mmHg (p = 0.6935). Partial success for IOP ≤ 16 mmHg was 95.23 and 92.26%, for IOP ≤ 18 mmHg was 91.66 and 90.47% and for IOP ≤ 21 mmHg, 90.00 and 93.10%, in groups A and B respectively. Twenty-three eyes received additional surgery (3.93%), 10 trabeculectomies and 2 cyclophotocoagulation in group A, and 9 trabeculectomies and 2 cyclophotocoagulation in group B. CONCLUSION: Canaloplasty and canaloplasty combined with phacoemulsification significantly lower the IOP and have a lower postoperative complication rate. Additional glaucoma surgery or medication following both procedures is necessary if target IOP is unsatisfactory. In this study, canaloplasty combined with phacoemulsification demonstrated superior success rate compared to canaloplasty alone.