Internal canaloplasty using the OMNI system versus external canaloplasty: A randomized, prospective comparative study

Purpose. Viscocanaloplasty is a non-filtering and tissue-­sparing procedure in glaucoma surgery. It works by probing and dilating Schlemm’s canal and thus the trabecular meshwork and the scleral collector vessels. Externally, Schlemm’s canal is prepared through the conjunctiva and sclera, while the ab-interno method is performed from the anterior chamber using the Visco 360/OMNI system. The aim of this study is to compare the efficacy and safety of both procedures.

Material and Methods. In a prospective clinical study, 53 eyes of 41 patients (n=53 eyes) underwent internal canaloplasty using the OMNI system. The results were compared with 50 eyes of 42 patients (n=50 eyes) who underwent external canaloplasty.

Patients with moderate open-angle glaucoma and insufficient efficacy or intolerance to pressure-lowering eye drops were included. The groups were assigned using simple randomization. The follow-up period of the study to date is 12 months.

Intraocular pressure (IOP; applanation) and the number of pressure-lowering eye drops were recorded and measured preoperatively and at 1, 3, 6, and 12 months postoperatively.

The primary endpoint was the reduction in intraocular pressure (IOP) at least 6 months after surgery. Secondary endpoints were the reduction in the number of glaucoma medications and the development of glaucoma diagnostics (Goldmann perimetry, retinal nerve fiber layer, or RNFL).

Results. A total of 13 canaloplasties ab interno were performed using the OMNI system and 40 canaloplasties ab interno were performed using the OMNI system in combination with cataract surgery. The average IOP 12 months after surgery was 14.24 (± 2.63) mmHg. This represented a statistically significant reduction compared to the baseline IOP of 18.80 (±4.25) mmHg.

In the comparison group, 28 external canaloplasties and 22 external canaloplasties combined with cataract surgery were performed. Twelve months postoperatively, the average IOP was 15.32 (± 3.86) mmHg, which was also a statistically significant reduction compared to the baseline IOP of 19.82 (±4.47) mmHg. The number of antiglaucoma medications administered 12 months after the procedure was 0.71 (SD 0.97) for the ab interno procedure and 0.46 (SD 0.78) for the ab externo procedure.

During the follow-up period, four follow-up operations were performed after ab interno canaloplasty: one anterior chamber irrigation for hyphema with tensiodepression and three follow-up pressure-reducing surgeries in three different patients with elevated IOP (trabeculectomy in two cases and Preserflo in one case).

Conclusion. Both the Visco 360/OMNI system and the ab externo procedure are efficient and safe methods of microsurgical minimally invasive glaucoma surgery and achieve significant results in reducing intraocular pressure and the number of antiglaucoma medications in moderate open-­angle glaucoma.