Circumferential viscodilation of Schlemm's canal for open-angle glaucoma: ab-interno vs ab-externo canaloplasty with tensioning suture

Purpose: To compare the efficacy of minimally invasive ab-interno canaloplasty (ABiC) vs ab-extemo canaloplasty (CP) in reducing intraocular pressure (IOP) and glaucoma medication dependence. Patients and methods: This nonrandomized, retrospective, single-center, paired eye study assessed the 12-month outcomes of 12 patients with primary open-angle glaucoma who underwent ABiC in one eye and CP in the other eye, either as stand-alone procedures or combined with cataract extraction. Primary endpoints included mean IOP and number of glaucoma medications at 12 months postoperative. Secondary endpoints included surgical complications and secondary interventions. Results: Four males and eight females with a mean age of 73.8 +/- 12.6 years were included. In the CP group, the mean preoperative IOP was 18.1 +/- 3.9 mmHg on 2.4 +/- 0.5 medications, which reduced to 13.5 +/- 2.2 mmHg (P<0.05) on 0.9 +/- 0.9 medications (P<0.001). In the ABiC group, the mean preoperative IOP was 18.5 +/- 3.4 mmHg on 2.4 +/- 0.5 medications and postoperative IOP was 13.8 +/- 2.2 mmHg (P<0.05) on 0.8 +/- 0.8 medications (P<0.05). There was no significant difference in IOP and medication use between treatment groups at 12 months postoperative. No serious adverse events were recorded in either group, though two patients in the CP group developed pressure spikes 10 mmHg beyond preoperative IOP. Conclusion: This paired eye study found ABiC to have comparable IOP lowering and glaucoma medication reduction to CP in open-angle glaucoma. This suggests ABiC may be a suitable method for improving aqueous outflow via the trabecular pathway. Further large-scale investigation is needed.