Positive correlation of blood reflux in Schlemm’s canal and reduction of intraocular pressure after ab interno 360‐degree viscocanalostomy in primary open‐angle glaucoma

Abstract

AbstractPurposeThe aim was to investigate the association between blood reflux in Schlemm’s canal (SC) and the reduction of intraocular pressure (IOP) after ab interno viscocanalostomy in primary open‐angle glaucoma (POAG).MethodsNon‐comparative study of consecutive patients with early to moderate POAG underwent ab interno viscocanalostomy with a follow‐up time of at least 12 months. Indications for glaucoma surgery were inadequate IOP and /or intolerance to eye drops. Through clear cornea incision, the IOP was lowered below episcleral venous pressure by aspiration of aqueous from the anterior chamber to provoke blood reflux into the SC. After a 1‐min waiting period, a goniolens was placed on the globe, and blood reflux was observed and classified into three filling patterns: no filling, partly filling and complete filling. Then, the anterior chamber was filled with viscoelastic material and ab interno viscocanalostomy was performed with a microcatheter system (Visco360).ResultsIn provocative gonioscopy, 12 eyes had no blood reflux (group 1), 19 had patchy blood reflux (group 2), and 14 had complete blood reflux (group 3). For the different reflux patterns, the preoperative IOP was 17.0 mmHg (SD ± 2.8) mmHg for group 1, 18.4 mmHg (SD ± 2.0) for group 2, and 22.2 mmHg (SD ± 2.8) for group 3. The IOP difference between preoperative and 6 months postoperative was 1.8 mmHg (SD ± 1.2) group 1, 4.9 mmHg (SD ± 0.9) for group 2, and 9.9 mmHg (SD ± 2.5) for group 3 (p < 0.001). In a linear regression model, there were highly significant differences between the groups even after adjustment for preoperative IOP (p < 0.001).ConclusionsBlood reflux in SC seems to be a significant positive prognostic indicator in uneventful ab interno viscocanalostomy concerning IOP reduction, possibly representing the patency of the physiologic aqueous outflow system.