Relationship of degrees of gonioscopy assisted transluminal trabeculotomy and trabecular shelf to success using a marker suture technique

Objective To evaluate the safety and efficacy of gonioscopy-assisted transluminal trabeculotomy (GATT) using a marker suture which could be a viable low cost alternative to an illuminated micro catheter, by helping the surgeon identify obstruction to suture passage, and estimate the degree of Schlemm’s canal cannulated. Subject/Methods Thirty four eyes with 360° of open angles with uncontrolled IOP despite maximal medical therapy, non-compliant to medical therapy or failed incisional glaucoma surgery underwent GATT. 5-0 or 6-0 Prolene® suture was used to cannulate Schlemm’s canal. An 8-0 Vicryl® suture was tied around the trailing portion of the Prolene® suture and acted as a guide to estimate the length of Schlemm’s canal negotiated. The degree of trabecular shelf seen was noted postoperatively. Results Mean baseline IOP was 24.7 ± 8.8 mm Hg (range 13–54 mmHg). Six patients had appositional angle closure and the rest had open angles. Patients were followed up for a period of 45.0 ± 14.6weeks (range 6 weeks-2 years). The mean IOP 6 weeks after surgery was 13 ± 3.3 mm Hg, and at 1 year was 13.5 ± 2.6 mm Hg. Mean degrees of cannulation achieved was 264.5 ± 84.0˚ (90-360˚). The mean number of medications prior to surgery was 2.1 ± 1.0 and at 6 months review was 0.15 ± 0.3. The absolute success was 92.6% 1 year after surgery. Nine patients lost some of their trabecular shelf in the postoperative period, but this did not seem to affect the short term success rate. Discussion Suture GATT is a safe and effective procedure to lower IOP even in patients with partial cannulation. Adding a marker suture is a useful adjunct to help identify the length of Schlemm’s canal successfully cannulated and monitor progress of the Prolene® suture.