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 degrees of open angles with uncontrolled IOP despite maximal medical therapy, noncompliant to medical therapy or failed incisional glaucoma surgery underwent GATT. 5-0 or 6-0 Prolene (R) suture was used to cannulate Schlemm's canal. An 8-0 Vicryl (R) suture was tied around the trailing portion of the Prolene (R) 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 +/- 8.8mm 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 +/- 3.3mm Hg, and at 1 year was 13.5 +/- 2.6mm Hg. Mean degrees of cannulation achieved was 264.5 +/- 84.0 degrees (90360 degrees). 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 (R) suture.