Purpose <p>To investigate the clinical results of Gonioscopy-Assisted Transluminal Trabeculotomy (GATT) performed with 5–0 or 6–0 polypropylene sutures and whether it makes a difference in anterior chamber (AC) morphology.</p> Methods <p>The file records of patients with primary open-angle glaucoma or pseudoexfoliation glaucoma who underwent GATT with 5–0 or 6–0 polypropylene sutures were reviewed. Patients were divided into two groups (GATT with 5–0 polypropylene suture: Group 1 vs. GATT with 6–0 polypropylene suture: Group 2). The clinical results of GATT, intraocular pressure (IOP) values, and parameters measured with Pentacam HR Scheimpflug camera system including anterior chamber angle (ACA), anterior chamber depth (ACD), anterior chamber volume (ACV), central corneal thickness (CCT), and pupil diameter (PD) of two groups at preoperative period, postoperative 1st, 3rd, and 6th months were compared.</p> Results <p>A total of 41 patients were included in the study (Group 1: n = 21, Group 2: n = 20). Approximately 60% reduction in IOP was detected in both groups and the rate of IOP reduction at each visit was similar between the two groups (<i>p</i> &gt; 0.05 in all). It was determined that there were no differences in AC parameters including ACA, ACD, ACV, CCT, and PD at any visit in either group. (<i>p</i> &gt; 0.05 in all). Also, there was no significant difference in the complication rates between the two groups.</p> Conclusion <p>It was observed that there were no significant differences in terms of success rate, complication rate, and the effect on AC morphology between performing GATT with 5–0 or 6–0 polypropylene sutures.</p>