Quantitative gonioscopic assessment of anterior chamber angle remodeling using the spaeth classification after Schlemm's canal-based MIGS (3T) in POAG: a one-year retrospective study.

BACKGROUND: Trabeculotome Tunneling Trabeculoplasty (3T) is a recently developed Schlemm's canal-based minimally invasive glaucoma surgery (MIGS) designed to reconstruct the trabecular meshwork-Schlemm's canal pathway to facilitate aqueous humor outflow, while minimizing disruption to ocular surface structures. Although this procedure is gaining clinical use in China, evidence regarding its long-term efficacy, safety, and anatomical impact remains limited. Few studies have systematically assessed postoperative changes in the anterior chamber angle, which plays a key role in intraocular pressure (IOP) control. This study aimed to evaluate the 1-year outcomes of 3T surgery in patients with primary open-angle glaucoma (POAG), including its effectiveness, safety profile, and angle remodeling assessed via gonioscopic imaging.

METHODS: This retrospective study included 25 patients (31 eyes) with primary open-angle glaucoma (POAG) who underwent Trabeculotome Tunneling Trabeculoplasty (3T) at Chengdu Integrated TCM and Western Medicine Hospital, also known as Chengdu First People's Hospital between December 2022 and October 2023. All patients were followed for 12 months. Clinical data including preoperative and postoperative intraocular pressure (IOP), number of anti-glaucoma medications, intra- and postoperative complications, and gonioscopic findings were collected and analyzed to evaluate the 1-year outcomes of the 3T procedure in terms of efficacy, safety, and anterior chamber angle remodeling.

RESULTS: Among the 25 patients (31 eyes) included in this study. Mean baseline IOP decreased from 24.8 ± 5.7 mmHg preoperatively to 16.8 ± 3.7 mmHg at 12 months (p < 0.001), with medications reduced from 2.6 ± 1.2 to 0.4 ± 0.9 (p < 0.001). The overall success rate was 93.6% (29/31 eyes), including 74.2% complete success and 19.4% qualified success. Complications included transient IOP spikes (51.6%, 16/31 eyes) and hyphema (6.5%, 2/31 eyes). No choroidal detachment, shallow anterior chamber, or other vision-threatening complications were observed. Gonioscopy showed stable iris root insertion and angle width postoperatively (p > 0.05). Pigment deposition and PAS increased in inferior/nasal quadrants postoperatively but stabilized by 3 months (p < 0.05). Trabeculotomy incisions narrowed due to PAS formation but stabilized without compromising IOP reduction. Schlemm's canal tension stitches remained intact at 12 months.

CONCLUSIONS: 3T surgery significantly reduced IOP and medication dependence in POAG over 12 months, with transient IOP spikes as the primary complication. Postoperative anterior angle anatomy remained stable, and PAS-related changes in trabeculotomy sites stabilized within 3 months without affecting efficacy. These findings support 3T as a promising minimally invasive approach for POAG, though further validation is needed.