Surgical Outcomes of Gonioscopy-Assisted Transluminal Trabeculotomy (GATT) in Primary and Secondary Open- and Closed-Angle Glaucoma

Background: Gonioscopy-assisted transluminal trabeculotomy (GATT) is a minimally invasive, ab interno conjunctival-sparing glaucoma surgery aimed at the trabecular meshwork and the inner wall of Schlemm’s canal. The goal of this study is to report on the success of GATT in a large group of patients with a wide variety of open- and closed-angle glaucomas with or without cataract extraction and to report on risk factors for failure. Methods: A retrospective chart review of consecutive patients with primary or secondary open- or closed-angle glaucoma who underwent GATT, with or without concomitant phacoemulsification. Demographics, baseline clinical characteristics, and postoperative outcomes were collected from patients’ medical records. Primary outcomes were success rates (IOP of 18 mmHg or lower and one of the following: IOP reduction > 30% from baseline on the same or fewer medications or an IOP ≤ baseline with fewer medications as compared to baseline) and complication rates. Intraocular pressure (IOP) and the number of glaucoma medications were secondary outcome measures. Results: GATT was performed on 126 eyes of 121 patients. Mean follow-up was 583 ± 266 days. Cumulative success at 1Y was 0.88 for GATT combined with cataract extraction, 0.96 for GATT alone, 0.88 for primary open-angle glaucoma (POAG), 0.89 for secondary open-angle glaucoma (SOAG), and 0.76 for primary angle-closure glaucoma (PACG). IOP decreased from a mean of 20.65 mmHg to 14.1 mmHg, and medication decreased from a mean of 3.47 to 1.4 at the last follow-up. Forty-four eyes (34%) were classified as failures. Factors associated with an increased risk of failure were worse preoperative corrected visual acuity (OR = 2.46, p = 0.024) and a postoperative IOP spike (OR = 2.62, p = 0.028). Twelve eyes (9.5%) required further surgery for IOP control. Risk factors for requiring further surgery for IOP control were preoperative maximal IOP (OR = 1.066, p = 0.047) and a postoperative IOP spike (OR = 4.531, p = 0.036). Conclusions: GATT achieved good surgical success with good IOP and medication reduction across a wide range of glaucomas, in combination with lens extraction or as a standalone procedure. GATT should be considered early in the treatment paradigm of medically uncontrolled glaucoma.