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 search for 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 and complication rates. IOP and the number of glaucoma medications were secondary outcome measures. Results GATT was performed on 127 eyes of 121 patients. Mean follow up was 8.7 ± 4.6 months (Range 3–23 months). Cumulative success at 6 months was 0.85 for GATT combined with cataract extraction, 0.92 for GATT alone, 0.9 for both POAG and SOAG and 0.73 for PACG. IOP decreased from a mean of 20.65 mmHg to 13 mmHg and 13.7 mmHg at 12 and 18 months, respectively. Medication decreased from a mean of 3.47 to 1.47 and 1.44 at 12 and 18 months, respectively. Twenty-five eyes (19.5%) were classified as failures. Pre-operative factors associated with an increased risk of failure requiring further surgery for pressure control were: preoperative maximal IOP (p = 0.001, OR: 1.177), post-operative IOP spike (p = 0.012, OR: 16.25), and prior incisional glaucoma surgery (p = 0.002, OR: 0.016). Conclusion 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.