Purpose: To evaluate the outcomes of gonioscopy-assisted transluminal trabeculotomy (GATT) under different levels of glaucoma severity.

Design: Retrospective, multicenter, before-and-after study.

Methods: One eye from all primary open-angle glaucoma patients who underwent GATT combined with cataract surgery (Phaco-GATT) or GATT stand-alone with 12 months of follow-up were included and divided according to glaucoma severity (mild = GI, moderate = GII, and advanced = GIII) and the outcomes compared.

Results: A total of 270 eyes were included: 90 in GI, 75 in GII, and 105 in GIII. The IOP was reduced from 18.6 ± 6.0 mm Hg in GI, 19.7 ± 6.4 mm Hg in GII, and 21.0 ± 7.9 mm Hg in GIII, preoperatively, to 11.9 ± 2.6 mm Hg in GI, 11.8 ± 2.1 mm Hg in GII, and 11.9 ± 3.0 mm Hg in GIII at 12 months postoperatively (P < .001 for all). The number of hypotensive ocular medications were reduced from 2.7 ± 1.0 in GI, 3.1 ± 0.8 in GII, and 3.2 ± 1.2 in GIII to 0.6 ± 0.9 in GI, 1.0 ± 1.1 in GII, and 1.2 ± 1.1 in GIII at the last postoperative visit (P < .001 for all). Relative success was achieved, at 1 year, in 93.8% of the eyes in GI, 89.0% in GII, and 88.1% in GIII (P = .3). Complete success was achieved in 61.8% of the eyes in GI, 43.8% in GII, and 37.6% in GIII (P = .007). No serious adverse event was observed in any group.

Conclusions: GATT is a safe and effective procedure in glaucoma, regardless of its preoperative severity.