Pattern of Long-Term Intraocular Pressure Variation Following Gonioscopy-Assisted Transluminal Trabeculotomy: Two-Year Outcomes
Authors: Bruno M. Faria, MD, PhD; Diego T. Dias, MD, PhD; Mariana A.O. Reis, MSc; Fabio B. Daga, MD, PhD; Ana L.B. Scoralick, MD, MSc; Leopoldo Magacho, MD, PhD; Pedro H.E. Ribeiro Junior, MD, MSc; Fabio N. Kanadani, MD, PhD; Vital P. Costa, MD, PhD; Tiago S. Prata, MD, PhD
Précis: Patients with clinically uncontrolled open-angle glaucoma who underwent gonioscopy-assisted transluminal trabeculotomy (GATT), alone or combined with phacoemulsification (PHACOGATT), achieved low mean intraocular pressures (IOP) and demonstrated stable IOP patterns during a 24-month follow-up.
Purpose
To assess the impact of gonioscopy-assisted transluminal trabeculotomy (GATT) on long-term intraocular pressure (IOP) variation.
Patients and Methods
A retrospective unicentric study was conducted with 169 consecutive patients with clinically uncontrolled open-angle glaucoma who underwent standalone GATT or PHACOGATT, with at least 12 months of follow-up. Long-term mean IOP, IOP peak, fluctuation, coefficient of variation, mean-positive IOP variation, sustained clinically significant positive IOP variation, and number of follow-up visits with IOP ≥15 mmHg were analyzed.
Results
Of the 169 eyes (GATT group = 101; PHACOGATT group = 68), mean long-term IOP (12.0±1.8 vs 11.2±2.0 mmHg), IOP peak (12.9±2.6 vs 11.8±3.5 mmHg), and coefficient of variation (0.07±0.08 vs 0.05±0.09) were lower in the PHACOGATT group, while mean IOP fluctuation (1.0±3.7 vs 1.2±1.8 mmHg) was slightly lower in the GATT group. Only 6.5% of patients had sustained clinically significant IOP variation, and IOP ≥15 mmHg occurred in 5.9% of visits.
Conclusions
Both GATT and PHACOGATT resulted in low and stable IOP patterns in patients with uncontrolled open-angle glaucoma. These findings reinforce the value of these minimally invasive techniques as viable options for cases requiring low and steady IOP.
Introduction
Elevated intraocular pressure (IOP) remains the primary risk factor for glaucoma progression. Gonioscopy-assisted transluminal trabeculotomy (GATT) is a minimally invasive glaucoma surgery that enhances aqueous outflow through Schlemm’s canal, reducing IOP via a 360° trabeculotomy using a microcatheter or polypropylene suture.
While GATT’s effectiveness in lowering mean IOP is established, few studies have evaluated its impact on long-term IOP variability—a factor increasingly recognized as critical in preventing disease progression.
Materials and Methods
This single-center, retrospective study adhered to the Declaration of Helsinki and was approved by the ethics committee of Onofre Lopes University Hospital, Natal, Brazil. Patients who underwent GATT or PHACOGATT between January 2017 and May 2022 were included if they had at least five postoperative IOP measurements over a minimum 12-month follow-up.
Patients with angle-closure glaucoma, corneal disease, ocular trauma, or previous intraocular surgery within 6 months before GATT were excluded. Glaucoma was defined by optic nerve and visual field changes consistent with glaucomatous optic neuropathy.
Surgical Technique: All procedures were performed by a single surgeon (B.M.F). After creating a nasal goniotomy, a 5-0 polypropylene suture was passed circumferentially through Schlemm’s canal, completing a 360° trabeculotomy. PHACOGATT involved standard phacoemulsification with intraocular lens implantation prior to GATT.
Postoperative Care: All patients received moxifloxacin and prednisolone acetate 1% drops tapered over four weeks.
Statistical Analysis
Normality was assessed using the D’Agostino-Pearson test. Comparisons between groups used ANOVA or Kruskal–Wallis tests, with significance set at p<0.05.
Results
The mean follow-up was 19.8±6.5 months for GATT and 19.9±6.1 months for PHACOGATT. The GATT group was older, had more advanced glaucoma, and more previous glaucoma surgeries.
IOP values remained stable across all timepoints (3, 6, 12, and 24 months) within both groups. Differences in mean long-term IOP and IOP peak were statistically significant but not clinically relevant.
At 24 months, mean IOP was 12.3±2.3 mmHg (GATT) and 11.9±4.1 mmHg (PHACOGATT). The number of glaucoma medications decreased from 3.4±0.8 to 1.3±1.0 (GATT) and from 3.1±0.8 to 0.9±1.1 (PHACOGATT).
Discussion
Sustained low and stable IOP levels are crucial for preventing glaucoma progression. In this study, GATT and PHACOGATT achieved both objectives. Despite minor differences between groups, both demonstrated excellent long-term IOP stability.
Previous major glaucoma trials (AGIS, CIGTS, OHTS, EMGT) established that fluctuations in IOP can influence disease progression, particularly in moderate-to-severe glaucoma. GATT’s ability to maintain consistent IOPs reinforces its role in managing these cases.
Although the PHACOGATT group showed marginally lower IOP and fewer medications, these differences were not clinically significant. The similar long-term stability supports both approaches as effective.
Limitations
This study’s retrospective nature introduces possible selection bias, and visual field progression was not analyzed. Nevertheless, its large sample and standardized surgical technique strengthen its findings.
Conclusion
Patients with medically uncontrolled open-angle glaucoma who underwent GATT or PHACOGATT achieved low, stable IOPs over 24 months. These results support the use of these minimally invasive surgeries as safe and effective options for glaucoma requiring sustained pressure control.
Reference: Journal of Glaucoma, Volume 34, Number 8, August 2025, pp. 630–636.