Systematic review and meta-analysis of treating open angle glaucoma with gonioscopy-assisted transluminal trabeculotomy

Authors: Guo ZZ, Chang K, Wei X

Geographical coverage: United States of America (USA), Germany, Japan

Sector: Open angle glaucoma

Sub-sector: Treatment

Equity focus: Not reported

Study population: Patients with open-angle glaucoma

Review type: Effectiveness review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background

Open-angle glaucoma (OAG) is typically managed with filtration procedures such as trabeculectomy or glaucoma drainage devices, which aim to reduce intraocular pressure (IOP) by allowing aqueous humour to drain from the eye. However, these conventional treatments can lead to scarring, surgical failure and other postoperative complications. Conventional trabeculotomy, an angle-based surgical technique, also yields only limited IOP reduction because it involves partial incision of the trabecular meshwork and opening of Schlemm’s canal. To address these limitations, gonioscopy-assisted transluminal trabeculotomy (GATT) was introduced in 2014. GATT is a minimally invasive ab interno procedure that spares the sclera and conjunctiva, thereby reducing scarring and simplifying the identification of Schlemm’s canal. Despite its theoretical benefits, research on GATT has been limited, prompting the authors to undertake a systematic review and meta-analysis of its efficacy and safety.

Objectives

The objective of this study was to systematically review and meta-analyse clinical studies of GATT in the management of OAG, in order to evaluate its effectiveness in lowering IOP and its safety profile.

Main findings

Overall, the review found that GATT appears to be a safe and promising treatment for patients with open-angle glaucoma. The pooled evidence indicated that GATT significantly lowered IOP and reduced the number of glaucoma medications required. In total, 108 records were identified from the literature search. Of these, ten studies met the inclusion criteria for the narrative synthesis and nine were included in the quantitative meta-analysis. The included studies were predominantly retrospective case series (80%), with the remaining 20% being non-randomised prospective studies. These studies were conducted in the United States, Germany and Japan, and were published between 2014 and 2018. Together, they involved 523 patients (537 eyes) with open-angle glaucoma. Eight of the ten studies were rated as high quality, while the other two were rated as poor quality.

The meta-analyses demonstrated that the mean IOP decreased by 9.81 mmHg after GATT (95% confidence interval (CI) 7.98–11.63), which was a statistically significant reduction from preoperative levels (Z = 10.52, P < 0.0001). Similarly, the pooled number of glaucoma medications declined by 1.67 (95% CI 1.31–2.04) after GATT (Z = 9.09, P < 0.0001). The combined surgical success rate was estimated at 85% (95% CI 0.73–0.96), while the pooled reoperation rate was 20% (95% CI 0.15–0.24).

Methodology

The authors performed a comprehensive literature search of five major electronic databases (PubMed, EMBASE, Ovid Medline, the Cochrane Library and ClinicalTrials.gov) to identify studies of GATT for open-angle glaucoma, without restricting by study design. Title and abstract screening and full-text review were conducted independently by two reviewers, with any discrepancies resolved through discussion. Study quality was evaluated using a validated 14-item checklist from the Review Body for Interventional Procedures.

Data from the included studies were synthesised using meta-analysis. A random-effects or fixed-effects model was chosen according to the degree of heterogeneity observed. All effect sizes (for example, mean IOP reduction) were reported as means with 95% confidence intervals. Heterogeneity among study results was assessed using the I² statistic, and if substantial heterogeneity was detected (I² > 50%), subgroup analyses were performed by relevant covariates.

Applicability and external validity

The applicability and external validity of the review’s findings were limited by the nature of the included studies. Most of these were retrospective case series without randomisation or control groups, and there was significant variation between studies in surgical techniques, follow-up duration, baseline IOP and patient characteristics. There was also concern about selection bias, as simpler cases were often chosen for the initial GATT procedures. These factors reduce confidence in the generalisability of the evidence. The authors therefore recommend that randomised controlled trials with larger sample sizes be conducted to draw more definitive conclusions.

Geographic focus

The review had a worldwide scope and did not specifically target any low- or middle-income countries. However, in practice all the included studies originated from just three countries: the US, Germany and Japan. The lack of data from other regions means that the findings may not generalise to different healthcare settings or populations.

Summary of quality assessment

The authors conducted thorough searches of published and grey literature, but they did not review the reference lists of included papers, which might have failed to identify additional studies. Meta-analyses were performed, and heterogeneity was reported for key outcomes. The risk of bias of each included study was assessed, but the results were not stratified by risk of bias, which is a limitation in interpreting the findings.