Non-penetrating filtration surgery versus trabeculectomy in postoperative astigmatism: a meta-analysis

Author: Peng X, Ling Q, Duan X.

Geographical coverage: Not reported

Sector: Astigmatism

Sub–sector: Glaucoma treatment

Equity focus: Not explicitly stated

Study population: Adult patients with glaucoma

Review type: Effectiveness review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background

Glaucoma is a leading cause of irreversible blindness and is expected to affect up to 111.8 million people worldwide by 2040, with substantial social and economic consequences. When pharmacological and laser therapies fail, surgical options such as trabeculectomy (Trab) and non‑penetrating trabecular surgery (NPTS)—including deep sclerectomy (DS), canaloplasty (CP) and viscocanalostomy (VCO)—are employed. Although Trab is regarded as the gold‑standard procedure, it carries risks that may lead to surgical failure. NPTS were developed to minimise these risks while maintaining effective intra‑ocular pressure (IOP) control. Despite advances that raise expectations of good postoperative vision, surgically induced astigmatism (SIA) remains a concern for both procedures, potentially hindering visual rehabilitation. The comparative impact of the two techniques on SIA is still uncertain.

Objectives

To compare the effect of trabeculectomy and non‑penetrating trabecular surgery on postoperative astigmatism in adults with glaucoma.

Main findings

Five studies involving 359 eyes (173 treated with Trab and 186 with NPTS) met the inclusion criteria and reported astigmatism at 6 months or later. Both procedures increased astigmatism, but NPTS induced significantly less astigmatism than Trab at 6 months post‑operatively (standardised mean difference, SMD = 0.40; 95 % confidence interval, CI = 0.19 to 0.61; P = 0.02). Heterogeneity was moderate (I² = 66 %, P = 0.02). Sensitivity analysis confirmed the robustness of the pooled estimate; however, publication bias could not be assessed because of the small number of studies.

Methodology

Eligible designs were randomised controlled trials or cohort studies that compared NPTS with Trab in adults and reported astigmatism 6 months after surgery. Searches of PubMed, Web of Science, the Cochrane Library and China National Knowledge Infrastructure (CNKI) were undertaken from database inception to April 2024. Two reviewers independently screened records against prespecified criteria. Methodological quality was appraised with the Cochrane risk‑of‑bias tool (for randomised trials) and the Newcastle–Ottawa Scale (NOS) for observational studies. Data were pooled in a meta‑analysis. Heterogeneity was explored with the Cochrane Q test and the I² statistic; a fixed‑effect model was used when heterogeneity was low, and a random‑effects model otherwise.

Applicability / external validity

The included studies were conducted in varied clinical settings, but the review did not explicitly discuss generalisability. Although some evidence suggests that Trab achieves lower IOP than NPTS, comparatively few studies have explored differences in postoperative astigmatism. Clinicians should consider local surgical expertise and patient characteristics when applying these findings.

Geographic focus

The location of included studies was not reported by the review authors.

Summary of quality assessment

The search strategy did not specify language restrictions, reference‑list checking, or author contact, and excluded studies were not listed. The number of reviewers who extracted data was unclear, and publication bias was not examined. These factors increase the risk of bias and imprecision, so the results should be interpreted with caution.