Comparison of Ahmed glaucoma valve implantation and trabeculectomy for glaucoma: a systematic review and meta-analysis

Methodological quality of the review: Medium confidence

Author: HaiBo T, Xin K, ShiHeng L, Lin L

Region: USA, Korea, Sri Lanka, Iran

Sector: Glaucoma

Sub-sector: Valve implantation; surgical procedure

Equity focus:  None specified

Review type: Other review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background:

Glaucoma is a common disease that results in blindness. There are various therapeutic

options for treating glaucoma, including anti-glaucoma medication, laser, and surgery. Trabeculectomy remains the gold standard surgical procedure for most glaucoma cases worldwide since it was first introduced. Although this procedure is very effective in reducing intraocular pressure (IOP) in the short term, surgical failure has often been observed over time.

Glaucoma drainage devices were initially introduced as surgical procedures for refractory glaucoma. Ahmed glaucoma valve implantation (AGV) is one such device. The implant is equipped with a valve to reduce the occurrence of hypotony and its related complications following the early postoperative period. In recent years, AGV implantation has gradually been performed as an alternative to trabeculectomy to treat all types of glaucoma.

Objectives:

To compare the efficacy and safety of AGV with trabeculectomy in the management of glaucoma patients.

Main findings:

In total, the authors included a total of seven studies in qualitative synthesis and six studies in the meta-analysis.

The authors included a total of 507 eyes from patients in their meta-analysis; 249 eyes were from patients in the AGV group, and 258 eyes were from patients in the trabeculectomy group. Two studies were performed in each of USA and Korea, and one was performed in each of Sri Lanka and Iran. Two of six studies had an RCT design, and four had a retrospective comparative design. The mean ages ranged from 10.9 to 69.9 years for the AGV patients and 9.1 years to 69.6 years for the trabeculectomy group patients. The Male:Female gender ratio varied from 0.44 to 4.0 in the AGV group and 0.49 to 1.0 in the trabeculectomy group. The majority of patients were Asian, followed by Caucasian, African, and Armenian patients. The mean duration of these included studies ranged from 12 to 31 months. The mean baseline IOP varied from 23.8 to 53.69 mmHg in the AGV group and 22.0 to 57.13 mmHg in the trabeculectomy group. Three of six studies reported patients with open-angle glaucoma (OAG), two studies reported neovascular (NVG) cases, and there was one report each of closed angle glaucoma (CAG) aphakic glaucoma, pigmentary and pseudo-exfoliative glaucoma patients.

The authors found no significant difference between the AGV and trabeculectomy in the IOPR% (weighted mean difference (WMD)= -3.04, 95% confidence interval (CI): -8.36- 2.26; P = 0.26). The pooled odds ratios (OR) comparing AGV with trabeculectomy were 0.46 (0.22, 0.99) for the complete success rate (P = 0.05) and 0.97 (0.78–1.20) for the quantified success rate (P = 0.76). The authors found no significant difference in the reduction in glaucoma medicines was observed (WMD = 0.24; 95% CI: -0.27–0.76; P = 0.35). AGV was found to be associated with a significantly lower frequency of all adverse events (RR = 0.71; 95% CI: 1.14–0.97; p = 0.001) than trabeculectomy, while the most common complications did not differ significantly (all p> 0.05).

Authors noted that AGV was equivalent to trabeculectomy in reducing the IOP, the number of glaucoma medications, success rates, and rates of the most common complications. However, AGV was associated with a significantly lower frequency of overall adverse events.

Methodology:

The authors considered studies eligible for inclusion in their meta-analysis if they met the following inclusion criteria:

1) study design: comparative clinical trials, including randomized controlled clinical trials (RCTs) and non-randomized controlled clinical trials (Non- RCTs);

2) population: patients (> four years of age) with glaucoma undergoing trabeculectomy or AGV;

3) intervention: AGV versus trabeculectomy;

4) outcome variables: at least one of the following outcome variables was included: IOPR, reduction in glaucoma medications, complete and qualified success rates, or incurrence of adverse events; and

5) duration: at least six months.

The following types of studies were excluded:

1) Reviews, case reports, editorial comments, duplicate publications or letters and

2) studies that included patients with repeated or combined glaucoma surgery, other types of glaucoma surgery, and other glaucoma drainage devices.

Two authors independently searched and extracted data of included studies.

The methodological quality was evaluated according to a system reported by Downs and

Blacks. The pilot checklist consisted of 26 items distributed between the following five sub-scales: reporting (nine items), external validity (three items), bias (seven items), and confounding (six items), and power (one item). The two observers discussed any difference in the studies until a consensus was reached. The total score of each trial obtained was expressed as a percentage of the highest scores of all items counted. The trials were deemed to have adequate quality when a quality score was over 50%.

Applicability/external validity:

There has been some controversy in previously published articles on the comparative

efficacy and safety of AGV versus trabeculectomy in the treatment of glaucoma. Therefore, the authors performed a meta-analysis of all eligible clinical trials to evaluate differences in the outcomes of the two surgical procedures for treating patients with glaucoma.

Geographic focus – None specified

Summary of quality assessment:

Overall, medium confidence was attributed in the conclusions about the effects of this review. Although the authors detailed the included studies fully, and separately assessed each for risk of bias and heterogeneity, they did not state whether they allowed for searching unpublished articles or whether they contacted relevant authors.