Methodologial quality of the review: Medium confidence

Author: Cheng JW, Cheng SW, Cai, JP, Li Y, Wei RL

Geographical coverage: Not reported

Sector: Glaucoma

Sub-sector: Treatment of open angle glaucoma

Equity focus: None specified

Review type: Effectiveness review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background: Recently, non-penetrating glaucoma surgeries (NPGS) have been used as they are assumed safer than classic trabeculectomy (TE). However, there have been strong discussions on the efficacy and longevity of NPGS, and the potential of NPGS to achieve target intra-ocular pressure (IOP).

Objectives: To evaluate the IOP-lowering effects achieved by NPGS and its modifications in patients with open angle glaucoma.

Main findings: 29 studies were included in this review. The results at two years showed that deep sclerectomy (DS) and viscocanalostomy (VCO) were less effective than TE in lowering IOP. The IOP was reduced by 35.2%, 30.2% and 45.6% for DS, VCO and TE respectively. Intraoperative use of implants and mitomycin C (MMC) were found to increase IOP-lowering effects of DS by 41.1% and 41.7% respectively.

The complete success rates at four years were 35.4% for DS and 22.7% for VCO, lower than that of TE (47.6%). The complete success rates of DS with implants and MMC of 64.6% and 52.1% respectively at four years were greater than that of primary DS. NPGS caused major complications in fewer patients than did TE.

Overall, authors concluded that DS and VCO can significantly lower IOP with fewer complications than TE. However, their IOP-lowering effect is lower than that of TE. The efficacy of DS can be improved with the intraoperative use of implants and MMC. However, further studies are required to determine the validity, reliability and sensitivity of the target IOP.

Methodology: PUBMED, EMBASE, and the Cochrane Controlled Trials Register were searched for randomised controlled trials (RCTs) using identified search terms. Reference lists of original reports and review articles retrieved through the search were reviewed for additional studies not included in the computerised databases. The searches were conducted independently by two reviewers.

The inclusion criteria were:

(a) Study type: RCTs, including placebo- or active-controlled

(b) Population: all patients with a diagnosis of open angle glaucoma (OAG), including primary and secondary

(c) Intervention: one of all the non-penetrating surgical procedures was un­dertaken

(d) Outcome variables: at least one of the follow­ing outcome variables – percentage of IOP reduction (IOPR) and complete success rates

(e) Duration: follow-up time of not less than six months post­operatively

(f) Publication parameters: written in any lan­guage.

The main outcome measures were the percentage IOPR and the complete success rate. Complete success was defined as target endpoint IOP (usually less than 21 mm Hg) without medications.

Data extraction was performed independently by two reviewers using a costumised form. Methodological quality of included studies was evaluated independently by two authors using the Delphi list on a scale from 0 to 20. Authors conducted a pooled analysis, which was calculated using the random-effects model.

Applicability/external validity: The authors did not discuss the applicability/external validity of the results.

Geographic focus: This review focused on all countries. Studies from low/middle-income countries were included.

Summary of quality assessment: Overall, there is medium confidence in the conclusions about the effects of this study. Although authors/experts were not contacted as part of the search strategy, a thorough search of the literature was conducted on relevant databases – avoiding language bias – to ensure that all relevant studies were identified. It is not clear whether authors did not restrict the research to published studies only. Authors used appropriate methods to sift through studies for inclusion, avoiding selection bias, and appropriately extracted data and assessed methodological quality using validated tools.