Non-penetrating filtration surgery versus trabeculectomy for open angle glaucoma

Methodological qualiy of the review: High confidence

Author: Elday MA, Bunce C, ElSheika OZ, Wormald R

Geographical coverage: Not reported

Sector: Glaucoma

Sub-sector: Open angle glaucoma, surgery

Equity focus: None specified

Review type: Effectiveness review

Quantitative synthesis method: Narrative synthesis and meta-analysis

Qualitative synthesis method: Not applicable

Background: Glaucoma is the second most common cause of blindness worldwide. Non-penetrating glaucoma surgeries have been developed as a safer and more acceptable surgical intervention for patients compared to conventional procedures.

Objectives: The objective of this review was to compare the effectiveness of non-penetrating trabecular surgery compared with conventional trabeculectomy in people with glaucoma.

Main findings: The authors included five quasi-experimental studies with a total of 311 eyes (247 participants). Three of the five trials were conducted in Europe, two in Italy and one in Turkey, and two were carried out in Asia, Japan and Saudi Arabia. 160 eyes that had undergone trabeculectomy (Trab) were compared to 151 eyes that had undergone non-penetrating glaucoma surgery (of which 101 eyes had undergone deep sclerectomy and 50 eyes viscocanalostomy).

The confidence interval (CI) for the odds ratio (OR) of success (defined as achieving target eye pressure without eye drops) does not exclude a beneficial effect of either deep sclerectomy or trabeculectomy (OR 0.98, 95% CI 0.51 to 1.88). The odds of success in viscocanalostomy participants was lower than in Trab participants (OR 0.33, 95% CI 0.13 to 0.81).

We did not combine the different types of non-penetrating surgery because there was evidence of a sub-group difference when examining total success. The OR for achieving target eye pressure with or without eye drops was imprecise and was compatible with a beneficial effect of either Trab or non-penetrating filtration surgery (NPFS) (OR 0.79, 95% CI 0.35 to 1.79). Operative adjuvants were used in both treatment groups; more commonly in the NPFS group compared to the Trab group but no clear effect of their use could be determined.

Although the studies were too small to provide definitive evidence regarding the relative safety of the surgical procedures, we noted that there were relatively fewer complications with non-filtering surgery compared to Trab (17% and 65% respectively). Cataract was more commonly reported in the Trab studies. None of the five trials used quality-of-life measure questionnaires. The methodological quality of the studies was not good. Most studies were at high risk of bias in at least one domain and for many, there was lack of certainty due to incomplete reporting. Adequate sequence generation was noted only in one study. Similarly, only two studies avoided detection bias. We detected incomplete outcome data in three of the included studies.

Based on these findings, authors concluded that this review provides limited evidence that control of intra-ocular pressure (IOP) is better with Trab than visconalostomy. For deep sclerectomy, the authors stated that they could not draw useful conclusions. This may reflect surgical difficulties in performing non-penetrating procedures and the need for surgical experience. The review authors also highlighted the lack of use of quality of life outcomes and the need for higher methodological quality randomised controlled trials (RCTs) to address these issues.

Methodology: Authors included relevant RCTs and quasi-RCTs on participants undergoing standard Trab for open-angle glaucoma to non-penetrating surgery, especially visconalostromy, with or without adjunctive measures.

The authors searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2013, Issue 8), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to September 2013), EMBASE (January 1980 to September 2013), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to September 2013), the metaRegister of Controlled Trials (mRCT), and theWHO International Clinical Trials Registry Platform (ICTRP). No date or language restrictions in the electronic searches for trials were applied. In addition, authors searched the abstracts of the Association for Research in Vision and Opthalmology for the years of 1988 to 2007.

Two authors independently screened and sifted studies for inclusion in the review, extracted data and assessed each included study for risk of bias. For data syntheses, the authors conducted a meta-analysis using the random-effects models to compare:

  1. deep sclerectomy versus conventional trabeculectomy;
  2. viscocanalostomy versus conventional trabeculectomy.

A sub-group analysis was also conducted for the type of non-penetrating filtration surgery (NPFS): sclerectomy or viscocanalostomy. The authors did not conduct a sensitivity analysis to assess the effect of excluding trials assessed as ‘high risk’ on any aspect of trial quality due to a small number of trials being identified.

Applicability/external validity: Authors noted that surgical expertise is one of the factors that can affect outcomes, and considering two different surgical procedures, and the difference in surgical expertise between procedures, might explain the difference in outcomes. None of the included studies within this review did not comment on the surgical expertise of the surgeons performing either procedure. In addition, authors also pointed out that there were differences in some specific features of the interventions in the trials, and none of the five trials used quality-of-life measure questionnaires.

Geographic focus: The authors did not focus especially on low/middle-income countries. Review authors included trials from Europe, Asia, Japan and Saudi Arabia. Due to the factors mentioned in the point above, the authors were not able to describe the applicability of the results, specifically to low and middle-income countries.

Summary of quality assessment: Overall, there is high confidence in the conclusions about the effects of this review. The authors conducted comprehensive searches of the literature to ensure that all potentially relevant studies were included. Authors used appropriate methods to screen, sift, extract and appraise the quality of included studies. Authors synthesised evidence in an appropriate manner.

Publication source: Eldaly MA1, Bunce C, Elsheikha OZ, Wormald R. Non-penetrating filtration surgery versus trabeculectomy for open-angle glaucoma. Cochrane Database Syst Rev. 2014 Feb 15;(2):CD007059. Source