Methodological quality of the review: High confidence
Author: Maier PC, Funk J, Schwarzer G, Antes G, Falck-Ytter YT
Geographical coverage: Not reported
Sub-sector: Open angle glaucoma
Equity focus: None specified
Review type: Effectiveness review
Quantitative synthesis method: Meta-analysis
Qualitative synthesis method: Not applicable
Background: Open angle glaucoma is one of the most common causes of blindness in developed countries. The most commonly used medications for glaucoma are to lower ocular pressure, despite conflicting evidence.
Objectives: The primary objective was to review systematically the literature with regards to the effectiveness of treatment of ocular hypertension and open angle glaucoma (both primary open angle glaucoma [POAG] and normal tension glaucoma).
Main findings: In the meta-analysis, five trials in ocular hypertension showed a significant (P = 0.01) preventive effect of reducing intra-ocular pressure (IOP) on progression to glaucoma (hazard ratio 0.56, 95% CI: 0.39 to 0.81). Pooled data of two studies in manifest glaucoma showed a significant (P = 0.003) delay of visual field deterioration (0.65, 0.49 to 0.87). The sub-group analysis showed a larger effect in patients with raised pressure and a reduced effect in normal tension glaucoma. Authors concluded that lowering IOP in patients with ocular hypertension or manifest glaucoma is beneficial in reducing the risk of visual field loss in the long term.
Lowering IOP has a significant benefit in reducing progression in glaucoma patients. Authors noted that further research is required in the sub-group of patients without increased IOP to determine which patients with normal tension glaucoma will benefit most.
Methodology: The following databases were searched for relevant studies: MEDLINE, EMBASE and the Cochrane Library. Reference lists of identified studies and experts were consulted for further studies. There were no language or publication restrictions applied to searches. Eligible studies were randomised controlled trials (RCTs) with a concurrent untreated control group, plus information on time to glaucomatous changes to visual field and optic disc.
Two authors independently screened studies for inclusion, extracted data and critically appraised included studies. Authors conducted a meta-analysis of included studies using appropriate methods to ensure that similar studies were combined. Authors assessed heterogeneity by analysing the forest plot, the X2 test as well as the I2 statistic. Authors also conducted a sensitivity analysis using the random- and fixed-effects models as well as pre-defined sub-group analysis of elevated and normal glaucoma.
Applicability/external validity: The authors did not discuss applicability/external validity.
Geographic focus: This review focused on all countries. It is not clear if the authors found any results from low/middle-income settings or not. However, the results may be applicable to low/middle-income settings.
Summary of quality assessment: Overall, high confidence was attributed in the conclusions about the effects of this study, as minor limitations were identified. Authors conducted a thorough search of the literature, avoiding restriction bias. Appropriate methods to screen studies for eligibility and data extraction were used. Although two authors independently critically-appraised included studies, it’s not clear which tool/criteria was used. Authors used appropriate methods to pool data of studies, conducting sub-group analysis where necessary and taking into account heterogeneity.