Non-contact tests for identifying people at risk of primary angle closure glaucoma (Review)

Author: Jindal A, Ctori I, Virgili G, Lucenteforte E, Lawrenson JG.

Geographical coverage: Asia

Sector: Service Delivery

Sub-sector: Screening

Equity focus: Not reported

Study population: Patients with primary angle closure glaucoma

Review type: Effectiveness review

Quantitative synthesis method: Narrative synthesis

Qualitative synthesis method: Not applicable

Background

Primary angle closure glaucoma (PACG) accounts for around 50% of global glaucoma-related blindness and disproportionately affects Asian populations. Over 75% of individuals with PACG reside in Asia. As PACG is often asymptomatic, early identification is challenging. Non-contact tests can be used by trained personnel as a triage tool to identify individuals at risk. Although these tests cannot replace gonioscopy, they may serve as useful supplementary tools.

Objectives

To determine the diagnostic accuracy of non-contact tests for identifying people with an occludable angle.

Main findings

Overall, non-contact tests like limbal anterior chamber depth (LACD) are effective and comparable to advanced imaging technologies for identifying individuals at risk of PACG.

The search identified 6719 articles, of which 47 studies involving 26,151 participants were included in this review. The majority of the studies (n=36, 76.6%) were conducted in Asia. Twenty-seven of the 47 included studies assessed anterior segment optical coherence tomography (AS-OCT), 17 assessed LACD, 9 studied Scheimpflug photography, 6 evaluated scanning peripheral anterior chamber depth analyser (SPAC), and 5 studies evaluated the flashlight test.

The diagnostic performance of LACD (LACD≤25%, 16 studies, 7540 eyes; sensitivity 0.83 [95% confidence interval (CI): 0.74 to 0.90], specificity 0.88 [95% CI: 0.84 to 0.92]) was comparable to more advanced imaging technologies such as AS-OCT (13 studies, 9242 eyes; sensitivity 0.85 [95% CI: 0.76 to 0.91]; specificity 0.71 [95% CI: 0.62 to 0.78]), Scheimpflug photography (9 studies, 1698 eyes; sensitivity 0.92 [95% CI: 0.84 to 0.96], specificity 0.86 [95% CI: 0.76 to 0.93]), and SPAC (4 studies, 4677 eyes; sensitivity 0.83 [95% CI: 0.70 to 0.91], specificity 0.78 [95% CI: 0.70 to 0.83]), but the flashlight test demonstrated inferior accuracy (5 studies, 1188 eyes; sensitivity 0.51 [95% CI: 0.25 to 0.76], specificity 0.92 [95% CI: 0.70 to 0.98]).

Methodology

The searches were conducted in PubMed, Embase, BIOSIS, OpenGrey, Cochrane Central Register of Controlled Trials (CENTRAL), Health Technology Assessment Database (HTAD), Aggressive Research Intelligence Facility database (ARIF), ISRCTN registry, clinicaltrials.gov., and World Health Organization International Clinical Trials Registry Platform. The searches were conducted on 3^rd October 2019 without any language or timeframe limits. Additionally, reference lists of the included studies were scanned to find additional relevant articles. All prospective and retrospective cohort studies and case-control studies that evaluated the accuracy of non-contact tests for diagnosing occludable angles in comparison to a gonioscopic reference standard were included.

Two reviewers independently screened the articles against the eligibility criteria. Any discrepancies between the two reviewers were resolved through discussion or by contacting a third reviewer. Authors of the included studies were contacted for further information where needed. Two reviewers independently extracted the data from the included studies. The reviewers resolved the discrepancies through discussion or if necessary, by contacting the study investigators for clarification or additional information. Two reviewers assessed the risk of bias in each included study using the QUADAS 2 tool.

The data was analysed at fixed thresholds for each index test. For each test, 2 x 2 tables were constructed, and sensitivity and specificity were calculated. A bivariate model was fitted to calculate pooled point estimates for sensitivity and specificity when four or more studies provided data at fixed thresholds for each test. A likelihood ratio test was performed comparing the model with and without the covariate for comparisons between index tests and subgroups.

Applicability/external validity

The review highlighted that most studies were conducted in Asian populations, affecting generalisability due to primary angle closure glaucoma prevalence. It also noted differences between primary and secondary care settings. Future research should focus on high-quality community-based studies to enhance external validity.

Geographic focus

The authors did not apply any geographical limits. However, most studies (76.6%) were conducted in Asia.

Summary of quality assessment

Overall, there is high confidence in the conclusions about the effects of this study. The review authors used rigorous methods to conduct the review, appropriately acknowledging review limitations.