The association between myopia and primary open-angle glaucoma: a systematic review and meta-analysis

Authors: Wu J, Hao J, Du Y, Cao K, Lin C, Sun R, Xie Y, Wang N.

Geographical coverage: Worldwide

Sector: Burden of disease

Sub-sector: Epidemiology

Equity focus: None

Study population: Patients with POAG

Review type: Other review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background: Previous studies identify myopia as a risk factor for primary open-angle glaucoma (POAG). However, recent studies have shown different results, and the definitive relationship between myopia and POAG remains controversial.

Objectives: The aim of this study was to investigate the relationship between myopia and POAG.

Main findings

Overall, the findings of this review demonstrate that myopia may be a risk factor associated with POAG and a possible protective factor for POAG progression – which may be due to myopia with the presence of a lamina cribrosa defect, slowing down the visual field loss and also POAG progression.

The literature search yielded 2,680 articles, of which 23 studies were included in the meta-analysis. Of these articles, 16 were cross-sectional studies for “myopia and POAG,” and seven were longitudinal cohort studies for “myopia and progression of POAG.” All cross-sectional studies were population-based studies, and all the longitudinal cohort studies were hospital-based studies. The meta-analysis comprised 69,249 individuals in cross-sectional studies and 1,687 in cohort studies.

Data on the association between myopia and POAG was obtained from 16 cross-sectional studies, and the pooled OR was 2.26 (95% confidence interval, 1.77-2.89, p <0.001) in random-effects model (I² = 86%; p <0.01). For the relationship of myopia and POAG progression, data from seven longitudinal cohort studies were included, and the pooled OR was 0.85 (95% CI, 0.73-0.99, p = 0.042) in the random-effects model (I² = 88%; p <0.01).

Authors identified certain limitations. Different diagnostic criteria for POAG were used in both cross-sectional and follow-up studies, but most studies adopted the diagnostic criteria proposed by the ISGEO or similar. There was a slight difference in the degrees of myopia selected in each study. There are very few reports elucidating the relationship between the different degrees of myopia and POAG progression. Studies used different covariables within their models, which may lead to related bias. Major published studies might have publication bias.

Heterogenity was found to be high for both sets of studies.

Authors reported the need for further research to determine the underlying mechanisms that determine the relationship between myopia and POAG.

Methodology:

Studies were included if they defined myopia clearly, had Primary Open-Angle Glaucoma (POAG) or its progression as the outcome, and evaluated the association using odds ratio (OR) or 95% confidence interval (CI), or allowed OR calculation from raw data. Studies were excluded if they involved participants under 18, were of an unmatched type like case reports or reviews, involved secondary or angle-closure glaucoma, were not in English, lacked clear myopia definition or detailed POAG description, or involved patients who converted from ocular hypertension to OAG. Only the most recent publication was included in case of multiple publications from the same study population.

Authors searched for published articles from PubMed, EMBASE and Scopus databases between 1970 and 2020. Titles and abstracts of the remaining studies were scanned by three ophthalmologists independently. Full texts were reviewed, and the reference lists extracted from the articles were checked.

A pooled analysis of the odds ratios (ORs) was performed using a random-effects model. ORs were combined from the cross-sectional studies and longitudinal cohort studies to estimate the pooled OR with 95% CI using the random-effects model separately. The ORs were compared between myopia (≥−0.5 D) and the non-myopia group. Sensitivity analysis was undertaken to investigate the contribution of each study to the heterogeneity. Publication bias was evaluated using Egger’s test. All statistical analyses were performed with the open-source R program.

Further stratified analysis was undertaken based on different degrees of myopia in included studies. These were divided into three groups but analysis didn’t significantly change conclusions.

Applicability/external validity: Authors note the study involved different degrees of myopia. However, this did not appear to impact on the results overall.

Geographic focus: Studies included in the review included India, China and Sri Lanka.

Summary of quality assessment:

Although the study identification, inclusion, and critical appraisal methods were fairly comprehensive, the search was restricted to English-language studies. The authors did not seem to include unpublished materials or consult with experts. There was no detailed quality assessment of the included studies. While the data analysis methods were generally robust, they did not specifically account for varying study quality. Due to these factors, we would classify our confidence in this study’s findings as low.