The prevalence of refractive errors in the Middle East: a systematic review and meta-analysis

Methodological quality of the review: High confidence

Author: Fahimeh Khoshhal; Hassan Hashemi; Elham Hooshmand; Mohammad Saatchi; Abbasali Yekta; Mohamadreza Aghamirsalim; Hadi Ostadimoghaddam; Mehdi Khabazkhoob

Region: Middle Eastern countries, including Jordan, Palestine, the United Arab Emirates, Iran, Bahrain, Turkey, Syria, Iraq, Saudi Arabia, Oman, Qatar, Kuwait, Lebanon, Egypt, Yemen, Libya and Algeria

Sector: Refractive error

Subsector: Prevalence of refractive errors

Equity focus: No

Study population: Adults

Type of programme: Clinic-based, school students-based and population-based

Review type: Other review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background: Refractive errors are one of the leading causes of visual impairment around the world and the second leading cause of blindness after cataract. Refractive errors are correctable with glasses, contact lenses or surgery when detected and diagnosed in a timely manner. However, lack of diagnosis or proper correction can turn them into a major cause of visual impairment and even blindness. The reported prevalence of refractive errors varies among different populations and, in addition to interstudy methodological differences, variations can be related to genetic backgrounds, environmental factors, access to facilities, and socioeconomic statuses. According to the literature review, most of the countries located in the Middle East have reported the prevalence of refractive errors.

Objectives: The objective of this review was to collect the previous study results, estimate the prevalence of different types of refractive errors in this region, and compare them to global statistics.

Main findings: A total of 47 articles met the criteria for inclusion in this meta-analysis. The 47 selected articles had a total of 550,354 participants. The prevalence of myopia, hyperopia and astigmatism was 4% (95% CI 4, 5), 8% (95% CI 6, 10), and 15% (95% CI 10, 19) in people less than or equal to 15 years and 30% (95% CI 25, 34), 21% (95% CI 15, 28), and 24% (95% CI 16, 31) in subjects over 15 years, respectively. The prevalence of myopia, hyperopia and astigmatism was 3.5%, 12.4%, and 9.0% in males,and 4.2%, 13.1% and 9.9% in female subjects aged B 15 years, respectively. In subjects aged [15 years, the prevalence was 31.7%, 14.5%, and 31.5% in males, and 31.9%, 11.2%, and 31% in females, respectively.

Methodology: All cross-sectional studies conducted in relation to the prevalence of refractive errors in Middle Eastern countries were included in the review. The outcome measure of the study was the prevalence of refractive errors, including myopia, hyperopia and astigmatism. The criterion for assessing the amount of refractive error is refraction with and without cycloplegia, which is determined using an auto-refractometer and a retinoscope as manifest, subjective and cycloplegic refraction. To determine refractive errors in subjects aged 15 years or younger, we included studies using cycloplegic refraction. Authors used articles published in the four credible databases of PubMed, Web of Science, Scopus, and Google Scholar until September 2019. The search strategy was based on a combination of the following keywords: refractive error OR refraction error OR refractive disorder OR eye disease OR ametropia OR ammetropia OR hyperopia OR hypermetropia OR farsightedness OR hyperop* OR myopia OR nearsightedness OR myop* OR astigmatism AND prevalence. The list of references of selected articles was also reviewed. Two researchers reviewed and selected articles independently, without being blinded to the authors’ names, journal name and research results. The quality of the studies in terms of their methodology and reporting was assessed using the STROBE checklist for cross-sectional studies. To examine the level of heterogeneity among studies, the chi-square test at a confidence level of 5% was used for the statistics, and the I² test was used for qualitative assessment of heterogeneity across studies. Based on the Higgins categorisation, an I² more than 75% was considered as heterogeneity. Data analysis was carried out using Stata version 11.

Applicability/external validity: The authors highlighted some limitations, mainly focused on the variations in the study methods, such as the use of different definitions and methods for refractive measurements, as well as different sampling strategies. Lack of a uniform distribution of studies in the different regions of the Middle East creates bias in the data.

Geographic focus: The authors reported that this meta-analysis estimated the prevalence of refractive errors based on available information and evidence in the Middle East region, which includes different racial groups, and showed that the overall prevalence of refractive errors in this region is in the mid-range compared to other parts of the world.

Summary of quality assessment:

Authors used appropriate and rigorous methods to conduct this review, therefore, there is high confidence in the conclusions about the effects of this study.