Systematic review and meta-analysis of myopia prevalence in African school children

Author: Ovenseri-Ogbomo G, Osuagwu UL, Ekpenyong BN, Agho K, Ekure E, Ndep AO, et al.

Geographical coverage: Africa

Sector: Epidemiology

Sub-sector: Burden of disease

Equity focus: Review focuses on school children.

Study population: School children in Africa aged 5-18.

Review type: Other review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background: Increased prevalence of myopia is a major public health challenge worldwide, including in Africa. While previous studies have shown an increasing prevalence in Africa, there is no collective review of evidence on the magnitude of myopia in African school children. Myopia is likely to be a particular challenge for Africa, given its disproportionately young population.

Objectives: To review the evidence on the prevalence of myopia in African school children.

Main findings:

In summary, authors found that myopia affects about one in 20 African schoolchildren, and it is overestimated in non-cycloplegic refraction.

A total of 24 studies were included in the review. Six of the included studies were from Ghana, four each were from South Africa and Nigeria, three were from Ethiopia, two were from Burkina Faso, and one each was from Sudan, Egypt, Equatorial Guinea, Somalia and Tunisia. Of the reviewed articles, 21 were school-based, cross-sectional studies, two were population-based, cross-sectional studies, while one employed a cross-sectional study design but did not report whether it was school or population-based. Of the reviewed studies, 13 performed cycloplegic refraction to determine the refractive error status of the children, while non-cycloplegic refraction was used in 11 of the studies. Regarding the technique used for refractive error measurement, over 20 studies performed objective refraction, and 4 performed subjective refraction. Data was included from 24 quality assessed studies, covering 36,395 African children.

Authors reported the overall crude prevalence of myopia over the last two decades is 4.7% (95% CI, 3.9-5.7) in African children. Although the prevalence of myopia was slightly higher in females (5.3%, 95%CI: 4.1, 6.5) than in males (3.7%, 95% CI, 2.6-4.7; p = 0.297) and higher in older [12-18 years 5.1% (95% CI, 3.8-6.3) than younger children (aged 5-11 years, 3.4%, 95% CI, 2.5-4.4; p = 0.091), authors report no significant differences. The review observed a significantly lower prevalence of myopia with cycloplegic compared with non-cycloplegic refraction [4.2%, 95% CI: 3.3, 5.1 versus 6.4%, 95%CI: 4.4, 8.4; p = 0.046].

Funnel plots and using Begg’s test for Myopia in Africa indicated homogeneity and meta-regression analysis of myopia by year of publication indicated that publication of year increased as the proportion of myopia decreased, but this relationship was not statistically significant.

The authors suggest that to reduce myopia prevalence, clinical interventions should focus on females and school children aged 12-18 years. They emphasize the need for monitoring myopia trends due to increased exposure to risk factors such as mobile device usage, near-work, online learning, and limited outdoor time among children in the region.

The authors caution that data on myopia prevalence from non-cycloplegic refraction could mislead researchers and policymakers. They recommend using cycloplegic refraction in all child myopia studies. They also call for future research to explore the impact of ethnicity on myopia prevalence in Africa, suggesting that comparing different ethnicities could reveal significant differences.


The review included studies published from 2000 to 2021 that investigated refractive error prevalence in school children aged 5 to 18. Eligible studies used a cross-sectional design, clearly described the sampling technique, stated the refractive error measurement method, and defined myopia criteria. Both school-based and population-based studies published in English were considered. Two independent reviewers assessed the articles for inclusion, with a third reviewer consulted in case of disagreement.

Two reviewers independently conducted a systematic search and review of myopia in Africa using data from the past two decades. The search, carried out on 25 May and 18 August 2021, focused on online articles in English discussing myopia prevalence in Africa. Disagreements were resolved by a third reviewer. Databases searched included Web of Science, PubMed, ProQuest, Medline, Scopus, and African Index Medicus, using keywords such as “refractive”, “error”, “Africa”, “children”, “prevalence”, “epidemiology”, “myopia”, and “school children”. Relevant studies were also identified through manual searches of reference lists.

Authors extracted all relevant data of each included study, such as year, study design, sample size, etc. Where the reported prevalence was not clearly defined, the corresponding author in the published article was contacted for clarification. The quality of each selected article was assessed using the checklist developed by Downs and Black and each included article was assessed and scored on a 10-item scale.

A meta-analysis was performed using Stata 14.0, generating forest plots to show myopia prevalence in school children by gender, age, and refraction technique. High inconsistency (I2 >50%) indicated the use of a random-effects model. Sensitivity analysis examined outlier effects by comparing pooled prevalence before and after removing one study at a time. Funnel plots and Begg’s test assessed potential bias and study effects. Prevalence was analysed in subsets based on overall prevalence, gender, and refraction type. Age groups were divided into 5-11 years and 12-18 years to study possible variations in myopia prevalence.

Applicability/external validity: Authors indicate that only studies published in English were included, so findings may be less applicable to non-Anglophone countries within Africa.

Geographic focus: Authors note much higher rates of myopia outside of Africa (especially in Asia), and a number of different characteristics of countries that might influence this (more time outside; less near-work). It is clear that these findings are primarily Africa-specific, and cannot be extrapolated to a wider range of low- and middle-income countries.

Summary of quality assessment:

While the approaches to the selection and critical appraisal of studies were generally robust, with key tasks being undertaken by at least two authors, the search was limited in that only studies published in English were included and no attempts were made to include published material. The former fact is likely to make the review less inclusive of data from non-Anglophone countries in Africa, as the authors acknowledge. While the approach to the analysis of the data is generally robust and thorough, no analysis is undertaken and there is no discussion in the text of the extent to which including articles with different risks of bias may have influenced the results. For these reasons, we have low confidence in the findings of this review.

Publication Source:

Ovenseri-Ogbomo G, Osuagwu UL, Ekpenyong BN, Agho K, Ekure E, Ndep AO, et al. (2022) Systematic review and meta-analysis of myopia prevalence in African school children. PLoS ONE 17(2): e0263335. journal.pone.0263335