Global prevalence and causes of visual impairment and blindness in children: a systematic review and meta-analysis

Authors: Yekta A, Hooshmand E, Saatchi M, Ostadimoghaddam H, Asharlous A, Taheri A, Khabazkhoob M.

Geographical coverage: Worldwide

Sector: Burden of disease

Sub-sector: Prevalence

Equity focus: Study focused exclusively on young people.

Study population: Young people aged under 20 years old.

Review type: Other review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background: While main studies have sought to estimate the prevalence of visual impairment and blindness, it seems necessary to have an estimate of the global prevalence and causes of VI in children to inform policies, especially the Vision 2020 initiative.

Objectives: To determine the global prevalence and common causes of visual impairment (VI) and blindness in children.

Main findings:

Authors note that despite differences in the definition of VI and blindness, based on PVA, 3.82%, and based on BCVA, 1.67% of the examined samples suffer from VI.

A total of 80 articles including 769,720 people from 28 different countries were included in the meta-analysis of this review. The prevalence of VI based on UCVA was 7.26%, PVA was 3.82%, BCVA was 1.67%, and blindness was 0.17%. Refractive errors were the most common cause of VI in the subjects of selected articles.

Authors found the global prevalence of blindness was 0.15% for criteria worse than 20/200 in the better eye and 0.17% for criteria worse than 20/400 in the better eye. Authors observed the highest rate of VI, based on uncorrected visual acuity (UCVA) of 20/40 or worse in the better eye, was 20.10% in the Pacific Region. The highest prevalence of VI, based on presenting visual acuity (PVA) of 20/40 or worse in the better eye, was 10.87% in the Pacific Region. The highest prevalence of VI, based on best corrected visual acuity (BCVA) of 20/40, was 0.91% in the Pacific Region. The highest rates of blindness were found in the African Region (1.91%) and the Eastern Mediterranean Region (1.94%).

Authors note that estimate of global prevalence is needed in order to inform global strategies.

Methodology:

All population-based cross-sectional studies concerning the prevalence of VI and blindness in individuals under 20 years of age were reviewed, regardless of publication and language, gender, region of residence and race. Of studies conducted on the same population, the one with a higher quality was included in this review. Authors included studies that were performed in all age groups and used the prevalence rates reported for the under-20-year age groups. The outcome of interest was the prevalence of VI and blindness and the causes of VI in the population.

VI was reported based on presenting visual acuity (PVA), uncorrected visual acuity (UCVA), and best corrected visual acuity (BCVA) of equal to 20/60 or worse in the better eye. Blindness was reported as visual acuity worse than 20/400 in the better eye.

A structured search strategy was applied to search electronic databases including PubMed, Scopus, and Web of Science, as well as the list of references in the selected articles.

Two researchers independently selected and assessed articles using the STROBE checklist, with an agreement index of 80.2%. Discrepancies were resolved through discussion or third-party consultation. Data extraction was based on predefined variables, including author name, publication year, study location, participant demographics, sample size, and prevalence of visual impairment (VI) and blindness. Studies were categorized into low, moderate, or high risk of bias based on reporting completeness. The k square test and I2 test were used to examine article inconsistency and result heterogeneity, respectively. Publication bias was not assessed due to the nature of prevalence data. Data analysis was performed using Stata Software version 11 with a random effects model.

Applicability/external validity: Not relevant

Geographic focus: The study sought to establish a worldwide estimate but does draw attention to some differences between low- and middle-income countries and others.

Summary of quality assessment:

While the review used thorough methods to select and critically appraise the selected studies, there was insufficient search of the literature – with no unpublished studies being included or evidence of contact with relevant experts. The methods to analyse the findings were generally thorough and robust; however, minimal consideration was given to the issue of combining studies from a wide range of different settings or the impact this might have on the reported results. For these reasons, we attributed low confidence in the findings of this review.

 

Publication Source:

Yekta A, Hooshmand E, Saatchi M, Ostadimoghaddam H, Asharlous A, Taheri A, Khabazkhoob M. Global Prevalence and Causes of Visual Impairment and Blindness in Children: A Systematic Review and Meta-Analysis. J Curr Ophthalmol. 2022 Apr 16;34(1):1-15. doi: 10.4103/joco.joco_135_21. PMID: 35620376; PMCID: PMC9128433.

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