Global Prevalence and Causes of Visual Impairment and Blindness in the Under-20-Year Population: A Systematic Review and Meta-Analysis

Purpose: Given the various studies conducted around the world and different estimations of the Prevalence and causes of visual impairment and blindness, the present study was conducted to determine the global prevalence and common causes of visual impairment and blindness.Methods: In this meta-analysis, 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 to identify all population-based cross-sectional studies that concerned the prevalence of visual impairment and blindness in populations under 20 years of age up to January 2018, regardless of the publication date and language, gender, region of residence, or race. The outcomes reviewed in this study were the prevalence of visual impairment based on uncorrected visual acuity (UCVA), presenting visual acuity (PVA), best corrected visual acuity (BCVA), and blindness with their 95% confidence intervals (CI), and the prevalence of the causes of visual impairment. The results of the studies were combined using a random effects model at a confidence level of 95%. The chi-square test at a 5% confidence level was used to examine the heterogeneity among studies and the I-square test according to the Higgins classification was used to quantitatively assess heterogeneity among results. Based on this classification, an I-square value more than 75% was considered as heterogeneity. Data analysis was performed using Stata statistical software version 11. Results: In the present study, 5711 articles were identified, and the final analyses were done with eighty articles including 769,720 people from twenty-eight different countries. Regardless of different diagnostic criteria, the overall prevalence of visual impairment based on UCVA was 11.05% (95% CI: 8.42% - 13.68%), PVA was 5.34% (95 CI: 4.63% - 6.05%), BCVA was 0.89% (95% CI: 0.76% 1.02%), and blindness was 0.16% (95% CI: 0.13% - 0.20%). Refractive errors were the most common cause of visual impairment in the subjects of selected articles: 77.20% (95% CI: 73.40% - 81.00%). The prevalence of amblyopia was 7.60% (95% CI: 05.60% - 09.10%) and congenital cataract was 0.60% (95% CI: 0.3% -0.9%. Cataract was the most common cause of blindness among available reports. Conclusion: Despite differences in the definition of visual impairment and blindness, based on PVA, 5% percent, and based on BCVA, 1% percent of the over 769,000 examined sample suffer from visual impairment. We also showed that cataract, as the most common cause of blindness in available studies, requires more attention from health policy makers in developing countries to expand surgical services to meet the needs for surgical intervention through increased training as well as patient financing in order to achieve the goals of the VISION 2020 Initiative for the prevention of avoidable blindness. Funding: None Declaration of Interest: No conflicting relationship exists for any author.