Prevalence of refractive error in Portugal – A systematic review and meta-analysis

PURPOSE: The aim of this study was to systematically review and meta-analyse epidemiological data of refractive error prevalence in Portugal. METHODS: A structured search strategy and systematic literature review was applied to multiple databases, such as MEDLINE/PubMed, Web of Science, Scopus, Google Scholar, official organizations and academic repositorium's, to identify all relevant epidemiological studies in Portugal until February 2021. The outcome measure was the prevalence of refractive error among the Portuguese population. The events and sample size were entered as raw data and the effect size parameters were computed by Comprehensive Meta-Analysis Software. RESULTS: A total of 9 studies were pooled for the meta-analysis. The fixed effects model points to an estimated effect size of 43% (95% CI: 41.9–44.1%). However, the statistics of heterogeneity (Q-value p < 0.001; I-squared =99.344) showed very high heterogeneity among studies and recommends using a random-effects model. The random effects model points to an estimated effect size of 31.9% (95% CI: 19.8–47.0%) prevalence of refractive error in the Portuguese population. CONCLUSIONS: A prevalence of refractive error in Portugal of 31.9% (95% CI: 20.0–47.0%) can be considered as a conservative approach to the real burden of this condition. However, it translates into at least 2 to 4.5 million Portuguese individuals with a refractive error. The high heterogeneity between studies, the wide estimate and the random effects involved demonstrate the need for more studies and consistent sources to obtain narrower estimates.