Prevalence and Risk Factors for Myopia in Primary School Children in Madrid: A School-Based Cycloplegic Refraction Study

Abstract

Objective: We assess the prevalence of myopia and its associated factors among schoolchildren in Madrid, Spain, where school-based data using cycloplegic refraction are currently scarce. Methods: A cross-sectional study was conducted in 39 randomly selected schools in Madrid, targeting children in the second (6–7 years) and sixth grades (11–12 years). Parents completed questionnaires detailing family ocular history, the child’s lifestyle, and screen time. Socio-economic status was inferred from the Human Development Index of school districts. Children were examined using a two-stage approach: initial screening with visual acuity testing and Plusoptix photorefraction (myopia screening cut-off ≤ 0.00 D spherical equivalent), followed by confirmatory cycloplegic autorefraction (three drops of cyclopentolate 1% administered at 10 min intervals), with myopia defined as spherical equivalent ≤ −0.50 D. Statistical analyses included chi-square tests and logistic regression models to evaluate associated factors. Results: Of 3680 children invited, 2489 (67.6%) were examined. Myopia prevalence was 6.5% in second grade and 18.7% in sixth grade. Family history of myopia was a significant risk factor (OR 2.04; 95% CI: 1.53–2.70; p < 0.001 for both parents). Outdoor activity during weekends was associated with lower myopia prevalence (OR 0.50; 95% CI: 0.37–0.66; p < 0.01 for 2–6 h). Screen time was not a significant factor in multivariate analysis. Conclusions: This large school-based study using cycloplegic refraction provides more accurate prevalence data for Spanish schoolchildren. It confirms family history as a major risk factor and highlights the association of outdoor activities with lower prevalence of myopia. These results underline the need for preventive measures and suggest areas for future interventional research.