Incidence and Risk Factors of Refractive Error in Children in Spain: CISViT Project.

Background: The incidence of refractive errors (RE), particularly myopia, has increased in recent years, presenting significant geographic variations. This prospective longitudinal cohort study aims to assess the incidence of RE in school-aged children in Spain and identify associated risk factors. Methods: The study followed 1,189 children with a one-year interval (mean age: 8.74 years at initial visit and 10.00 years at follow-up) in northeast Spain (2021–2024). RE was measured using an autorefractometer and retinoscopy without cycloplegia. A preliminary questionnaire collected data on risk factors such as visual habits and socioeconomic status. Results: The spherical equivalent (SE) at the initial visit was +0.29 ± 0.03D, decreasing to +0.14 ± 0.04D at follow-up. The prevalence of myopia increased from 12.3% at baseline to 17.1% at follow-up. Fifty-six incident cases were identified, corresponding to a cumulative incidence of 4.8%. Myopic progression, defined as a change in SE greater than −0.50 diopters, was observed in 24.6% of children; among them, 10.0% exhibited mild progression, 10.6% moderate, and 4.0% severe. Factors associated with myopia progression included paternal unemployment (OR = 1.479, p = 0.005), maternal unemployment (OR = 2.260, p = 0.015), low outdoor exposure (OR = 1.964, p < 0.001), and older age (OR = 1.256, p < 0.001). Conclusions : The incidence and progression of myopia in Spanish schoolchildren increased noticeably over one year. Older age, reduced outdoor time, and both paternal and maternal unemployment were associated with higher risk of myopic progression.