Spherical Equivalent Percentile Curves in a Portuguese School-Aged Population

Abstract

Bacground/Objectives: This study aimed to develop age- and sex-specific spherical equivalent (SE) percentile curves and estimate the prevalence of refractive errors (REs) in Portuguese schoolchildren aged 6–17 years. Methods: A cross-sectional study was conducted in three schools in Lisbon, including 2205 children (mean age = 9.3 ± 2.6 years; 49.3% boys). Vision was assessed using non-cycloplegic static retinoscopy (chosen due to feasibility in school settings) and visual acuity tests. SE percentile curves (P5–P95) were generated by age and sex. SE values and RE distribution (hyperopia, emmetropia, and myopia) were compared across four age groups (6–8, 9–11, 12–14, and 15–17 years). Results: SE values decreased significantly with age (p < 0.001). Median SE ranged from +0.50 D (6–8 years) to 0.00 D (15–17 years), with no sex differences. Hyperopia predominated in younger children (60.6% at 6–8 years), whereas myopia increased in older ages (32.2% at 15–17 years). Conclusions: This study presents the first SE percentile curves for Portuguese schoolchildren, providing a practical, age-specific reference for vision screening. The progressive shift from hyperopia to myopia highlights the importance of early detection and monitoring to prevent visual impairment.