Prevalence and risk factors of premyopia in preschoolers: a kindergarten-based cluster sampling study

Identifying the prevalence and risk factors of premyopia in preschoolers is crucial for early intervention. This knowledge provides a basis for developing public health policies to address the rising trend of myopia and protect children's eye health. The aim of this study is to evaluate the prevalence of premyopia and identify genetic and other risk factors among children aged 3-6 years. A cluster-randomised sampling study was conducted between December 2020 and February 2021, involving 2,109 children from 23 kindergartens in Haidian disctict, Beijing, China. Cycloplegic refraction was assessed using 1% cyclopentolate. Premyopia was defined as a spherical equivalent refraction (SER) of > -0.50 D and ≤+0.75 D in the eye with the less SER value. Myopia was defined as an SER of ≤-0.50 D, while hyperopia was characterised as an SER of >+0.75 D. Parents were asked to complete a questionnaire regarding refractive status, categorised as: no myopia ( > -0.5 D), low/moderate myopia (≤-0.5 D to ≥-6 D), and high myopia ( < -6 D). The prevalence of myopia, premyopia, and hyperopia among the children was 4.60%, 24.32%, and 71.08%, respectively. Boys exhibited higher prevalence rates for premyopia (28.03%; 95% CI, 25.45%-30.75%) and myopia (5.64%; 95% CI, 4.43%-7.17%) compared to girls (premyopia: 20.30%; 95% CI, 17.93%-22.89%, myopia: 3.47%; 95% CI, 2.50%-4.78%; both p < 0.001). Significant risk factors for premyopia included male gender (adjusted OR, 1.62; 95% CI, 1.32-2.00), paternal low/moderate myopia (adjusted OR, 1.50; 95% CI, 1.18-1.92), paternal high myopia (adjusted OR, 1.99; 95% CI, 1.41-2.81), and maternal high myopia (adjusted OR, 1.89; 95% CI, 1.35-2.64). Prevention and control of premyopia in preschool children should be emphasised, particularly for boys and children with myopic parents, due to their higher risk of developing premyopia.