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

Clinical relevance: 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.

Background: 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.

Methods: 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).

Results: 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).

Conclusions: 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.