Design and Baseline Data of the Guangzhou Child and Adolescent High Myopia Study

Purpose To establish a longitudinal, school-based cohort to investigate physiological and pathological ocular changes and identify associated risk factors in children and adolescents with high myopia in South China.Methods This three-year cohort recruits students aged 6–18 years from 1,438 schools in Guangzhou, China (April 2018-August 2024). Eligible participants have a cycloplegic spherical equivalent (SE) ≤−3.00 D (ages 6–8) or ≤−6.00 D (ages 9–18). Annual follow-up includes demographic, behavioural, and familial questionnaires and comprehensive ophthalmic assessments, including visual acuity, ocular biometry, cycloplegic refraction, fundus photography, and optical coherence tomography/angiography. The study adheres to the Declaration of Helsinki and was approved by the Ethics Committee of Zhongshan Ophthalmic Centre (approval number: 2017KYPJ100). Written informed consent is obtained from all participants and their guardians. Generalized estimating equations and mixed-effect models assess ocular changes and associations with environmental and biometric factors.Results 1,331 participants were enrolled at baseline (mean SE= −7.34 ± 2.38 D; axial length = 26.21 ± 1.30 mm). Older age was associated with more myopic SE (β= −0.26, p < 0.001) and longer axial length (β = 0.18, p < 0.001). Males had longer axial length (β = 0.42, p < 0.001), and higher corneal power was linked to shorter axial length (β= −0.29, p < 0.001). Behavioural factors showed no significant associations with SE or axial length.Conclusions These baseline preliminary analyses show that demographic factors and corneal power, rather than behavioural factors, are significantly associate with ocular dimensions in early-onset high myopia. This longitudinal cohort provides a vital platform to track ocular growth, early pathological changes, and progression risk factors.