Ocular and vision development during childhood: Insights from a large prospective cohort study in Chinese children

Purpose: To document age-related ocular and visual acuity (VA) development during childhood. Methods: The Zengcheng schOOl Myopia Study is a prospective cohort study which recruited four cohorts of children from Guangzhou, China in 2018: first-year kindergarten (N = 1366, 48.32% girls, mean age: 3.68 [0.35] years, range: 2.51–4.50 years), first-year primary school (N = 1461, 44.15% girls, mean age: 6.80 [0.35] years, range: 6.00–7.75 years), fourth-year primary school (N = 2333, 45.86% girls, mean age: 9.55 [0.41] years, range: 8.50–10.84 years) and first-year junior high school (N = 1193, 45.43% girls, mean age: 12.60 [0.40] years, range: 11.15–13.57 years). Cycloplegic autorefraction (KR8800), ocular biometry (IOLMaster 700) and VA (ETDRS chart) measurements were conducted at baseline and annually afterwards. Results: From 2018 to 2023, 4016 children (mean age: 7.51 [2.73] years, 41.81% girls) remained non-myopic and were included in the analysis. Both uncorrected and best-corrected VA improved rapidly and typically achieved adult level (nearly 20/20) around age 7, with minimal difference in-between. Best-corrected VA of 20/20 was attainable as early as age 4 across a spherical equivalent (SE) range of −0.375 to 4.825 D, indicating VA development largely independent of SE changes. Mean SE showed a gradual myopic shift, from 1.375 D in 3-year-olds to 0.375 D in the 15-year-olds, with notable inflection points at ages 7 (around 1.25 D) and 11 (around 0.75 D). Lens power consistently decreased. Axial length (AL) increased steadily with marked deceleration around age 11. AL increases were significantly associated with height increases (p < 0.001) before age 11 but not afterwards. Conclusion: We observed asynchronous development of VA, SE and ocular biometrics. Best-corrected VA develops mainly due to maturation of retinal circuits, even under conditions that lead to marked changes in the development of refractive errors.