Associations between refraction and ocular biometry in Chinese preschoolers aged 3–6 years: a cross-sectional study in Shunyi, Beijing

Abstract

Objective To estimate the associations between refraction and ocular biometry of preschool children (3–6 years old) in Shunyi District, Beijing.Design Cross-sectional study.Setting This study was conducted in 11 kindergartens in Shunyi District, Beijing.Participants A total of 1186 Chinese children aged 3–6 years old without any history of Down’s syndrome, epilepsy, history of ophthalmologic surgery and other psychiatric disorders were selected. Exclusions: Children who were unable to cooperate with the examination. 1141 preschoolers completed the examination. 555 subjects (48.6%) were boys and 586 subjects (51.4%) were girls. Cycloplegic refraction, axial length (AL), anterior chamber depth (ACD) and corneal radius (CR) were measured for all children. AL-to-CR ratio, lens power (LP) and spherical equivalent (SE) were calculated. Those children were divided according to SE into three groups: hyperopia group, premyopia group and myopia group.Interventions None.Primary and secondary outcome measures Refraction and ocular biometric parameters.Results The prevalence of myopia, premyopia and hyperopia was 2.7% (95% CI 1.8% to 3.7%), 27.3% (95% CI 24.7% to 29.8%) and 70.0% (95% CI 67.4% to 72.7%), respectively. The mean SE was (1.15±0.76) D, and the refraction in the premyopia group was about 1 D lower than in the hyperopic one. The mean AL, ACD, CR, AL/CR and LP were 22.28±0.67 mm, 3.33±0.67 mm, 7.74±0.25 mm, 2.88±0.06 and 25.62±1.46 D, respectively. Differences in AL, ACD, AL/CR and LP among different age groups were statistically significant. Premyopic children had longer eyes, greater ACDs and higher AL/CR ratio than hyperopic children. SE was negatively correlated with AL, ACD, AL/CR and LP.Conclusions The most common refractive status of children aged 3–6 years in Shunyi District, Beijing, was hyperopia. The prevalence of premyopia was by no means low. Understanding the refractive status of preschoolers and associations between ocular biometric parameters and refraction might be helpful in providing more effective prevention before the onset of myopia.