The relation between birth size and the results of refractive error and biometry measurements in children

Aim: To examine the association of birth parameters with biometry and refraction in Singapore Chinese schoolchildren. Methods: Chinese children aged 7 - 9 years ( n = 1413) from three schools in Singapore were recruited. Birth parameter information on birth weight, head circumference, length at birth, and gestational age were obtained from standard hospital records. Cycloplegic autorefraction, keratometry and biometry measures ( axial length, vitreous chamber depth, lens thickness, and anterior chamber depth) were obtained. Results: Across the normal birthweight range (2.0 - 4.9 kg), children with birth weights greater than or equal to 4.0 kg had longer axial lengths ( adjusted mean 23.65 mm versus 23.16 mm), compared with children with birth weights <2.5 kg, after controlling for age, sex, school, height, parental myopia, and gestational age. For every 1 cm increment in head circumference at birth, the axial length was longer by 0.05 mm. For every 1 cm increment in birth length, the axial length was longer by 0.02 mm in multivariate analysis. Additional week increases in gestational age till 46 weeks resulted in axial lengths that were longer by 0.04 mm, controlling for age, sex, school, parental myopia, and height. Children with larger birth weights, head circumferences, birth lengths, or gestational ages had deeper vitreous chambers and larger corneal curvature radii; however, there were no significant associations with refraction. Conclusions: Children who were born heavier, had larger head sizes or lengths at birth, or who were born more mature had longer axial lengths, and deeper vitreous chambers; but there were no differences in refraction at ages 7 - 9 years, possibly because of the observed compensatory flattening of the cornea.