Analysis of ocular biometry in 4- to 9- year-old emmetropic children

This study aimed to determine the average axial length in emmetropic Korean children between four and nine years old and to identify the factors that influence axial length in this age group. The retrospective multicenter study enrolled children whose cycloplegic refraction results showed spherical equivalent values ranging from − 0.75 to + 1.00 diopters. Axial length measurements were carried out using the IOLMaster 700 (Zeiss, Germany), and refractive errors were assessed with the KR-8900 autorefractor (Topcon, Japan) after cycloplegia. The study excluded children with astigmatism of 1.5 diopters or greater, a history of intraocular surgeries such as cataract or retinal procedures, and those who had received or were receiving myopia control treatments. Three hundred ninety six eyes were analyzed. Axial length increased from 22.55 ± 0.53 mm at age 4 to 23.63 ± 0.86 mm at age 9 in boys, and from 22.01 ± 0.49 mm at age 4 to 23.03 ± 0.79 mm at age 9 in girls. Each year, axial length increased by approximately 0.06 to 0.32 mm. A positive correlation between axial length and age was demonstrated, with a correlation coefficient (r) of 0.52 and a p-value of 0.01, indicating that axial length tends to increase as children grow older. Conversely, axial length showed a negative correlation with corneal curvature (r = -0.27, p = 0.03), suggesting that eyes with longer axial lengths have flatter corneas. This study established age- and sex-specific normative axial length values in emmetropic Korean children. It found that boys tended to have longer axial lengths than girls within the same age group, and axial length increased with age. Among children with longer axial lengths, the corneal curvature tended to be flatter, which appears to compensate for potential refractive errors. These results provide a reference framework for pediatric ocular growth and may support future comparative studies aimed at understanding degree of myopia in children.