No association was found between BMI and ocular biometrics and refraction in this study. Photo: Getty Images. Click image to enlarge.

With myopia on the rise, researchers and clinicians are searching for factors to help reveal the potential mechanism of incidence. Postnatal eye growth involves proportional changes to ocular biometric parameters like axial length (AL), anterior chamber depth, lens thickness and more to bring the eye to emmetropization, but when this highly coordinated process is disturbed, it gives rise to refractive error. As such, Chinese researchers recently investigated the association of ocular biometrics and body stature in a preschool population, since it’s believed a shared mechanism exists—accounting for simultaneous eye and body growth.

Throughout the city of Shenzhen, 373 preschool children aged three to six were randomly selected from 10 kindergartens. Their ocular biometric parameters of AL, anterior chamber depth, vitreous chamber depth, corneal radius curvature (CR), axial length to corneal radius ratio (AL-to-CR ratio) and lens thickness were all measured. Cycloplegic refractions were also obtained. Body height and weight were measured and the association between body stature and ocular biometrics was analyzed.

The parameters of AL, anterior chamber depth, vitreous chamber depth, CR and AL-to-CR ratio were all positively associated with height and weight; lens thickness was the only parameter to be negatively associated with height and weight. There was no observed association of stature with central corneal thickness or refraction. After adjusting for age and sex, AL displayed positive association with height and weight, but refraction had no significant association with stature parameters.

Put more simply, taller and heavier preschoolers were found to have eyes with greater AL, deeper vitreous chamber and flatter corneas. As the authors posit in their journal article on the work, “the significant associations between body stature and ocular biometric parameters reveal the driving influence of body development on the growth of eyeballs in preschoolers.”

They also add that “the current study enrolled preschool children who were free from education pressure and mostly emmetropia, which enables us to investigate the direct relationship between body stature and ocular biometrics during emmetropization.”

Upon discussion, the authors elaborate that most juvenile myopia occurs due to AL elongation, which is considered the most crucial determinant of myopia incidence. In this study, every 10cm increase in height resulted in a 0.20mm difference of AL elongation, which is less than other rates found in previous studies.

However, these results do reflect other aspects of prior research, like one birth cohort study that reported taller and heavier neonates had longer AL at six years old. Another found that taller kids at birth as well as at 12, 24 and 36 months had longer AL at three years old.

Also similar to previous studies was the observation that taller and heavier children have deeper vitreous chambers and flatter corneas. The authors suspect other than elongation, this may be due to other ocular biometrics growth being concurrent with and driven by physical development.

This all reflects one of the main results of the study: “The growth of eyeballs in preschoolers may be driven by physical development.”