Investigating possible causes of myopia in schoolchildren aged 3-14 years in Tokyo

Researchers have suggested numerous theories about the etiology of myopia that include accommodative-lag, peripheral hyperopic defocus, light environment, lifestyle, and environment, but the cause remains unknown.

Japanese investigators led by Tomoki Maruyama, MD, and colleagues found that about half of preschoolers in Tokyo are myopic, indicating the epidemic proportions the disease has reached. The investigators also reported that the association between lens thickness and near work may vary with the type of near work performed.

Maruyama is from the Department of Ophthalmology, and the Laboratory of Photobiology, Keio University School of Medicine, Tokyo.

Researchers have suggested numerous theories about the etiology of myopia that include accommodative-lag, peripheral hyperopic defocus, light environment, lifestyle, and environment, but the cause remains unknown.

The current large cross-sectional study,1 which included 2,140 children ranging in age from 3 to 14 years in Tokyo, looked at the distributions of ocular biometry and refraction among Japanese children across a wide age range and evaluated the associations between refraction and environmental factors including near work and ocular biometry under non-cycloplegic natural conditions, Maruyama described.

Myopia study results

The investigators reported that the prevalence rates of spherical equivalent (SE) of −0.75 diopter or less among preschoolers aged 3–6 years, elementary school students aged 6–11 years, and junior high school students aged 12–14 years were 49.7%, 72.4%, and 87.7%, respectively.

Linear regression analyses showed that the time spent using digital devices was associated positively with the lens thickness (P < 0.050) but not the SE, axial length, or vitreous chamber depth.

The time spent reading was associated negatively with the lens thickness (P < 0.050), SE (P < 0.010), axial length (P < 0.001), and vitreous chamber depth (P < 0.001).

The authors commented, “To our knowledge, this is the first large-scale study to describe sex- and age-specific various comprehensive ocular component data and refraction in a wide age range of Japanese schoolchildren and analyze their associations with environmental factors. We found that the prevalence of myopia among preschoolers was almost half. The effect of the lens thickness differed depending on the type of near work and may be a clue to investigating the relationship between near work and myopia.”

Reference
1. Maruyama T, Yotsukura E, Torii H, et al. Children in Tokyo have a long sustained axial length from age 3 years: the Tokyo Myopia Study. J Clin Med. 2022; 11: 4413; https://doi.org/10.3390/jcm11154413