Distribution and Time Trends of Refractive Errors in Japanese Spectacle Wearers

Abstract

Purpose: This study aimed to estimate the distribution and temporal trends of refractive errors among spectacle wearers in Japan using a nationwide database of optical chain stores. Methods: Data from 4,525,689 individuals (53.0% women and 47.0% men; age range, 6-35 years) who purchased spectacles at 434 optical chain stores across Japan between 2021 and 2023 were analyzed. For individuals aged <15 years, prescriptions issued by ophthalmologists were used. The spherical equivalent (SE) was calculated, and its distribution was described according to age, sex, and geographic region. The annual progression rate of refractive error was estimated for individuals with multiple purchases. Linear mixed models and generalized additive mixed models were applied for the analyses. Results: The SE shifted in the myopic direction with advancing age and stabilized at approximately 30 years in men and 29 years in women (median SEs, -3.3 diopter [D] and -3.5 D, respectively). Hyperopia accounted for approximately 30% of cases at the age of 6 years but decreased significantly by the early teenage years. High myopia (SE ≤ -6 D) was observed in 1.3% of children aged <10 years. The most rapid myopic progression occurred at the age of 7 years (median, -1.1 D/year). Joinpoint analysis indicated that myopia progression decelerated between 9 and 19 years, with an additional inflection point at 12 years in women. Conclusions: Myopia progression becomes significant at the age of 6 to 7 years, highlighting the need for early surveillance and timely intervention to limit progression.