Epidemiology of Astigmatism in Japan: Analysis of More Than 9,000,000 Spectacle Prescriptions

The purpose of this study was to characterize the prevalence of astigmatism and stratify it by age, sex, and geographic region and evaluate interocular differences in cylinder power in a large-scale Japanese population using spectacle prescription data.

This retrospective cross-sectional study analyzed de-identified spectacle prescription data collected from a nationwide optical retail chain between September 2021 and August 2023. The targeted individuals were aged 6 to 89 years. They were categorized based on their cylinder power and axis orientation. Step 1 involved evaluating these parameters across different ages, sexes, and regions. Step 2 involved quantifying the interocular differences in the individuals with astigmatism (cylinder power of ≥0.25 diopter [D]) in at least one eye.

We analyzed 9,204,993 prescriptions (50.8% female subjects). The cylinder power increased progressively with age, and this was accompanied by a shift from with-the-rule (WTR) to against-the-rule (ATR) orientation. Men had slightly higher cylinder powers and a higher prevalence of ATR astigmatism than women. The regional variation across Japan was modest. Interocular comparison revealed that 81.6% and 9.4% of the individuals had differences in cylinder power of ≤0.50 D and ≥1.00 D, respectively. These findings indicate substantial bilateral symmetry in most individuals.

This nationwide analysis of spectacle prescription data provides an updated epidemiologic overview of astigmatism in Japan. We characterized the age-, sex-, and region-related variations in cylinder power and axis orientation and quantified the interocular asymmetry at the population level. These findings highlight the value of large-scale prescription databases as a novel resource for population-based vision research.