The prevalence of myopia and high myopia, typically defined as −6.00 D or worse, are both increasing, particularly in east Asia.
1 A 2021 International Myopia Institute (IMI) report on the impact of myopia,
2 noted that “the rate of change in prevalence of high myopia appears to be disproportionately greater compared with the rate of change in the prevalence of myopia” in East Asian and Asia-Pacific countries. For example, over a 15-year period, the prevalence of myopia among high school students in Fenghua City in mainland China, increased from 79.5% to 87.7% while the prevalence of high myopia more than doubled from 8.0% to 17.5%.
3 Similarly, in Taiwan, the prevalence of myopia among first year university students increased from 91.3% to 95.9% over 18 years, but the prevalence of high myopia grew from 23.5% to 38.4%.
4 The IMI authors
2 hypothesize that a number of factors may be responsible for this disproportionate increase in the prevalence of high myopia, including children developing myopia at earlier ages than before,
5 faster myopia progression in Asian children compared with other races,
6,7 and a faster rate of myopia progression in younger compared with older children.
8,9
Assessment of distributions by prevalence values presents statistical challenges. A preferred approach is to use the logit function, that is the log of the odds, because of its amenability to statistical analysis. Prevalence values are bound at both ends (0% to 100%), odds are bound at the lower end (0 to infinity), where the logit is symmetrical around 0 and continuous from –infinity to +infinity. Here, we apply this approach and examine a sample of studies containing prevalence data to draw inferences on the origin of the putative disproportionate increase in the prevalence of high myopia.