The higher prevalence of myopia in children and young adults in Singapore, Taiwan, and Hong Kong,37,63,64
in comparison with children in western countries such as Australia,65
is well established.
Population based data in adult Asian populations suggest a more complex picture (table 3). The Tanjong Pagar Survey first suggested that the prevalence of myopia (more than −0.5 dioptres spherical equivalent) in Chinese adults 40 years and older was nearly twice the rates in similarly aged white populations,12
including the Baltimore Eye Study,66
and the Melbourne Visual Impairment Project.67
However, more recent studies in Taiwan,8
indicate that the rates of myopia in other Asian adult populations are not much higher than rates in white adult populations.3
The reasons for the higher prevalence of myopia in Singapore compared to other Asian countries are unclear, but do suggest that the concept of a myopia “epidemic” should not be generalised to all of Asia.
Table 3Prevalence of refractive errors in Asia, major population based studies
While the overall rates of myopia may vary between Asian populations, the majority of these studies demonstrate a clear trend of declining prevalence of myopia with age, with younger participants generally having higher myopia rates than older participants.8,12,19,22,32
The Tanjong Pagar Survey showed that the difference in myopia rates between younger and older people was largely explained by longer axial lengths in younger people.13
This contrasts with a study in rural Mongolia that reported a low myopia prevalence and no variation in axial lengths between younger and older participants.70
These observations suggest that the higher myopia prevalence in younger Singaporeans are probably attributable to differences in ocular dimension between birth cohorts, related possibly to improved nutrition, higher education, and an intense near work environment.37
Perhaps more important than overall prevalence, there have been suggestions that a significant proportion of Asian adults have high myopia, and may therefore be at risk of potentially blinding conditions such as myopic degeneration.37
While the prevalence of high myopia (less than −5.0 dioptres) is less than 2% in most Western studies,66,67
it was reported to be nearly 10% in the Tanjong Pagar Survey.12
Again, this pattern is not universal to other Asian populations. Recent data from the Beijing Eye Study indicate a high myopia (less than −5.0 dioptres) prevalence of only 3.3%,19
and in rural populations such as in Sumatra, Indonesia, the prevalence of high myopia (less than −6.0 dioptres) was even lower (0.6%).32
Risk factors for myopia in adults have been reported in most studies, and include higher education, urban versus rural residential status, and various socioeconomic indicators (for example, higher income, professional occupation).8,12,19,22,32,71
Many of these risk factors may be proxies for an intense “near work” visual environment, which has been investigated extensively in Asian schoolchildren.37
There are substantial amounts of data on the epidemiology of other refractive errors, such as hyperopia and astigmatism (table 3). Because refractive errors other than myopia have also been linked with potential ocular morbidity,72
eye care efforts should not solely focus on the potential impact of myopia.