Why are 80% of kids in Singapore nearsighted? Perhaps it’s a nature-deficit disorder. 

Singapore has one of the highest rates of nearsightedness or myopia in the world, and parts of China and Taiwan are not far behind.

Most people assume it’s just genetics. 

And there’s certainly a lot of evidence suggesting a genetic link. In Australia, for example, if both parents have myopia, a child is eight times as likely to have it as well, and if both parents have severe myopia (at least -6 diopter), a child is 22 times as likely (Ip et al. 2007).

People of Chinese origins are particularly prone to myopia (Pan et al. 2012).

But here’s the Singapore twist. The city-state is a melting pot of Chinese, Indian and Malay ethnicities. Yet Singapore has a far higher myopia prevalence rate than India or Malaysia and a slightly higher rate than China.

Genetics almost certainly plays a role in myopia, but families generally share not only genes but also environments.

While our genetic DNA in “pen” and cannot be changed, some of our genes are written in “pencil” and can be rewritten by environmental factors.

Worldwide, there’s an urban-rural divide in myopia rates. In Nepal, for example, urban children age 15 have a 27% prevalence rate while it is less than 3% for rural children the same age (Pan et al. 2012).

So what’s different for many urban kids?