The Incidence of Myopia

What is myopia?

In order to understand how prevalent myopia is, it is first pertinent to understand how myopia itself is defined. In essence, myopia is diagnosed by the presence of a spherical refractive error in the eyes. What this entails is that as the eye is growing, it grows too long in its front-to-back (horizontal) dimensions. 

So what if my eye has a larger horizontal dimension?

When the eye lengthens horizontally, the distance between the cornea and retina elongates. This greater distance between the two simply means that when light enters the eyes, instead of focusing on the retina, the light rays are focused in front of it. This in turn results in objects at a distance appearing out of focus. 

Is myopia very common?

To begin to grasp how wide spread myopia is, studies that have been done on a global scale need to be comparable in terms of the factors measured as well as their sample sizes. This can prove to be highly complex. This complexity arises as there is no gold standard in conducting such studies and therefore methodologies can greatly differ. 

Having said that, a number of studies have been conducted on various ethnic groups around the world and the results seem to indicate that certain regions report a higher occurrence of myopia. In fact, studies done on American children showed that across each ethnicity presented, only less than 10% were myopic. Whereas, studies conducted in Asia showed that in some regions (Singapore), as many as 36.7% of children between the ages of 7-9 presented with myopia. 

Global vs local

While myopia occurs globally, when considering the prevalence of it in different ethnic groups, studies have shown that statistically it is more common amongst East Asian populations and more specifically, Singaporeans. While studies do show that East Asian children do present with myopia more frequently than other ethnicities, there is no explanation for its etiology. 

Singaporeans present with the highest incidence of myopia worldwide. Local data findings show that in the similar age bracket, about 65% of Singaporean children are myopic compared to only 12% Australian and 29% British children.

Furthermore, studies have shown that children raised in urban areas are more likely to be myopic than their rurally raised counterparts. In fact, the trends studied seem to indicate that there is a correlation between the incidence of myopia and higher levels of education as well as higher levels of income.