If you are severely short-sighted (with an eye prescription of -6D or more) you might wonder if your children are likely to inherit the condition. Is high myopia hereditary, and what are the chances of passing it on?
Now, thanks to a number of research studies on the genetics of myopia, we have a better understanding of how and why it develops.
In a healthy eye, light enters the lens of the eye and is refracted (bent) onto the retina to form an accurate, sharp image that the brain can decode. In short-sighted people, the refraction doesn’t work properly; the light is bent so that it focuses in front of the retina, creating a blurry image. This happens if the eye is the wrong shape – the eye may be too long, or the cornea might curve at the wrong angle.
A study from 2013, published in Nature Genetics, identified 24 genes that make myopia more likely. These genes are responsible for a range of different functions, including eye development, and can be inherited, explaining why myopia often seems to run in families.
Since then, researchers have gone on to identify additional genetic factors that play a part in the development of myopia and high myopia. Earlier this year, the International Consortium for Refractive Error and Myopia (CREAM) described 161 genetic risk factors linked to myopia.
But developing myopia isn’t purely a case of genetic inheritance. Our living environments play a part in determining whether the genes we carry will actually be triggered. The more we understand about these environmental factors, the more we can do to prevent myopia in future generations. There’s still a lot of work to be done in this area, but there are some factors that do seem to be linked to elongated eyeballs, which can lead to myopia.
Scientists have found that time spent indoors, doing close-up work such as reading, is linked to a higher risk of short-sightedness. That explains the popular stereotype of bookish types and their bottle-top specs, although researchers are as yet unsure whether it’s the lack of daylight or the close-up work that is more of a factor. In any case, this is a risk factor that can be minimised in early childhood: “Send your kids to play outside for two hours every day,” advises Professor Norbert Pfeiffer, co-author of the CREAM study.
Ultimately, myopia seems to develop due to a complex mix of genetic and environmental factors, but if it’s written in your genes, it may be impossible to avoid. Luckily, there are a range of treatment options available.
If your myopia has left you resigned to a life of wearing glasses or contacts, there may be hope. In previous years, people with high myopia were often told that laser eye correction was not an option for them because of thin corneas. Due to advances in laser technology, that no longer has to be the case, and laser eye surgery can usually be carried out on patients with a prescription of up to -10D.