24 Genes Responsible For Short-Sightedness Identified

The vision of a person with Myopia - everything looks blurred.

Researchers from King's College London have identified 24 new genes that are responsible for causing myopia, a very common eye disorder also known as short-sightedness.

The finding, published in Nature Genetics, finally reveals the genetic causes of the condition; this is very promising and could finally be the basis for future treatment of the disorder.

There is currently no cure for myopia, a condition which affects 30 percent of Westerners and up to 80 percent of Asians. Researchers from the Australian National University in Canberra reported in The Lancet that approximately 80% to 90% of 18-year-olds (school-leavers) in China, Taiwan, Japan, Singapore, Hong Kong and South Korea suffer from myopia.

Myopia occurs when light does not properly focus on the retina of the eye, a refractive error resulting in blurred vision.

Myopia begins to develop in childhood and adolescence when the eye grows too much in length, causing light to focus in front of the retina rather than directly on it. The only way that sight can be corrected is with glasses, contacts or undergoing surgery. In high degrees of myopia the retina becomes so thin it can lead to a series of health complications, such as glaucoma, macular degeneration or retinal detachment.

Myopia is heritable, however, little was known about the genetics behind it until now.

The researchers, who all belonged to the Consortium for Refraction and Myopia (CREAM), collected data from over 45,000 people across 32 different studies. They analyzed their genetic and refractive error data to identify any genes responsible for the disorder.

Genetic factors identified

They identified a total of 24 new genes linked to myopia and confirmed two previously reported genes. The genes they found were responsible for eye development, eye tissue signaling and the structure of the eye. They were associated with a high risk of myopia, potentially increasing a person's risk tenfold.

A combination of genetic predisposition and environmental factors significantly increases the likelihood of developing myopia. Environmental factors include reading, limited outdoor exposure, a higher level of education, and living in urban areas. However, how these factors actually cause the disorder remains a mystery. Further investigation by the consortium is necessary to fully understand these links.

Lead author of the paper, Professor Chris Hammond, from the Department of Twin Research and Genetic Epidemiology at King's College London, said:

"We already knew that myopia, or short-sightedness, tends to run in families, but until now we knew little about the genetic causes. This study reveals for the first time a group of new genes that are associated with myopia and that carriers of some of these genes have a 10-fold increased risk of developing the condition."

He added:

"Currently myopia is corrected with glasses or contact lenses, but now we understand more about the genetic triggers for the condition we can begin to explore other ways to correct it or prevent progression. It is an extremely exciting step forward which could potentially lead to better treatments or prevention in the future for millions around the world."

There aren't many treatment options to reduce the progression of myopia at the moment, the only drug developed so far, called atropine, has been reported to dilate the pupils and cause light sensitivity.

The findings from this study will hopefully help pave the way for future treatment options.