An international team of scientists has discovered 24 new genes that cause refractive errors and myopia (short-sightedness). Myopia is a major cause of blindness and visual impairment worldwide, and currently there is no cure. These findings, published in the journal Nature Genetics, reveal genetic causes of the trait, and may help in finding a solution.
Thirty per cent of Western populations and up to 80 per cent of Asians suffer from myopia (nearsightedness). During visual development in childhood and adolescence, the eye grows in length, but in myopes it grows too long, and light entering the eye is then focused in front of the retina rather than on it. This results in a blurred image. This refractive error can be corrected with glasses, contact lenses or surgery. However, the eye remains longer, the retina is thinner, and this may lead to retinal detachment, glaucoma or macular degeneration, especially with higher degrees of myopia. Researchers have known for decades that refractive errors tend to run in familes, however up until now, very little was known about the specific genes involved.
To find the genes responsible, researchers from the United States, Europe, Asia, and Australia collaborated as the Consortium for Refractive Error and Myopia (CREAM). They analyzed genetic and refractive error data of more than 45,000 people from 32 different studies. They confirmed two previously reported genes and identified 24 new genes for this trait. Remarkable was that the genes did not show significant differences between the Europeans and the Asians. The new genes include those which function in brain and eye tissue signalling, the structure of the eye, and eye development. The genes lead to a high risk of myopia: carriers of some of these genes had a tenfold increased risk of developing the condition.
“Identifying these genes is big a first step; nature and nurture interact in very complex ways to affect myopia,” said Robert Wojciechowski, PhD, an author of the study and assistant professor of epidemiology with the Johns Hopkins Bloomberg School of Public Health. “We currently don’t know exactly how these genes are involved in regulating eye growth or whether we can trick them into not causing myopia.”
Leading author Professor Chris Hammond of King’s College London, said: “It was already known that environmental factors, such as reading, lack of outdoor exposure, and a higher level of education can increase the risk of myopia. The condition is more common in people living in urban areas. An unfavourable combination of genetic predisposition and environmental factors appears to be particularly risky for development of myopia. How these environmental factors affect the newly identified genes and cause myopia remains intriguing, and will be further investigated by the consortium.”
Dr. Hammond also commented: “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.”