Nearsightedness—also known as myopia—is a major cause of blindness and visual impairment worldwide, affecting 30 percent of Western populations and up to 80 percent of Asian people. At present, there is no cure.
During visual development in childhood and adolescence the eye grows in length, but in people with myopia the eye grows too long. Light entering the eye is then focused in front of the retina rather than on it, resulting in a blurred image.
The refractive error can be corrected with glasses, contact lenses, or surgery. But the eye remains longer and the retina is thinner, and could lead to retinal detachment, glaucoma, or macular degeneration, especially with higher degrees of myopia. Myopia is highly heritable, although up to now, little was known about the genetic background.
To find the genes responsible, researchers from Europe, Asia, Australia, and the United States analyzed genetic and refractive error data of over 45,000 people from 32 different studies, and found 24 new genes for this trait, and confirmed two previously reported genes.
Interestingly, the genes did not show significant differences between the European and Asian groups, despite the higher prevalence among Asian people. The new genes include those which function in brain and eye tissue signaling, the structure of the eye, and eye development. The genes lead to a high risk of myopia and carriers of the high-risk genes had a tenfold increased risk.
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 unfavorable 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.