Refractive errors and short-sightedness are globally increasing
Text: Jaakko Kinnunen
Photo: Teemu Launis
A recent study examining the genetic basis of myopia found 161 new independent genetic signals that have an effect on refractive errors, including myopia. The study is the largest genetic mapping that accounts for nearly eight per cent of the risk of myopia and significantly specifies previously available findings.
The study was published in Nature Genetics. The genome-wide association meta-analysis included 160,000 people and 37 different studies worldwide. Professor Terho Lehtimäki from the University of Tampere was one of the researchers.
“We found several genetic changes affecting gene expression especially in the retina and the genes that guide its functionality, which have an effect on the development of myopia,” Lehtimäki says.
Previous studies had found 37 genes which play a role in the development of myopia and the present study also confirmed the existence of those genes. In addition, a high genetic correlation between European and Asian populations was found.
Lack of light can cause myopia
Myopia is rapidly increasing worldwide with even as many as 95 per cent of 20-year-olds suffering from it in the big cities of East Asia, such as Seoul and Singapore. In the United States and West Europe, refractive errors affect every other young adult.
Myopia is caused by both genetic and lifestyle factors. The most established lifestyle factors for myopia are high level of education, lack of outdoor exposure, and excessive near work.
The study found that light plays a central role in the development of myopia.
“It is interesting that all the cells that are in charge of the function and growth of the retina, of which there are about ten, are involved in the development of myopia; especially the ones that are in charge of light detection and processing. Our results support the finding that the amount of light and, in particular, the lack of it, predispose to myopia,” Lehtimäki says.
High myopia may lead to blindness
Patients with higher genetic risk are more likely to develop myopia.
“People in the highest decile, who have a high genetic risk for developing refractive errors, have about forty times the risk of developing myopia compared to the lowest decile,” Lehtimäki says.
Myopia is high when it is –6 diopters or worse. One in three individuals with high myopia develop irreversible visual impairment or blindness.