This is an antibody-stained cross section of a mouse retina. Credit: Andrei Tkachenko/Columbia University Medical Center
Vision researchers have discovered a gene that causes myopia, but only in people who spend a lot of time in childhood reading or doing other ‘nearwork.’ Using a database of approximately 14,000 people, the researchers found that those with a certain variant of the gene – called APLP2 – were 5X more likely to develop myopia in their teens if they had read an hour or more each day in their childhood. Those who carried the APLP2 risk variant but spent less time reading had no additional risk of developing myopia.
This is the first known evidence of gene-environment interaction in myopia,” says Andrei Tkatchenko, MD, PhD, of CUMC. Although it’s not yet known how genetic variation at the APLP2 gene causes myopia, they think the risk variant may increase the amount of APLP2 protein produced in the eye, which in turn may cause the eye to undergo excessive elongation. They found that mice exposed to a visual environment that mimics reading were less likely to develop myopia when little APLP2 protein was present in the eye.
“By reducing the level of APLP2 in the eye, you can reduce susceptibility to environmentally induced myopia. This gives us an opportunity to develop a therapy to prevent myopia in everyone, regardless of the APLP2 variant they carry,” Dr. Tkatchenko says. The therapy which would take years to develop, would be most effective in young children, before the eye has started to elongate and become myopic. There are probably hundreds of genes that can cause myopia, and so far, only 25 candidates have been identified. The high-risk variant of APLP2 occurs in ~1% of the population.
“We pretty much know all the environmental risk factors: time spent reading increases the risk, while time spent outdoors reduces it,” Dr. Tkatchenko says. In the U.S., 44% of adults are now nearsighted, up from 25% 30 years ago. And in some parts of Asia, 80% of young adults are now myopic.
>>Preventing myopia not only reduces the need for vision correction, but also prevents potentially blinding eye conditions later in life eg cataracts, glaucoma, and retinal detachment later in life. “Even in people with mild myopia there is a significant risk, but it’s especially high in people who need five or more diopters of vision correction (about 20/400 vision). That’s why it’s important to study myopia.” http://newsroom.cumc.columbia.edu/blog/2015/08/31/gene-leads-to-nearsightedness-when-kids-read/
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