Health & Medicine - Posted by Emma Reynolds-Kings College London on Tuesday, February 12, 2013 12:50 - 4 Comments 
(No Ratings Yet)
Loading ...
(No Ratings Yet) Loading ...24 new genes linked to nearsighted vision
"We already knew that myopia—or short-sightedness—tends to run in families, but until now we knew little about the genetic causes," says Chris Hammond, a professor at King’s College London. (Credit: "eye exam chart" via Shutterstock)
KING’S COLLEGE LONDON (UK) — Scientists have identified 24 new genes that play a critical role in nearsightedness, a finding that could point to ways to treat and possibly prevent the condition.
Share this article
Email
Republish this article
The text of this article by Futurity is licensed under a Creative Commons Attribution-No Derivatives License.
Nearsightedness—also known as short-sightedness or 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.
“We already knew that myopia—or short-sightedness—tends to run in families, but until now we knew little about the genetic causes,” says Chris Hammond, a professor at King’s College London and lead author of the paper published in the journal Nature Genetics.
“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.
“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.”
Source: King’s College London
Please wait
4 Comments
Joyce Smith
Leighton Brooks
You have a point that it is genetic, however, reading and staring at a computer screen for too long really do have an effect on myopia. When focusing on things that are of close proximity to the eye, the sight worsens since the eyes become lazier and then shortsightedness significantly worsens. It is not the core reason FOR myopia but it has a very strong effect on it. The eyes need a serious rest afterwards and sight may sometimes not improve for a few days. Looking at green plants usually helps since the reflection of light on green surfaces puts less pressure on your eyes.
Chad Schobert
As a current optometry student, I figured I should try to clarify this article some. Joyce: I can understand the skepticism for the claims the article makes, but allow me to make a case for why it is actually correct.
First, myopia is NOT a pathological process or a disease process. For the vast majority there is no tissue damage, no inflammation, or any other malfunctioning tissues. The eye can change its length through a feedback system that is based on how the eye is used.
When you do lots of near work, the eye has to focus up close, and this causes the eye to have to constrict the ciliary muscle. When we look at distance, this muscle is relaxed and the eye does not have to expend effort to focus. Since constantly firing the ciliary muscle to see up close is tiring, the eye adapts: it changes shape and lengthens to reduce the strain of constantly focusing up close. This system is native to the eye itself and requires no direction from the brain. If you cut the optic nerve, the eye will still change shape depending on the task it is performing.
So the myopia shift seen in people who do lots of near work: students (especially graduate and doctorate), those who read a lot and those who are rarely outdoors allowing their accommodation to relax will see this shift most. So you are correct, that it doesn’t DIRECTLY cause the eye to grow longer, but the eye does intentionally lengthen when exposed to constant near work.
Joyce Smith
Thanks for the clarification – I had no idea that the eyeball was able to adapt in that way. As a “high myope” myself, I know it is not a disease process, but always thought it was just due to inherited shape of the eyeball. I always did read a lot, but also spent, and continue to spend, large amounts of time outdoors. It never improved my vision!
Sorry, can’t agree with their basic premise that “reading, lack of outdoor exposure, and a higher level of education can increase the risk of myopia”, especially since the second paragraph clearly states that myopia occurs because the eye is too long and the cornea then focuses the image in front of the retina. Neither reading, lack of outdoor exposure nor education lengthen the eyeball.