An international team of scientists led by King's College London
has discovered 24 new genes that cause
short-sightedness.
Short-sightedness, or myopia, is a major cause of blindness and
visual impairment worldwide, and currently there is no cure. These
findings reveal genetic causes of the trait, which could lead to
finding better treatments or ways of preventing the condition in
the future.
Thirty percent of Western populations and up to 80 percent of
Asian people suffer from myopia. 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 and the retina is
thinner, which may 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 its
genetic background.
To find the genes responsible, researchers from Europe, Asia,
Australia and the United States collaborated as the Consortium for
Refraction and Myopia (CREAM). They analysed 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 signalling, 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 10-fold 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 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.
Professor Chris Hammond of King's College London said: "We
already knew that myopia - or short-sightedness - tends to run in
families, but until now we knew little about the genetic causes.
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."
The paper, Genome-wide
meta-analyses of multiancestry cohorts identify multiple new
susceptibility loci for refractive error and myopia, is
published in Nature
Genetics.