Myopia and Genes
Myopia is commonly known as being nearsighted or shortsighted)and is a condition of the eye where the light that comes in does not directly focus on the retina but in front of it. This causes the image that one sees when looking at a distant object to be out of focus, but in focus when looking at a close object. In other words, close is good and far is blurry. Scientists have now discovered 24 new genes that cause refractive errors and myopia — an important cause of blindness and visual impairment worldwide, which has no cure to date. The findings, published in Nature Genetics, reveal genetic causes of the trait, and this may help in finding a solution.
Causes of Myopia have never been clear cut. Congenital myopia, also known as infantile myopia, is present at birth and persists through infancy. Youth onset myopia occurs in the early childhood or teenage. School myopia appears during childhood, particularly the school-age years. This form of myopia is attributed to the use of the eyes for close work during the school years.
Thirty per cent of Western populations and up to 80 per cent of Asians suffer from myopia. This refractive error can be corrected with glasses, contact lenses or surgery. However, the eye remains longer, the retina is thinner, and this 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 the genetic background.
To find the genes responsible, an international team of researchers including academics from the University of Bristol’s School of Social and Community Medicine, collaborated as the Consortium for Refraction and Myopia (CREAM). They 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.
Remarkable was that the genes did not show significant differences between the Europeans and the Asians. 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: carriers of the high-risk genes had a tenfold increased risk.
Cathy Williams, Consultant Senior Lecturer in the University of Bristol’s Center for Child and Adolescent Health, commented: "The ALSPAC study is an important part of the CREAM consortium and we are delighted that we have been able to join forces with researchers to shed light on the causes of myopia."
Leading author Professor Chris Hammond of King’s College London, said: "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 by the consortium."
The National Institutes of Health says there is no known way of preventing myopia, and the use of glasses or contact lenses does not affect its progression. There is no universally accepted method of preventing myopia; proposed procedures have not been studied for effectiveness.
Eyeglasses, contact lenses, and refractive surgery are the primary options to treat the visual symptoms of those with myopia. Lens implants are now available offering an alternative to glasses or contact lenses for myopics for whom laser surgery is not an option. Eye care professionals most commonly correct myopia through the use of corrective lenses, such as glasses or contact lenses.
For further information see Nearsighted Gene.
Eyeglasses image via Wikipedia.