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24 new genes for nearsightedness identified

Scientists have 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.

Thirty per cent of Western populations and up to 80 per cent of Asians suffer from myopia (nearsightedness). 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, 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 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. 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 Centre 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 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.“

Corresponding author Professor Caroline Klaver from Erasmus Medical Center Rotterdam, added: “Currently, possibilities to reduce progression of myopia are very limited. While one drug, called atropine, may reduce progression, it dilates the pupil and causes problems with light sensitivity and difficulty with reading.  New options are necessary. Chances are good that the insights gained from this study will provide openings for development of new strategies.”

University of Bristol, Senate House, Tyndall Avenue, Bristol BS8 1TH, UK. Tel: +44 (0)117 928 9000

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