Genetic clues to the cause of short-sightedness have been uncovered that could lead to new treatments.
Scientists discovered 24 new genes that help trigger the condition. They include genes involved in brain and eye tissue signalling, eye structure, and eye development.
Carriers of the highest risk genes have a 10-fold increased likelihood of developing short-sightedness, or myopia.
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An estimated 30% of western populations and up to 80% of Asian people are short-sighted.
The problem occurs when the eye grows too long and light is focused in the wrong place, in front of the retina's photo receptors. This results in a blurred image.
The error can be corrected with glasses or contact lenses, but high levels of myopia are associated with an increased chance of retinal detachment, glaucoma and macular degeneration.
Although myopia is highly heritable, information about the genes responsible has been lacking.
Scientists analysed data on more than 45,000 individuals, finding 24 new genes for the trait.
The research is reported in the journal Nature Genetics.