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February 11, 2013

New Genes for Nearsightedness Identified

Scientists have discovered 24 genes that cause most common vision defects worldwide. These genes are thought to be involved in a complex biological network that regulates eye growth and can ultimately lead to nearsightedness (myopia) or farsightedness. The researchers recently published their breakthrough in journal Nature Genetics. One of the leading causes of visual impairment worldwide, Myopia has no cure to date. The findings reveal genetic causes of the optical defect and may help in finding a solution.

At least 30 percent of people in Western countries, and up to 80 percent of Asians suffer from myopia. During visual development in childhood and adolescence, the eye grows in length but in myopes it grows too long. As a result, light entering the eye is focused in front of the retina rather than on it. This causes blurred distance vision which can often 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. Researchers have known for decades that refractive errors (which include nearsightedness and farsightedness) are partly inherited although, up until now, very little was known about the specific genes involved.

To find the genes that control refractive errors, researchers from the United States, Europe, Asia, and Australia collaborated as the Consortium for Refractive Error and Myopia (CREAM). They analyzed refractive error data and over 4 million genetic markers of more than 45,000 people from 32 different studies. They confirmed two previously reported genes and identified 24 new genes for this trait. The genes include some that function in brain- and eye-tissue signaling, the structure of the eye, and eye development.

“Identifying these genes is big a first step; nature and nurture interact in very complex ways to affect myopia,” said Robert Wojciechowski, PhD, an author of the study and assistant professor of epidemiology with the Johns Hopkins Bloomberg School of Public Health. “We currently don’t know exactly how these genes are involved in regulating eye growth or whether we can trick them into not causing myopia.” The new genes include those which function in brain and eye tissue signaling, the structure of the eye, and eye development, but can also lead to myopia.

Co-investigator Caroline Klaver, a professor with Erasmus Medical Center Rotterdam, said, “Currently, possibilities to reduce progression of myopia are very limited. The few drugs that have shown some promise either cause unacceptable side effects or are only marginally effective. New options are necessary. Chances are good that the insights gained from this study will provide openings for development of new treatment or prevention strategies.”

Johns Hopkins Bloomberg School of Public Health media contact: Tim Parsons at 410-955-7619 or tmparson@jhsph.edu.