Scientists have discovered genes for the two most common eye disorders, nearsightedness and glaucoma.
Nearsightededness, or myopia, is the most common eye disorder in the world. The disease, which makes it difficult to focus on distant objects, is usually diagnosed in childhood and worsens as a person ages.
In the United States alone, experts say, more than $5 billion is spent every year to correct myopia with prescription eyeglasses, contact lenses or laser eye surgery.
One-third of American adults require some sort of corrective lenses for nearsightedness.
But in parts of Asia, upwards of 80 percent of adults are nearsighted, according to Terri Young, an ophthalmologist at Duke University Medical Center in Durham, North Carolina. "Singapore, for instance, is very concerned that they have no military recruits who are non-myopic to fly their fighter pilot military jets. So, for them, they feel it is a military security issue," she said.
Young was part of an international team of researchers that has identified a genetic abnormality that is responsible for myopia.
In a few years, Young says, it is quite likely there will be some sort of gene therapy to correct myopia. "We can reintroduce that gene into the retina by injections at this point, and the retina will take up the healthy gene product and start to produce it and the retina no longer degenerates and the vision improves," she said.
The retina is the light-sensing tissue in the back of the eye that sends signals to the brain which produces a clear image. Young says an estimated two- to three-percent of people with severe myopia are at increased risk of retinal detachment and cataracts.
Statistics show that myopia is increasing in the general population, according to Young, who says the percentage of those with serious eye disease is also likely to rise.
She says that is why it is important to develop a treatment for nearsightedness beyond corrective lenses.
In another development holding promise for the treatment of vision problems, researchers at deCODE, a biotechnology firm in Reykjavik, Iceland, have discovered a genetic abnormality that increases the risk of a common form of glaucoma, a leading cause of blindness worldwide..
In a study involving 40,000 subjects, the deCODE researchers found that six percent of people of European descent carry a genetic variant that puts them at risk of a type of the disease known as primary open-angle glaucoma. Just one percent of the Chinese subjects in the study carry the defective gene.
Kari Stefansson, deCODE's founder and senior researcher, says being able to predict who is likely to develop glaucoma could lead to treatment to slow progression of the disease. "You can use this genetic test for this variant to select people who should be screened frequently, who should be followed carefully and who should be treated early," she said.
Studies describing the DNA mutations responsible for nearsightedness and glaucoma are published in the journal Nature Genetics.