Enlarge By Daniel Burke, Children's Hospital of Philadelphia/AP Doctors Albert Maguire, right along with wife Jean Bennett at the University of Pennsylvania are part of two teams of scientists in the U.S. and Britain that are using gene therapy to dramatically improve vision in four patients who inherited eye disease. YOU CLICKED: WEEK'S MOST POPULAR HEALTH STORIES YOU CLICKED: WEEK'S MOST POPULAR HEALTH STORIES 1: Feds rate U.S. nursing homes 2: Doctors detail first U.S. face transplant 3: Surgeon finds foot in newborn's brain tumor 4: Nursing homes talk new ratings 5: Colonoscopy prep pills carry kidney risk 6: Duggars welcome 18th child No. 7-10: Diabetes drug risks, placebo effect For the first time, doctors have used gene therapy to restore vision in patients with a rare and usually incurable form of blindness, researchers announced Sunday. Experts say the results are a welcome success in gene therapy, a promising idea that has had several major setbacks during the past 15 years. "It's a breakthrough," says Ronald Crystal, chairman of the department of genetic medicine at New York's Weill Medical College of Cornell University. "It really helps to validate that gene therapy can work and is going to be important." None of the six patients treated regained normal vision, but four have much better eyesight than before, according to two studies published online in The New England Journal of Medicine. The patients had a rare inherited disorder called Leber's congenital amaurosis, which begins eroding eyesight at birth and leaves them blind by their mid-20s. Though cataract surgery and medication can restore sight in patients with other eye ailments, doctors have never before been able to restore vision to patients with this kind of hereditary degenerative disease, says Albert Maguire, an associate professor at the University of Pennsylvania School of Medicine and co-author of one of the studies. Leber's congenital amaurosis afflicts 2,000 to 10,000 people in the USA, says Maguire's co-author Jean Bennett, a professor at the University of Pennsylvania. There is no effective treatment. She hopes gene therapy may work for patients with more common kinds of blindness. Two patients in her study began the trial barely able to see hand movements. After treatment, they became three times as sensitive to light and could read lines on an eye chart, according to an international team led by doctors at the Children's Hospital of Philadelphia and the University of Pennsylvania. Stanford University researcher Mark Kay, former president of the American Society of Gene Therapy, says the studies suggest gene therapy may be most successful in patients in early stages of the disease, while they still have some vision. In gene therapy, doctors aim to replace defective genes with normal ones, using harmless viruses as delivery vehicles, Crystal says. Crystal says gene therapy may work particularly well with eye disorders because the immune system, which can reject the virus carrying the genes, isn't as active in the eye. And because it's easy to test vision, doctors know quickly whether the therapy works. Despite high hopes for gene therapy, scientists have struggled to realize its potential. For example, doctors have treated 20 to 30 children who suffer from a rare and severe immune disorder. Though most of the children are healthy, several developed leukemia. And in 1999, a teenager named Jesse Gelsinger died after gene therapy at the University of Pennsylvania. Guidelines: You share in the USA TODAY community, so please keep your comments smart and civil. Don't attack other readers personally, and keep your language decent. Use the "Report Abuse" button to make a difference. You share in the USA TODAY community, so please keep your comments smart and civil. Don't attack other readers personally, and keep your language decent. Use the "Report Abuse" button to make a difference. Read more