Scientists for the first time have used gene therapy to dramatically improve sight in people with a rare form of blindness, a development experts called a major advance. • Some vision was restored in four of the six young people treated, teams of researchers in the United States and Britain reported late last month. Two of the volunteers who could only see hand motions were able to read lines of an eye chart.
Experts said the technique has the potential to reverse blindness due to other kinds of inherited diseases.
"I think this is incredibly exciting," said Dr. Jean Bennett, a professor of ophthalmology at the University of Pennsylvania and a leader of the Philadelphia study. "It's the beginning of a whole new phase of studies."
The National Eye Institute is funding a third, similar study at the University of Florida.
The two teams of scientists, working separately, each tested gene replacement therapy in three patients with a form of a rare hereditary eye disease called Leber's congenital amaurosis. There currently is no treatment for the disease, which appears in infancy and causes severe vision loss, especially at night.
An estimated 2,000 Americans have this form of the disease.
Gene therapy, replacing faulty genes with a normal version, has been studied in humans for more than 15 years, with limited success.
The early results of the eye experiments should give the field a boost, some experts said.
"I think it's really a big shot in the arm for gene therapy and for medicine in general," said Dr. Ronald Crystal, head of genetic medicine at Weill Cornell Medical College in New York.
The participants had mutations in a gene that makes a protein needed by the retina, which senses light and sends images to the brain. People without the gene gradually lose sight, until they are blind in early adulthood.
The retina itself stays in relatively good shape for a while, making it a good candidate for gene therapy, said Robin Ali, a professor at University College London, who led the British team. He likened the defective gene to a missing spark plug in a car engine.
"The whole engine can be absolutely fine, but if it doesn't have a spark plug, the car's not going to work," Ali said.
For the experiment, the scientists injected millions of copies of a working gene beneath the retina in the back of the eye. Only the worse eye was treated, in case anything went wrong.
After the treatment, the patients' eyesight and light sensitivity were measured periodically; mobility was tested in a maze or an obstacle course.
All three of those treated in Philadelphia showed significant improvement in their vision, the researchers said. The volunteers ranged in age from 19 to 26. The longest follow-up for these patients was six months.
In addition to reading lines on an eye chart, they could see better in dim light, Bennett said.
"We were not expecting to restore their vision to 20/20," she said.
In the British group, the treatment only worked in Steven Howarth, 18, whose disease was less advanced than the other two. Howarth said he used to rush home from school because he was worried about getting around in the dark, according to remarks issued by the university.
"Now, my sight when it's getting dark or it's badly lit is definitely better,'' said Howarth, who lives in Bolton, England.
After the injection last July, Howarth said his eye felt like sandpaper. It was better after a week.
There were no serious side effects reported in either group. The researchers hope to see better results with higher doses and in younger patients who have less eye damage.