Researchers have reported success in using gene therapy to treat a rare type of inherited blindness, called Leber congenital amaurosis (LCA), according to New England Journal of Medicine online Sunday.

The success will boost hopes for hundreds of thousands of patients with inherited forms of vision impairment, the journal added.

LCA damages light receptors in the retina. Children with the disorder are born with severely impaired vision that deteriorates over the course of their lives until they are totally blind in childhood or adolescence. There has been no treatment for it.

Leber's congenital amaurosis affects about 3,000 people in the United States and perhaps one in every 50,000 worldwide.

Two groups of researcher used a common cold virus as a delivery vehicle, or vector to deliver a normal version of one damaged gene that causes the disease, called RPE65, directly into the eyes of patients.

Although both trials were only testing for safety, patients reported they could see a little better afterwards, the researchers told a meeting of eye specialists in Florida.

The Pennsylvania group treated three patients, ages 19, 26 and 26. Between October and January, Dr. Albert M. Maguire injected a relatively small amount of the vector below the retina in each of the patient's most severely damaged eyes.

Beginning two weeks after the injections, all three patients reported improved vision in the injected eyes, said Maguire of the University of Pennsylvania School of Medicine

They found that light sensitivity had improved about three-fold. The treatment also reduced nystagmus, an uncontrollable roaming of the eye often seen in blind people.

Patients also performed better on more subjective tests. One patient's vision on an eye chart, according to Dr. Jean Bennett, the lead author of the study.

The therapy produced no inflammation in the eye or any other toxic side effects, the researchers said. One patient did develop a small hole in the retina that they believe most likely was a result of the surgery. It did not interfere with vision.

Researchers believed the approach can ultimately be used for a much broader spectrum of disorders, including retinitis pigmentosa and macular degeneration.

The next stage of testing will involve treating children, whose eyes have deteriorated less and who have a better chance of improving, Ali said.

"We are pretty convinced that once we can do this with younger children we will be able to arrest the damage," said Targeted Genetics Chief Executive Stewart Parker.

(Agencies/Xinhua News Agency April 28,2008)