Gene therapy breakthrough

For the first time, researchers have used gene therapy to improve the vision in patients who are virtually blind. The breakthrough is offering hope to hundreds of thousands of patients with vision impairment, including macular degeneration sufferers.

Even though the experiments were conducted on those with a rare form of blindness called Leber's congenital amaurosis, researchers believe the approach can ultimately be used for a broad spectrum of disorders, including retinitis pigmentosa and MD.

The experiments were done in both the United States and Britain. In London, three patients were treated, with no ill effects. Even though they did not improve their visual acuity, one of them, 18-year-old Steven Howarth (below), had improved light sensitivity, especially at night.

Before the operation, Howarth was made to walk through a maze. He kept bumping into things and was disoriented. Six months after treatment, he walked through as fast as a normal person!

In Pennsylvania, the results were more impressive. The three patients were treated in one eye each. After two weeks, all reported improvement. One of them could read 3 1/2 lines better on an eye chart.

"All three subjects are asking if they can have their other eye injected," said Dr. Katherine A. High of Children's Hospital of Philadelphia. "That's a pretty good indicator of its effectiveness."

Another researcher hailed the results as a "landmark" and the most important therapeutic discovery in four decades in the field of retinal dystrophies.

Dogs given the same treatment have remained stable for at least eight years.

Gene therapy is when a defective gene is replaced with a good one. In the case of the Leber's, both groups of researchers used a gene called RPE65 that is defective in many Leber's patients.

For MD, it is caused by other defective genes. But the treatment principle would be the same. Researchers would have to design a specific delivery vehicle, or vector, for each disorder bearing the proper gene.