Inherited blindness treatable via gene therapy

By Sheilah Downey (sheilahd@foodconsumer.org)

Adults born with a rare, incurable blindness saw their vision increase 1,000 fold when treated with gene therapy, say scientists in a study to be published Thursday in the New England Journal of Medicine.

One year after three blind patients, ages 21 to 42, were given doses of corrective genes to their retinas, their brains re-wired themselves to adapt to the new field of vision, said researchers in a University of Florida news release.

"When one patient came back for her 12-month visit, she said she could read the digital clock in her parent's car with her treated eye -- something she was never able to do before," said Dr. William Hauswirth, professor of ophthalmology at the University of Florida College of Medicine.

In an added bonus to their research, said scientists, treated parts of the retina acquired enough strength to rival the retina's usual visual point for the brain's attention.

"What's truly astounding is the brain, even in an adult, is still adaptable enough to learn to use these regions of the retina," said Hauswirth.

The patients were born with a rare form of blindness called Leber congenital amaurosis type 2, the most common cause of blindness in infants and children. In the type 2 form, photo-receptor cells cannot respond to light because a gene called RPE65 does not produce necessary proteins.

To deliver the proteins necessary for vision, scientists used a harmless virus that already exists in most people to deliver RPE65 to a small area of the retina.

The study was led by Dr. Samuel G. Jacobson, professor of ophthalmology at the University of Pennsylvania and was supported by the National Eye Institute.