Health Team

Gene therapy helps the nearly blind

Posted May 2, 2008 3:48 p.m. EDT
Updated May 2, 2008 6:22 p.m. EDT

Some scientists say it is a breakthrough: Gene therapy has dramatically improved the sight of a handful of patients.

Two teams of scientists used an experimental gene-replacement therapy on six volunteers – from Italy and the United Kingdom – all of whom have Leber's congenital amaurosis, a rare hereditary disease. Four of the patients experienced improved vision.

LCA causes severe vision loss, especially at night, but 17-year-old patient Stephen Howarth, from England, says he can now make out details on a dimly lit street.

"Before all I could see was street lights," Howarth said.

Like all LCA patients, Howarth has mutation in a gene that makes a protein needed by the retina, which senses light and sends images to the brain. He faces gradually losing all his sight in early adulthood.

In the experimental treatment, scientists injected millions of copies of a working gene beneath the retina in one of Howarth's eye. Doctors treated one eye in case of mistakes and to use the second as a control.

Before the treatment, Howarth took 77 seconds to stumble through a dimly lit maze. Six months after gene therapy, he zipped through it in 14 seconds and did not bump into any obstacles.

"I used to be shy and silent, but now I've got confidence to walk around on my own," Howarth said.

"I'm exhilarated; this is so exciting," said Dr. Jean Bennet, at the University of Pennsylvania, who worked on the trial.

"One of our subjects lived near the mountains, and she could look up and see the snow-capped mountains above, which was very exciting to her," Bennet added.

Scientists cautioned that the patients' successful results are only preliminary, and they do not know if the improvement will be permanent.

Doctors said they hope that the trial will lead to gene therapies that can reverse more common forms of inherited eye disease, such as macular degeneration and glaucoma.

"This really is the first step at the bottom of a tall ladder, but it's an important step," Dr. Katherine High, of the University of Pennsylvania, said.