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Altered Viruses Reversed Progressive Blindness, Studies Say
The Pennsylvania team, whose patients were ages 19 to 26, reported the more impressive results. All three scored better on visual acuity tests, showing improvements equivalent to being able to read three lines lower on a standard eye chart, after initially not being able to make out the very largest letter. The treated eyes of all three patients also became about three times more responsive to light as measured by how much the pupils contracted.
One patient suffered retinal damage, apparently as a side effect, though team members said they think they know how to avoid that in the future.
One patient also experienced a small improvement in an untreated eye. That unexplained effect in part highlights the limitations of acuity tests, which are subject to factors such as general health, mood and the placebo effect.
Indeed, experts said, there is no way short of an autopsy to know whether the injected genes integrated into the retinal cells and are functioning.
The British study, using a somewhat different viral vehicle made by Targeted Genetics of Seattle, treated three patients, ages 17 to 23. Only one-third of the retina of each treated eye was injected, out of an abundance of caution. One patient had significant improvement in light sensitivity, but none had better acuity.
In both studies, some patients were for the first time able to get through a cluttered, dimly lit room unaided, according to the reports. They will be published in May but were released yesterday to coincide with a presentation at a medical conference.
"Before treatment, you can see he bumps into the walls and he's disoriented and has to be pointed in the right direction. He clearly just feels his way around," Ali said of one patient, who was videotaped before and after. "Six months after surgery, he could walk through without bumping into anything and take the same length of time that a normal person could."
That patient, Steven Howarth, said in a statement released by Targeted Genetics that he is pleased.
"Now, my sight when it's getting dark or it's badly lit is definitely better. It's a small change -- but it makes a big difference to me," Howarth, 18, said.
Paul A. Sieving, director of the National Eye Institute, which led the research that identified the rpe65 gene but was not involved in the latest research, said Howarth's anecdote jibes with his observation that even modest improvements in vision can make for big gains in the quality of one's life.
"From the numbers, you can't imagine there's any real improvement," Sieving said. "But if I give you just a little vision, someone on the street can't even tell you have an impairment."
About 450 genes have been implicated in eye diseases, Sieving said, suggesting that the approach could have potential for many.
Arthur W. Nienhuis, president of the American Society of Gene Therapy and a faculty member at St. Jude Children's Research Hospital in Memphis, called the results "highly encouraging."
"I think the field is really beginning to turn the corner," Nienhuis said.