"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 said in a statement.
GREAT HOPE
"The fact we see any evidence of improvement under these circumstances gives great hopes for the effectiveness of the treatment," Ali said in a telephone interview.
In High's trial, three patients aged 19, 26 and 26, all reported better vision.
"Patients' vision improved from detecting hand movements to reading lines on an eye chart," said Dr. Albert Maguire of Children's Hospital.
In each case, only one eye was treated, so the other eye could be used as a "control" to tell whether vision improved.
Ali and his team are working on the research with Targeted Genetics Corp, which made the genetically engineered virus. The Children's Hospital and University of Pennsylvania team developed their own virus, called a vector, to carry the corrective gene.
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.
One important thing both teams were looking for was proof the virus did not leave the eye. "It stays in there. It doesn't go anywhere else," Parker said.
Both safety and efficacy have held back the field of gene therapy. One experiment cured two French boys with a rare immune disorder but gave them leukemia in 2002, and an Arizona teenager died in a 1999 gene therapy experiment.
