Eli Wheatley and Christian Guardino are among a growing number of patients whose lives are apparently being saved or radically improved by gene therapy.

Wheatley, 3, of Lebanon, Ky., and Guardino, 17, of Patchogue, N.Y., were both diagnosed with what were long thought to be incurable genetic disorders. In the past, Wheatley's condition would have probably killed him before his first birthday. Guardino's would have blinded him early in life.

But after receiving experimental gene therapies, both seem to be doing fine.

"It's a very exciting time for the field," says Carrie Wolinetz, the associate director for science policy at the National Institutes of Health.

So far, gene therapy has only been tested on a relatively small number of patients who have been followed for relatively short periods of time. Many more patients will have to be studied for longer periods before anyone really knows how well the therapies work, how long the benefits last, and whether the therapies are safe.

But doctors and families of those helped so far are elated at the progress.

"This is really an important time in gene therapy," says Dr. David Williams, professor of pediatrics at Harvard Medical School and chief scientific officer at Boston Children's Hospital, who was not involved in these children's treatment, but has recently achieved similar success with another genetic condition.

Eli's mother, Natalie Wheatley, had been terrified there was something wrong with Eli even before he was born. He barely moved during her pregnancy, she recalls, and never seemed quite right in the first weeks of his life.

Finally, doctors told her that her worst fears were true: Her son had spinal muscular atrophy, a disease of motor neurons that was destroying his muscles.

"They basically told me he wouldn't make it to his first birthday," says Wheatley. Take him home and love him and spend as much time with him as you can, she remembers the health team telling her.

"I was devastated — devastated," she says.

Guardino was diagnosed with a different condition — Leber's congenital amaurosis, a disease of the eye's retina — when he was born. The disorder isn't fatal. But it was destroying his vision.

"I wouldn't be able to walk around outside on my own," says Guardino. During the day, he says, the world looked "incredibly dark" and blurry. "It was sort of like watching your world fade away."

Now Guardino can see things he'd only dreamed about.

After the gene therapy treatment, he says, "I was able to see things for the first time — like the moon. I was able to see stars for the first time – fireworks — all these amazing things that I've never been able to see before."

And Wheatley's son, Eli, seems to be thriving.

"He just started preschool in September," his mom says. "He goes to preschool alone. He eats in the cafeteria with all the other kids. He's doing extremely well. It's been amazing — truly amazing."