A girl saw her mother’s face for the first time. A boy tore through the aisles of Target, marveling at toys he never knew existed. A teen walked onto a stage and watched the stunned expressions of celebrity judges as he wowed America’s Got Talent.

Caroline, Cole, Christian. All had mere glimmers of vision and were destined to lose even that because of an inherited eye disease with no treatment or cure.

Until now.

On Thursday, U.S. Food and Drug Administration advisers will consider whether to recommend approval of a gene therapy that improved vision for these three youths and some others with hereditary blindness.

It would be the first gene therapy in the United States for an inherited disease, and the first in which a corrective gene is given directly to a patient. Only one gene therapy is sold in the U.S. now, a cancer treatment approved in August that engineers patients’ blood cells in the lab.

Children, parents, doctors and scientists will tell the FDA panel what it’s like to lack and then gain one of our most primal senses.

Cole Carper, an 11-year-old boy who got the therapy when he was 8, describes how sight changed what he knew of the world. When he returned to his home in Little Rock, Ark., after treatment, “I looked up and said, ‘What are those light things?’ And my mom said, ‘Those are stars.’ ”

His sister, 13-year-old Caroline Carper, treated when she was 10, said that afterward, “I saw snow falling and rain falling. I was completely surprised. I thought of water on the ground or snow on the ground. I never thought of it falling,” because the sky was something she couldn’t see, along with other things like her mother’s smile.

The treatment, Luxturna, is made by Philadelphia-based Spark Therapeutics. It does not give 20-20 vision or work for everyone, but a company-funded study found it improved vision for nearly all of those given it and seemed safe. The company’s Nasdaq ticker symbol is ONCE, for how often it hopes the therapy is needed.

“It’s exciting” and in some cases might be a cure, although how long the benefits last isn’t known, said Dr. Paul Yang, an eye specialist at Oregon Health & Science University who is testing gene therapies for other companies. “There’s nothing else for these kids.”

How it works

The therapy has wider implications but was tested for Leber congenital amaurosis, or LCA, caused by flaws in a gene called RPE65. Those with it can’t make a protein needed by the retina, tissue at the back of the eye that converts light into signals to the brain that lets us see. People often see only bright light and blurry shapes and eventually lose all sight.

Parents are carriers of the flawed gene and it can lurk undetected for generations, suddenly emerging when an unlucky combination gives a child two copies of it.

An obstacle course known as a mobility maze was designed to test vision after treatment.

Eighteen of 20 treated study participants improved on the mobility maze a year later, and 13 passed the test at the lowest light level. None in a comparison group of nine patients did.

That group was allowed to get the therapy after waiting one year, so in all, 29 were treated, plus more in earlier studies. The two who did not improve may not have had enough healthy retinal cells to respond to treatment; one improved on other tests and another stopped deteriorating.

Seeing gold

For Christian Guardino, a senior at Patchogue-Medford High School on Long Island, the most remarkable part about performing on America’s Got Talent a day before his 17th birthday earlier this year wasn’t winning the golden buzzer that showered gold confetti on him and sent him into further competition. It was seeing the confetti thanks to his gene therapy several years ago.

“I walked out on that stage all by myself,” he said. “I saw the judges. It was incredible.”

His mother, Beth Guardino, said the judges didn’t know about Christian’s blindness and gene therapy until after his audition.

Before treatment, “It was dark, life without light,” Christian said. “I found a way to work through it, to cope with it, and that was music.”

Since treatment, “I’ve been able to see the most incredible things. I’m able to see stars, I’m able to see fireworks, snow falling,” he said. His favorite? “The moon. Most definitely. I’m a huge astronomy fan.”