It was one thing for the patients to think they could see better. But the team needed hard data.

In March, Bennett flew her three Italian patients back to Philadelphia for tests.

A new vision

With Bennett at her side, Josalinda peered into the twin eyepieces of the pupillometer, a device that repeatedly flashed light into her eyes.

Bennett needed to measure how much her pupils would constrict. Before the surgery, they barely responded.

For each round of testing, Josalinda kept her eyes closed until Bennett gave her the go-ahead, in a mixture of Italian and English.

"Uno, due, tre . . . Open!" Bennett called out each time.

Then finally: "Bravo, bravo! You did a wonderful job."

Bennett would need to scrutinize the data, but the machine seemed to confirm what Josalinda and the other two patients had told her: Their vision had improved. Their eyes were apparently making the enzyme they needed for sight.

Later analysis would show that the injected eyes of all three patients became roughly three times as sensitive to light.

Furthermore, all three were better able to read eye charts - though they did so slowly, haltingly, sitting less than two feet away from letters a couple of inches tall.

Before the surgery, Tommaso's right eye could barely perceive someone waving a hand right in front of him. His eye was so bad it was hard to quantify, but compared to 20/20 vision, his right eye was at 20 over several thousand. After treatment, the eye improved to 20 over 710.

It had been 23 years since Bennett and her husband had first discussed the idea. Now, it had happened.

"To go from zero to anything, it's just . . . " She shrugged, unable to finish her sentence.

Within weeks, Bennett's team would send the results to the New England Journal of Medicine. She learned that a British team working on a similar experiment had submitted results, too. The journal would agree to publish both papers together.

Gene therapy remains in the experimental stage, and will be for years. The improved vision of three blind patients does not change that. It is just one study, involving an organ in which success may not translate elsewhere in the body.

Still, the results are promising for retinal disease.

After spending hours putting her patients through yet more tests, Bennett was done.

It was time to celebrate.