From the day Christian Guardino was born, his mother, Elizabeth, knew that something was wrong with his eyes. They would jiggle and jerk and roll up into his head. One eye turned inward. When she fed him, instead of gazing up at her, Christian would stare at the brightest light around—a lamp if they were indoors, the sun if they were out. It was unsettling.
The first eye doctor who saw Christian grimly referred the family to a specialist at New York’s Mount Sinai Hospital. The specialist performed an electroretinogram (ERG), a procedure in which a tiny electronic sensor placed on the eye measures the retina’s response to bursts of light. A healthy retina will respond by firing an electrical signal down the optic nerve that produces, on the ERG machine’s printout, a deep valley followed by a tall peak. Christian’s ERG produced no such thing: only squiggles, ill-formed and weak.
Christian, the doctor told Elizabeth, had a retinal disease called Leber congenital amaurosis (LCA). His vision, already bad, would never significantly improve. Nothing could be done. The boy would see little of the world and would always walk, once he learned how, with a cane.
Christian did need a cane, and his mother’s guiding hand, when in 2012, at age 12, he first visited a clinic run by the University of Pennsylvania’s Scheie Eye Institute. Yet this January he walked through the institute’s main building cane free and seemingly fearless. Joking and chatting, the teen led a klatch of Ph.D.’s, M.D.’s, lab techs, and me through the airy lobby. He marveled at the towering atrium, the shiny balconies where people sat having coffee.
“Whoa!” he said as we neared the building’s exit—for before us an enormous revolving door turned its huge blades. His mother was some distance behind; he was on his own. Christian neither stopped nor paused. He walked calmly through the opening of the spinning wedge of steel and glass and held his pace as one glass wall closed behind him and another smoothly swung out of his way. He stepped into the sunlight.
Christian Guardino could see. Everything that had posed an obstacle before—light and dark, steel and glass, the mobile and the immovable—now brought him pleasure. The world had opened before him.
“Can you believe this?” Elizabeth asked a few minutes later. Ahead of her, Christian walked with Jean Bennett, whose lab at Penn produced the gene-laced fluid that gave Christian sight. “It happened so fast,” Elizabeth said. Just three days after his first eye was treated, Christian could see her. “I went from wondering if my son would ever know what I looked like to … well, this,” she said, gesturing at him walking unaided. “It’s like a miracle.”
Christian’s miracle was hard-won. It rose from 20 years of unrelenting work by Bennett and her collaborators, who identified the genetic mutation that crippled Christian’s retina, then figured out how to sneak a good copy of that gene into his eye. Bennett started trials for the therapy merely hoping “that we could detect some hint of improvement.” Nine years later she is astonished that it seems to have worked so well.
Bennett takes care not to aggrandize her work or underplay the obstacles to further progress. Yet the gains so far for Christian and other patients give Bennett guarded hope that this basic gene-replacement approach might work for other forms of blindness. She and others believe that variations on her technique might soon help doctors find and fix similar genetic defects early enough—perhaps even in utero—to reverse or prevent eye damage.
Within roughly the past decade, efforts in two other areas, stem cells and biomedical, or “bionic,” implants, have also given at least some sight to people previously sightless. Stem cells—cells in early stages of development, before they differentiate into the building blocks of eyes, brains, arms, and legs—show increasing promise to replace or revive the failing retinal cells that underlie many causes of blindness. And the first generation of bionic retinas—microchips that replace failed retinal cells by collecting or amplifying light—is bringing a low-resolution version of sight to people who for years saw nothing.