The Girl Who Couldn't See: A Story That Changed Everything

The world came to Corey Haas on a Tuesday morning in October, when he was just three days old. His mother, Ethan, held him in the hospital bed in Hershey, Pennsylvania, exhausted from the delivery but wide awake with the wonder that every new parent feels. She looked down at her son, studying the curve of his nose, the tiny fingers curled into fists, the dark tuft of hair on his head. And then she noticed something else—something that would set her on a journey she never could have imagined.

Corey's eyes, even in those first moments of life, didn't quite seem right. They moved strangely, darting from side to side in a way that seemed more like searching than the normal, lazy gaze of a newborn. When she brought him close to her face, he didn't focus on her. When she waved her hand in front of his eyes, he didn't track it. "It's probably nothing," the nurses said. "Newborns don't see well at first. Their eyes are still developing." Ethan smiled and nodded, trying to believe them. But something in her mother's heart knew differently.

The months that followed were a slow dawning of worry. Corey didn't reach for toys the way other babies did. He didn't seem to notice the mobile that hung above his crib, with its colorful spinning animals that delighted other infants. When visitors came to the house, he didn't turn to look at them. He would sit in his high chair, eyes moving restlessly, as if searching for something just beyond his grasp. "Maybe he's just delayed," people said. "Every child develops differently." But Ethan and her husband, Chad, couldn't shake the feeling that something was wrong.

At six months, they took Corey to an ophthalmologist. The doctor's office was dark, filled with strange instruments and charts with letters too small for Corey to read. The doctor performed test after test, shining lights into Corey's eyes, measuring his responses, frowning as he worked. Finally, he sat back in his chair and looked at the young parents with an expression that Ethan would never forget—a mixture of compassion and clinical precision.

"I believe your son has Leber congenital amaurosis," the doctor said. The words landed like stones in a still pond, sending ripples of fear through everything Ethan thought she knew about her child's future. "It's a rare genetic condition that causes severe vision loss from birth. His retina isn't functioning properly. I'm sorry to have to tell you this, but there's no cure. The best we can do is help him adapt."

Leber congenital amaurosis, or LCA, takes its name from Theodor Leber, a German ophthalmologist who first described the condition in the nineteenth century. But the name tells you nothing about what it feels like to watch your child struggle to see the world. Nothing about the way he would bump into furniture, his small hands reaching out to feel his way along walls. Nothing about the way other children would stare at him, confused by the strange movements of his eyes—a condition called nystagmus, where the eyes drift involuntarily, giving the appearance that he's not quite looking at you even when he is.

LCA is caused by mutations in any of more than 20 different genes, each playing a crucial role in the development and function of the retina. In Corey's case, doctors would later identify a mutation in a gene called RPE65. This gene carries the instructions for making a protein that is essential for the visual cycle—the cascade of chemical reactions that allows the retina to convert light into electrical signals that the brain can interpret as images. Without a functioning RPE65 protein, the retina gradually dies. The photoreceptor cells, the rods and cones that catch light and begin the process of vision, wither and stop working. For most children with LCA, the world grows darker and darker until, by adolescence or early adulthood, they are completely blind.

Ethan walked out of that doctor's office carrying Corey in her arms, and the world looked different to her now. The sunlight streaming through the windows, the green of the trees outside, the faces of strangers passing by—all of it suddenly precious and fragile, a gift that she had never fully appreciated until she understood what it meant to live without it. She looked down at her son's face, those searching eyes, and made a silent promise. She would do whatever it took to help him. She would learn everything she could about his condition. She would find others like him. She would never stop searching for something better.

What Ethan didn't know—what no one could have known at that moment—was that a small group of scientists hundreds of miles away, at the University of Pennsylvania and the Children’s Hospital of Philadelphia, were working on an idea so bold, so seemingly impossible, that it would have sounded like science fiction just a decade before. They were trying to fix broken genes. They were developing a way to deliver working copies of genes into a patient's cells, essentially rewriting the code of life itself to cure diseases that had been considered irreversible. And they were about to choose Corey Haas as one of the first patients to receive this experimental treatment.

The concept behind gene therapy is deceptively simple: if a disease is caused by a faulty gene, then providing the patient with a working copy of that gene should fix the problem. The reality, of course, is infinitely more complicated. To understand why, you need to understand something about the remarkable structure of the gene itself and the equally remarkable challenge of getting a therapeutic gene into the right cells in the body.

Genes are segments of DNA—the long, coiled molecule that carries the instructions for building and running every living thing. In humans, DNA is organized into 23 pairs of chromosomes, twisted together like a ladder that has been twisted into a spiral, a shape called a double helix. The rungs of the ladder are made of pairs of chemical bases—adenine paired with thymine, and guanine paired with cytosine. The sequence of these bases, like the letters of an alphabet, spells out the instructions for making proteins. Change one base, and you might change one amino acid in a protein. Change enough bases, or change them in critical positions, and the protein might stop working altogether. That's what happens in genetic diseases: a typo in the genetic code leads to a malfunctioning protein, and the malfunctioning protein leads to disease.

In Leber congenital amaurosis caused by RPE65 mutations, the faulty gene means that retinal cells can't produce a working version of the RPE65 protein. This protein is an enzyme called a isomerase, and its job is to convert a molecule called all-trans-retinal into 11-cis-retinal. This might sound like alphabet soup, but it's actually the heart of the visual cycle. When light hits the retina, it causes a change in 11-cis-retinal, setting off a cascade of events that ends with an electrical signal being sent to the brain. Without enough 11-cis-retinal, the cycle breaks down. The photoreceptors die, and with them, vision.

The challenge for gene therapists is to get a working copy of the RPE65 gene into retinal cells. This requires a delivery vehicle, something that can carry the therapeutic gene through the cell membrane and into the nucleus, where the cell's DNA resides. The vehicle that researchers settled on is called a viral vector—a modified version of a virus that has been stripped of its ability to cause disease but retains its ability to infect cells. Viruses are remarkably efficient at getting their genetic material into cells; it's how they replicate. By replacing the viral genes with therapeutic genes, scientists can hijack this delivery system for medical purposes.

The virus used in the LCA trials is called adeno-associated virus, or AAV. AAV is a small, relatively simple virus that doesn't cause human disease and, importantly, doesn't integrate into the patient's DNA. Instead, it delivers its car