Born without sight, 7-year-old Lucas Murray used to be so afraid of walking he wouldn't take a step without his parents by his side.
"He would walk, but he would hold our hands. Always," said his mother, Sarah Murray of Dorset, England. "When he was younger, he wouldn't even walk on a bumpy surface."
But now Lucas has become more mobile than his parents ever imagined, running with friends, playing basketball and jumping on a trampoline -- all on his own.
The incredible change, his mother said, is owed to a technique called echolocation, similar to the method used by dolphins and bats, that allows Lucas to paint a picture of his surroundings using sound he creates himself.
To "see" the world around him, he clicks his tongue on the roof of his mouth and listens to the echo that bounces back. From the sound, he can make out the location, depth and shape of objects around him, allowing him to navigate even unfamiliar areas.
Though it's estimated that only about 5 to 10 percent of the blind population now uses a sonar-type approach, the Murrays and others hope it could someday become as common as the widely-adopted white cane.
Inspired by a documentary about a blind American boy who had mastered echolocation, Sarah Murray and her husband Iain Murray reached out to Daniel Kish, a blind psychologist who has practiced the technique since childhood and has been teaching it for more than 15 years.
Two years ago, Kish traveled to the Murrays' hometown and worked with Lucas for four days, teaching him not just echolocation, but convincing Lucas and his parents that blindness doesn't need to be a limiting condition.
"You have to be able to let go, and it's the hardest thing in the world," said Sarah Murray. The family lives by a lake, and when Kish suggested the family let Lucas walk along the shore on his own, she said, "It was terrifying. And Lucas found it terrifying too."
"I had to walk with my hands in my pockets and grip them tightly," she said.
But after the family overcame the initial fear, Lucas' progress skyrocketed.
He advanced from learning how to detect different sized bowls and cardboard panels by clicking to navigating grocery stores entirely on his own. In addition to clicking, Lucas also uses a white cane to find his way.
"He likes exploring things, he likes climbing things," his mother said. "He likes supermarkets and going off on his own… He'll go up the escalator. That wouldn't have been conceivable in a million years."
She said the frequency of Lucas' clicks depends on the environment and how familiar he is with it, but the technique is second nature to him now.
"It's quite nice really," said Lucas. "I just do it. It just works really."
And, as his confidence has grown, his parents' perception of his future has been transformed.
"We had a vision of Lucas needing assistance, having a [guide] dog, and now he's never going to be able to see but I don't see any limits on what he can achieve," said Sarah Murray.
Kish said that mindset is the goal of his echolocation technique, which he calls FlashSonar.
"Although FlashSonar seems to be the most inspiring and impressive part of our work, to us, it's really not the end, it's really a means to an end," he said. "The goal is what we call self-directed achievement."