Erik Weihenmayer wears sunglasses often. He was wearing them to protect his eyes when he reached the summit of Mount Kilimanjaro in 1997. He had them on when he completed the 2003 Primal Quest, the world's toughest multi-sport adventure race. And, he put on a pair during a recent visit to the National Eye Institute (NEI).But this last set is no ordinary pair of Oakley sunglasses.Weihenmayer looks through them, peering down at a white note card on a table. He silently moves his head back and forth, up and down. After a few moments, he says, "Is that a 12?"Richard Hogle, sitting next to him, nods his head. "Yep," he confirms, "and you were still well zoomed out." The sunglasses are wirelessly connected to Hogle's laptop, so he can monitor Weihenmayer's view. "I'm amazed," Hogle comments.Weihenmayer laughs. "How could I make money off this device?" he asks. "Doing some kind of card trick at a party...I could really freak people out!"He is one of only 40 people ever to use this specially outfitted type of sunglasses, but all have one thing in common: they're blind.Erik Weihenmayer tests the third-generation BrainPort device.The sunglasses are part of a breakthrough vision device known as BrainPort, under development by the NEI-supported researchers of Wicab, Inc., for which Hogle serves as director of product development. BrainPort is built on the concept of sensory substitution, which means that when one sense malfunctions, another sense can compensate, serving as a stand-in."Even a blind person walking down the street with a cane is basically using a form of sensory substitution," says Michael D. Oberdorfer, Ph.D., of the NEI extramural research program.With BrainPort, the tongue ultimately replaces the eyes in transmitting visual input to the brain. But first, a small video camera on the nose bridge of the sunglasses acts as "eyes" to gather visual information. The images are transmitted in black, gray and white to a handheld computer, slightly larger than an iPod, which translates the visual information into electrical signals.Next, these signals are transformed into gentle electrical impulses that end up on the tongue when BrainPort users place a lollipop-sized electrode array in their mouths. The white portions of images become strong impulses, the gray become medium impulses, and the black result in no impulses. The tongue sends these impulses to the brain, where they are interpreted as sensory information that substitutes for vision.This process works in much the same way that the optic nerve in the eye transmits visual information to the brain. Thus, this device supports the idea that we may not need our eyes to maintain our "vision." As BrainPort inventor Paul Bach-y-Rita, M.D., was known to say: "We don't see with our eyes, we see with our brain."When Weihenmayer was a toddler, his parents took him to an ophthalmologist after noticing that he had abnormal eye movements. Doctors ruled it a temporary condition, but a year of additional testing revealed that he had retinoschisis, a genetic disease in which small cysts grow within the delicate retinal tissue in the back of the eye.In time, the layers of Weihenmayer's retina would begin to split apart. By his teenage years, doctors warned, he would go blind.To this day, no treatment or cure exists for retinoschisis. In Weihenmayer's case, doctors recommended that he avoid contact sports, as a blow to his head could lead to earlier blindness."What was I going to do, live in a bubble?" Weihenmayer asks. "You can't. Even at that age I knew, if I'm going to go blind a year earlier, I'm still going to live my life."Like a typical boy, he wrestled and played football. By the time he was 8, however, he had trouble following the action during basketball games. His parents would yell, "ball change," when a pass was made, and Weihenmayer could track his position on the floor only by following the painted lines.Even so, he says he didn't notice he was different until other kids did simple tasks that eluded him. "That was frustrating and sometimes lonely, especially being a boy in gym class," he says.Still, his father, Ed, remembers, "Erik was fighting to stay in the sighted world up to a point." He put off using a cane and learning Braille until he couldn't function without them. But soon he learned that with them, he could finally participate in class and interact with friends more easily."The very things that he thought were going to separate him by making him different actually kept him closer," Ed Weihenmayer says.There was no dramatic moment when Erik Weihenmayer realized he was blind. Some days he woke up in darkness, but could see by the afternoon. Eventually when he became a teenager, however, he realized that the light would never turn back on."My brain had to adjust [to going blind], and that was much more difficult than actually going blind," he says.His family had to adjust as well. "There wasn't anything that we could do about the blindness," Ed Weihenmayer says. "What we could do is embrace the challenge with him as a new adventure. His problem led to more curiosity, more innovation and more fulfillment for everyone around him."As a teenager, Weihenmayer enrolled in rock climbing classes through a school for the blind. "I thought [rock climbing] was an awesome sport for a blind person," he says. "Maneuvering myself up the rock face was unbelievably engaging."As an adult, he transitioned from a once-a-year climber to a "weekend warrior" who soon became the only blind person to summit the highest peak on every continent. Though he can't see the vistas at the top, Weihenmayer says he still appreciates the scenery."The crunch of the ice under my feet or hands, the pattern within the rock that I'm connecting with...It's all my body in relationship to the rock face or the mountain," he explains.And when he reaches the top? "I can hear space."When Ed Weihenmayer learned that his son would go blind, he says that one thought kept passing through his mind: "Let me please learn how to help him so that he can live a life that is meaningful to him."It was Ed who read a newspaper article about BrainPort in the early 2000s and contacted Bach-y-Rita to ask if Erik could test the device.Bach-y-Rita had thought of the concept for BrainPort nearly 40 years earlier, around the time Erik Weihenmayer was born. His first sensory substitution device consisted of a chair with pins that popped out in shapes against a person's back. Much like the guessing game in which one person draws words on another's back, the person in the chair could feel and identify the shape through touch instead of sight.Bach-y-Rita, who received his first NEI research grant in 1993, later found that the fingertips were even more sensitive to touch than the back. But in trying to create an electrical device, he realized that fingertips lack a moist environment to conduct a charge, and layers of dead skin prevent vibrations from having a strong impact. However, the tongue, which is exquisitely sensitive to touch, circumvented both of these problems.Aimee Arnoldussen, Ph.D., worked with Bach-y-Rita to develop BrainPort until the inventor passed away in 2006. Though the device does give users visual input, she cautions that it does not allow them to "magically see the way you see with your eyes.""It's much more akin to a language in that you develop a skill," says Arnoldussen, a neuroscientist and current leader of the research.After five minutes with BrainPort, users can learn to operate the device, she explains. Within an hour, they can identify the location and size of small objects. In a few more hours, larger objects and an obstacle course may become visible.Weihenmayer vividly remembers his first experience with BrainPort. He tested an early prototype, a bulky device hooked to a desktop computer that relied on a webcam for visual input. He says he could feel the electrical impulses move along his tongue as a ball rolled across the floor in front of him."It took just five minutes before I was reaching out and grabbing it," he says. "I just thought it was so cool how my brain caught on to what I was feeling with my tongue."Next, BrainPort researchers went to his home in Colorado to test the second-generation device, one that had three cameras for different fields of view and more electrodes to create a better image resolution.Over several hours, Weihenmayer played tic-tac-toe with his daughter, built a snowman, and scaled a rock wall at his local gym. "I started learning how to climb like a sighted person," he remembers.To date, no one, including Weihenmayer, has used BrainPort for more than 10 hours total. In the near future, Wicab researchers plan to apply for device approval from the Food and Drug Administration, so the general public could gain access to the device, in addition to those who have been testing it in clinics."We want to get this device into the hands of as many people as possible because that's the way that we'll be able to develop the technology and optimize it for the most possible blind [people]," says Robert A. Beckman, president and CEO of Wicab, Inc.Back in the room with Hogle, Weihenmayer finishes testing the third-generation BrainPort, which allows users to select custom-designed image modes for use indoors, outdoors and while reading. Hogle repacks the device into its lunchbox-sized case, which is smaller than the entire first-generation version."You can take it with you," Hogle says. And with that, Weihenmayer will become the first blind person to take BrainPort home and use it on his own, as part of Wicab's latest clinical testing of the device.Weihenmayer says he hopes to try the device on the ski slopes someday soon, but as he has already adapted to living as a blind person, the device won't be a life-changing element."It's not like I'm sitting in suspended animation, waiting for some new technology that's going to bring my life back," he says.Still, Beckman reminds people that the device was primarily created for users to perform everyday tasks that may seem simple to the sighted, such as reading street signs and searching for empty seats on a bus. BrainPort is not meant to replace the cane or guide dog for the blind, but to add "an additional bit of information to make their lives a little bit easier and a little safer," he says.However, even the world's most famous blind adventure athlete, and father of two, has something modest in mind when he returns home with the device.After he switches the BrainPort to 8-year-old Emma's "Dora the Explorer" lunchbox for fashion purposes, Weihenmayer says he'll take a trip to a prestigious art museum--located in his basement--where he'll "have the kids draw pictures for me to see."