Watching the sun rise, four friends reflected on the accomplishment they completed the night before— running across all 46 miles of the Grand Canyon, the span of the national landmark. A feat for any athlete, theirs was even more special because four of them were guiding their friend Dan Berlin, who is blind.

At 5:20 a.m. on Tuesday, Oct. 7, the group started from the South Rim, ran down to the Colorado River, across the canyon floor, up to the North Rim and back the way they came in 28 hours, crossing nearly 23,000 feet of elevation change.

Berlin, 44, and co-owner of Custom Blending, Inc., was diagnosed with retinal degenerative disease when he was 7 years old. By the time he reached his mid-20s, his central vision had significantly decreased. In his 30s, it got worse and he was unable to drive or read.

“[My vision] was going down, down, down in my mid-30s, losing my ability to do things I really liked,” Berlin told FoxNews.com. “I really needed to come up with something that would break that cycle.”

While running in his Fort Collins, Colo. neighborhood was challenging at first, Berlin found that memorizing his route, using his hearing and running with other people made things easier. He signed up for a half marathon for motivation and ran the race with a guide.

In 2011, he and longtime friend Charles Scott, 46, ran the New York City Marathon together.

“My first reaction was I had no idea how to do it. He said, ‘Don’t worry, I’ll show you how,’” Scott told FoxNews.com. “It opened a whole new world to me, using your athletic abilities to help others.”

During the 2013 Toughman Half Triathlon, Scott introduced Berlin to Alison Qualter Berna, 42. The duo guided Berlin and, inspired by their experience and looking for a new adventure, Scott or Qualter Berna — the two aren’t sure who brought it up first— suggested the Grand Canyon run to Berlin.

Along with Brad Graff, 46, a longtime friend of Scott’s whom Berlin just met, the group worked to guide Berlin across, with one lead guide and the rest following. Unlike when Scott guided Berlin in marathons and they ran shoulder-to-shoulder with a strap between them, for this, the lead held a hiking pole that Berlin would hold with his right hand.

Scott guided most of the way down the North Rim, Graff across the base, and Qualter Berna back up the North Rim, which Scott noted was the most intimidating part of the route. A fourth friend, Pete Kardasis, 40, joined them for guiding duties.

Along the way, the group adapted to figuring out which verbal cues worked best for Berlin and Berlin adapted to each guide’s signals, creating a system that made everyone feel safe.

“For a guide, you had to pay lots of attention to all the details that could trip up someone who couldn’t see,” Scott said. “Dan couldn’t have been more gracious or trusting… [you] have to fully trust your guide.”

That trust was especially important when they came to narrow parts of the trail.

“There are dangerous sections where a mistake could lead to death,” Scott said. “He was, of all of us, the calmest.”

For the guides, leading Berlin taught them to take the focus off their own emotions and physical challenges. Once, Qualter Berna found herself guiding on a part of the rim where only 4 inches separated them from a dangerous drop.

“By focusing on him not falling off the rim, I didn’t think about myself not falling off the rim. I shifted into the mode that my job is to keep Berlin in line and get him up to the top and we’re going to have the best celebration ever,” she said.

“Alison didn’t tell me this until we got to the top,” Berlin added.

“I realized in my first stretch of seven miles going over, ‘huh, you really don’t think about yourself,’” Graff told FoxNews.com. “You think, ‘hey, I can’t fall over the edge,’— that’s a lot bigger than, ‘hey, my leg’s sore.”

Guiding in the pitch black of night put the able-visioned guides in Berlin’s shoes.

“I find it interesting that in my most fearful times when it was pitch-black … at some points I would close my eyes and see how many seconds I’d last without seeing— I couldn’t do it,” Qualter Berna said. “[I had] the realization of how lucky it is to open your eyes.”

For Berlin, who hadn’t really run on trails before, the trip was just another way to look at his daily challenges.

“It’s kind of the way of life for somebody who is vision-impaired … we jump into this not knowing what we were going to do … got in there, had to solve the problem by putting ourselves in the situation,” he said. “Pretty much a summary of how I live my life these days.”

To his friends, Berlin’s attitude served as inspiration.

“Dan has such an obvious disability that many people assume would define his life, instead, he’s showing all of us what’s possible,” Scott said. “I’ve used two words— grateful and privileged— after that run.”

The team ran to raise money for the Foundation Fighting Blindness and the Blind Institute of Technology.  The Foundation Fighting Blindness focuses on research for the prevention, treatments and cures for retinal degenerative diseases. The Blind Institute of Technology aims to empower blind people with meaningful careers by educating employers on the high-level skills they have.

“A lot of people like me train ourselves to be problem solvers because there’s no other way to accomplish what you want to do,” Berlin said. “Out of 20 million blind Americans, only 20 percent of those of working age have jobs.”

As the group watched the sun rise over the Grand Canyon, they all agreed the experience was enlightening and rewarding.

“Coming out of the Canyon’s south rim, it was such an empowering emotional feeling. It’s hard to put into words the sense of accomplishment,” Berlin said. “My wife sums it up really well: You don’t look at it as a disability or inconvenience.”

Click to donate to The Blind Team Challenge via YouCaring.