In the world of running, the Grand Canyon Double Traverse is a legendary and challenging 46-mile run featuring rocky trails, steep cliffs and brutal temperatures. To complete the rim-to-rim-to-rim course is a notable achievement  — and to do it completely blind is something else entirely. 

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

Berlin, 43, was diagnosed as a child with cone rod dystrophy, a degenerative eye disorder that over time can lead to permanent blindness. A lifelong athlete, he turned to running in his late 30s as a means to stay in shape and break the depression he felt from losing his sight. 

"I knew I was going down the path of feeling sorry for myself and not being able to do a lot of things I wanted to do," Berlin told Trail Runner magazine. "It seemed like day by day, I was losing some ability, even going to the grocery store and trying to read what’s on the shelf. I was looking for some way to regain control."

After completing the 2011 New York City Marathon with the help of friend and fellow runner Charles Scott, as well as the 2013 Toughman Half Triathlon, Berlin decided his next adventure would be the Grand Canyon Double Traverse. On the morning of Oct. 7, he set out with four guides down into the heart of the canyon, returning 28 hours later as the first blind runner to complete the course. 

"I ran with two trekking poles, and I would often have a guide in front of me hold onto one pole, so I’d have a rigid tether connection to him, with some direction," Berlin explained. "Otherwise, I don’t push off with the poles. I use them in front of me, almost like a spider would walk, so that I can feel the ground coming up."

For those portions of the trail that skirted the edges of the canyon, Berlin's guides used voice commands and watched carefully to make sure Dan's footwork kept him safe. 

"When we were in the danger sections on the North Rim in particular, where a couple feet to one side was a sheer drop-\off to certain death, we would have the guide in front giving those commands and then a second guide very close behind Dan so if he happened to step to one side or slip a little bit, the second guide could grab him or nudge him away from the edge," shared Scott. 

Going forward, Berlin and his team are looking to turn their adventures into an annual event, raising money for charities and inspiring other blind athletes.

"I don’t look at being blind so much as being a disability, more like an inconvenience," he said. 

Check out a video of Berlin's epic achievement at the Grand Canyon below. 

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