- [Brian] I cannot see, but I can hear the world around me.

- [Narrator] Meet Brian,

he's known as the world's best totally blind mountain biker.

(bell dinging)

- [Brian] When I was younger I had functional vision,

and I played sports.

I had dreams of becoming a professional athlete.

- [Narrator] And then suddenly when he was 14,

he completely lost his sight over

the course of three months.

His optic nerves

inexplicably failed, and all he could see was darkness.

He wasn't able to bike ride or participate in the sports

he once enjoyed.

- [Brian] I couldn't play hockey;

I had to stop roller blading,

couldn't read the classroom board anymore.

My world had shrunk.

- [Narrator] He had to find a new way

to navigate the world.

He found his cane limiting, but when he learned

to make a tongue click,

his world changed again for the better.

And it wasn't long until he ventured back outdoors.

- [Brian] I really missed bike riding,

and I really wanted to be active,

I just didn't know how to do it.

As a blind rider it was a goal for me

to get off the tandem

and have the experience of being able to pilot

my own bike.

It all starts with a zip tie.

A sighted person would attach it to

their frame and angle into the bike wheel.

The bike wheel would make noise

and the sound would follow while we still actively click.

- [Narrator] Eventually,

Brian was able to mountian bike alone

and without the zip tie.

- [Brian] When I'm riding my bike

down a mountain,

it's the same thing bats are using, eco-location.

I can make my active sonar signal by making

a tongue click.

I start off with trying to find

the object furthest in the distance and then piece

the world together with things closer and closer.

- [Narrator] Brian has to enter

an almost meditative state

and remain extremely focused.

- [Brian] Everything has to leave my brain

and those sounds are painting a picture

in my head-a vivid world of acoustic images.

- [Narrator] He didn't keep his passion

to himself though.

He's helped teach over thousands of people

to hear their world a little bigger.

- [Brian] This is a teachable thing.

Anybody can do this.

And I'm happy to show them.

Riding my bike was something I never thought I'd be able

to do again, and now that I'm doing it,

it serves as a great example

to challenge preconceived ideas.