Transcript for Men Thrive In Sports Despite Sudden Blindness
He calls it his magical medical mystery tour. What one hell think young college kid went through. The fact was, he was going blind and no one knew why. That is until his mother sprang into action and saw what the doctors had missed. Here's our Chris Connelly. Reporter: How good did Jeremy poincenot have it in high school? She was his classmate and friend, Emily from the "Blurred lines" video. But back then, couldn't have predicted how out of focus his own life would soon become. ♪ Blurred lines ♪ here with his family in carlsbad, California, near San Diego, the eldest of three children, Jeremy was loving his life, a life that from the very beginning featured plenty of time on the golf course. Golf was my favorite sport. My dad and I played every single Sunday. Reporter: In the fall of 2008, Jeremy, a college sophomore, began to see the world very differently. I called my mom and said, hey mom, I have to squint to read certain things. Reporter: An appointment with an optometrist took an unexpected turn. Everything is really routine, until he has me cover my left eye. When I cover my left eye, I can't read anything on the eye chart, I couldn't even see the big E. Can you see a letter straight ahead? No. The optometrist seemed way more concerned than I was. Reporter: In fact, he was. He said, um, I don't think he has a brain tumor. All I heard were my son's name and "Brain tumor" in the same sentence. Reporter: What goes through your heart when you hear those two things? Just fear, fear. Reporter: After an mri ruled out a brain tumor, that fear only increased. Two weeks later, there was a shocking development. Instead of the one eye that was affecting getting better, suddenly, the other eye started very quickly getting worse. Reporter: In less than a month, Jeremy was legally blind. It's very, very depressing, and hard to take in at 19. I was waiting to wake up from a nightmare, really. I was researching every night. I was on the internet looking for what causes painless loss of vision. Reporter: Then Lissa came across a rare eye disease that caused rapid blindness, especially in young men -- lhon. Leber's hereditary optic neuropathy. It seemed to describe what was happening to him. Reporter: But doctors were skeptical, perhaps because the malady affects just 1 in 50,000. Very often the ophthalmologist who first sees the patient has never seen a case of Leber's and doesn't recognize it, and maybe hasn't even heard of it. Reporter: Because Leber's is genetically passed down from a mother to all her children, Lissa scoured her maternal bloodline looking for clues. Her sole living relative on that side revealed to her that his father had gone blind. That was the eureka moment. Reporter: Within weeks she had gotten Jeremy tested and diagnosed with Leber's. But the diagnosis meant that Jeremy's blindness was almost surely irrevocable. He was losing so many things. Reporter: Reading, movies, sports on television. When he went back to college, I was afraid that he would jump off of a very tall building. I would sleep in until noon, 1:00 in the afternoon, and my dad came up to me one day, woke me up, said, hey, why don't you wake up at 9:00, 9:30 and be productive and get your days going, maybe that will help you be happier and my response to my dad was, dad, when I'm sleeping, in my dreams, I can see. Reporter: How would you describe what your vision is today? If you were to put your hands directly in front of your face like this, that's what my vision is like. I've got nothing in the center but I have compete peripheral vision. To see things I can look above, below, that gets weird with girls, don't look at them like this, can't do that. Reporter: So what can those with Leber's do? Meet Brett devloo, the Canadian who calls himself "The blind skateboarder," which makes him a pretty big deal here in the town of stonewall just outside Winnipeg. Brett went blind at 16, baffling his doctors. I saw like five specialists in seven days. They all did these eye tests, like, oh, your eyes are working fine, they're fine, they're fine, I don't know what's wrong. Reporter: He waited six months for a diagnosis. I got the test back and my parents both came into my room at the same time and I'm like, nope, this isn't good. Reporter: But he has refused to let Leber's knock him off his board. There's nothing I can do about it, right? I got to keep going and keep my head up. Reporter: Still, a blind skateboarder? Believe it, says Brett. It's like second nature to me. I can -- just like breathing, you know? The way I've always skated is, if I fall, I get up and do it until I make it. Reporter: With some help from siri, he's a social media mainstay. All on his own, but not always on his own. Chicks dig the blind kid stick. Hi, Brett! Hi. It's not too difficult to meet girls. Bump into them with the stick, like, oh, my god, I'm so sorry, I didn't know you were there what's your name? And we go from there. Reporter: But how would Jeremy rediscover the joy in his life after going blind? Lissa was determined to help that happen. For Jeremy, Normal equals sports. So, I started looking up blind golf, U.S. Blind golf association, realized there were tournaments. And in my mind, I am suddenly thinking, "Oh my gosh, you know, here is, here is the solution. I kind of laughed at her and thought she was joking. I said, mom, when, when do blind people play golf, at midnight? Reporter: But with his father as his guide, his game steadily improved. Jeremy and his dad even wound up in England at the world blind golf championship competing against 60 other visually impaired players from 14 countries. Come into the pro shop, and a big british guy grabs me by the shoulder and says, "Jeremy, you tied for the win, you're going to a playoff." Reporter: On the first playoff hole, Jeremy faced a challenging pitch just to get the ball close. I hit the shot, came off the club perfectly and I hear just a little, dink. My dad is on my right, he said it went in. I was like, holy crap! Everything after that I say, was a blur. No pun intended. It's like a movie. I was literally living a movie. Reporter: With his vision stabilized, Jeremy has also started sharing his inspiring story as a motivational speaker. If you could give me my sight back today, I wouldn't take it, because at 23 years old and legally blind, I'm happier than where I was 19 and fully sighted. It's been five years. I still see in my dreams. I still see 20/20 in my dreams.
This transcript has been automatically generated and may not be 100% accurate.