♪ I, I'm thinking it's a sign - [Speaker] There's no treatment.

There's nothing they can do about it.

- It's just too much.

You're powerless.

- [Jason] The National Geographic documentary, "Blink," presents the story of a family in which three of the four children have been diagnosed with retinitis pigmentosa.

- [Speaker] Let's go all in and fill their visual memory with as much beautiful things as we can.

- [Jason] The family sets out on a journey to show their kids the world while they can still see it.

- [Speaker 2] See a sunrise on a mountain, make friends in other countries.

(kids yelling) - [Jason] Good chance you've never heard of retinitis pigmentosa, and there's good reason for that as it affects just one in roughly every 4,000 people.

- It is considered to be a rare genetic condition, but nevertheless, there are about 100,000 Americans living with it.

- I didn't even know this disease existed.

- [Jason] So what exactly is retinitis pigmentosa?

- Retinitis pigmentosa is a genetic condition that affects the retina.

The retina is the light sensitive part of the eye that is really the only part of the eye that can do the actual seeing.

- [Jason] The retina's photoreceptor cells are responsible for capturing light, but over time, retinitis pigmentosa causes those cells to break down, with the damage eventually spreading throughout the retina.

Symptoms usually begin in childhood.

- It's sort of been my whole life.

I've known I had bad night vision.

- Brothers Quinn and Reid Manning didn't think or know anything was wrong when their symptoms first arose.

- You know, we lived in Florida at the time.

We were going to Disney World, Universal, things like that, and yes, they could not navigate the "Pirates of the Caribbean," you know, in the dark.

- We had a field trip to Universal Studios and we were going through the "Mummy" ride, like through the line.

It gets pretty dark in there and I kept whacking into like the barrier.

So I had to have my friend guide me through, you know?

- For me, it would be like the movie's ended, right, and you're trying to sneak out before, you know, the last credits are still rolling and they haven't turned the lights on and the boys are a little bit more challenged with that.

- [Jason] This video demonstrates what a healthy eye normally sees, then one affected with retinitis pigmentosa.

Huge difference.

- And it leaves the patient with sort of a tunnel vision type of an experience.

And then in the more advanced stages of disease, even that central vision can get affected and that would impact one's ability to read or recognize faces.

So as you can imagine, can have quite a profound effect on somebody's quality of life.

- It was finally when we went to visit Reid at college and were in the aquarium and he was grabbing onto my arm and I went, "Really, seriously?"

- [Jason] Martina first took her sons to an optometrist, then an ophthalmologist, - And that's when they were like, "Oh, something might not be right."

Then they sent him to a retina specialist and the retina specialist was like, "Eh, something might not be right."

And then that's when we went to Duke.

- You do all the tests and they're telling us, "Yeah, so you have this eye condition that makes it so, you know, the cells in your eyes are dying and, you know, you'll go blind eventually."

- Well, I did not process it well, I'll put it that way.

Yeah, I mean, I'm sorry for getting emotional.

I had a hard time with it.

- [Producer] Yeah.

- Yeah.

- [Jason] Due to its complexity of being a collection of hundreds of genetically different conditions and not a singular one, retinitis pigmentosa is a moving target of sorts.

There is no cure.

- As we talked about, no cures right now and unfortunately no real treatments right now for the majority of these.

- So I feel like I can kind of see stuff in the dark if I stare directly at it.

But my peripheral vision is completely gone.

- [Jason] As the disease progresses, it can lead to complete and total blindness.

- [Kevin] The scary part of it all is the word progression, right?

It's bad today, it's gonna be worse tomorrow, it'll be worse the next day.

This just is gonna continue on in that path.

So, you know, back then it was just, you know, they had bad vision, deal with it.

The fact that it's gonna, you know, now that we know more, it's just gonna get worse, that's the part that's the challenge.

- Really, it's a long-term disease, right?

Because like the degradation, that happens over decades.

- It is outta my control.

You know, listen, I had a very hard time with it for a very long time.

I walked the neighborhood, crying probably for months.

But eventually I kinda got to this point where, you know, I have to be proactive.

I can't just be feeling sorry for myself or my children.

- [Jason] RP is not something anyone can get.

It's an inherited disease, passed down generation to generation.

Kevin Manning didn't know it, but he was a carrier.

He doesn't have RP, but others on his side of the family did, - You know, in the family that we're talking about, it was a more unique kind of a situation where it can actually skip generations, which is something that occasionally happens, yeah.

- I was ignorant of it.

Didn't think it applied to me, right?

So this was a big learning shock to the system, honestly.

- [Producer] Yeah.

- You know, and then it's one thing that their eyes are a challenge and now the other thing is that, you know, technically I'm the one responsible for it.

- [Producer] How does that make you feel?

- Oh, pretty poor, right?

I don't know what the rating on this video is, but, you know, fill in the bad words, right?

I mean, that's hard to bear.

You spend your life trying to do the best you can for your kids and the big challenge they're gonna face is, you know, you caused, unknowingly.

- [Jason] Chalk it up to youth or just being boys.

Reid and Quinn are taking their new reality in stride, about as well as anyone could.

- At least we're both in it together.

We sort of got someone who's going through the same thing.

And I don't wanna say I was like happy to be diagnosed with it, it isn't great.

But I'm like, you know what?

It's not the worst case scenario.

- Obviously I don't exactly wanna go blind, but at the same time, there's not exactly a cure for it.

So I don't feel like I should really get too like built, worked up over it.

So it's more just like an acceptance sort of thing of understanding, well one day, you know, I will have these problems, but right now I don't.

So I guess just enjoy being able to see why I can.