Science Friday - What Greenland Sharks Are Teaching Us About Aging Eyes

Episode Date: January 15, 2026

As we age, our vision gets blurrier, we form cataracts, and we have a higher risk of glaucoma. But Greenland sharks live for hundreds of years and still maintain healthy, functional eyeballs. So what gives?Host Ira Flatow talks with molecular biologist Dorota Skowronska-Krawczyk, who studies the mechanisms of aging, about what we can learn from these fishy eyeballs and how it could help us.Plus, listener Leon called us with a question: Is it true that the James Webb Space Telescope’s gold-plated mirror is so perfectly flat that if it were the size of the United States, the highest bump would be the size of a baseball? Not quite. Host Flora Lichtman discusses this feat of engineering with JWST project scientist Macarena Garcia Marin.Guests:Dr. Dorota Skowronska-Krawczyk is a molecular biologist and associate professor at the University of California, Irvine. She studies the mechanisms of aging.Dr. Macarena Garcia Marin is a project scientist for the James Webb Space Telescope at the Space Telescope and Science Institute in Baltimore, Maryland.Transcripts for each episode are available within 1-3 days at sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

Hi, this is Science Friday. I'm Iraflito. Today on the show, eyeballs. As we age, all sorts of things can go awry in our eyes. Our vision gets blurry, cataracts may make our eyes cloudy, and we're more at risk for diseases like glaucoma. So how do we keep our eyes healthy for longer? According to new research published in nature communications, one clue may lie in the eyeballs of, you're going to guess this, the eyeballs of, the eyeballs of, of Greenland sharks. These sharks can survive for more than 400 years. And because they live for so long, and their eyeballs look glazed over, scientists thought they were basically blind. That is until this new study found that the shark's eyes are healthier than we originally thought. So, how can Greenland sharks maintain their healthy eyes for so long? And can't tell us anything about preserving our own eyesight. Joining me is the study author, Dr. Dorota Skofranska Kravchik, Associate Professor at the University of California, Irvine,

who studies the mechanisms of aging. Welcome to Science Friday. Yeah, hello. Thank you for having me. Nice to have you. So what is it about Greenland sharks that caught your eyes, so to speak? Yes. There was a study in 2016 in science, so very good journal.

talking about how long shark can live. And they found that these sharks can live, as you said, over 400 years. But at the same time, they released a lot of movies. And the movies were really cool. I mean, you know, they were like people swimming along the shark and filming them. And what I noticed is that the sharks are observing the swimmers. So they're looking back at the swimmers who are looking at them, is what you're saying. Exactly. They were following them with their eyes. Well, that was just

first observation. So I was really, I mean, for me as an eye lover, it was very interesting and so on. And then I read the paper carefully and I realized that there is a strong assumption that those animals do not see. That was weird for me because they were definitely following the light especially. And that was like a-ha moment there. Yeah. Yeah, that was surprising. And then the occasion came when we realized that we can actually contact the scientist there and ask if they still have some leftover eyeballs from their studies because they collected some eyeballs exactly for the carbon dating, which they did on the lens. So what did you do? Just order up a box of shark eyeballs here? Something like this. Well, of course, we wrote to them a nice message and asked if they are interested in this collaboration.

They said, yes, sure, we can send you some ice we have in freezer, but we can also collect some more ice during our next trip. Wow. That was amazing. So, please, describe what these eyeballs look like from me. Spare no details here. I want to know exactly. Well, they are quite slimy. They are quite slimy.

So when you get them, they are frozen, usually. And first of all, they are size of the, let's say, small apple or big plight. You know? Wow. So they are pretty big. And then when we get them frozen, we don't want to lose the specimen. So what we do, we actually cut them with a little thin saw in half. I'm cringing.

I'm cringing. I know it sounds like that. But, you know, we don't want a spare material. Those animals are living so long. And we want to be sure we study everything we can with the material we have. So what's it like once you get cut through it? What's it like to do that? Well, it's just, it's like ice, right?

It's frozen, so it's like cutting through ice. But what is really amazing when you open, you just see cross-section, you know, like through the eye. And it's see how beautiful, how big it is, and also how protected it is from the pressure. There is a very thick walls around. So the eye is not collapsed when they are deep in the sea. It's just already, you know, like amazing. You just already see that there are adaptations to how they live. where they live. So it is a low light detecting. So there's no really high resolution. But they

definitely see shapes passing by, a light passing by, and of course, probably see if there's big, small, and so on, so on. And of course, with these sharks living up to 400 years, I would expect that when you cut open the eye, you might see aged things like we have, like cataracts and signs of aging, but you didn't see that, did you? So that's the surprising part. There is no signs of the deposits behind the retina. There is no signs of some degeneration of the part of it, some cells disappearing. Everything looks very organized and ready to go, ready to work.

As opposed to that happening in humans. Yes, yes. As we get older. Exactly. When you start to look at the human eyeballs, which we fortunately receive from donors, we can see already like around 40, 50 years old donors, we start to see some deposits, some debris, some, you know, things in the eye

that we can presume they were already disturbing a little bit vision. But then with 60, 70 years old, the eyeballs, now we start to see plethora of different problems. So what is it about aging that our eyes fall apart as we get older? What's going on there? I don't want to be pessimist, but actually we all fall apart. Everything falls apart, not just your eyes. Not just our eyes.

Our eyes seem to actually work pretty well for a long time, and they have really a lot of mechanisms to resist the stress. But what seems to happen is that our eyes are exposed to many different small stresses impacts and challenges through the life. And they always have to repair themselves. So there's always a little bit damage, repair, damage, repair. But, you know, if you have it so often, sometimes the repair will not be perfect, right? Or sometimes the mechanism of repair is not efficient in given type of damage.

So that's why with time, you know, the system is less and less resilient or more and more susceptible to next stress. And this is how it happens, you know, with time, the tissue goes mad. Tell me about it. I'm a direct witness to that. Well, what is it? I guess this is what you would like to know. What is it about the Greenland sharks that they can prevent all of this? Is it something genetic, do you think? So, yes. So there are two things. things that we think happen. First of all, the environment is really cold, so it slows down metabolism. But then we looked into the, more into molecular biology of these eyeballs, and we realized that at the molecular level, they seem to have very efficient, highly expressed or highly

present DNA repair mechanism, which means there is a push to keep this vision. healthy, longer. Do we have the same gene mechanism that maybe is not expressed? That's actually a beautiful question. We have exact same mechanism. We have exact same genes. But maybe they are not expressed highly enough. So one of those genes that we shown, we have studied a little bit before.

So we know already that this mechanism is crucial. But now we have a proof that if you actually turn it up, it may be protective. So what we need to do is figure out how to hack the Greenland Sharks' eye-saving method and the genetics and possibly use it for a treatment for us? That would be the simplest translation, right, of the findings. And obviously, it sounds like that. We have to test it very much.

But I do think that if we can increase the efficiency of the DNA repair mechanism, we actually may be able to protect vision longer. So now we started many different experiments to think about it creatively, how we could really bring it to human. Where do you go from here? Yeah, thank you for that question. So what our laboratory is interested in

is to really use the knowledge about the DNA damage repair mechanism and how it's boosted in the shark eye to try to understand whether we can do the same first in mammals, so like in mouse, and then hopefully we can translate it nicely to the human eye. We just need to think about the ways either through small molecules or maybe even gene therapy to bring this to human. And that's where you come full circle because you're a molecular biologist. Yes, this is how we work.

Well, I'm glad you've shared that with us. Thank you for taking time to be with us today. Thank you. Thank you for asking those great questions and having me share my love. Dr. Dorota Skofranza Kravchik, associate professor at the University of California, Irvine, who studies the mechanisms of aging. Coming up after the break, a different kind of eye. This one is the eye in the sky that's changing our understanding of the universe.

Of course, I'm talking about the James Webb Space Telescope. Stick around. Hey, it's Flora. Speaking of remarkable eyes, one of you, dear listeners, called us with questions about the biggest eye in the sky, the James Webb Space Telescope and what kind of technology had to be invented to see farther back in time than ever before. And we live to serve. So here to see that we get some answers is the James Webb Space Telescope Project scientist, Dr. Makarena Garcia-Marine. Welcome back, Makarina, and thanks for doing this. Thank you so much for having me, Flora.

lovely to be back. Let me start by introducing you to our listener who called with this question. Hi, my name is Leon, and I'm from Kennewick, Washington. Leon's 18 years old. So I'm just finishing up high school, but I'm taking classes at the local community college, and then I'll be going to university after I serve a mission for two years for my church. And Leon's into space, and he's into James Webb, and he heard this thing about the James Webb, Space Telescope that caught his ear. I heard once that the gold-plated mirrors on the James Webb Space Telescope have remarkably small imperfections.

The analogy I heard was that if it were the size of the United States, the highest bump would be the size of a baseball. Macarena, that seems wild to me. Is that true? It's actually not quite true because it is better than a baseball. Really? Yeah, really. And I think Liam is referring to those tiny bans imperfections that, you know, they are there and you cannot do anything about them.

And those would be, give or take, a 30% smaller than a baseball if a mirror would be the size of the United States. We're in golf ball territory. Oh, yeah. That's amazing. I mean, why do you need such a perfectly flat mirror? Well, because when you want to observe the very first galaxies that were created in the world, the universe or when you want to observe nearby objects, but with a really exquisite detail, you do need that size and you do need that perfection. Otherwise, things will be blurry.

For sharpness, for acuity. It is sharpness and acuity. Okay. Let's get to Leanne's other question. Here's what he wants to know. My question is what the biggest hurdles were in terms of what technology they needed to develop and how they got past those and how they got past those and how figured out solutions to their most complex problems. What were the biggest challenges? Are there things that still haunt you? No, because he's going so well. Well, because he's interested on the mirrors, there were many technologies developed. The manufacturing of the mirrors was fresh and new, but specifically the polishing of the

mirrors require new technologies and the measurement of those imperfections required development. of new techniques. And this is because when you build one of these telescopes, they are a one-off. So you really have to do new things to make it as perfect as possible. So what did you have to develop to make sure it was as flat as it was? There is a lot when it comes to building this telescope of processes and engineering. So in this case would be, first of all, select the right material, make sure the material is going to behave well when it gets really, really cold because it's in a space and it would be very cold, but also make sure that the polishing, they are made out of beryllium metal and that they had to be polished to perfection.

So, for instance, there was a development of a technique to measure those tiny bumps, to measure them very precisely to measure that it was as flat as possible. And today, that technique, or part of that technique, it's used to diagnose and to really measure surfaces of eyes to make sure that they can be perhaps be used by optometrists or by doctors to go surgeries. Oh, to see if your if your eye has any imperfections on it. Right. Just to measure the surface of the eye. So it is actually using medicine, which is one of those, you know, spinoffs as NASA calls them. Technology you develop for a purpose and then it trickles down into society. Wow. That's really cool. That's exactly what Leon was asking about.

Yeah, he has really good questions. You know, before I hung up, I asked Leon why he was interested in space. And his answer caught me off guard. This might be an unusual answer, but I'm a deeply religious person. And science is kind of, for me, has strengthened my relationship with God. And I feel like helps me to understand the creator a little bit better. And so it just makes me feel, I guess, hope and joy for something greater out there than us. Makarina, I loved this sentiment, and I wondered how it would hit you.

That's a lovely answer. I think when it comes to the universe and we look at any of, you know, even the night of sky or any of the telescopes, results, you always wonder about the big questions, as in where do we come from, where are we going, what is the origin of everything, in this case, what is the origin of the universe in the big band. So I think there is an interplay that is very clear there. Yeah, and there's awesomeness in both fields, right? And I mean that in the, you know, the true sense of the word, that there's awe. Yeah, there is absolute awe.

And think of the Big Bang, right, that particular moment, which is the creation of our universe. So we can study the universe afterwards, but it can also be addressed from a religious perspective as the moment of creation. So I think there's a lot to think about that. Leon had one more thing to tell you, Macarena. What you've done is super awesome. And thank you for, for. what you've done for science and exploring space. That's fantastic.

Thank you to Liam, but this is, of course, the effort of thousands and thousands of people. It takes a village. And none of this happened by chance. These were very well planned and thought of engineering the science and science objectives and really teamwork that made it happen. But thank you. And it really works by day to hear that. Thank you, Macarena.

Thank you for joining us today. Thank you. Dr. Macarena-Garcia-Marine is a project scientist for JWST. And Leon, thank you for the wonderful question. This show is produced by Russia Oridi. And if you have a question that you need an answer to, give us a ring. 8774 SciFry. Catch you tomorrow.

I'm Flora Lichten.