Science Friday

What Greenland Sharks Are Teaching Us About Aging Eyes

January 15, 2026

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  • Greenland sharks maintain remarkably healthy eyes over their centuries-long lifespans, contrasting sharply with age-related vision decline seen in humans. 
  • The longevity and eye health of Greenland sharks appear linked to highly efficient, highly expressed DNA repair mechanisms at the molecular level, which humans possess but may not express strongly enough. 
  • Technology developed for the James Webb Space Telescope's mirror polishing and measurement, intended for extreme flatness, has spun off into medical applications, such as diagnosing eye surface imperfections. 

Segments

Intro and Shark Eye Research
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(00:00:26)
  • Key Takeaway: Greenland sharks’ long lifespan suggests superior eye health mechanisms compared to humans who suffer age-related vision issues.
  • Summary: Human aging leads to vision blurriness, cataracts, and glaucoma risk, prompting research into how Greenland sharks maintain functional eyeballs for centuries. Initial observations suggested the sharks might be blind due to glazed-over eyes, but new research indicates their eyes are healthier than previously assumed. The study aims to understand how these fish preserve eyesight to potentially inform human treatments.
Acquiring Shark Eyeballs
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(00:02:47)
  • Key Takeaway: Researchers collaborated with scientists who previously studied shark longevity to obtain frozen Greenland shark eyeballs for molecular analysis.
  • Summary: The study author contacted scientists who had previously dated shark lenses via carbon dating to request leftover frozen eyeballs. The collaborating scientists agreed to send existing samples and collect more during their next research trip. The eyeballs are described as slimy, about the size of a small apple or large plum, and are cut in half while frozen, like cutting ice, to study the cross-section.
Shark Eye Structure and Health
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(00:04:49)
  • Key Takeaway: Greenland shark eyes are structurally adapted for low-light detection and lack the typical signs of aging, such as debris or degeneration, found in older human eyes.
  • Summary: The shark eyes are adapted for low light, seeing shapes and light passing by, but lack high resolution. Upon cutting the eyes open, researchers found no deposits behind the retina or signs of cellular degeneration, unlike human donor eyes from individuals over 40. Older human eyes (60s and 70s) show a plethora of problems, whereas the shark eyes remain organized and functional.
Mechanisms of Human Eye Aging
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(00:06:17)
  • Key Takeaway: Human tissues, including eyes, degrade over time because cumulative, imperfect repairs following constant exposure to small stresses eventually overwhelm the system’s resilience.
  • Summary: The general aging process affects all parts of the body, not just the eyes, which generally function well for a long time due to repair mechanisms. Eyes constantly undergo damage, repair, damage, repair cycles throughout life. Over time, repairs become imperfect, or repair mechanisms become inefficient for certain damage types, leading to tissue degradation.
Shark Longevity Secrets
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(00:07:38)
  • Key Takeaway: Greenland shark eye preservation is attributed to a cold environment slowing metabolism and, crucially, highly efficient DNA repair mechanisms that are genetically present but less active in humans.
  • Summary: Two factors contribute to the shark’s eye health: the cold environment slows down metabolism, and molecular analysis revealed highly expressed DNA repair mechanisms. Humans possess the same genes for this mechanism, but they are likely not expressed highly enough to offer the same protection. Increasing the efficiency of this DNA repair mechanism could potentially protect human vision longer.
Future Research Directions
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(00:08:46)
  • Key Takeaway: Future research aims to translate the shark’s eye-saving genetics by boosting DNA repair efficiency in mammals, potentially via small molecules or gene therapy.
  • Summary: The next steps involve testing how to boost the DNA repair mechanism first in mammals, such as mice, before attempting translation to the human eye. Researchers are creatively exploring methods like small molecules or gene therapy to deliver this protective effect. This work directly utilizes the molecular biology knowledge gained from studying the shark’s superior repair systems.
JWST Mirror Precision Listener Question
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(00:10:35)
  • Key Takeaway: The James Webb Space Telescope mirror’s imperfections are significantly smaller than the commonly cited ‘baseball’ analogy when scaled to the size of the United States.
  • Summary: A listener asked if the JWST mirror’s highest bump, scaled to the size of the US, would be the size of a baseball. The expert clarified that the imperfections are actually about 30% smaller, putting them in ‘golf ball territory.’ Such extreme flatness is necessary for the telescope to achieve the sharpness and acuity required to observe the universe’s first galaxies in exquisite detail.
JWST Tech Spin-offs
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(00:13:37)
  • Key Takeaway: The specialized measurement techniques developed to ensure the JWST mirrors’ perfection are now being adapted for medical use in diagnosing human eye surfaces.
  • Summary: Manufacturing the one-off JWST mirrors required developing new technologies for polishing the beryllium segments and precisely measuring their imperfections. A technique developed to measure these tiny bumps is now being used in medicine to diagnose and measure the surfaces of human eyes for optometrists and surgeons. This is cited as an example of a technology spin-off from NASA development.
Awe and Science
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(00:16:19)
  • Key Takeaway: Exploring the universe through tools like the James Webb Space Telescope reinforces a sense of awe and can strengthen religious perspectives by addressing fundamental questions of origin.
  • Summary: A listener shared that studying space science strengthens their relationship with God by helping them understand the Creator better, bringing hope and joy. The discussion concluded that looking at the universe naturally leads to pondering big questions like the origin of everything and the Big Bang. Both science and religion can address the moment of creation, fostering a sense of absolute awe.