Greenland sharks' eyes defy aging, offering clues to human vision loss

A 200-year-old eyeball, the size of a baseball, arrived at a UC Irvine laboratory on dry ice. Emily Tom, a 28-year-old Ph.D. student, opened the package and found herself staring back at the preserved eye of a Greenland shark—a creature that had been alive for two centuries and might have lived for two more. The moment crystallized a question that had puzzled scientists for years: How do animals that live for 400 years manage to keep their eyes working?

Greenland sharks hold the record as the longest-living vertebrates on Earth. Some individuals have survived for as long as four centuries, their thick gray bodies and small heads adapted to the perpetual cold and darkness of Arctic waters. Yet their eyes have always seemed like a liability. They appear cloudy and almost lifeless, and parasites frequently attach directly to the eyeballs. For decades, researchers assumed these sharks were functionally blind—that they had simply abandoned vision as an unnecessary expense in a world without light.

That assumption crumbled when Dorota Skowronska-Krawczyk, an associate professor of physiology and biophysics at UC Irvine, watched video footage of a Greenland shark in motion. "You see it move its eye," she recalls. "The shark is tracking the light—it's fascinating." The observation contradicted everything the field had assumed. If the shark was blind, why would it track anything? Skowronska-Krawczyk, who studies the molecular mechanisms of age-related eye diseases, decided to investigate.

She and her collaborators obtained Greenland shark eyes caught between 2020 and 2024 near Disko Island in Greenland. The specimens came from sharks of various ages, including individuals estimated to be around 200 years old. Tom carefully thawed the preserved tissue, a process that required precision—warm it too much and the cells would begin to decay. The lab, she remembers, smelled like a fish market. But the tissue held. Under microscopic examination, Tom found something unexpected: no evidence of retinal cell death. The retina, the light-sensitive tissue at the back of the eye, showed no signs of the degeneration that normally accompanies extreme age.

More striking still was the discovery of active rhodopsin, a protein essential for vision in dim light. In Greenland sharks, this protein was tuned specifically to detect blue light—a wavelength that penetrates Arctic waters better than others. The sharks' eyes, it turned out, were not relics of an abandoned sense but finely calibrated instruments adapted to their environment. The findings, published in Nature Communications and co-authored by researchers from the University of Basel, suggested that some DNA repair mechanism was preserving the integrity of the shark's visual system across centuries.

The implications extend far beyond shark biology. Age-related vision loss affects millions of humans. Macular degeneration and glaucoma rob people of sight in their later years, and current treatments can only slow the damage. If Greenland sharks have evolved a way to prevent retinal degeneration over 400 years, understanding that mechanism could point researchers toward new strategies for protecting human vision. Skowronska-Krawczyk sees the work as foundational—not a cure, but a clue. "What I love about my work is that we are the first in the world to see results," she says. "At the forefront, finding new mechanisms, rules and discoveries."

The research also raises broader questions about how tissues remain functional over extreme timescales and whether protective mechanisms evolved in one species might be adapted for another. For now, the work remains preliminary, and Skowronska-Krawczyk has expressed concern about the uncertainty of federal research funding. But the 200-year-old eyeball on dry ice has already changed how scientists think about aging, vision, and the possibility that some of nature's longest-lived creatures might hold secrets to human longevity.