Scientists Thought Greenland Sharks Were Blind. A New Study Says Otherwise

Greenland sharks have long been assumed to be functionally blind — they live in the pitch-dark waters of the Arctic, and their eyes often appear cloudy, with parasites frequently dangling from the cornea. A new study from the University of California, Irvine says that assumption doesn’t hold up: these sharks, some of which live up to 400 years, may see just fine well into old age.

The idea took shape after Dorota Skowronska-Krawczyk, an associate professor at UC Irvine, watched video of a Greenland shark drifting through dark Arctic water and noticed it tracking the light with its eyeball — behaviour inconsistent with blindness. That observation prompted a closer look at the animal’s actual eye tissue.

Between 2020 and 2024, researchers collected Greenland sharks near Disko Island in Greenland and sent preserved eyes to Skowronska-Krawczyk’s lab for analysis. PhD student Emily Tom examined the tissue and found no evidence of retinal cell death, while rhodopsin — a protein critical for vision in dim light — remained fully functional and tuned specifically to detect blue light, the wavelength that travels furthest underwater.

The findings appear in Nature Communications, in a paper titled ‘The visual system of the longest living vertebrate, the Greenland shark,’ co-authored with University of Basel researchers Walter Salzburger and Lily G Fogg. The study points to a DNA repair mechanism that seems to protect the shark’s retina from the damage that typically builds up over time.

Because the human eye is often among the first organs to show signs of ageing — leading to conditions like macular degeneration and glaucoma — scientists say understanding how the Greenland shark’s retina resists decline for centuries could open new avenues for treating human vision loss.