Dead Human Eyes Respond to Light Five Hours After Donor Passed

Scientists have managed to re-activate certain cells in human eyes that were removed up to five hours after the donor's death, raising questions about when neurons can be said to have truly died.

The question of when human cells die is an important one for medical science in part because it allows doctors to know when certain organs can be transplanted. Kidneys, for example, can remain viable outside the body for between 24 and 36 hours under the proper conditions according to the Donor Alliance tissue bank.

Tissues from the central nervous system are thought to lose their potential for re-use quickly after blood circulation stops, but scientists aren't too sure why or what the potential for revival is.

Human eye
Scientists have released a study in which they had success in reviving eye cells from deceased organ donors. A stock photo of a human eye close up. Digital Vision/Getty

To find out, researchers used retinas collected from both humans and mice after death to find out when neurons associated with sight could be revived.

They discovered that they could "wake up" photoreceptor cells—cells that detect light and enable us to see—up to five hours after an organ donor's death. These cells could respond to bright light, colored lights, and even very dim flashes of light.

But there were still problems. The researchers found that the photoreceptor cells were not able to communicate with other cells in the retina. They determined that a lack of oxygen was the critical factor leading to this lack of communication.

To overcome this issue, researchers said they made an effort to obtain donor eyes quickly —less than 20 minutes after death—and also designed a special transport unit to provide the eyes with oxygen and nutrients.

With this approach, they found that they could make the retinal cells communicate in the same way they do in living bodies.

"Past studies have restored very limited electrical activity in organ donor eyes, but this has never been achieved in the macula, and never to the extent we have now demonstrated," said Frans Vinberg, a Moran Eye Center scientist who took part in the study, in a University of Utah Health press release. The macula is the part of the retina at the back of the eye which is crucial for vision.

The results of the study could reduce scientists' reliance on animal testing which does not always produce results that are relevant to humans. It could also lead to potential new therapies for blinding diseases.

"The scientific community can now study human vision in ways that just aren't possible with laboratory animals," says Vinberg. "We hope this will motivate organ donor societies, organ donors, and eye banks by helping them understand the exciting new possibilities this type of research offers."

"Going forward, we'll be able to use this approach to develop treatments to improve vision and light signaling in eyes with macular diseases, such as age-related macular degeneration," Dr. Anne Hanneken, a retinal surgeon involved in the study, said in the press release.

The study, titled Revival of light signalling in the postmortem mouse and human retina, states that its findings raise questions "about the irreversibility of neuronal cell death."

It was published in the journal Nature on May 11.