In a groundbreaking development that marks a significant stride toward whole-eye transplantation, researchers have succeeded in keeping human retinas active and responsive to light for up to 10 hours after death. This achievement, which doubles the duration previously recorded by scientists, was made possible by mimicking the physiological conditions of the human body to sustain the delicate ocular tissue.
The retina—the light-sensitive tissue situated at the back of the eye—is extraordinarily vulnerable to ischemia, a form of cellular degeneration triggered by oxygen deprivation. Even brief periods without oxygen can cause irreversible damage to its complex neural circuits. While corneal transplants have long been a routine procedure to restore vision, transplanting a whole eye remains an elusive medical goal. This is primarily because the retina, as an extension of the central nervous system, degrades rapidly once blood flow ceases. Indeed, a historic whole-eye transplant performed in 2023 failed to restore the recipient's sight due to this rapid cellular decay.
To address this challenge, Eimear Byrne and her team at the Barcelona Institute of Science and Technology in Spain designed an innovative perfusion system. Dubbed the "Eye-in-Care-Box," the custom-built apparatus inserts a flexible tube into the ophthalmic artery to supply the eye with a specialized oxygenated solution. Sensors within the device automatically monitor and regulate both pressure and flow to replicate natural circulation.
The researchers tested their device using eyes donated by deceased individuals. In an initial test involving six donors, one eye from each donor was connected to the perfusion system while the other was left untreated. The perfused eyes maintained their structure and cellular viability for 24 hours, whereas the non-perfused eyes deteriorated rapidly.
Subsequent tests on 36 additional perfused eyeballs yielded even more remarkable results: 15 of the retinas generated electrical responses to light similar to those observed in living patients. These responses persisted for up to 10 hours post-mortem, doubling the previous benchmark of five hours set in 2022. It remains unclear, however, why the remaining 21 eyeballs did not exhibit the same electrical activity.
Thomas Johnson, an ophthalmologist at Johns Hopkins University who was not involved in the research, lauded the accomplishment, describing the preservation of light responses outside the body as a "tremendous feat." He noted that while this technology does not solve the challenge of regenerating severed optic nerve fibers—the crucial link required for the eye to communicate with the brain—it dramatically reduces ischemic damage. Furthermore, the Eye-in-Care-Box could serve as a valuable tool for testing drugs and experimental therapies directly on human eye tissue, offering a more accurate alternative to animal testing.