A groundbreaking study has demonstrated that human retinas can be kept alive and responsive to light for up to 10 hours after death, a significant advancement in the quest to restore vision for millions. Researchers achieved this feat by supplying donor eyes with oxygenated blood, successfully preserving the delicate light-sensing tissue at the back of the eye.
The work, led by Eimear Byrne and her colleagues at the Barcelona Institute of Science and Technology in Spain, involved developing a sophisticated system to mimic the body's internal conditions. A flexible tube was inserted into the ophthalmic artery, which delivers blood to the eye, and a custom-built device called the Eye-in-Care-Box then perfused the donated eyes with an oxygen-rich solution. Sensors within the device automatically regulated pressure and flow, ensuring optimal conditions.
To test their method, the team took both eyes from six donors, perfusing one eye and leaving the other untreated. They observed that the perfused eyes maintained the structural integrity of the retina and the health of surrounding cells for up to 24 hours, while the non-perfused eyes rapidly degraded. Further experiments with 36 additional donor eyeballs revealed that 15 of these retinas produced electrical responses to light, mirroring those seen in living individuals. These responses persisted for up to 10 hours post-mortem, effectively doubling the previous record of five hours achieved by other scientists in 2022.
This achievement marks a crucial step towards the possibility of whole-eye transplantation, a procedure that has long eluded medical science. While corneal transplants are a well-established treatment for damaged corneas, addressing retinal conditions like age-related macular degeneration, which affects over a million people in the UK, presents a much greater challenge due to the retina's connection to the central nervous system. Thomas Johnson from Johns Hopkins University, who was not involved in the research, described maintaining light responses outside the body as a "tremendous feat."
Despite this progress, significant hurdles remain. A major challenge for restoring vision through a transplanted eye is the regeneration of fibres in the severed optic nerve to reconnect with the brain's visual centres. The current research does not solve this issue, but by keeping donor eyes metabolically healthy for longer, it could significantly enhance the viability of future vision-restoration strategies, ensuring that donated eyes are in a better state for transplantation and nerve regeneration attempts.