At first this may sound like tabloid exaggeration or even wholesale fabrication, but it is essentially true – surgeons at NYU Langone Health have performed the world’s first whole eye transplant. The critical question that this fact immediately raises is – was vision restored? The answer is no, but that does not mean this isn’t an important step forward, and the details are interesting.
The patient is a 46-year-old military veteran from Arkansas who was injured on the job by a high-voltage exposure. As a result of the injury he lost his left arm above the elbow, his nose, mouth, left eye, and left cheek. The injury occurred in June of 2022. Since then he has had multiple reconstructive surgeries.
In May 2023, as part of this reconstruction, he underwent a partial face transplant from a deceased donor. Face transplants themselves are rare, with only 19 ever being done in the US, and only the fifth by the lead surgeon, Eduardo D. Rodriguez, MD, DDS. The surgery took 21 hours to complete.
The decision was made to perform a whole eye transplant at the same time, to replace his left eye which was damaged and had to be removed because it was causing serious pain. This was felt to be low risk, because the patient was already receiving a face transplant from the same donor and would have to be on immunosuppressing drugs to avoid rejection anyway. The operation itself was considered successful, but the real question is the long term fate of the transplanted eye.
There are two basic questions – how long and how well will the eye biologically survive, and will any function be restored. Regarding the first question, the transplanted eye has exceeded expectations. The surgeons were hoping the eye would survive for at least 90 days. So far it has survived over five months. The cornea and retina are getting blood supply. The eye is plump and retains its fluids. Overall the eye is healthy.
There are also two aspects of function to consider. One relates to the restoration of the muscles around the eye. These were also reconnected, although I could not find any mention if the muscles themselves were donor muscles or patient muscles. In any case, so far no movement of the eye has been restored. Also, the muscle that raises the lid is not demonstrating any function, so he cannot open or blink the eye. According to reports, however, the team has detected some flicker of activity in the muscles, just not enough to actually move the eye or the lid.
Of course the big functional question is, will vision be restored to any degree? When the damaged eye was removed the surgeons cut the optic nerve as close to the eye as possible, to facilitate potential later transplant. When the donated eye was transplanted the connected the ends of the optic nerve. They also took bone marrow from the donor and converted the cells into adult-derived stem cells. During the transplant they injected these stem cells at the point of connection of the optic nerve. The hope was that this would make it more likely for the two ends of the optic nerve to grow together.
There really wasn’t an expectation that this would work. It seems this was more of a – do it and let’s see what happens – approach. The entire surgery (the whole eye transplant part) should be considered exploratory. Again, the very low threshold for success was considered the eye itself surviving for 90 days. It has passed that. Everything else is gravy. In this way the transplant is considered to be cosmetic, rather than functional.
How big a deal is the qualified success of this surgery? From a transplantation perspective, I think this is a significant milestone. It is the first successful whole eye transplant, able to restore blood flow and result in a long term healthy eye. This is a necessary step toward a future where functional eye transplants are possible. But obviously it is not sufficient. And arguably, functional restoration is by far the more difficult task.
Unlike peripheral nerves, the optic nerve is actual considered part of the central nervous system, and it lacks the capacity to regenerate. So the optic nerve, on its own, will not regenerate and form a new connection between the eye and the brain. Apparently, just putting a patch of adult-derived stem cells on the optic nerve is not enough to provoke regeneration. However, central nervous system regeneration, including optic nerve regeneration, is an active area of research. It is no inconceivable that in the future we will be able to coax the optic nerve to fully regenerate. But we cannot yet say how long it will take to develop this capability. It could be decades off.
Eye muscle restoration is also a difficult task, but easier than optic nerve regeneration because the nerves and muscles that move the eye are peripheral, and do have some capacity to regenerate. Although it has not yet happened in this patient, this is not entirely new.
Still, the “holy grail” of eye transplantation remains the regeneration of the optic nerve. Once this technology has been achieved (which again, could take decades) that would open up exciting possibilities. Whole eye transplants that are fully functional could restore vision to many people.
The next question, however, will then be – how will the brain adapt? How well will the brain be able to map to the new connections to the transplanted eye? Generally when nerves regenerate, they don’t go back to exactly where they were before. This doesn’t matter much if you are connecting a large muscle. It does matter when nerves to fine muscles, like those in the face, regenerate. The optic nerve is exquisitely mapped to the visual cortex, and remapping may take a long time and be only partial. In other words, even if optic nerve regeneration were possible, the degree of functional recovery remains to be seen.
The ability to regenerate the optic nerve also opens the door further to prosthetic functional eyes. A robotic eye that is essentially a digital camera with a brain-machine interface to a functional optic nerve is theoretically possible. If this technology advances sufficiently, it make be preferred to a donor biological eye. There is no issue with rejection. Also, the robotic eye may be able to use AI to map its signals to the brain, rather than requiring the brain to map to the new pattern of incoming signals.
And since we are speculating about future technology, we can also envision a future in which eyes can be grown from a patient’s own cells, essentially cloned eyes. This removes the need for a donor, and also removes the problem of rejection and the need for immunosuppressive drugs. While this is also an area of research, it also likely lies decades in the future.
For now whole eye transplants should be considered cosmetic, with any functional implications exploratory. Still, this is an important step and does make possible a potential future of functional eye transplants.