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Researchers developed a system capable of preserving a human eye outside the body for hours, while different teams investigate the obstacles that still separate this experimental advance from a transplant that restores vision.
Researchers at the University of Miami, in the United States, developed a portable device capable of keeping a human eye irrigated and with functional tissues for hours after removal from a donor.
Called eye-ECMO, the system pumps oxygenated blood mixed with a preservation solution through the vessels of the eyeball.
The technology is part of a project conducted by the Bascom Palmer Eye Institute, the Miller School of Medicine, and the College of Engineering at the University of Miami.
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The initiative received funding of up to US$ 5.3 million from the Advanced Research Projects Agency for Health in the United States, ARPA-H.
The support began on December 2, 2024.
The equipment was tested during the removal of a human donor eye.
Connected to the organ immediately after the procedure, the device maintained circulation for several hours and allowed the team to assess the viability of the tissues and the functioning of the retina.
The results were released by the University of Miami on July 24, 2025.
According to the researchers, the tests identified circulation in the retina and activity of the retinal tissue while the eye remained outside the body.
Despite the results, the experiment does not represent a transplant capable of restoring vision.
The preservation of the organ is just one of the stages investigated by the project, which still needs to address issues related to the optic nerve, immunological rejection, and the connection between the transplanted eye and the brain.
How the eye-ECMO keeps the human eye irrigated
The eye-ECMO was inspired by extracorporeal membrane oxygenation, known by the acronym ECMO.
In hospital procedures, this type of equipment can temporarily take over functions related to blood circulation and oxygenation when the heart or lungs cannot perform them adequately.
In the version created for the human eye, the principle was adapted to operate on a smaller scale.
The machine drives oxygenated blood, combined with a specific solution, into the organ’s vessels and maintains a continuous flow after donor removal.
This circulation, called perfusion, supplies oxygen to the tissues during the period between the recovery of the eye and its analysis.
Without the blood supply, the cells of the retina and other ocular structures can suffer damage due to lack of oxygen.
The expression “heart-machine” used in the title figuratively describes the function of pumping fluid through the eye’s vascular system.
The technical name adopted by the University of Miami team is eye-ECMO.
David Tse, professor of ophthalmology and orbital surgeon at the Bascom Palmer Eye Institute, explained that the eye needs to continuously receive oxygenated blood.
He leads the transplant project alongside Daniel Pelaez, associate professor of ophthalmology at the university.
“To ensure the viability of a donor eye, we must maintain this flow, or perfusion, and avoid any loss of tissue oxygenation during removal and the implantation process,” stated Tse in the institution’s statement.
To connect the organ to the equipment, engineers developed a small-sized cannula.
The tube is inserted into the main blood vessel of the eye and allows the constant passage of the solution driven by the machine.
The piece has been created and perfected with the support of the 3D printing structure of the University of Miami’s College of Engineering.
According to the institution, the shape needs to be adjusted to allow circulation without damaging the vessels involved in the procedure.
First test of the eye-ECMO evaluated a donor’s retina
The device was used when the team received authorization to recover its first human donor eye within the project.
During the surgery, ophthalmologists, neurosurgeons, plastic surgeons, scientists, and engineers participated in the removal and connection of the organ to the system.
After being removed, the eye was placed in a support and connected to the eye-ECMO.
The circulation remained active for several hours, during which researchers conducted exams to verify the condition of the tissues.
A fluorescent dye was introduced into the circuit to track the path of the liquid.
The team observed the substance passing through the retinal vessels, according to the report published by the University of Miami.
Optical tests also recorded retinal activity.
The institution reported that the results were obtained on the team’s first attempt with a donor human eye connected to the equipment.
The analysis did not demonstrate that the organ would be capable of producing vision after being transplanted.
The procedure evaluated whether circulation and certain cellular functions could be temporarily maintained outside the body.
The retina is located at the back of the eyeball and contains cells that respond to light.
These cells transform light stimuli into electrical signals, which need to be conducted by the optic nerve to the brain to participate in the formation of images.
Therefore, detecting activity in the retina does not mean that all the components necessary for vision are functioning.
For a transplant to restore the ability to see, the signals produced in the eye also need to reach and be processed by the recipient’s nervous system.
Commenting on the first procedure, Tse said that the main steps occurred according to the team’s planning.
“There were some setbacks along the way, but all the main steps happened as we had planned. And, without the eye-ECMO, it wouldn’t have worked,” he stated.
Eye-HOLDER was created to transport the organ
In addition to the circulation system, the engineers produced a structure called eye-HOLDER.
The support keeps the eye in a controlled position while the organ is transported between the operating room and the laboratory.
The team is working on a new version with a stabilization mechanism similar to a gimbal.
This type of structure compensates for part of the base movements and reduces the displacement of the supported object.
According to the project leaders, the mechanism should protect the eye during journeys within the hospital.
The proposal also considers the possibility of transport between medical units or cities, as occurs with other organs intended for transplants.
The development of the equipment was coordinated by biomedical engineer Ashutosh Agarwal, a faculty member at the University of Miami and director of engineering and applied physics at the Desai Sethi Urology Institute.
The laboratory directed by Agarwal works with devices known as “organs on chips.”
These systems replicate characteristics of human tissues in controlled environments and are used in research on diseases and treatments.
The development also involved PhD students Emma Drabbe and William Raeter, master’s student Alexander Carrieri, lab technician Matthew Koble, and Atharva Dapse, a visiting researcher from the Indian Institute of Technology Gandhinagar.
According to the University of Miami, the project brings together 17 faculty members, in addition to other professionals.
The team includes specialists in ophthalmology, surgery, neuroscience, biomedical engineering, and organ preservation.
Optic nerve remains a challenge for restoring vision
The researchers point out the optic nerve as one of the main challenges for restoring vision.
This structure connects the retina to the brain and carries the electrical signals generated when the eye cells respond to light.
During the removal of an eye, the nerve needs to be cut.
Unlike other tissues, its fibers do not spontaneously recover all the necessary connections to reestablish communication with the brain regions linked to vision.
For this reason, keeping the eyeball alive does not, by itself, solve the problem.
Even with blood vessels, retina, muscles, and other structures preserved, the recipient will not see if the signals cannot cross the optic nerve and reach the brain.
Tse and Pelaez stated that the team still needs to determine the best way to preserve the donor’s nerve.
Another aspect of the work seeks to establish how this structure can be connected to the recipient’s nervous system.
