Is a whole eye transplant possible?

When we talk about an eye transplant, we usually refer to a cornea transplant, in the present day scenario. No one so far has been able to remove a complete eye from a donor, and transplant it into a recipient and make the eye function. But it looks like this is about to change...


Researchers at University of California, San Diego School of Medicine have been granted $1 million dollars by the U.S. Department of Defense to study the possibility of implantation of an entire, functional eye.

Parts of an eye (from insetfair.com)

What the researchers plan to do sounds simplistic: Surgeons would implant a donor eye in the recipient's eye socket. The vascular system to the eye would be re-established, as would the eye’s musculature to enable normal movement. This will be followed by the retinal neurons connecting to the brain through the optic nerve (which is the focus of the grant). This is more difficult than it sounds when we realize that there are more than millions of retinal cells that send their nerves out through the optic nerve.

Past experiments at University of Pittsburg Medical Center have demonstrated the ability to perform whole eye transplants in genetically inbred rats (which are selected to minimize issues of tissue rejection). But while retinal tissue in the transplanted eyes appeared healthy, the optic nerves did not recover and regenerate connections, eliminating the possibility of restored sight.

To circumvent that problem, researchers at UC San Diego and Harvard University have developed a variety of molecular techniques for enhancing optic nerve regeneration. One of the primary objectives is to assess whether these different techniques can be combined for greater therapeutic effect.

Among the most promising is restoring the embryonic ability of adult nerve cells to grow and blocking production of molecules that squelch nerve cells’ initial intrinsic regenerative properties. This loss of regenerative capacity is similar to what happens in spinal cord injuries that result in permanent paralysis.

Scientists have also identified proteins in the optic nerve known as neurotrophic factors that are involved in growth, survival and maintenance of developing neurons and have developed techniques for enhancing their signaling to nerve cells. Other molecular tricks will be used to try to overcome the inhibitory environment for re-growth normally found in the optic nerve.

If successful, researchers suggest whole eye transplants might restore sight in a wide range of patients who are blind due to structural or functional problems in the eye.

Note: If these experiments prove to be successful in restoring vision in transplanted eyes, it would open a totally new way of helping those who are blind see again. 

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