While complete eye transplantation is not possible due to the complexity of the human eye and brain, it is possible to transplant the cornea, the transparent tissue in the front of the eye. Corneal transplantation is performed more than 40,000 times each year, but it usually only performed as a last resort, as the procedure is quite complex and risky.
Why Corneal Transplantation Is Performed
When the cornea is damaged by disease or injury, it may become slightly opaque or have an irregular surface, which prevents clear, focused light from reaching the retina; the result may be impaired vision, or even blindness. There are many reasons why a corneal transplant may be performed, including Fuchs’ dystrophy, corneal ulcers, scarring, keratoconus, viral infections, and injury.
Cornea donors are recently deceased people whose eyes are healthy, without any condition or disease that might affect the viability of the corneal tissue.
Types of Corneal Transplantation
Penetrating keratoplasty is the removal and replacement of the entire thickness of the cornea.
Lamellar keratoplasty involves replacement of only the anterior (front) layers of the cornea. The most commonly performed lamellar transplant is called a Deep Anterior Lamellar Keratoplasty (DALK), in which only very deepest layer of tissue, called Descemet’s membrane, is left. This procedure leaves the eye with more strength than the traditional penetrating keratoplasty, and may decrease the rates of rejection.
Endothelial keratoplasty involves replacement of the endothelium, the back surface of the cornea. This layer is responsible for pumping fluid out of the cornea back into the eye. Without a healthy endothelium the cornea would swell with fluid and get cloudy. This procedure is usually only performed for diseases that affect only the endothelium.
What to Expect
Unlike other types of transplantation, corneal tissue in many countries is readily available and is not scheduled on a “waiting list.”
Your face will be washed and draped, and you will be sedated; you may be put under general anesthesia, or you may only be given a local anesthetic, in which case you will be awake (but relaxed) during the procedure. Your eye will be held open with an eyelid speculum.
Using a powerful surgical microscope, the surgeon will remove the center of the cornea—the damaged part—with a cookie-cutter-like instrument called a trephine. The donated tissue is then placed in the spot where the old tissue was removed and sewn into place with a thread that is one third the thickness of a human hair. The procedure will generally take an hour or two.
After the operation is performed, the eye will be covered with gauze and a hard plastic shield or eye patch, in order to protect the eye from injury or infection. Your eye will be examined the following day. Typically, vision is still extremely blurry the day after surgery.
Your surgeon will prescribe multiple eye drops that prevent infection and minimize inflammation. You will need to use these drops regularly throughout the healing process, which may take several months to a year, depending on the type of transplant. For a penetrating or lamellar keratoplasty, the sutures will be left in the eye for some time, and your ophthalmologist may remove some or all of them. Removing the sutures is not painful.
Risks of Corneal Transplant
Apart from the risk of infection (which is a concern in any surgery), the most significant risk associated with this procedure is rejection of the transplanted tissue. Roughly 20 percent of recipients (around 7,000 each year) reject their transplants. Rejection is when the immune system does not recognize the donor eye tissue and starts to attack it.
RSVP is a helpful mnemonic you can use to know when you should contact your surgeon. You should call your doctor immediately if, following corneal transplantation, you experience:
- Redness of the eye lasting more than a few days
- Sensitivity to light (photophobia)
- Vision blurring
Most surgeons recommend an extended (or even lifelong) course of topical steroid eye drops to reduce the risk of corneal transplant rejection.
Alternatives to Keratoplasty
Many diseases of the cornea can be effectively treated with rigid, gas-permeable contact lenses. These lenses provide a smooth, regular surface, which can minimize the blurring associated with distorted, irregular corneal surfaces. Often, these lenses can provide good enough vision that a cornea transplant is not needed.
Talking to Your Doctor
Here are some questions you can ask your doctor about corneal transplantation:
- Will a corneal transplant restore my vision?
- Are there any non-surgical alternatives to transplantation?
- Am I a candidate contact lenses rather than transplantation?
- How long will it take for my eye to heal following surgery?
- What type of corneal transplant is best for my eye?
- Is there anything we can do to minimize the risk of tissue rejection?
- Are my eyes healthy enough to allow for me to donate my corneal tissue? Do I need to contact an eye bank, or is it enough just to have my driver license indicate that I am an organ donor?