About Corneal Transplantation
The cornea is the normally clear, front window of the eye that covers the colored iris and round, dark pupil. Light is focused while passing through the cornea, allowing us to see. If the cornea is injured, it may become swollen or scarred, and its smoothness and clarity may be lost. Scars, swelling, or an irregular shape can cause the cornea to scatter or distort light, resulting in glare and blurred vision.
When is a Cornea Transplant Necessary?
There are many conditions that can affect the clarity of the entire cornea. For instance, trauma or injury to the cornea can cause scarring, as can infections (especially herpes keratitis). A hereditary condition called Fuchs’ dystrophy causes corneal failure.Keratoconus (pictured) causes a steep curving of the cornea. Sometimes corneal failure can occur after an eye surgery such as cataract surgery.
Corneal Transplant Surgery Options
A corneal transplant is done using a human donor cornea. Before a cornea is released for transplant, tests are done for viruses that cause hepatitis, AIDS and other potentially infectious diseases. The cornea is also checked for clarity.
With traditional full corneal transplant surgery (known as penetrating keratoplasty), a circular portion is removed from the center of the diseased cornea. A matching circular area is removed from the center of a healthy, clear donor cornea, placed into position and sutured into place.
With an EK cornea transplant procedure (endothelial keratoplasty), only the abnormal inner lining of the cornea is removed. A thin disc of donor tissue containing the healthy endothelial cell layer is placed on the back surface of the cornea. An air bubble pushes the endothelial cell layer into place until it heals in an appropriate position.
With a lamellar corneal transplant procedure, the superficial layers of the cornea are removed and replaced with donor tissue. Sutures are used to secure the new tissue into place.
A generous gift of sight
Corneal transplant would not be possible without the thousands of generous donors and their families who have donated corneal tissue so that others may see. Each year, nearly 50,000 people with corneal disease are given the gift of sight through cornea donors.
Which Parts of the Eye Can Be Transplanted?
You may have heard about someone having an “eye transplant,” but what exactly does that mean? As it turns out, only one part of the eye can be transplanted. Medical science has no way to transplant whole eyes. When someone receives an “eye transplant,” they are being given a donor cornea, the clear front part of the eye.
Your eye is a complex organ connected to your brain by the optic nerve. The optic nerve sends visual signals from the eye to the brain, where they are interpreted as images. The optic nerve is relatively small, varying in length between 1.3 and 2.2 inches, and at its widest point, inside your cranial cavity, it is still less than one-fifth of an inch wide. Yet the optic nerve is made up of more than one million tiny nerve fibers, much like a fiber optic cable. Once these nerve fibers are cut, they cannot be reconnected. That is why it’s impossible to transplant a whole eye. Even if a surgeon could implant the eye into the eye socket, the eye still would not be able to transmit signals to the brain through the optic nerve and thus would not provide sight.
By contrast, corneal transplantation is not only possible, it is a procedure more than a century old.
A healthy, clear cornea is necessary for good vision. If your cornea is injured or affected by disease, it may become swollen or scarred. A cornea with scarring, swelling or an irregular shape can cause glare or blurred vision. In a corneal transplant, the damaged or unhealthy cornea tissue is removed and clear donor cornea tissue is put in its place. Read more about corneal transplant surgery options.
While corneal transplants are the most common type of eye-related transplantation, it is not the only one. Surgeons have also been able to successfully perform eyelash transplantation. However, the procedure carries significant risks, including scarring, and is not recommended as a cosmetic procedure.
In patients suffering from disorders of the sclera or the conjunctiva (the external eye), doctors have been able to transplant amniotic membranes which have aided in the healing and regeneration of ocular surface tissues.
Doctors continue to explore whether it is possible to transplant other parts of the eye. In July 2010, French doctors announced that they had transplanted eye lids and tear ducts as part of a full-face transplant for a man with a genetic disorder. Researchers are also focusing on how to replace damaged retinal cells with healthy transplants.
In fact, it has been shown in recent clinical trials that human stem cells can be cultivated to become retinal pigment epithelium (RPE) cells. In the near future, we can expect RPE transplants. This is good news for people suffering from macular degeneration and Stargardt’s Disease.
Source : www.geteyesmart.org