A cornea transplant replaces diseased or scarred corneal tissue with healthy tissue from an organ donor.
There are two main types of cornea transplants: traditional, full thickness cornea transplant (also known as penetrating keratoplasty, or PK) and back layer cornea transplant (also known as endothelial keratoplasty, or EK).
A graft replaces central corneal tissue, damaged due to disease or eye injury, with healthy corneal tissue donated from a local eye bank. An unhealthy cornea affects your vision by scattering or distorting light and causing glare and blurred vision. A cornea transplant may be necessary to restore your functional vision.
Corneal eye disease is the fourth most common cause of blindness (after cataracts, glaucoma and age-related macular degeneration) and affects more than 10 million people worldwide.*
More than 47,000 cornea transplants will be performed in the United States in 2013, according to an estimation by the Eye Bank Association of America. Since 1961, more than one million people have had their sight restored with a cornea transplant.
Do You Need A Corneal Transplant?
A healthy, clear cornea is essential for good vision. If your cornea is damaged due to eye disease or eye injury, it can become swollen, scarred or severely misshapen and distort your vision.
A cornea transplant may be necessary if eyeglasses or contact lenses can't restore your functional vision, or if painful swelling can't be relieved by medications or special contact lenses.
Certain conditions can affect the clarity of your cornea and put you at greater risk of corneal failure. These include:
Scarring from infections, such as eye herpes or fungal keratitis.
Scarring from trichiasis, when eyelashes grow inwardly, toward the eye, and rub against the cornea.
Hereditary conditions such as Fuchs' dystrophy.
Eye diseases such as advanced keratoconus.
Thinning of the cornea and irregular corneal shape (such as with keratoconus).
Rare complications from LASIK surgery.
Chemical burns of the cornea or damage from an eye injury.
Excessive swelling (edema) of the cornea.
Graft rejection following a previous corneal transplant.
Corneal failure due to cataract surgery complications.
Are You A Corneal Transplant Candidate?
A cornea transplant is performed to improve the function of the cornea and improve vision. If pain is caused by a significantly diseased or damaged cornea, a cornea transplant may relieve that symptom.
With these factors in mind, you also should consider several important questions before you decide to undergo a corneal transplant:
Does your functional vision impede your job performance or your ability to carry out daily activities?
Can your vision be corrected with special or other less invasive measures?
How will the cost of cornea transplant surgery affect your financial situation if your
does not cover everything from pre-screening to post-operative consultations?
Are you able to take enough time off from work or school (up to six months to a year in some cases) to recover properly?
All of these questions, in conjunction with a thorough screening and consultation with your eye doctor, must be carefully considered before you make the final decision to have a corneal transplant.
Before A Keratoplasty Procedure
Once you and your eye doctor decide a cornea transplant is the best option for you, your name is placed on a list at a local eye bank. You may need to wait a few days to weeks for suitable tissue from a donor eye to become available for a corneal transplant.
Before a donor cornea is released for use in transplant surgery, it is checked for clarity and screened for the presence of any diseases such as hepatitis and AIDS, in accordance with the Eye Bank Association of America's strict medical standards and FDA regulations.
Only corneas that meet these stringent guidelines are used in corneal transplant surgery to ensure the health and safety of the graft recipient.
During A Corneal Transplant
Your eye surgeon will first administer either local or general anesthesia, depending on your health, age, eye injury or disease, and whether or not you prefer to be asleep during the procedure.
If local anesthesia is used, an injection is made into the skin around your eye to relax the muscles that control blinking and eye movements, and eye drops are used to numb your eye. You will be awake during the procedure and most people don't report any discomfort.
After the anesthesia has taken effect, an instrument called a lid speculum is used to keep your eyelids open. Your surgeon then measures the affected corneal area to determine the size of the donor tissue needed.
Traditional corneal transplant surgery. During traditional corneal transplant surgery, or penetrating keratoplasty (PK), a circular button-shaped, full-thickness section of tissue is removed from the diseased or injured cornea using either a surgical cutting instrument called a trephine or a femtosecond laser.
A matching "button" from the donor tissue is then positioned and sutured into place. The sutures (stitches) remain in place typically for a year or more after surgery.
Lastly, a plastic shield is placed over your eye to protect it during healing.
Penetrating keratoplasty surgery generally takes one to two hours and most procedures are performed on an outpatient basis, meaning you can go home a short while after the surgery (though you will need someone to drive you home).
Endothelial keratoplasty. In the past decade, a newer version of corneal transplant surgery called endothelial keratoplasty (EK) has been introduced for certain corneal conditions.
Endothelial keratoplasty selectively replaces only the innermost layer of the cornea (endothelium) and leaves the overlying healthy corneal tissue intact. The endothelium controls the fluid balance in the cornea, and if it becomes damaged or diseased, this can cause significant corneal swelling and loss of vision.
In EK, the surgeon makes a tiny incision and places a thin disc of donor tissue containing a healthy endothelial cell layer on the back surface of your cornea. An air bubble is used to position the new endothelial layer into place. The small incision is self-sealing and typically no sutures are required.
Donating Eye Tissue
Who Can Be A Corneal Tissue Donor?
How old is too old to donate eye tissue for a corneal transplant?
A decade ago, it was common for surgeons to reject corneas from people over 65 years old. But the Cornea Donor Study has concluded that corneas from people aged 34-71 are likely to remain healthy for most recipients after 10 years, with a success rate of 75 percent.
In the United States, about three-quarters of corneas come from this age range, with one-third from people aged 61-70.
Since corneas from people under age 34 do perform better in corneal transplants, it has been suggested that younger people should receive these younger corneas.
But Mark Mannis, MD, chair of ophthalmology at the University of California, Davis, and co-chair of the study, commented, "Although the results suggest that age-matching may be appropriate for the very youngest donors and patients, we do not think it is necessary in the vast majority of cases."
U.S. eye banks supply corneas to other countries, too — about 20,000 corneas were exported in 2012 — but the need is much greater than the supply.
If you would like to learn more about donating organs and tissue, please visit the Donate Life America website.
The most common type of EK procedure is called Descemet's Stripping Endothelial Keratoplasty, or DSEK. The American Academy of Ophthalmology in 2009 endorsed DSEK as superior to the conventional full-thickness corneal transplant procedure (penetrating keratoplasty) for better vision outcomes and stability, as well as fewer risk factors.
Endothelial keratoplasty has several advantages over full-thickness penetrating keratoplasty. These include: faster recovery of vision; less operating time; minimal removal of corneal tissue (and therefore less impact on the structural integrity of the eye and less susceptibility to injury); no related suture complications; and reduced risk of astigmatism after surgery.
Within a relatively short period of time, the EK corneal graft procedure has become the preferred technique for patients with Fuchs' dystrophy and other endothelial disorders of the cornea. However, traditional full-thickness PK is still the most appropriate option when the majority of your cornea is diseased or scarred.
Recovering From A Corneal Transplant
Total cornea transplant recovery time can be up to a year or longer. Initially, your vision will be blurry for the first few months — and in some cases may be worse than it was before — while your eye gets used to its new cornea.
As your vision improves, you gradually will be able to return to your normal daily activities. For the first several weeks, heavy exercise and lifting are prohibited. However, you should be able to return to work within a week after surgery, depending on your job and how quickly your vision improves.
Steroid eye drops will be prescribed for several months to help your body accept the new corneal graft, as well as other medications to help control infection, discomfort and swelling. You should keep your eye protected at all times by wearing a shield or a pair of eyeglasses so that nothing inadvertently bumps or enters your eye.
If stitches were used in your surgery, they usually are removed three to 17 months post-surgery, depending on the health of your eye and the rate of healing. Adjustments can be made to the sutures surrounding the new corneal tissue to help reduce the amount of astigmatism resulting from an irregular eye surface.
As with any type of surgery, always follow the instructions of your eye surgeon to help minimize corneal transplant complications and expedite healing.
SEE RELATED: Tarsorrhaphy
Cornea Graft Rejection
Cornea transplants are performed routinely and have a reasonable success rate. In fact, cornea grafts are the most successful of all tissue transplants.
Cornea transplant rejection can be reversed in 9 out of 10 cases if detected early enough.
Like any other surgical procedure, a cornea transplant comes with certain risks. But, for most people, having their vision improved or restored outweighs the potential complications associated with cornea transplant surgery. It is a very personal decision for a patient to decide to undergo cornea transplant surgery.
Complications of a corneal transplant can be significant and can include cornea graft rejection, eye infection and problems associated with the use of stitches.
Rejection of the donor tissue is the most serious complication after a corneal transplant and occurs in 5 to 30 percent of patients. Transplant rejection is when your body's immune system detects the donor cornea as a foreign body and attacks and tries to destroy it.
Research** indicates that having glaucoma and corneal swelling associated with previous cataract surgery can increase your chances of cornea graft rejection.
Recognizing the main warning signs of corneal transplant rejection is the first step to preventing graft failure. These can be remembered using the acronym RSVP :
R edness
Extreme S ensitivity to light
Decreased V ision
P ain
Rejection signs may occur as early as one month or as late as several years after surgery. Your eye doctor will prescribe medication that can help reverse the rejection process. If detected early, the graft will be successful 9 out of 10 times, according to the Cornea Research Foundation of America.
Should your graft fail, corneal transplant surgery can be repeated. While repeat surgery generally has good outcomes, overall rejection rates increase with the number of corneal transplants you have.
Vision After A Corneal Transplant
Your eyesight should gradually improve a few weeks after a corneal graft, but it could take anywhere from a couple of months up to a year to have stable vision in the eye that receives the donor tissue.
After your cornea transplant has fully healed, it's possible to undergo LASIK eye surgery to improve your vision.
You will be left with a degree of myopia (nearsightedness) and astigmatism, because the curve of the new corneal tissue can't match exactly the curve of your natural cornea.
Post-surgery refraction is somewhat unpredictable, and large amounts of astigmatism will still present a challenge when fitting those patients with glasses afterwards.
Mild refractive errors caused by corneal transplant surgery can be corrected with glasses; otherwise contact lenses are required.
Rigid gas permeable contact lenses, also known as RGP or GP lenses, and hybrid contact lenses usually are the most suitable contacts for corneal transplant patients due to the irregularity of the cornea after transplant. However, soft contact lenses often are an option as well.
Because your vision will fluctuate during the first few months following your surgery, it is advisable to wait until your eye doctor tells you your vision is stable before you fill an eyeglass prescription or are fitted for contact lenses.
After your eye has fully healed and any stitches used have been removed, you may be eligible to undergo laser eye surgery such as LASIK or PRK to improve your ability to see with or without glasses or contacts by reducing myopia and astigmatism.
Artificial Corneas and Biosynthetic Corneas
Human donor tissue is the preferred — and most successful — option for replacing a diseased or injured cornea. However, for patients who are at high risk of corneal transplant failure with a human donor (such as multiple failed human cornea transplants) and have no other options to improve vision, artificial cornea tissue might be used.
Artificial corneas, also known as "keratoprosthesis" or "K-pro," are made from a biologically inert material and typically are reserved for patients who have: a severe autoimmune disease; chemical burns; limited or no access to human donor tissue; or have had multiple previous human donor transplant failures.
Another area of ongoing research is biosynthetic corneas. The resultset1 resultset2 resultset3 resultset4 from a recent early-phase clinical trial has shown that a biosynthetic cornea made from a human gene that regulates the natural production of collagen can regenerate and repair damaged eye tissue.
While the field of biosynthetic corneas is still in its infancy, with further research this approach potentially could be an effective option if human donor tissue is not appropriate or available.
Aimee Rodrigues also contributed to this article.
