A corneal transplant, also known as keratoplasty, is used to restore vision. To do this, doctors surgically remove the old cornea in the eye and insert the cornea of a donor. This procedure is often the only help in the case of severe injuries or if the cornea is very cloudy .
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A corneal transplant is the transplantation of a human cornea or parts of the cornea. For this, the diseased recipient requires an organ or tissue donation from a donor.
In medical parlance, it is called "keratoplasty". Corneal transplantation is a form of treatment for irreversible changes to the cornea, e.g. following serious inflammation or injury.
A corneal transplant can be performed under general or local an esthesia. This depends on the type of keratoplasty that is used.
The eye perceives visual stimuli from the environment and transmits them to the brain. The brain processes the information and then reacts accordingly.
The cornea plays an important role in enabling our eyes to perceive sharp images.
It refracts most of the light before it reaches the retina. The brain then receives the transmitted signals.
The structure of the human eye - The cornea curves forward in front of the iris (iris)
The cornea forms the front end of the eye and merges into the conjunctiva. The cornea is a clear, transparent tissue that contains no blood vessels.
It consists of six different cell layers:
In order for the cornea to function properly, it must be moistened with tear fluid.
As the cornea is an important part of the visual system, a disruption can lead to serious visual defects. If the cornea becomes cloudy, the eye does not absorb enough light and visual performance is reduced. In the worst case, there is a risk of blindness. Corneal opacity can develop over the course of a lifetime or be present from birth.
In some cases, corneal clouding can be treated with certain contact lenses or surgically.
In cases of severe corneal damage or incurable disease, a transplant can restore vision.
This is the case with advanced corneal dystrophies. In this disease, the cornea becomes increasingly cloudy. As a result, the cornea loses its transparency.
Doctors perform a corneal transplant if the cornea has irreversible changes that significantly restrict vision.
These can be
Figure 1: Severe inflammation of the cornea caused by soft contact lenses. This will leave a permanent opacity in the cornea, which leads to considerable visual impairment and can be treated in the long term by a corneal transplant if necessary.
The corneal changes described above lead to an increasing, irreversible deterioration in vision. Depending on the severity of the loss of visual acuity, the ophthalmologist will determine the indication for a corneal transplant.
He can usually make the diagnosis by examining the eye with a slit lamp. Sometimes a so-called topography ("map") of the cornea is also helpful to confirm the diagnosis.
A corneal transplant is useful for the following diseases:
If a corneal transplant is necessary, the doctors must first find a suitable transplant. The doctors search for this in the so-called cornea bank. This can take some time and is associated with hurdles. This is because there are fewer transplants than people who need a new cornea.
As a cornea transplant is a tissue or organ donation from a human being, there are certain legal requirements. For example, two doctors must independently determine the donor's brain death beyond doubt within certain time frames.
Certain medical criteria must be met to determine brain death. Furthermore, the donor must have consented to the removal of tissue for the corneal transplant during his or her lifetime.
This consent can be given through statements, written declarations or by means of an organ donor card. If no consent has been given, relatives of the donor can also give their consent if it corresponds to the donor's wishes.
Coordination of donor and recipient
Donor material can be collected within 72 hours of the death of the deceased. The donor must not have any contraindications, which is statistically the case for over two thirds of donors.
These would be HIV or other infectious diseases, for example. Other visual impairments such as cataracts or glaucoma and the age of the donor are not contraindications.
During removal, doctors cut out a corneoscleral disc (a slice of cornea and sclera) from the donor eye and remove it.
The donor material can be stored in the cornea bank for up to four weeks after collection. Placement centers assign the material to a suitable recipient on the waiting list.
The potential recipient then receives notification from their attending physician. For the corneal transplant itself, he or she visits an appropriate clinic.
During the operation, the patient receives either a local anesthetic or a general anesthetic. Doctors remove the cornea either completely or only partially from the eye.
After removing the diseased corneal material, the recipient receives the donor material, which doctors stitch to the remaining cornea.
Depending on the type of corneal disease and the location and intensity of the corneal change, different methods of corneal transplantation are possible.
There are basically two main procedures that are used here:
In lamellar keratoplasty, experts differentiate between posterior and anterior lamellar keratoplasty.
In the case of extensive opacities, they perform a classic corneal transplantation of all layers (penetrating keratoplasty).
Doctors open the recipient's eye completely by punching a central slice out of the middle of the cornea. They cut an equally large slice from the donor cornea and sew it into the recipient eye (Figure 2).
The operation is performed under a microscope. Lamellar corneal transplants are used for changes that occur in the anterior or posterior layer of the cornea. Here, part of the patient's cornea is retained. This generally enables faster healing with a lower risk of rejection.
Figure 2: Eye after corneal transplantation. Two very thin, continuous, star-shaped, opposing corneal sutures are visible. These must remain in the eye for several months until the findings have stabilized.
After removal, doctors insert the new donor cornea and suture it. They cut the cornea beforehand so that it fits exactly into the patient's eye. The stitches are only removed after several months, as injuries to the eye take a long time to heal. Only after this period can doctors determine whether the transplantation was successful.
In penetrating keratoplasty, doctors remove the cornea using a special device. The procedure is called trephination. They remove a circular piece of the cornea from the eye. They then insert the precisely cut donor cornea. They stitch this to the remaining cornea using fine sutures.
The doctor can either stitch two sutures in a star shape or use individually tied sutures. Which of the two techniques is used depends on the circumstances of the operation in question.
The penetrating keratoplasty is the most frequently used transplantation worldwide. The level of knowledge and experience is therefore very high. Furthermore, the transplant used is very small, which reduces the risk of a rejection reaction.
Posterior lamellar keratoplasty is also known as inner layer transplantation. It is used when the endothelial layer of the cornea is diseased.
To remove it, doctors score the damaged endothelial layer and Descemet's membrane in a circular pattern and then detach them. They roll up the corresponding part of the donor cornea and insert it through a tiny lateral incision.
It unfolds in the eye, where an air bubble presses it into the right place. The patient has to lie on their back for 24 hours after the operation. One advantage of this method is the short healing time, as no stitches are required. The patient can see well again after around three months.
This is also known as an outer layer transplant. It is basically the opposite of the inner layer transplant.
Here, doctors separate and remove the remaining corneal layers from the Descemet's membrane and endothelial layer. They then replace the layers with a transplant.
Here they fix the donor tissue again with sutures. As with penetrating keratoplasty, they use two or single sutures. By preserving the endothelial layer, the risk of rejection is greatly minimized.
A transplant can always lead to a rejection reaction in the body. The body registers the transplant as a foreign body and initiates defense measures. This leads to the immune system fighting the cornea.
In this case, the cornea may become cloudy again. A rejection reaction usually occurs within the first five years after the operation.
Symptoms are
Those affected should consult their doctor immediately so that he or she can take countermeasures.
Overall, the risk of rejection is lower than with transplants of other organs. The new transplant can also become diseased again.
If it becomes cloudy again, only another transplant can provide a remedy. This has the same risks and chances of success as the previous transplant.
Furthermore, perforating keratoplasty can lead to chronic endothelial loss. The cell density in the endothelial layer continues to decrease. A follow-up keratoplasty is then necessary 15 to 20 years after the operation.
The healing process after a corneal transplant can take weeks to months, depending on the type of operation.
After a penetrating keratoplasty, the corneal sutures must remain in place for up to a year or longer. The patient must also take long-term eye drops. During this time, the refractive power may still change, meaning that glasses cannot yet be fitted.
In addition, the suture can cause a very severe curvature of the cornea, which limits vision and makes it difficult to fit glasses.
Laser treatment to reduce corneal curvature with the excimer laser ("refractive surgery") can be useful and successful in some cases. In some cases, patients achieve 100% visual acuity with an intact retina. Often, however, visual acuity is between 40 and 80 percent.
In some patients, a rejection reaction may occur in the course of the procedure. The cornea then becomes cloudy and gives up its function.
The risk of rejection is greater if:
After a corneal transplant, patients must have regular (daily to twice-daily) check-ups with the ophthalmologist.
Corneal transplants are usually performed in hospital. Close monitoring is guaranteed there (e.g. for tightness of the wound). Over time, the intervals between check-ups will increase (initially weekly, later monthly).
In addition to the regular application of eye drops and, if necessary, taking medication, glasses with side protection may be useful at the beginning.
After corneal transplantation, the patient must protect themselves from foreign bodies or minor injuries to the eye.
They often do not notice these at first because the donor tissue does not initially contain any nerve fibers from the recipient. These are important for sensation and the feeling of foreign bodies.
It takes several months for the new nerve fibers from the recipient to grow in the donor tissue. It often takes months before glasses can be fitted to improve visual acuity.
After a corneal transplant, the patient must take eye drops several times a day (months to years), initially every hour.
These are eye drops containing cortisone, initially antibiotics. He should also regularly drip tear substitutes ("artificial tears").
In the case of high-risk operations with an increased risk of rejection, patients also receive tablets that suppress the body's own immune response (immunosuppressants). These must also be taken for several months after the corneal transplant.
The patient should avoid contact sports, as a transplanted cornea is initially much more unstable than a non-operated eye.
In the long term, suitability for sport depends on the findings and the type of corneal transplant. You should discuss this individually with your ophthalmologist.
The eye surgeon performs corneal transplants. After studying medicine, an eye surgeon has completed 5 years of specialist training in the field of ophthalmology. Most corneal transplant specialists also undergo intensive further training in the field of eye surgery.
You can find your corneal transplant specialist here and contact them directly!
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