Why can't the whole eye be transplanted?
What is a corneal transplant?
However, many people do not even know that there is a corneal donation option. If you have severe inflammation of the cornea (keratitis) that causes scarring or peeling of the cornea, a corneal transplant may be necessary. This can be used to remedy the damage. A donor's cornea is needed for a corneal transplant. The use of artificial corneas is still under research.
The transparent cornea is the outer boundary of the eye, which closes the round eyeball at the front. One can only see clearly when the cornea is transparent and curved. Any change in their clarity leads to a deterioration in vision.
Once cloudiness is present, it usually does not recede. From a certain stage onwards, the only solution is to replace it with a healthy, clear cornea from a deceased donor, a so-called corneal transplant (keratoplasty).
When does a corneal transplant make sense?
A new cornea is primarily required by people whose cornea has become opaque due to deformations or scars. There are various reasons for this, injuries with subsequent scarring are among the most common.
People whose cornea was so badly inflamed that scars remained often need a replacement. This occurs, for example, after an infection of the cornea with herpes viruses (herpes keratitis).
But corneal changes can also occur due to age or after surgery, which makes a transplant necessary. Another possible cause is congenital corneal disease.
Can there be rejection reactions?
Defense cells of the immune system, which recognize other cells as foreign and can trigger a rejection reaction, are located in the bloodstream.
There are no blood vessels in the clear cornea, as nourishment takes place through the tear secretions. Because of the lack of contact between the immune cells and the transplant, there is usually no rejection process there.
The situation is different if blood vessels have crept into the cornea due to an illness (vascularization). In such cases, the donor corneas must be carefully analyzed and selected so that they match the recipient's own tissue in as many properties as possible. In this way, the risk of rejection can at least be reduced.
The coordination of recipient and donor characteristics is carried out by a corneal bank in cooperation with the eye clinics. Since corneas can be donated between the ages of ten and 85, old people are still potential organ donors.
How are the required donor corneas obtained?
If a person has died, for example in a fatal accident, the relatives are informed about the possibility of organ donation and, in particular, corneal donation. Corneas can be removed up to 76 hours after death. This leaves the bereaved time to calmly consider whether or not to consent to a removal. However, you can also decide to donate while you are still alive and will then receive an organ donation card that indicates that you are ready.
If the patient has such an ID or if the bereaved decide to have it removed, the corneas are removed and placed in the corneal bank. Glass prostheses that look like their natural eyes are inserted into the deceased.
Preparation of the cornea
Careful analysis and subsequent observation of the cornea ensure the provision of high quality grafts. At the same time, microbiological tests and examinations of the donor blood rule out the possibility of pathogens such as HIV and hepatitis B viruses being transmitted to the recipient.
Selection of recipients
In addition to checking the donor organs, the corneal banks also organize the assignment of the transplants to the recipients. Since the corneas can survive in the incubator for four to six weeks, there is enough time to calmly order the patients to the clinic and prepare for their operation.
Great progress has been made in the testing and research of artificial corneas in recent years. However, widespread use of this technology is not yet possible.
Corneal transplantation risks and complications
The success rate with corneal transplants is normally, that is, if there is no acute inflammation or vascular sprouting, very high at over 90 percent.
However, if the above changes exist, the donor corneas need to be examined and selected more carefully in order to achieve a good match between the donor and recipient tissues. The risk of rejection is thus reduced, but is still around 40 to 60 percent.
Surgical complications due to infections are very rare, especially if the donor cornea has been cultivated in a corneal bank.
The most common complication is the rejection reaction, which, however, can be contained under certain circumstances by the administration of certain medications. If the new cornea is not accepted by the body, a new transplant can take place.
How does an operation work?
The operation can be carried out in the hospital or on an outpatient basis. The surgical procedure is relatively simple: First, the doctor cuts the cloudy area out of the patient's cornea. Then he punches a suitable disc out of the donor cornea, inserts it into the gap and sews it up. In most cases, not the entire cornea but only the central part around the pupil is transferred.
In principle, the procedure can be performed under local anesthesia, but most ophthalmologists recommend general anesthesia because this reduces the risk of sudden eye movements. The sutures are only pulled after twelve to 18 months, as the wounds of corneal transplants heal very slowly.
If there was no inflammation in the eye before, the new cornea heals without pain after the operation. However, if the eye was severely inflamed, pain may persist in the further course, but this may gradually subside with painkillers.
What is the follow-up treatment like?
In the first year after the operation, frequent ophthalmological examinations must be carried out in order to detect and treat possible inflammation or a possible rejection reaction at an early stage. Any medication prescribed must be taken or used regularly.
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