Ophthalmology

Corneal transplant

synonym

Keratoplasty

English: corneal crafting

definition

Corneal transplantation is the transfer of parts of the cornea or the entire cornea of a donor's eye to a recipient's eye.

Corneal transplant procedure

Corneal transplants are usually carried out in full thickness today. This process is also known as perforating keratoplasty. The prerequisite is that the other functions of the eye that contribute to vision are preserved. In particular, retinal function, intraocular pressure, and tear production must be normal.
Read also: glaucoma

Corneal cells cannot be produced synthetically, i.e. To be able to insert a cornea into a recipient, you need a cornea donor.
The cornea is usually removed from the dead. The prerequisite is that the endothelium of the donated cornea is intact and vital. This assumes that the cornea is removed from the deceased promptly. For this reason, a collection time of 12-18 hours after death should be observed. The corneas of young donors are better suited for corneal transplants than of older ones, because older corneas are often associated with a loss of endothelial cells.

After removal, the cornea must be placed in an appropriate nutrient solution. This increases the survival time of the donor organ by a few days. Whether a cornea is intact or not can be, among other things, by the opacity of the cornea, because a defective cornea is a lot more cloudy than an intact one.
The donor is checked for infectious diseases prior to collection. A HIV infection/ AIDS or Hepatitis B. or Hepatitis C. -Infection includes one Corneal transplant out.

Come one Corneal transplant weighing all factors into consideration, the cornea will have a surrounding stripe of about 5 mm removed and placed in the nutrient medium that consists of Hyaluronic acid, Chondroitin sulfate and one antibiotic consists.

Only during the operation is the corneal disc cut out with a very thin knife. The instrument, also known as a trepan, is capable of very precise and smoothly delimited shapes from the Cornea cut out.

A distinction is made between motorized and hand-operated treks Corneal transplant. There is also the option of cutting the cornea with a laser (Excimer laser) cut out. The diameter of the cut out cornea is between 6.5 mm and 8 mm. At the recipient, the cornea is cut out of the same size and the cornea is sewn in with a very thin thread. This is usually around 30 micrometers thick. The seam technique of a Corneal transplant varies depending on the surgeon.So-called single button seams and continuous seams can be made. The sutures are removed no earlier than 12 months after the operation. The time it takes for the cornea to grow in depends on how well preserved the transplanted cells are.

There is also the option of transplanting individual layers of the cornea. One also speaks of lamellar keratoplasty. Here only the upper corneal layer is removed and inserted into the recipient.
The prerequisite is that the recipient's cornea is not completely destroyed and that Endothelium is still preserved and vital. The lamellar surgical procedure is technically more difficult and fraught with more complications.

Reasons for a corneal transplant

Keratoplasty / corneal transplantation is required when large parts of the cornea have been destroyed. In the vast majority of cases, the causes are traumatic. Chemical burns from accidents at work or perforations make up the largest share. However, foreign bodies that are left in the eye for too long and thus scratch the cornea can, in extreme cases, make keratoplasty necessary. Improperly processed or inserted contact lenses can also lead to a corneal transplant. In addition to the traumatic reasons for a corneal transplant, infections and inflammation of the cornea are another reason for this procedure. If the infection is very violent or chronic (chronic keratitis, herpes zoster, infection of the eye), it may also be necessary to seal the patient's cornea transplant.

It rarely happens that the cornea has to be transplanted as a result of a complication after an eye operation. In laser eye therapy, which is used to correct ametropia, parts of the cornea are removed with a laser in order to change the refractive power of the eye. Too much removed cornea not only ensures that the tasks performed by the cornea can no longer be guaranteed, but also make a complete corneal transplant necessary in rare individual cases.

In the case of only superficial injuries and resulting scars, a lamellar keratoplasty can be considered, as the cornea is only superficially injured. In the case of injuries, including deeper layers, a complete transplant is definitely necessary.

This article might also interest you: Corneal dystrophy

diagnosis

For extreme injuries to the eye, such as Injuries to the eye from chemical burns or perforations, the eye diagnosis by the viewer is often sufficient. In the case of minor injuries and formed scars, however, the damage is not so easy to recognize. Applying a helps here Fluorescent fluid, which is then illuminated with a blue light. As a result, scars and small injuries to the cornea shine yellow in the light of the slit lamp. Depending on the severity of the injured cornea and the depth of the injury, the indication for a corneal transplant is then made.

Corneal Transplant Risks

In addition to infections, wound healing disorders and bleeding during and after corneal transplantation, there is also the risk of the recipient rejecting the donated cornea. The healing of the implanted cornea depends on the immune defense / immune system of the recipient against the inserted cornea. If the transplant is vascular-free, the likelihood of a rejection reaction after the corneal transplant is reduced, since the donor's immune cells cannot enter the recipient's new organism. Otherwise, the risks of a rejection reaction increase sharply. The reaction can be suppressed by giving ciclospoprin A.

The drug-based suppression of the recipient immune system has made it possible in recent years to increasingly transplant corneas with ingrown vessels without major risks. To a rejection reaction after the Corneal transplant preventive measures can also be taken before the procedure tissue-competent typing so that the recipient only receives corneal transplants of his own cell type (HLA Specificity). But you can never rule out a rejection reaction. For this reason, in addition to the very careful operation, follow-up treatment of the patient is essential. Regular follow-up examinations can make an impending transplant rejection clear. Patients who have had a foreign body sensation in the eye should see an ophthalmologist within one day, who can use a slit lamp examination to immediately reveal corneal swelling, which could indicate that the transplant reaction has started.

Corneal transplant duration

The process and the duration of the corneal transplantation have been improved and optimized over time, so that the procedure is now one Routine matter is. With a so-called "Trepan", a special round knife, the Corneal defect removed and into the resulting gap in the cornea the new cornea sewn in. Here the surgeon uses extra thin and fine suture material to keep the impairment of vision as low as possible.

With experienced surgical teams the procedure takes about one half a hourduring which the patient sleeps under general anesthesia and is not aware of the procedure. The eye is bandaged and the operation is complete. In principle, the whole thing can also outpatient take place, which means that the patient is discharged home on the day of the operation and thus saves a night stay in the hospital. The sewn-in threads in the eye that initially attached the new cornea no longer necessary after 9-12 months because the new cornea completely attached is and will be in a second, brief intervention drawn.

Follow-up treatment for a corneal transplant

On the day of the operation itself, the patient either stays in the hospital overnight or is discharged home on the same day (outpatient procedure), but then has to go to an ophthalmologist's practice for a check-up the following day. The Vision of the treated eye becomes not fully restored in the first few days immediately afterwards be. thats why increased caution in everyday life and especially advisable in traffic. Special precautions are usually not to be observed, except that the patient should be Take care of your eyes and protect against mechanical stress should, so don't rub it.

Eye drops containing cortisone and antibiotics promote the healing process. Should be in the next few weeks to months Ophthalmologist regularly check the eyeto see the progress.
Since the new cornea still numb for about a year after the transplant the patient should avoid activities such as drilling, welding, chiselling, etc. Protect eyes from dust.

When is the right time to Removal of the sutures the attending ophthalmologist decides during one of the check-ups. Usually it is after nine to twelve months the case, but in individual cases it can extend up to two years. After the stitches are removed, that will Fully normalize the eye and now can new glasses fitted if necessary as the eye is unlikely to change any further.

Corneal transplant costs

The affected patient does not normally have to worry about the costs incurred for an upcoming corneal transplant. The cost will be from the statutory health insurance (short GKV) accepted. However, as is usual for other interventions, these pay just the standard treatment. Anything that the patient wishes for additional treatment, he must pay himself.
At private health insurance (PKV for short) the whole thing looks a little different. Here the insurance decides in individual cases and depending on the conditions of the insurance. Normally, however, any additional costs incurred for special treatments are also covered here.

Whether the cornea transplant at all necessary is decides of course the attending physician. This then provides one Application for reimbursement with the statutory health insurance and proves that the diagnosis made is correct and that the corneal transplant is inevitable. Since this is now a routine operation, the assumption of costs is usually quick and unproblematic.

Willingness to donate

Similar to liver or kidney donation, there is a chronic shortage of donors in Germany. Of all transplants, the corneal transplant is the most common transplant performed in medicine. The supply-demand ratio is also favorable for the cornea of the eye, so that most patients who need a cornea can be transplanted relatively quickly.

Summary

The Cornea of Eye has a variety of tasks. In addition to contributing to sharp vision through the additional refraction of the incident light, the cornea also has the task of protecting the eye from bacterial and viral intruders, it also leads to a cushioning of the intraocular pressure.
Leaked aqueous humor is also pumped back into the interior of the eye through the cornea. Cornea cannot regenerate. Once it is severely damaged, the only treatment option that has to be transplanted is the cornea to save the patient's eyesight.

Reasons for a Corneal transplant are therefore damage by corrosive substances (Work accident), Perforations and punctures, but also foreign bodies that have got onto the cornea and are left there, can scratch the cornea when the eyelid is knocked open or down.

Infections and complications from previous eye operations are less common reasons for a corneal transplant.
Injuries to the cornea can either be seen with the naked eye (with extensive injuries) or by the slit lamp with fluorescent liquid. This turns small scratches and resulting scars yellow.
If only the superficial layer of the cornea is scratched, a so-called lamellar corneal transplant carried out in which only the top layer of the cornea is transferred.
If deeper layers of the cornea are also injured, the entire thickness of the cornea must be used Corneal transplant be transmitted. For this purpose, the cornea of a dead person is removed and placed in a nutrient solution, whereby a shelf life of several days can be achieved. It is important that the corneal harvest should be carried out within 12-18 hours after the donor's death, as this is the only way to achieve the necessary vitality.

A layer a few micrometers thick is then cut out of the removed cornea into a shape cut out by the recipient using a fine knife. The cornea then transferred is then sutured with a continuous suture or with single button sutures at the recipient.
The seams must remain in place for about 12 months. How quickly a transplanted cornea grows depends on the vitality of the transplanted material and the occurrence of complications. Transplant rejections can occur after the Corneal transplant occur and are usually noticeable by a foreign body sensation in the eye. What is important in this case is one Ophthalmologist is visited within a day.
In order to prevent transplant rejection, on the one hand, tissue typing of the donor organ can be carried out; on the other hand, the recipient can receive an immune-suppressing therapyCiclosporin A) after Corneal transplant are given.

Vessel-free grafts lead less often Rejection reactions as vascularized. Corneal transplantation is the most common medical one Organ transplant in Germany.