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Keratoplasty is an operation on the cornea of the eye. A corneal transplant takes place.
Keratoplasty is one of the eye operations. In this process, tissue in the cornea that is diseased is replaced with donor material, which is a corneal transplant. In addition, a physical action on the tissue of the cornea can take place in the context of a keratoplasty in order to change the corneal refractive power. In this way, ametropia can be treated.
For a corneal transplant, suitable donor material is required from a human. The corneas that are used for a transplant are removed from deceased people. They already agreed to the removal during their lifetime. The donor corneas are managed by a special corneal bank. To ensure the integrity of the corneas, they are stored in nutrient fluid. It is also important that the organ is well tolerated in order to counteract rejection reactions. The cornea of the eye is its anterior outer shell. It is transparent and smooth.
Due to its curvature, it reaches a certain refractive power. Together with the lens of the eye, the cornea bundles the incoming light rays, which forms a sharp image on the retina of the eye.
When it comes to keratoplasty, it is important to distinguish between three different types. These include thermokeratoplasty, perforating keratoplasty and lamellar keratoplasty. In the context of thermokeratoplasty, the curvature of the cornea is influenced by the local action of heat. This procedure is part of refractive surgery and does not require any corneal donor tissue.
The situation is different with perforating keratoplasty. With this method, all layers of the damaged cornea are removed by trephination during the procedure. The surgeon then inserts the donor's corneal slices. A lamellar keratoplasty is when individual layers are grafted in isolation. For example, a corneal disc can be sewn onto the cornea, which can be compared to a contact lens.
Keratoplasty is intended to enable the patient to achieve optimal vision without a visual aid. However, it is not uncommon for an irregular astigmatism to remain as a result of the operation, which is compensated for with a dimensionally stable contact lens. There are various indications that damage the cornea so severely that a keratoplasty is necessary. These can be severe bacterial inflammation of the cornea, mechanical injuries that lead to piercing of the cornea, burns, chemical burns or corneal ulcers.
In some cases, hereditary diseases or severe inflammations such as Fuchs endothelial dystrophy or keratoconus, in which the cornea bulges like a cone, can damage the cornea. Other indications are severe corneal opacities and a corneal scar, which severely impair vision. Depending on the extent, either a lamellar or a perforating keratoplasty is performed. In order for a corneal transplant to be performed, the patient must meet certain requirements. He should be able to close his eyelids completely, have a normal intraocular pressure value and have a sufficient tear film.
Before a perforating keratoplasty, the patient is usually given general anesthesia. Local anesthesia is also possible. The first step of the procedure is to cut out the damaged cornea in a special size. The surgeon cuts the donor's cornea so that it can be implanted exactly into the gap that has formed. The recommended diameter is between 6.5 and 8.5 millimeters. After the corneal discs have been inserted, they are fixed with a fine suture.
As part of a lamellar keratoplasty, the surgeon only removes the anterior part of the cornea and replaces it. In contrast, the inner tissue layers remain in place. However, lamellar keratoplasty is rarely used because it is considered more difficult than perforating keratoplasty, which involves completely replacing the cornea.
Performing a keratoplasty is not free from risks. There is therefore a risk that various parts of the eyes or adjacent body structures will be affected by the procedure.
Bleeding occurs rarely, but it can never be completely ruled out. Infections can also occur.Furthermore, it is possible that the sutures of the corneal suture loosen up. If the cornea is not tightly sealed, additional threads must be laid.
Other conceivable complications after a keratoplasty are disturbances in the healing process of the cornea and the appearance of corneal opacities or scars. In extreme cases, the eyesight worsens significantly. Even blindness and loss of the eye are possible. However, these serious complications are extremely rare.
Since the perforating keratoplasty is a transplant, there is also the risk of a rejection reaction of the tissue that has been newly implanted. However, the risk of corneal transplantation is considered to be lower, as there is no blood flow to the corneas. However, after burns or inflammations, blood vessels can develop on the recipient cornea, which increases the risk of rejection.
So that there is no rejection reaction in the first place, the patient receives immunosuppressants in the form of eye drops. These have the property of suppressing defense reactions of the body, counteracting infections and inhibiting inflammation. In addition, the ophthalmologist must carry out regular check-ups. After a period of one year, the ophthalmologist carefully pulls the threads on the cornea, giving the patient a local anesthetic.