Keratoplasty is the term used to describe an operation on the cornea of the eye. In this procedure, a corneal transplant takes place.
What is keratoplasty?
Keratoplasty is the name given to an operation on the cornea of the eye. In this procedure, a corneal transplant takes place. Keratoplasty is one of the eye surgeries. In this procedure, tissue of the cornea that is diseased is replaced with donor material, which is a corneal transplant. In addition, keratoplasty may involve physical action on the corneal tissue to alter the corneal refractive power. In this way, refractive errors can be treated. For corneal transplantation, suitable donor material from a human being is needed. The corneas used for transplantation are taken from deceased persons. These have already consented to the removal during their lifetime. The administration of the donor corneas is done by a special cornea 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 achieves a certain refractive power. Together with the eye lens, the cornea focuses incoming light rays, forming a sharp image on the retina of the eye.
Function, effect and goals
In keratoplasty, it is important to distinguish between three different types. These include thermokeratoplasty, penetrating keratoplasty, and lamellar keratoplasty. In thermokeratoplasty, the curvature of the cornea is influenced by the local application of heat. This procedure belongs to refractive surgery and does not require corneal donor tissue. On the other hand, the situation is different with penetrating keratoplasty. In this method, all layers of the damaged cornea are removed by trephination during the procedure. Then the surgeon inserts the donor corneal flaps. Lamellar keratoplasty is when the transplantation of individual layers is performed in isolation. For example, a corneal flap 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 irregular astigmatism to remain as a result of the surgery, which is compensated for by a form-stable contact lens. There are various indications that damage the cornea to such an extent that keratoplasty is required. These can be severe bacterial inflammations of the cornea, mechanical injuries that result in corneal perforation, 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, also lead to corneal damage. Other indications include severe corneal opacities as well as corneal scarring, which severely impairs vision. Depending on the extent, either lamellar or penetrating keratoplasty is performed. In order for a corneal transplant to be performed, the patient must meet certain requirements. For example, he or she should be able to close his or her eyelids completely, have a normal intraocular pressure, and have an adequate tear film. Before penetrating keratoplasty, the patient usually receives general anesthesia. Local anesthesia is also possible. First step of the procedure is cutting out the damaged cornea in a special size. The surgeon cuts the cornea of the donor in such a way that it can be implanted exactly into the resulting gap. The recommended diameter is between 6.5 and 8.5 millimeters. After the corneal flaps have been inserted, they are fixed in place with a fine suture. In lamellar keratoplasty, the surgeon removes and replaces only the anterior portion of the cornea. In contrast, the inner tissue layers remain in place. However, lamellar keratoplasty is rarely used because it is considered more difficult than penetrating keratoplasty, which involves the complete replacement of the cornea.
Risks, side effects and dangers
Performing keratoplasty is not free of risks. For example, there is a risk that various parts of the eye or adjacent body structures may be affected by the procedure. Rather rarely, bleeding occurs, although it can never be completely ruled out. Infections can also occur. Furthermore, it is possible that a loosening of the threads of the corneal suture occurs. If there is no tight closure of the cornea, it is usually necessary to lay additional sutures. Other conceivable complications after keratoplasty are disturbances in the healing process of the cornea and the appearance of corneal opacities or scars. In extreme cases, the vision of the eye deteriorates significantly. Even blindness and loss of the eye are in the range of possibility. However, these severe complications manifest themselves extremely rarely. Since penetrating keratoplasty is a transplantation, there is an additional risk of rejection of the tissue that has been newly implanted. However, the risk is considered lower with corneal transplantation because there is no blood flow to the corneas. However, after burns or inflammation, blood vessels can develop on the recipient cornea, increasing the risk of rejection. To prevent a rejection reaction from occurring in the first place, the patient receives immunosuppressants in the form of eye drops. These have the property of suppressing the body’s defense reactions, counteracting infections and inhibiting inflammation. In addition, regular check-ups must be performed by the ophthalmologist. After a period of one year, the ophthalmologist gently pulls the stitches on the cornea, and the patient receives a local anesthetic.
