Corneal transplantation

A keratoplasty is surgery of the cornea ( cornea), is replaced by suitable donor material in either diseased corneal tissue ( transplantation) or by localized physical action on corneal tissue a change in corneal power is intended to reduce, for example, refractive errors.

Species

The donor material required for the operation is obtained from a human donor cornea and is usually edited before surgery in an eye bank or eye bank. There are different types of keratoplasty:

• The thermokeratoplasty, wherein by localized heat the corneal curvature should be controlled. This surgery is a refractive surgery and not dependent on corneal donor tissue.
• The penetrating keratoplasty, in which all layers of the diseased cornea is removed in a bulbuseröffnenden intervention using trepanation and a corresponding corneal flap of a suitable donor is inserted.
• The lamellar keratoplasty, individual layers are transplanted isolated in the. For example, comparable sewn with a contact lens, a corneal flap on the cornea at a so-called Epikeratoplastik.

From a tectonic keratoplasty occurs when donor material is on or sewn on the patient's cornea to cover small surface defects (eg, corneal perforation ). If this form of corneal transplant must be performed emergently and still inflamed cornea conditions (eg perforated corneal ulcer ), one speaks of a keratoplasty à chaud. This procedure is usually only a temporary solution without the objective improvement in visual acuity, but primarily serves the preservation of the eye. Tectonic keratoplasty can be performed (usually as Epikeratoplastik ) both perforating and lamellar.

Contact lens care after keratoplasty

The visual target keratoplasty is that the person can see well without corrective lenses. Often, however, remains after complete healing of the cornea left an irregular astigmatism, which can only be compensated with a rigid contact lens.

History

The idea of the cornea transmission from animal to human or from human to human is about 200 years old. It was formulated for the first time in 1813 by Karl Gustav Himly. Were first made ​​in 1824 by Franz Reisinger perforating keratoplasty in rabbits. R. Kissam 1843 led the first penetrating keratoplasty by humans. Arthur von Hippel then led lamellar keratoplasty and penetrating by means of a contrived by him trephine, the results of which he presented in 1886 in Heidelberg Ophthalmological Society. The first penetrating keratoplasty with clear medium-term graft ( more than one year postoperatively ) was conducted in 1905 by the Viennese ophthalmologist Eduard Zirm in Olomouc ( Czech Republic). The first attempt of a keratoprosthesis led by Nussbaum also unsuccessful. The introduction and improvement of microsurgical techniques in this century, such as the binocular microscope and the continuous monofilament plastic yarn, keratoplasty has become a standard operation. Today keratoplasty is the most commonly performed tissue transplantation worldwide.

Indications

• Corneal dystrophy with involvement of the endothelium (forecast: good) Primary disease: Fuchs endothelial dystrophy (forecast: good)
• Secondary disorders: Bullous keratopathy after intraocular surgery or after a protracted attack of glaucoma (forecast: moderate )

• Keratoconus (prognosis: excellent)

• Friable Dystrophy, Lattice dystrophy

• After herpetic keratitis and other corneal infections (forecast: moderate )
• After scrofulous keratoconjunctivitis ( Phlyktenulosa ) (forecast: good)

Operation

Most keratoplasty was performed in retrobulbar anesthesia, with five milliliters of local anesthetic are injected retrobulbar. In order to reduce the glass body pressure, a Okulopressor is usually applied and administered 250 mg acetazolamide intravenously. A general anesthesia is required at very anxious or mentally handicapped. The trephination is usually done with a Handtrepan, first for the donor cornea from within, and then for the subject's cornea from the outside. The graft is usually first with four Einzelknüpfnähten of monofilament nylon thread of strength 10.0 at the 3 - and 12 fixed - clock position -, 6 -, 9. After that, usually twice a continuous crossed diagonal seam is placed by Hoffmann with two sets of eight punctures. Advantage of this suture technique is that gaping inner and outer edges of the wound and postoperative filament migration can be avoided. The Einzelknüpfnähte are usually removed at the end of the operation. The operation takes a practiced hand usually about 45 minutes. The removal of the first continuous filament was made after a minimum of four to six, the second after at least 12 to 18 months. Only after this time can be expected with a stable refraction.

In addition to the trepanation by a Handtrepan there is the possibility for contact-free trepanation by excimer laser in some centers. Advantages are less tilting, twisting and better adaptation of the graft.

Cornea donation

Since the human cornea is a non- perfused tissue and the corneal endothelium is fed through the aqueous humor, cornea removal on corneal donor can be up to 72 hours after death. There are two main techniques for corneal removal on corneal donors:

• Corneasklerale technology: this under sterile conditions as possible is a 15 mm disc at the front of the eye trepanated ( cornea and a 1-2 mm wide scleral rim ). The eye - as such - there remains only the " windshield " on the eye is removed.

• Enucleation: Here, the entire eyeball is removed and used a suitable prosthesis. The Hornhauttrepanation then takes place under sterile conditions in a cornea bank.

In both sampling techniques after removing the lid of the deceased is closed. So it is not visible from the outside as a rule that a cornea donation has been made.

In active tuberculosis patients, the bacteria can be detected even in the cornea.

Complications

Rejection reactions ( immune reactions)

Rejection after penetrating keratoplasty usually occur within the first five years. About 20% are affected. Early symptoms include watery eyes, eye redness and visual loss. If the rejection is detected early and conducted an intensive treatment, a permanent graft failure ( whitening ) can be usually prevented. However, a rejection yet been shown to significantly shorten the life of the graft.

Chronic endothelial cell loss

The endothelial cell density of corneal grafts after penetrating keratoplasty falls yet unknown reason continuously. This postoperative loss of graft endothelial cells is about 10 %, well over a year of natural age-related Endothelzellverlustrate not transplanted corneas of only 0.5 % per year. Consequently, is not excluded that after 15-20 years Folgekeratoplastiken often may be necessary due to a failure of the Transplantatendothels.

Further clouding causes

• Spontaneous Endothelversagen long after Keratoplasty by the idiopathic endothelial cell
• Superficial disorders of the transplant ulcers
• Herpetic keratitis
• Overgrowth by conjunctival tissue ( subjunctive unreality ) at about Limbusinsuffizienz

Similar treatments

• Keratoprosthetics
• Descemet Membrane Endothelial Keratoplasty