Keratoplasty

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Eye one day after cornea transplantation: The continuous suture and the previously placed individual sutures are clearly visible.

A keratoplasty is an operation of the cornea (cornea), is replaced by suitable donor material in which either diseased corneal tissue ( transplant ) or a change in the corneal power is sought by localized physical action on corneal tissue, for example, visual defects to be reduced.

species

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

  • Thermokeratoplasty, in which the curvature of the cornea is to be influenced by localized heat. This surgery is a refractive procedure and does not rely on corneal donor tissue.
  • The perforating keratoplasty, in which all layers of the diseased cornea are removed in an eyeball-opening procedure by means of trephination and a corresponding corneal disc from a suitable donor is inserted.
  • Lamellar keratoplasty, in which individual layers are transplanted in isolation. For example, in a so-called epikeratoplasty, comparable to a contact lens, a corneal disc is sewn onto the cornea.

A tectonic keratoplasty is used when donor material is sewn on or sewn onto the patient's cornea in order to cover small-area defects (e.g. corneal perforation). If this form of corneal transplantation has to be carried out in an emergency and when the cornea is still inflamed (e.g. perforated corneal ulcer), it is called keratoplasty à chaud . This intervention is mostly only a temporary solution without the aim of improving visual acuity, but primarily serves to preserve the eye. Tectonic keratoplasty can be performed both perforating and lamellar (usually as epikeratoplasty).

Contact lens care after keratoplasty

The visual goal of keratoplasty is that the person can see well without visual aid . Often, however, after the cornea has completely healed, an irregular astigmatism remains, which can only be compensated for with a dimensionally stable contact lens .

history

The idea of ​​corneal transfer from animals to humans or from humans to humans is around 200 years old. It was first formulated in 1813 by Karl Gustav Himly . In 1824, Franz Reisinger first performed keratoplasties to perforate rabbits. R. Kissam performed the first perforating keratoplasty on humans in 1843. Arthur von Hippel then performed lamellar and perforating keratoplasties using a trephine constructed by himself, the results of which he presented to the Ophthalmological Society in Heidelberg in 1886. The first perforating keratoplasty with a medium-term clear transplant (over a year postoperatively) was performed in 1905 by the Viennese ophthalmologist Eduard Zirm in Olomouc (Czech Republic). Nussbaum's first attempt at a keratoprosthesis was also unsuccessful. With the introduction and improvement of microsurgical techniques in the 21st century, such as the binocular microscope and the continuous monofilament plastic thread, keratoplasty has now become a standard operation. Today, perforating keratoplasty is the most commonly performed tissue transplant worldwide.

Indications

surgery

The keratoplasty was usually performed under retrobulbar anesthesia, with five milliliters of a local anesthetic being injected retrobulbarly . In order to lower the vitreous pressure, an oculopressor is usually put on and 250 mg acetazolamide is administered intravenously. Intubation anesthesia is required in very anxious or mentally handicapped patients. The trepanation is usually done with a Handtrepan, first for the donor cornea from the inside, and thereafter for the patient's cornea from the outside. The graft is usually first fixed with four single sutures made of monofilament nylon thread of size 10.0 at the 3, 6, 9 and 12 o'clock position. Then, as a rule, a double, crossed diagonal seam according to Hoffmann's method with two eight perforations is placed. The advantage of this suturing technique is that gaping inner and outer wound edges and postoperative thread penetration are avoided. The single sutures are usually removed again at the end of the operation. The operation usually takes about 45 minutes with a trained hand. The first continuous thread was removed after four to six months at the earliest and the second after 12 to 18 months at the earliest. Only after this time can a stable refraction be expected.

In addition to trephination using a hand trephine, some centers also offer the option of non-contact trephination using an excimer laser. The advantages here are less tilting, torsion and better adaptation of the transplant.

Corneal donation

Since the human cornea is a tissue with no blood supply and the corneal endothelium is nourished by the aqueous humor, a corneal donor can be removed up to 72 hours after death. There are two main techniques for corneal removal from the corneal donor:

  • Corneas scleral technique: Here, under the most sterile conditions possible, an approx. 15 mm large disc is trepanned on the front of the eye (cornea and an approx. 1–2 mm wide scleral margin). The eye as such remains.
  • Enucleation: The entire eyeball is removed and a suitable prosthesis is used. Corneal trepanation is then carried out under sterile conditions in a corneal bank.

With both removal techniques, the lid of the deceased is closed after the removal. As a rule, it cannot be seen from the outside that a cornea donation has taken place.

In people actively suffering from tuberculosis , the bacteria can even be detected in the cornea.

Complications

Rejection reactions (immune reactions)

Rejection reactions after perforating keratoplasty usually occur within the first five years. About 20% are affected. The early symptoms are tearing, reddening of the eyes and deterioration in vision. If the rejection is recognized early and intensive treatment is carried out, permanent opacity of the graft (white discoloration) can usually be prevented. However, a rejection reaction leads to a considerably shortened lifespan of the transplant.

Chronic endothelial cell loss

The endothelial cell density of corneal transplants after perforating keratoplasty is continuously decreasing for reasons that are still unknown. This postoperative loss of transplant endothelial cells is around 10% annually, well above the natural age-dependent endothelial cell loss rate of non-transplanted corneas of only 0.5% per year. Consequently, it cannot be ruled out that after 15–20 years, subsequent keratoplasties may be necessary more often due to failure of the transplant endothelium.

Other causes of cloudiness

  • Spontaneous endothelial failure long after keratoplasty due to idiopathic endothelial cell loss
  • Superficial disorders of the transplant
    • Ulcers
    • Herpetic keratitis
    • Keratoconus
    • Overgrowth by conjunctival tissue (conjunctivalization), for example in limbal insufficiency
  • Increased eye pressure
  • Relapse of the underlying disease

Similar treatments

Web links

literature

  • Theodor Axenfeld (founder), Hans Pau (ed.): Textbook and atlas of ophthalmology. 12th, completely revised edition. With the collaboration of Rudolf Sachsenweger and others Gustav Fischer, Stuttgart and others 1980, ISBN 3-437-00255-4 .
  • Albert J. Augustin: Ophthalmology. 3rd, completely revised and expanded edition. Springer, Berlin et al. 2007, ISBN 978-3-540-30454-8 .
  • Franz Grehn: Ophthalmology. 30th, revised and updated edition. Springer Medicine, Heidelberg 2008, ISBN 978-3-540-75264-6 .

Individual evidence

  1. ↑ EJ Catedral, RE Santos, MDB Padilla, C. Fajardo-Ang: Detection of Mycobacterium tuberculosis in corneas from donors with active tuberculosis disease through polymerase chain reaction and culture. In: British Journal of Ophthalmology . Vol. 94, No. 7, July 2010, pp. 894-897, doi : 10.1136 / bjo.2008.153270 , PMID 19850582 .