With this operation the donor cornea, called button, is transplantet in a diameter of a 6,7 or 8mm in full thickness. For this purpose of the patients's cornea a circular piece of tissue is trephined out and a donor button of same size is sutured into this opening of the patient's cornea. Of great importance is the generation of the same size of donor and recipient both regarding the diameter and the under cut, with is the circular angulation of the transplant's edge. THe technical difficulty of this procedure consists in really creating identical dimensions between the recipient's bed and the donor button.
We have developed the Guided Trephine System (GTS) that desirable to cut identical buttons despite differenc arc length between transplant and the recipient's bed by using different Obturators inside the trephine for first the cut on the donor tissue then for the cut on the recipient's tissue. The obturator maintain the natural curvature of the cornea during the cut on both sides.
Even if a femtosecond laser is used to cut the cornea buttons to date there is no possibility to generate identical dimensions as different arc lengths of donor and recipient's bed can not be incorporated so that the different arc length may lead to irregularities and astigmatisms. In Germany the GTS is used in 80% of the corneal transplants.
Healing of the donor tissue in almost all cases happens without complications. But one never can exclude a reaction between the two different tissues, which is called immune reaction and happens in 6% of the of the uncomplicated cases but up to 30% in cases with more severe impairments of the recipients cornea. In case a immue reaction happens or for prophylactic reasons medication may be applied of weeks of months. These medications, in particular Cellcept or Cyklosporin A are expensive and leads to massive stress for the body. This is one of the reasons that a Deep Lamellar Keratoplasty should be chosen if any possible.
Within the last 10 year, a new measure to prevent an immune reaction is the metallic Ring of Titanium, Kobalt, Molybdenum alloy, which is placed into the wound between the donor and recipient. The Ring seems to reduce immune reaction by about 50% (reference). Also the ring provides a faster healing so that the patients can be back to work in 4-6 weeks postoperatively.