A number of corneal disorders sooner or later call for a decision as to whether
corneal grafting is necessary. The problems of the current gold standard treatment, conventional
penetrating keratoplasty (PKP), have yet to be fully solved, namely accelerated postoperative endothelial cell loss, endothelial immune reactions and the induction of
astigmatism, which depends among other things on the
trephination technique used. The use of a hand trephine may lead to different cutting angles between donor and recipient, resulting in increased postoperative
astigmatism. This technique is therefore now only used for certain indications. One major advantage of mechanically guided trephine systems, which are now considered standard, is the possibility of
trephining the donor disc from the epithelial side to avoid donor oversizing, therefore reducing postoperative
astigmatism. Even less
astigmatism is induced in
keratoconus patients using an
Excimer laser for
trephination, as this technique does not lead to corneal deformation during
trephination. Furthermore, this non-contact method can also be used to trephine unstable corneas. Femtosecond
lasers allow the creation not only of straight but also profiled
trephination edges, leading to more stable wound healing and hence earlier
suture removal.