[Keratoplasty: laminate or penetrate? Part 1: penetrating keratoplasty]

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.