If the central layer of the cornea, the stroma, is clouded, which may be the case after severe corneal infections (corneal ulcer, herpes infection), the surgical methods "DALK" (Deep Anterior Lamellar Keratoplasty) and "PK" (Penetrating Keratoplasty) are applied.
In the case of Keratoconus, a disease that typically affects young men and results in conreal thinning of the stroma, "DALK" will be performed if possible. The innermost layer of the cornea stays intatct and, therefore, the risk of rejection of the graft is reduced dramatically. The cornea is incised (trephined) partially under general anesthesia. Using a special canula, air is injected into the corneal stroma. This often results in the creation of a "big bubble" that pushes the Descemet membrane backwards. Then the altered corneal stroma can be removed selectively. The healthy Descemet membrane and the endothelial cells stay intact. The donor tissue is then fixated with sutures. The benefit of this new technique is the decreased risk of rejection of the graft in comparison with the conventional corneal transplantation method (PK).
In cases of severe thinning in progressed Keratoconus as well as eyes with deep corneal scars, the conventional "PK" may still be the surgery of choice. The transplant is also held in place by sutures which are removed in the office (outpatient) typically 1 - 2 years after surgery.