Patients with corneal endothelial problems account for about 60% of transplant cases, although very few have benefited from this procedure, because it is not widely used due to its surgical complexity. Currently, only a small number of surgeons perform the operation, and they include Dr Gerrit Melles from the Netherlands Institute for Innovative Ocular Surgery in Rotterdam (the pioneer of the technique), Dr Friedrich Kruse from the University of Erlangen (Germany) and the specialist in cornea and refractive surgery from IMO, Dr José Luis Güell.
DMEK and posterior lamellar keratoplasty enable the corneal endothelium to be replaced by only selecting the inner layers of the cornea without affecting the middle layers. Surgery is performed in a controlled manner by means of a microincision that facilitates rapid rehabilitation and prevents fragility in the event of trauma after other interventions, counters high astigmatism and precludes the need to use the typical sutures that are characteristic of traditional corneal transplantation (penetrating keratoplasty).
As a result, the patient recovers more rapidly, and the level of vision obtained (between 90 and 100%) is much higher than can be achieved through traditional transplantation. As well as benefiting the patient, another important advantage of this technique is that one donor cornea can be used to treat two different patients. For example, a patient with damage to only the anterior part of the cornea (keratoconus) can have the epithelium and stroma transplanted, while the endothelium and Descemet’s membrane can be used on a second patient with damaged inner layers.
Dr José Luis Güell is one of the very few experts who can perform this surgery
If the cells of the corneal endothelium fail to extract fluid from the cornea, the resultant build-up, or oedema, can reduce the cornea’s transparency and impair vision. This is the case, for example, with patients who suffer from Fuchs’ dystrophy, an inherited condition that usually ends in corneal transplantation, or with patients after cataract surgery involving intraocular lens implantation.
To perform a DMEK, the donor cornea is prepared and the Descemet’s membrane and the endothelial cell layer are stained. They are then carefully separated from the back of the cornea and allowed to roll up to form a small tube, which is inserted into an injector. At the same time, the recipient’s Descemet’s membrane and endothelium are removed through a small opening in the cornea, and the donor tissue is injected. With the use of air, the tissue is carefully unrolled onto the patient’s iris, positioned correctly and adhered to the base of the cornea.
A course for European colleagues
If the tissue detaches, which is quite rare, as the rejection rate is very low, it has to be reattached by means of intraocular air or gas. If the procedure fails, it can be repeated, or a traditional transplant can be used. This year, surgeons from all over Europe can learn about the technique during a DMEK course that Dr Güell is planning for his European colleagues.