Optimal Donor Tissue Use
One of our aims at NIIOS is to make optimal use of donor graft tissue (acquired altruistically) and minimize its waste. Thanks to our lamellar surgical techniques for corneal transplantation such as (advanced) DMEK and Bowman layer transplantation, we have been able to increase the global pool of donor tissue. On this page, we present several examples.
More Tissue Suitable for Lamellar Keratoplasty
Donor corneal tissue is more often suitable for use in a posterior lamellar keratoplasty (which replaces only one layer of the cornea) such as DMEK than in a penetrating keratoplasty (which replaces the whole cornea). Because penetrating keratoplasty replaces all the layers of the patient’s cornea with donor tissue, the entire cornea must be suitable for surgery or it cannot be used at all. In a posterior lamellar keratoplasty, only one layer of the cornea is replaced, which means it is only important that that single layer contains enough vital endothelial cells. This means that the same amount of donor tissue can be used to help more patients.
One Donor for Two Patients
In lamellar corneal transplant surgeries, only one or a few layers of the cornea are replaced by donor tissue, instead of the entire cornea. This means that one donor cornea can be used for two patients. We can use the front (anterior) layers of the donor cornea for a DALK (deep anterior lamellar keratoplasty) or a Bowman layer transplantation. We can use the innermost (posterior) layer for a (advanced) DMEK. Here, too, the techniques developed by NIIOS enable more people around the world to undergo corneal surgery using the available amount of donor tissue.
Surgical Adaptation Increases Donor Pool
NIIOS recently adapted the existing technique for DMEK surgery to waste even less donor tissue. The new version of the technique is called hemi-Descemet membrane endothelial keratoplasty. Instead of using a circular graft of 8.5 – 9.5 mm diameter, hemi-DMEK uses a semi-circular full diameter graft (approximately 12 mm) — that is, a full-size graft that has been split in two. An even more recent development is quarter-DMEK, which only uses one-fourth of a full diameter DMEK graft. Since hemi- and quarter-DMEK enable us to obtain two or even four endothelial grafts from one donor cornea, these techniques have the potential to greatly increase the pool of donor endothelial tissue for corneal transplantation.
Reduce the Risk of Contamination
To keep bacteria and viruses away from donor corneas at our eye bank, we have developed several new decontamination methods and tested their effectiveness and safety. By adding an extra cleaning step, we have reduced the number of contaminations at our eye bank to 0.5%. Reducing the contamination rate obviously increases the availability of transplantable corneas from the same pool of donor tissue. For further reading, please see:
van Luijk CM, Bruinsma M, van der Wees J, Lie JT, Ham L, Melles GRJ. Combined chlorhexidine and PVP-I decontamination of human donor eyes prior to corneal preservation. Cell and Tissue Banking 2012;13:333-9
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