The deepest layer of the cornea is called the endothelium and is made up of endothelial cells. These cells do not regenerate and therefore gradually decrease in number throughout life. In addition, they allow the cornea to remain transparent. Some patients may have a constitutional decrease in the number of endothelial cells (called “Cornea Guttata”). In addition, if the number of endothelial cells drops below a minimum threshold, the cornea will no longer be transparent. Moreover, quality of vision will fall sharply due to oedema of the cornea known as “endothelial decompensation”.
Endothelial decompensation can be triggered spontaneously or after ophthalmologic surgery (most often cataract surgery), especially in patients with “cornea guttata”. The only treatment for endothelial decompensation is corneal transplant.
Corneal transplantation is a surgical procedure to treat endothelial decompensation. The purpose of corneal transplantation is to provide the patient’s eye with endothelial cells from a donor graft to repopulate the patient’s cornea and restore the transparency of the cornea, making the corneal edema disappear.
There are 2 types of corneal transplants:
This is the classic technique where the patient’s cornea is removed in its full thickness to be replaced by a graft. This surgery has several drawbacks. First, it requires general anaesthesia and having stitches all over the cornea to suture the graft. In addition, there are increased risks of transplant rejection and graft infections. Also, there may be a significant corneal astigmatism due to the stitches and the cutting of the patient’s cornea.
It is now the modern technique of choice in endothelial decompensation. This type of transplant involves cutting the posterior part of the donor graft to keep only the endothelium of the graft and injecting it into the patient’s eye without removing his cornea. The graft endothelium will then slide under the patient’s cornea and will stick in place thanks to the action of an air bubble injected into the eye.
This technique preserves the architecture of the patient’s eye by making only a small corneal incision. The advantage is that it greatly reduces the risk of rejection and transplant infection and does not cause corneal astigmatism. There will be only a very few stitches and they can be removed soon after. Consequently, follow-up is more straightforward, post-operative care is simpler and shorter. Another advantage of this technique is that it does not require general anaesthesia. Indeed, a simple local anaesthesia is sufficient. It may be necessary to re-inject an air bubble after the operation (under local anaesthesia) if the graft has not bonded well. For the moment, vision recovery is not superior in endothelial graft when compared to transfixing keratoplasty but the risks are far fewer. This is why this technique is preferred today.
Endothelial grafting benefits from constant technical improvements, particularly in terms of cutting the endothelium from the graft. It can be entirely laser cut allowing which automates and simplifies this delicate gesture. The most modern endothelial grafting technique is DMEK (Descemet’s Membrane Endothelial Keratoplasty). It consists in inserting into the eye a graft of Descemet’s membrane only (pure endothelium, without any part of the corneal stroma). This, more difficult technique gives better visual results than other older endothelial grafting techniques like DSAEK (Descemet Stripping Automated Endothelial Keratoplasty). In this technique, the graft consisted of the Descemet membrane plus the corneal stroma.
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