When is a corneal transplant considered?
Since the year 2000, major strides were made in the development of new surgical techniques for corneal transplantation, so that a number of new procedures are available today.
In the past, the approach was to remove a central full-thickness ‘button’ of tissue, consisting of all the corneal layers, and replace this with donor tissue of a similar configuration. As this entails the introduction of foreign tissue into the recipient, there is a risk of a host immune reaction and thus a corneal rejection. Even though corneal transplants are known among other types of transplants for their high success rate, the goal would be to minimize the risk of rejection.Three types of rejections may be distinguished in the field of corneal transplant surgery, namely:
- Epithelial rejection (only of academic importance, since the epithelium is replaced by the proliferation of the host limbal stem cells) and does not carry a long-term risk.
- Stromal rejection.
- Endothelial rejection.
Although a full-thickness, penetrating keratoplasty is still the gold standard today, a number of lamellar corneal techniques became available. These techniques are aimed at only replacing the affected layer of the corneaThe cornea is the clear, transparent 'front window' of the eye through which light enters the eye. It handles about two-thirds of the focusing power of the eye and is critical for good vision. See Info on Eyes – Anatomy., thereby decreasing the chances of rejection. If a patient has a stromal pathology, it is needless to also replace the endothelium and thereby risk endothelial rejection as well.