The cornea consists of 3 layers:
There are various conditions that must be met before a corneal transplant can be considered. The most common indications are:
In the last 50 years penetrating keratoplasty (PKP) or the replacement of the full thickness of the cornea by donor tissue, was the standard treatment for patients with corneal disorders. Although the anatomical results are outstanding, the visual results in terms of speed, quality and predictability are less favourable. A typical patient undergoing a corneal transplant can continue to suffer from impaired vision for 2 years. It is very difficult to predict the final curvature of the cornea. Hence, in most cases, glasses or contact lenses need to be worn after the operation. The stitches are only removed after a long period of time, and rupture of the wound due to an accident is always a major risk. Patients with bilateral disorders often have to wait a long time until the first treated eye is healed, before their second eye can be treated.
In recent years cornea specialists have developed techniques to replace just the diseased layer of the cornea, instead of the full thickness: these are known as lamellar keratoplasty techniques.
If the front part of the cornea is the reason for poor sight, such as with keratoconus or corneal dystrophy, only the epithelium and the stroma are replaced (the largest part of the cornea). This is referred to as Deep Anterior Lamellar Keratoplasty (DALK). Descemet’s membrane and the endothelium of the patient remain intact and form the surface support for the donor tissue. This technique ensures that the healing process is faster and the refractive result more predictable: the patient has a better chance of improved sight and the eye is stronger than before.
DALK will increasingly replace PKP in the future.
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