The cornea is the eye’s outermost layer. It is a clear dome of tissue that allows light to enter the eye. If the cornea becomes diseased or damaged, it can distort or even block the normal path of light into the eye. When this happens, light does not focus normally on the retina, the layer at the back of the eye that is responsible for sight. As a result, there can be significant loss of vision in the affected eye.
When corneal conditions cause serious vision problems that can’t be reversed, a corneal transplant is sometimes needed. During surgery, the diseased or damaged area of the cornea is removed. The removed tissue then is replaced by a section of healthy cornea that has been taken from the eye of a deceased donor.
There are two types of corneal transplants. The first type is the traditional full-thickness technique or Penetrating Keratoplasty (PK) where the surgeon removes the central portion of the cloudy cornea and replaces it with a clear cornea, donated through an eye bank. The surgeon places the new donor cornea in the opening and sews it into place with several very fine sutures. Visual recovery is slow, and can take up to one year.
The second type of corneal transplant is called Endothelial Keratoplasty (EK). This is the preferred method to restore vision when the inner lining (endothelium) of the cornea is damaged in conditions such as Fuchs’ dystrophy, or bullous keratopathy. EK only replaces the very thin diseased inner lining of the cornea, and leaves the rest of the healthy cornea intact. The advantage of EK over PK is that the eye is much stronger, visual recovery is faster, and there is less chance of rejection.