The cornea is made of multiple layers of cells. These layers must remain clear for optimal vision; if any becomes cloudy for any reason--disease, trauma or infection--vision becomes blurry. Corneal transplantation is an option if the problems with the cornea cannot be corrected by medication or the vision cannot be corrected by glasses. There are several types of corneal transplantation; the type of procedure performed depends on the area of the cornea that is affected by disease or scarring.
Penetrating Keratoplasty (PKP)
As of July 2010, penetrating keratoplasty is the most common form of corneal transplantation surgery. In this procedure, the surgeon removes the center of the diseased cornea using an instrument that cuts out the entire section like a cookie cutter. The surgeon then uses a donor cornea from the eye bank and stitch the new tissue into the opening using thin suture material. After the procedure, the patient will use eye drops to help the donor cornea heal. There is a risk of rejection with this type of procedure, so anti-inflammatory drops are part of the post-surgical regimen. Once the healing is complete, the surgeon removes some or all of the sutures. Because of the number sutures that are used in this procedure, the cornea transplant may be irregular and a contact lens may be needed.
Lamellar Keratoplasty
Some corneal transplant surgeries do not involve the full thickness of the cornea. If only the outer layers of the cornea are damaged, the surgeon may only remove those layers--meaning that the transplant would not be full thickness through the cornea. The surgeon then sews donor corneal tissue in place. This surgery has less risk for rejection because the inner layer, or endothelium, of the cornea is not disturbed; this surgery also has less recovery time and less astigmatism afterwards.
Descemet's Stripping Endothelial Keratoplasty
A newer types of corneal transplant involves only the inner layer of cells. There are diseases that only involve the endothelium of the cornea; when this layer of cells is damaged, the cornea often becomes swollen. In Descemet's Stripping Endothelial Keratoplasty, the surgeon only removes the inner layer of the cells through a small incision and replaces them with donor endothelial cells. The surgeon then places an air bubble inside of the eye to flatten the layer against the recipient tissue. The recovery after this procedure is much shorter; this type of surgery does not alter the glasses prescription very much.
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