A cornea transplant, also called a keratoplasty, is a surgical procedure thatreplaces part of a diseased or injured cornea with healthy tissue from a carefully screened organ donor.
The traditional cornea transplant is called a penetratingor full-thickness transplantation and is still the most commonly performed procedure. It has a very high success rate for patients with diseases such as keratoconus or corneal scars from trauma or infection. The full-thickness transplant involves replacing a central portion of the cornea and stabilizing it with multiplesutures. These sutures may be selectively removed over the course of a year to improve vision by decreasing astigmatism, irregularities in the shape of the cornea.
Advances in surgical technique have led to the development of selective cornea transplants in which only the diseased portion of the cornea is removed. In these surgeries, either the front layers of the cornea are replaced, as in Deep Anterior Lamellar Keratoplasty (DALK), or the back layers of the cornea are replaced, as in Descemetas Stripping Endothelial Keratoplasty (DSEK). Eyes with full-thickness abnormalities may not qualify for these newer techniques, but patients with Fuchs dystrophy and bullous keratopathy are usually excellent candidates for DSEK. The advantages of these techniques are that they result in faster visual recovery, improved structural integrity and, in some cases, a decreased risk of graft rejection.
During the most common type of cornea transplant (penetrating keratoplasty), the surgeon cuts through the entire thickness of the abnormal or diseased cornea to remove a small button-sized disc of corneal tissue. An instrument that acts like a cookie cutter (trephine) is used to make this precise circular cut. The donor cornea, cut to fit, is placed in the opening. The surgeon then uses a fine thread to stitch the new cornea into place. The stitches may be removed at a later visit.
With some types of cornea problems, a full-thickness cornea transplant isn't always the best treatment. Partial-thickness (lamellar) transplants may be used in certain situations. These types of procedures include:
Replacing the inner layer of the cornea. This procedure, called a deep lamellar transplant, replaces only the innermost layer of the cornea's five layers. A small incision is made in the side of the eyeball to allow for removal of the cornea's inner layer without damaging the outer layers. A donor graft replaces the removed portion.
Replacing the surface layers of the cornea. The outer layers of the cornea that have been damaged by certain diseases and conditions can be replaced using a procedure called surface lamellar transplant. These surface layers, too, can be removed and replaced with a donor graft.