Corneal Transplant Surgery
A corneal transplant replaces a scarred or diseased cornea with a healthy corneal tissue from an organ donor. There are two main types of corneal transplant surgeries, traditional full thickness cornea transplant, also known as penetrating keratoplasty (PKP) and back layer corneal transplant, also known as endothelial keratoplasty.
During a traditional corneal transplant surgery or PKP, there is complete removal of the diseased or injured central cornea using a surgical instrument called a trephine. A matching circular corneal “button” from a human donor is then position and sutured into place with fine stitches. The interface between the new and old cornea can take up to year to heal and never fully achieves the strength and stability of the original unaltered cornea. It can take 6 to 12 months to achieve the best vision and this is usually with glasses or contact lenses. Full thickness transplants today are reserved for patients in which their entire cornea is diseased from severe keratoconus or severe scarring from disease, injury or infection.
Endothelial keratoplasty is a newer version of corneal transplant surgery which replaces only the bottom layer of the cornea leaving the overlying healthy corneal tissue intact. The most common type of endothelial keratoplasty is Descemet’s Stripping Automated Endothelial Keratoplasty (DSAEK). This technique is reserved for corneal diseases that affect the bottom layer of the cornea known as the endothelial layer. This layer is one cell layer thick and can be damaged by surgery or from trauma or the cells can die over time (a condition known as Fuchs’ Dystrophy). When there is not enough endothelial cells, fluid can build up in the cornea causing cloudy vision and vision loss. In the past, replacing the endothelial cells could only be done with the surgeon performing a full thickness corneal transplant. In DSAEK, only the diseased portion of your cornea is removed, or “stripped” and replaced with a donor tissue containing a healthy endothelial cell layer. This replacement is done through a small one-quarter of an inch incision. Once the donor tissue is placed in the eye, air is used to float the tissue up to the recipient cornea to allow it to attach in the exact location where the original tissue was removed. An air bubble is then left in the anterior chamber of the eye to continue to allow the donor graft to adhere to the recipient cornea.
The sophisticated DSAEK surgery has now essentially replaced the majority of full thickness corneal transplants today. The advantages of DSAEK surgery over full thickness transplants are numerous. It is a safer procedure compared to a full thickness corneal transplant. In DSAEK, a smaller incision is done which allows for fewer or no sutures. By leaving the front surface of the cornea without sutures there is a much shorter healing and recovery time for the patient. This also means there are smaller changes in astigmatism, near sightedness or farsightedness after surgery allowing for a better balance between the two eyes and a more stable refractive outcome. Also, the cornea is much stronger after DSEAK surgery compared to full thickness corneal transplant surgery. Another advantage of DSAEK surgery is there is less chance for a graft rejection to occur since there is less tissue being replaced. Vision is usually better within one week. By the first month, 75% of the healing has taken place but vision can continue to improve up to a year after the surgery.