Corneal Transplant Surgery
Overview
When do you need a Corneal Transplant?
The cornea is the clear, front portion of the eye that permits light to enter the eye, and focus on the retina. A healthy cornea is extremely clear. However, various eye conditions can cause the cornea to become cloudy or misshapen, causing decreased vision or in severe cases, blindness. Diseased corneas can be replaced successfully through transplantation of a human donor cornea.
Ocular conditions that result in irreversible scarring, swelling, or thinning of the cornea require a corneal transplant in certain instances to restore vision. Each year approximately 40,000 corneal transplants are performed in the United States. There are three commonly performed techniques used in corneal transplant surgery:
Penetrating Keratoplasty
This is a full-thickness corneal transplant. A circular section of the cornea is cut and removed, and a new circular donor cornea is sewn into place with sutures. Sewing a corneal transplant into place is an extremely delicate microsurgical surgery, performed with the aid of an operating microscope at magnifications of 10 to 25 times. The sutures are about one tenth the diameter of a human hair. At the end of surgery, the tension of these sutures are adjusted to minimize astigmatism, giving a patient the best possible visual outcome. Further Reading
DSEK
Descements’ Stripping Automated Endothelial Keratoplasty (DSEK, sometimes written as DSAEK) is a newer form of corneal transplant surgery. Instead of replacing the entire cornea, with certain eye conditions only the back-most layer of the cornea is damaged. DSAEK surgery replaces just the back-most layer of the cornea, (the endothelium, along with a thin segment of the posterior stroma). This transplant is about thick as a human hair, around 100 microns, or 1/10th of a millimeter. DSAEK surgery may be used in eye conditions like Fuchs’ Corneal Dystrophy, Pseudophakic Bullous Keratopathy, or ocular herpes.
DSEK has a much faster recovery time compared to a Penetrating Keratoplasty, and no sutures are required to hold the transplant in place. Further Reading
DMEK
Descements’ Membrane Endothelial Keratoplasty (DMEK) is the newest technique in corneal transplantation surgery. This is considered a variant of the technique used in DSEK, though a highly specialized skill set needed for this surgical technique because the graft is so thin. The thickness of the tissue transplanted with DMEK is only 5-10 uM; it is a single sheet of cells on a membrane. This extremely delicate procedure transplants the least amount of tissue possible, and as a result, patients have the lowest possibility of graft rejection.
DMEK also provides rapid visual recovery, frequently to 20/20 once the eye has fully recovered. DMEK gives a 'high-definition' quality of vision. Further Reading
The Gift of Sight
Corneal Transplant Surgery may improve vision
Corneal Transplant Surgery
Corneal transplantation surgery is the most successful kind of organ transplant surgery in all of medicine. For many patients, their vision after transplant surgery represents a life-changing improvement. As the eye is considered an immunoprivileged zone, patients are not taking lifelong systemic immunosuppressants or steroids. Many patients will require prolonged usage of steroid eyedrops; however these have minimal absorption into the body, and unlike other organ transplant patients, patients after corneal transplant surgery are not considered to be immunocompromised.
The Eye Bank Network
Corneas for corneal transplant procedures come from organ donors; people who have donated their eyes to be used after their death for the benefit of others. A nationwide eye bank network facilitates the processing and distribution of donor tissue, usually within 24 hours. The eye bank carefully screens all donor tissue to ensure that it is healthy and in excellent condition. This includes screening for diseases such as hepatitis, AIDS, and most recently, COVID-19.
As the eye is considered an immunoprivileged zone, donors and recipients do not need to be genetically type-matched. Factors such as sex, race, color of the iris, or the previous vision of the donor have no influence on the surgical result. With few exceptions, donor tissue from people ranging in age from one to 65 is usable. Donor corneal tissue can be used for up to seven days after death of the donor. Since we have a nationwide network of eye banks to obtain corneal tissue, patients do not have to be placed on a waiting list for their corneal transplant.
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