Innovative Corneal Transplantation: DSEK Descemet’s Stripping Endothelial Keratoplasty
The human cornea is composed of three layers, the outer or epithelial layer, the middle or stromal layer (which comprises about 90% of the total corneal thickness), and the inner or endothelial layer. The endothelial layer is composed of a single layer of thousands of small pump cells. These endothelial pump cells are responsible for pumping fluid out of the cornea so it can remain clear and thin and provide good vision for the eye. If the pump cells should become dysfunctional, damaged, or destroyed, the corneal fills up with fluid and becomes swollen and cloudy, and causes blurry vision.
What is DSEK?
DSEK is a recently developed form of corneal transplantation in which the diseased or damaged endothelial cell lining is replaced with a new endothelial lining harvested from a donated cornea.
DSEK is an outpatient procedure that does not require hospitalization. Ophthalmic researchers and surgeons have long recognized that for many patients needing a corneal transplant, only the diseased or missing endothelial cells needed to be replaced, as the stroma and epithelial layers were otherwise normal. Recently, a new technique called DSEK has evolved in corneal transplant surgery which accomplishes the goal of replacing only the endothelial cell layer. A thin button of donor tissue containing only the endothelial cell layer is inserted onto the back surface of the patient’s cornea. This new technique appears to be a significant improvement over the standard operation. The surgical skill and expertise required is the same, but the surgery itself takes less time with an experienced surgeon, involves a smaller surgical incision, requires far fewer sutures, heals faster and more reliably, and the vision returns faster.
It is generally performed using a local anesthetic and supplementary intravenous sedation.
Who are candidates for DSEK?
Patient’s with symptomatic swelling in the cornea caused by damage to the inner endothelial lining of the cornea. The endothelial cells can be lost due to aging, from inherited diseases (such as Fuchs’ Corneal Dystrophy), from trauma, or from previous intraocular surgery. If a critical number of endothelial cells are lost, and the cornea becomes swollen and cloudy, medical therapy is usually not helpful and a corneal transplant operation is indicated. The remainder of the corneal layers, the stroma and the outer epithelium, are usually healthy. A large number of patients requiring corneal transplant surgery have these sorts of problems where only the endothelial cells have been or injured or lost.
What is the difference between DSEK and a conventional corneal transplant?
DSEK replaces only the endothelial lining of the cornea, while the rest of the cornea is undisturbed. The new donated endothelial lining is held in place with an air bubble in the first 2-4 days without corneal sutures.
A conventional corneal transplant replaces the entire thickness of the cornea with a donated cornea and is held in place by up to 16 corneal sutures.
Corneal Transplantation: Traditional Penetrating Keratoplasty
Traditional corneal transplant surgery has consisted of removing the entire cloudy cornea and replacing it with a full thickness donor cornea, thereby replacing all three layers of the cornea. This surgery was first developed one hundred years ago, and the wonderful 90% success rate reported today is based on numerous refinements to this same basic technique. It has certainly stood the test of time.
The advantage of the traditional corneal transplant operation is the long and successful track record that we have with it. There is a 90% success rate. The rate of rejection is only about 8%. It is relatively easy to combine other surgery with it such as cataract extraction or glaucoma surgery. The disadvantages of the traditional corneal transplant operation are the time involved in performing the actual operation (45 to 60 minutes), the difficulties in suturing the new cornea in place, and occasional problems with the sutures which can come loose, cause infections, or cause astigmatism (an irregular corneal shape) . The astigmatism after traditional corneal transplant surgery can be so significant that eyeglasses alone won’t give adequate vision and some patients ultimately require contact lenses or additional surgery to reduce or eliminate the astigmatism. Because the wound is a full 360 degrees, and the sutures used are finer than human hair, the corneal transplant wound is always very delicate and at risk to rupture or break open from mild or incidental trauma, even several years after the surgery. The visual recovery can take 6 to 12 months.
Transplantation involves replacing the damaged cornea with a healthy one from a donor (usually through an eye bank). Keratoplasty is a low-risk procedure - it is the most common type of transplant surgery and has the highest success rate.
During the procedure, a circular incision is made in the cornea. A disc of tissue is removed and replaced with healthy tissue; these discs may be thin (lamellar keratoplasty) or as deep as the entire cornea (penetrating keratoplasty, the technique used in almost all corneal transplants). Local or general anesthesia may be used. The entire procedure lasts only 30-90 minutes.
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