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 cornea fills up with fluid and becomes swollen and cloudy, and causes blurry vision.
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 injured or lost.
Ophthalmic researchers and surgeons have long recognized that for many patients needing a corneal transplant, only the diseased or missing endothelial cells need to be replaced, as the stroma and epithelial layers were otherwise normal. A new technique called Descemet’s Stripping Endothelial Keratoplasty (DS+EK) has evolved in corneal transplant surgery and accomplishes the goal of replacing only the endothelial cell layer. A thin button of donor tissue containing only the endothelial cell layer is inserted into the back surface of the patient’s cornea. This new technique appears to be a significant improvement over the standard operation. The surgical skills and expertise required are 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.
There are several significant advantages to the DSEK operation compared to the standard corneal transplant operation. The operation is faster, the wound is smaller and closer in size and location to a cataract surgery incision. Because the wound is smaller and requires far fewer sutures, there is very little postoperative astigmatism. The maximum return in vision takes only about 3 to 4 months following DSEK. Since only the thin inner layer of the cornea is replaced, over 90% of the patient’s own cornea remains behind contributing to greater structural integrity and a reduced incidence of rejection.
DSEK is not for everyone. Some patients with corneal scarring or other conditions are not suitable candidates for DSEK. There are risks involved with the DSEK operation. Since corneal specialists have only been performing DSEK for the past 2 to 3 years, there is no long-term follow-up. There is a risk of the thin button of endothelium becoming displaced within the first few days or weeks after surgery and requiring reposition. If the DSEK operation fails, the operation can be repeated with another button of donor endothelium. If the DSEK fails, either after one or multiple attempts, a traditional corneal transplant operation can be performed.