Who is a candidate for DSAEK?
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 (edema) and cloudy, and causes blurry vision. Sometimes the corneal swelling can be severe enough to cause tiny blisters which may burst causing intermittent eye pain.
The endothelial cells can be lost due to aging, from inherited diseases (such as Fuchs Corneal Dystrophy), from previous intraocular surgery or from trauma. If a critical number of endothelial cells are lost, and the cornea becomes swollen and cloudy, medical therapy may not be helpful and a corneal transplant operation is indicated. The remainder of the corneal layers, the stroma and the outer epithelium, are usually healthy and DSAEK, which transplants only the innermost corneal layer, can be performed to restore vision.
How is DSAEK Performed?
The surgery is performed on an outpatient basis with local or general anesthesia. The inner corneal endothelial layer along with Descemets membrane is stripped from the back surface of the cornea. An incision that is similar to a cataract incision but slightly larger is made. A partial-thickness donor cornea is prepared at the Eye Bank by removing the front layers of the cornea. The partial-thickness donor tissue is then inserted into the eye and the incision is sutured close. An air bubble is injected to float the donor tissue to the back surface of the cornea and allow it to adhere there. Part of this air bubble is released before the end of surgery, but a small air bubble will remain in the eye for the first few days after the surgery. During this time it is important to maintain a face-up position to help support the donor tissue.
Advantages of DSAEK
Although traditional full-thickness corneal transplants have a long track record with a 90% success rate, DSAEK offers several advantages over the older technique. The surgical skill and expertise required is the same in both procedures, but the DSAEK 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. Since only the thin inner layer of the cornea is replaced, over 90% of the patients own cornea remains behind contributing to greater structural integrity, reduced incidence of rejection and faster visual recovery.
DSAEK is not for everyone. Some patients with corneal scarring or other conditions are not suitable candidates for DSAEK. There are risks involved with the DSAEK operation. Since corneal specialists have only been performing DSAEK for the past 5-6 years, there is no long-term follow-up.
Once the graft has been positioned onto the back surface of the patients cornea, in the majority of cases the tissue quickly adheres. However, sometimes in the first few days after the surgery the donor graft becomes un-stuck from the back surface of the cornea and dislocates. If this occurs, another procedure will be needed to reposition the graft with a new air bubble. Rarely this procedure needs to be repeated.
Because the donor cornea is living foreign tissue, there is always the potential for the body to reject the corneal graft which can lead to graft failure. The donor corneal tissue is preserved in an Eye Bank and checked for adequacy prior to transplantation. However, sometimes the graft fails because the endothelial pump cells have been damaged or depleted. This can occur at the time of surgery or later. If the corneal graft fails, the DSAEK surgery can be repeated with another button of donor cornea. And if the DSAEK fails, either after one or multiple attempts, a traditional full-thickness corneal transplant operation can be performed.
What to expect after surgery
The eye will be red, sore and watery for the first 1-2 weeks. Initially, the vision can be quite hazy because the cornea is still swollen. As the graft begins to function and pump out fluid, the cornea will clear and vision will improve. It can take up to a maximum of 4 months following DSAEK for vision to be restored.
At the end of the surgery, a small air bubble is left in the eye and this will be absorbed within the first few days. While the air bubble is still present in the eye, it is important to maintain a face-up position to help support the donor tissue on the back surface of the cornea. Face-up positioning also makes it unlikely for the air bubble to move behind the iris. Although this is an extremely rare problem, if the air bubble does move behind the iris, there can be an immediate and extreme rise in eye pressure and excruciating eye pain. It is also important to avoid eye rubbing, especially in the first few weeks after surgery, to prevent dislocating the graft. Lifting, bending over and heavy activity should also be avoided.
Steroid and antibiotic drops will be used after the surgery. Steroid drops reduce the risk of rejection and will be continued indefinitely.
Risks and complications of DSAEK corneal transplant surgery
The general risks of the DSAEK include the risk of hemorrhage in the eye, infection, swelling of the retina causing temporary or permanent blurring of vision, a retinal detachment, glaucoma or high pressure in the eye, chronic inflammation, double vision, a droopy eyelid, loss of corneal clarity, poor vision, total loss of vision, or even loss of the eye. Although the transmission of infectious diseases like Hepatitis has been reported in the past, the corneal donor is routinely and rigorously tested for these diseases before the tissue is approved and released for transplantation.
There are also complications from the local anesthesia including perforation of the eyeball, damage to the optic nerve, a droopy eyelid, interference with the circulation of the blood vessels in the retina, respiratory depression, and hypotension. On rare occasions, useful vision can be permanently lost.