DSAEK and DMEK Corneal Endothelial Transplants

Descemet’s Stripping Automated Endothelial Keratoplasty (DSAEK)
Descemet’s Membrane Endothelial Keratoplasty (DMEK)

DSAEK and DMEK are techniques for partial thickness corneal transplantation that can help many patients who previously required a full thickness corneal transplant. Both the conventional corneal transplant technique and endothelial keratoplasty require use of a donor cornea, but DSAEK and DMEK replace only the diseased posterior portion of the cornea. This procedure, which requires minimal suturing, provides patients with more rapid visual rehabilitation, less discomfort, and a reduced risk of sight-threatening complications.

The cornea is the clear window at the front of the eye that bends and helps focus light onto the back of the eye (the retina). In order for vision to be good, the cornea must be clear. Corneal disease can cause the cornea to become opaque or cloudy, preventing light from passing through clearly.

Disease can occur anywhere on the cornea. DSAEK only treats disease that occurs on the posterior or inside surface of the cornea. Corneal disease can be caused by a wide range of problems that can be present from birth or develop later in life due to heredity. It can be caused by trauma or injury or as a complication from other types of eye surgery. It can also be caused by excessive dryness of the cornea, often due to the eyelids’ not being able to close completely. Ulcers and other infections can erode and even perforate the cornea. Some types of corneal disease can be managed by medical treatments other than a corneal transplant.

The cornea consists of several distinct layers. In the diagram above, from top to bottom, the layers are: the outer surface (epithelium); the middle layer (stroma); and the bottom, or inner layer (Descemet’s membrane). Descemet’s membrane is lined with a separate single layer of cells, called “endothelial” cells.

The outside layer of the cornea, called the epithelium, is similar to very sensitive skin. The cells in this layer reproduce, allowing for rapid healing of most superficial injuries, such as abrasions. The bottom, or inner layer of the cornea, called the endothelium, has minimal ability to regenerate or grows new cells. These cells serve to keep the cornea clear by constantly pumping out excess fluid. Cells that are damaged by trauma or degenerative disease cannot be replaced. Remaining cells become larger and more sparse, filling in areas where cells are lost.

When their pumping action is impaired, it allows the cornea to retain too much fluid, resulting in a cloudy cornea (like steam on a window).

With a conventional corneal transplant, the full thickness of the cornea is completely removed, and a whole new, full thickness donor cornea is sutured in place around the entire circumference, attaching the donor cornea to the remaining edge of the original cornea. These sutures can remain in the eye for over a year and often causes the cornea to take on an irregular shape during the healing process that is difficult to correct with glasses or contact lenses. This results in less than optimum vision throughout the healing process. DSAEK and DMEK, on the other hand, involve removing only Descemet’s membrane and the damaged endothelial cells and leaves the outer surface of the cornea with a more regular shape. It may be necessary to remove the outer epithelial cell layer if it has an abnormal contour or if it is cloudy. In this event, a “bandage” contact lens is placed onto the surface for both better comfort and faster healing.

The surgery is usually performed on an outpatient basis. The individual is sedated, and the eye is completely anesthetized. A small incision is made to allow the surgeon to remove the diseased Descemet’s membrane and the damaged endothelial cells. Next, the bottom or inner layer of a donor cornea with healthy endothelial cells attached to its Descemet’s membrane is inserted through the same incision. After it is placed in position, an air or gas bubble is used to hold the transplanted tissue in place.

Immediately after the procedure, you will be taken into recovery where you will lie flat, FACE-UP, for about an hour to let the air bubble continue to press against the transplanted donor cornea to better secure it in place. The eye is patched carefully before leaving for home. Antibiotic eye drops are used to help prevent infection, and both steroid and non-steroid eye drops are used to help control inflammation, limit discomfort, and prevent rejection. It is best to continue lying in a face-up position as much as possible for the first 3 – 4 days. You should not, under any circumstances, be with your face toward the ground until your doctor tells you the air bubble is gone. You may not fly on an airplane with a gas bubble in your eye.

Most people can resume many normal activities within a couple of weeks. With conventional full thickness corneal transplantation vision typically does not improve for many months or even a full year or more, while with DSAEK and DMEK visual improvement often occurs within weeks after the procedure. If someone needs transplants in both eyes, DSAEK and DMEK allows them to have the second transplant within months, versus a year or more if they were to have a conventional transplant.

In order to make your procedure a success, it is important that ALL scheduled appointments are kept and ALL medications are used as directed. Any pain, redness or reduced vision should be reported immediately. Rejection could happen at ANY time in the future following a Corneal Transplant. However, if the transplanted tissue should be rejected, fails or does not “take”, or if it moves out of position, it is usually possible to have the procedure successfully repeated. The possibility of a full thickness corneal transplant also remains an option if any of these events occur.

DMEK is an even more advanced procedure than DSAEK. It involves transplanting a thinner piece of donor corneal tissue, replacing only what is removed and no additional tissue layers. Not everyone is a candidate for DMEK and your doctor will tell you if you are. The advantages of DMEK over DSAEK include slightly better vision and lower chance of rejection compared to DSAEK. There is, however, a slightly higher chance of needing a “re-bubble” or repositioning of the graft in the early post-op period, which may require an additional trip to the operating room.