DISCLAIMER! The information on this website is general information. Please discuss with your surgical provider your concerns and questions about the procedure. Your personal health information may differ from the information presented here.
DMEK (Descemt Membrane Endothelial Keratoplasty) Cornea Transplant
You have a condition that has affected your cornea (the front part of your eye). Your doctor has determined that you need a corneal transplant. This involves having surgery to replace your cornea with a cornea that has been removed from someone who has died. The cornea you will receive is referred to as the donor cornea. The donor cornea to be used for your transplant will be provided by an Eye Bank.
This technique is a modification of the split thickness forms of corneal transplantation originating from Deep Lamellar Endothelial Keratoplasty (DLEK) which we developed and introduced to the United States in the year 2000 and which we later modified into Descemet’s Stripping Endothelial Keratoplasty (DSEK). DLEK, DSEK and DMEK are all forms of “endothelial keratoplasty” and are used instead of the full thickness traditional method called “penetrating keratoplasty” (PK).
First, we want you to know that your condition can be treated with any technique of surgery: PK, DLEK, DSEK or DMEK. Before you decide whether to have DMEK, please take as much time as you need to ask any questions and to discuss the program with the doctor and the medical staff, or with family, friends or your personal physician.
If you have been advised that DMEK would be a reasonable procedure for your treatment because only one part of your cornea is not working properly. The endothelium layer of your cornea is failing and is causing your cornea to become swollen. The endothelium is the layer of cells on the inside surface of your cornea. It is this layer that needs to be replaced. Until recently, the only way to replace that layer of cells was with a full thickness corneal transplant. (PK)
A split thickness transplant of this inner layer is called an “endothelial keratoplasty”. The DMEK technique would remove (or “strip”) only the diseased portion of your cornea (like “stripping” wallpaper off of a wall) and then use a specialized technique of preparing a donor tissue consisting only of the strip of membrane as a carrier for the membrane carrying healthy pump cells (endothelial cells) which have been affected and diseased in your eye. This technique replaces only the diseased tissue and leaves the rest of your cornea intact.
DMEK, being a modification of DLEK and DSEK, is highly specialized. The benefits it offers over DSEK or DLEK are more rapid visual recovery and higher chance of obtaining close to the vision potential of the eye. In addition, there appears to be a lower rate of tissue rejection with the DMEK procedure than with DSEK or other forms of corneal transplantation. There are greater challenges in performing DMEK mostly related to the difficulty of preparing the donor tissue as well as implanting the fragile tissue in the eye. If during the surgery the donor tissue is damaged, we may consider proceeding with surgery using a split thickness graft and thus perform DSEK. If the DMEK donor graft is successfully prepared and transplanted in your eye, we will be watching you closely for dislocation of the graft in the first weeks after surgery. If at any time, the edges of the graft detach or are loosened or the graft is fully dislocated, we will return to the clinic minor operating room to reattach the graft using an air bubble injection. It may require more than one such intervention in the postoperative period to ensure full adhesion of the graft.
The type of transplant procedure that replaces only the diseased endothelial tissue is called an “endothelial keratoplasty” and is a procedure that was developed here in Portland at Devers Eye Institute and has been done under a scientific protocol here at Devers for over 13 years. The procedure has been performed by Dr. Terry and his team on over 2,000 patients (as of September 2013) with follow-up of up to 13 years. Over 99% of the surgeries have been successful in providing a clear cornea and getting rid of the swelling f the patient’s cornea.
Split thickness lamellar corneal transplants have been performed for many years to replace the front part of the cornea and have been highly successful. Dr. Terry and his team of corneal surgeons have performed many split thickness corneal transplants to replace the front portion of the cornea over the past 20 years. What is different about this program is that the surgical procedure involves replacement of the back layers of the cornea rather than the front layers of the cornea. This replacement is done through a small pocket incision to avoid changes in the front surface of the cornea. By leaving the front surface in the cornea without sutures or incisions there is an advantage in healing and recovery time for the patient. We have confirmed in our study done from 2000 to today that EK surgery is able to make healing time even faster and more predictable than with standard PK surgery.
If you choose to have a DMEK surgery, you will be scheduled on a routine basis that is convenient for you and corresponds to our normal surgical schedule. The surgery will be performed under local anesthesia unless there is a reason for which you would do better with general anesthesia Local anesthesia is when you are “numb” and cannot feel pain, but are awake enough to answer questions. General anesthesia is when you are completely asleep during the procedure.
During the surgery a single 3 .5 mm long line incision is made in the cornea, a pocket is formed, and just the diseased endothelial layer of your cornea will be removed by gently “stripping” the diseased tissue off, like peeling wallpaper off of a wall. The donor endothelium carried on a membrane called the Descemet’ s membrane of the donor cornea is then placed through the incision and pocket and placed into position on the back surface of your cornea to replace the diseased tissue that was removed. A large gas bubble (20% SF6 inert gas) is placed to keep the tissue firmly in place until after a few minutes it can adhere on its own. A small opening is made in the iris (the colored part of the eye) to help prevent high pressure buildup in your eye during the first few days after surgery. The initial incision is then closed with one small sutures and the procedure is completed.
The surgical procedure will take about one hour to perform, slightly longer than a standard PK (45 minutes). If you also have a cataract of the lens of the eye, then cataract surgery can be performed at the same time as DMEK surgery. If cataract and DMEK surgery are done, then the surgery takes about 1 and a half hours. You will be required to lie flat on your back, facing the ceiling for one hour immediately after the operation to help the bubble help the tissue to adhere. Surgery is usually done as an outpatient procedure at the hospital and you are sent home with a patch on your eye that same afternoon. We ask that you try to lie flat facing the ceiling as much as possible after you get home for the first night of surgery. You should have minimal discomfort after surgery, and standard over-the-counter pain medications can be taken if necessary. You will return to see your surgeon the next day. The patch will be removed and your eye will be examined. You will be placed on antibiotic and steroid drops to prevent infection and to help with healing. This first visit after surgery will only take about 15 to 30 minutes, and is primarily done to check the pressure and to be sure that the donor disc is in good position. If the donor disc is detached or is at risk of detaching, you will be taken back to a clinic minor room for more air bubble to be injected in your eye to help with reattachment. You will have a brief visit to the clinic weekly for two or three visits after surgery, and then again at three months. The visits after 3 months can be done by your local referring doctor if it is more convenient for you and if your referring doctor agrees with this. Later visits at 6, 12, and 24 months will require extra testing of your vision and of the cornea and will take about 45 minutes to an hour. We would like to do those visits here at Devers Eye Institute, but if it is more convenient for you and if your referring doctor agrees, those visits also can be done locally by your referring doctor for your convenience. We will of course see you at any time that you have any concerns, questions or problems after your surgery.
The tests that you will have performed at the pre-op visit and after surgery at the 6, 12, and 24 months visits are a vision test, a check for glasses, examination with the standard clinic microscope, a pressure check, and measurements of your cornea with various optical machines which record light reflections from the cornea (corneal maps). None of these tests will be difficult or uncomfortable for you. Once again, if your referring physician is able and willing to perform these tests and send the information to us, then your pre-operative testing and post operative testing can be done locally by your referring doctor for your convenience.
Risks and Discomforts
The following risks and discomforts of DMEK corneal transplant surgery are the same whether you have a full thickness PK corneal transplant or a split thickness EK corneal transplant. These include:
- There is often mild discomfort and “scratchiness” for one week after surgery that may be treated with Tylenol or another drug by mouth. Immediately after surgery your eye will be red. There may be temporary discomfort to you from the eye examination or eye drops. This may include stinging, redness or itching.
- A serious infection or bleeding occurs in 1 in 1,000 patients.
- Serious problems caused by anesthesia occur in 1 in 10,000 patients including not awakening from anesthesia or having neurological problems from the anesthesia.
- Developing high pressure in your eye (glaucoma).
- Additional surgery due to healing problems, retinal swelling or detachment, or loss of vision.
- About 20% of the time after PK surgery the body’s immune system produces an inflammation of the donor cornea. This is often called a “rejection” reaction. The rejection reaction is usually reversible if treated promptly but sometimes it leads to a failure of the transplant. Information to date indicates that DLEK, DSEK and DMEK surgery may have a much lower rejection rate than PK (only 1 % for DMEK and 9% for DSEK), but more studies need to be done to determine if this is true.
- The transplant may become cloudy either because of rejection, as described above, or for other- reasons. If this happens it may be necessary for you to have another transplant. The risk of the transplant failing varies, depending upon what your current corneal condition is. Your doctor may be able to provide more precise information about your particular risk.
Risks of split thickness corneal transplant surgery that are unique to split thickness surgery include:
- Movement of the lamellar corneal transplant tissue (“disc”) within the eye. If the disc is in good position on the first week after surgery, then it is extremely rare for the disc to dislodge later. Should the donor tissue disc be found on the first week after DMEK surgery to be fully dislocated or partially detached at its edges, then it would require one or more procedures to either put the tissue back into the proper position or rebubble to help with adherence of the graft. If the tissue could not be repositioned we would then perform a second EK surgery and possibly instead of DMEK a different form of EK (i.e. DSEK). The documented dislocation rate in our hands for DSEK surgery is only 2.5% but DMEK surgery has a slightly higher chance of dislocations and failures. However, the significantly better vision and more rapid vision recovery seen in DMEK as compared to DSEK, as well as a lower rejection rate is why a patient would choose DMEK rather than DSEK, despite the slightly higher re-bubble rate.
- During surgery, your surgeon may find that it is not possible to continue or complete the DMEK surgery safely. Because safety of your eye is the highest priority, he/she may decide to stop the DMEK procedure and change the surgery to a standard EK transplant (DSEK), but this is very rare.
- The area over the pupil where the donor tissue attaches to your own cornea is an area of healing. During the healing process, this attachment area (the “interface”) has the potential to develop a haze or clouding which can decrease your vision from its full potential. If this happens, then a full thickness transplant could be necessary to restore the vision. In our protocol DLEK series and in our initial DSEK series, the interface area is extremely clear.
Full understanding of the healing of the interface and it’s affect on final vision is still a matter of research. We have found much better interface clarity with DMEK.
- It is unknown whether the split thickness tissue has a higher risk of becoming cloudy than full thickness corneal tissue. Current information suggests that the risk is less than standard PK surgery. However, there is the possibility that the endothelial cells of the split thickness tissue could fail and the tissue become cloudy. This has occurred in only a few of the over
- 2,000 cases of DLEK/DSEK surgeries we have performed. In each case, the cloudy donor disc was removed and replaced with another donor disc, restoring the corneal clarity. There is not enough information in regards to this matter after DMEK. If there is ANY problem after your DLEK, DSEK or DMEK surgery, you always have the option of a standard full thickness PK surgery.
- General Anesthesia: The risks are the same or less as with any other surgery requiring general anesthesia Serious risk or injury such as neurologic (brain) damage or death occurs less than I in 30,000 cases. Your individual risk can be more thoroughly discussed with the anesthesiologist prior to the time of surgery. We wish to avoid ANY risk to your general health, and that is why we usually recommend DSEK surgery with local anesthesia
Although we have tried to list all possible risks and discomforts with this DMEK procedure, there may be others that we do not know about at this time.
There are possible direct benefits to you as a patient receiving DMEK surgery; however, there are no guaranteed benefits.
- Patients who have a split thickness corneal transplant such as DLEK/DSEK/DMEK have been shown to have a smoother corneal surface than patients that have a full thickness standard corneal. This occurs because the natural surface of the cornea is not replaced so the focusing power of the cornea remains more natural than with a full thickness corneal transplant. Of the patients in our DLEK program that have had a PK in one eye years ago and a DLEK or DSEK transplant in the other eye recently, most have stated that the quality of vision of the EK eye is superior to the quality of the vision in the PK eye. This has been true even when the PK eye measures 20/20 vision and the EK eye measures slightly worse at 20/25 or 20/30 vision. This subjective preference by the patient for the DLEK/DSEK/DMEK eye is currently being studied, and preliminary data indicates that patients subjectively prefer the DMEK eye over the DSEK eye when they have one of each.
- The one to three tiny sutures that are used in these EK procedures to close the scleral or corneal wound are not irritating. Patients who have a standard full thickness corneal. transplant require either 16 sutures or one to two long looping sutures in a circle, all of which cause more discomfort and more irregularity to the surface than has been shown with the DLEK/DSEKDDMEK technique.
- If the endothelial cells that are transplanted by this split thickness corneal transplant function normally as expected, then the cornea will lose its swelling and become clearer at a much faster rate than with a standard full thickness corneal transplant.
- A smoother surface for focusing and a clearer transplant has allowed many of our patients to see better in a matter of weeks as compared to months or years with a standard full thickness corneal transplant.
- Because there are no sutures in your surface cornea in this study, the cornea is stable more quickly than with a full thickness corneal transplant requiring less changes of glasses than a full thickness corneal transplant. Also, after full thickness corneal transplant, up to 20% of patients require a contact lens to see and cannot simply wear glasses. After DSEK or DMEK surgery, over 98% of patients are able to obtain excellent vision without the need for contact lenses.
- Because the corneal surface remains smooth and relatively unchanged from the curvature before transplant surgery, there is expected to be better matching between the focusing power of your lens (or the artificial lens you received at the time of cataract surgery) and the focusing of the surface of your cornea (This is what we have found in our protocol study patients.) Therefore there is less of a chance of requiring thick glasses after transplant surgery with the DMEK/DSEK technique compared to full thickness corneal transplant surgery of PK.
Alternative procedures or treatments
You do not have to have a DMEK technique surgery to receive a corneal transplant. Your surgery can be done with our previous DSEK technique or with a standard full thickness corneal transplant (PK).
Unavailability of a Donor Cornea for the DMEK Program
In the unlikely event that a donor cornea is not available or the donor cornea is damaged during the preparation process, your surgery would have to be cancelled and rescheduled. This may occur on the day of surgery but prior to the start of anesthesia.
The Cornea Service at Devers Eye Institute, St. Vincent Hospital, or Good Samaritan Hospital will not pay for any of the costs of your medical care. The surgery and all of your follow up care would be needed whether you had PK, DSEK or DMEK transplant surgery. Therefore, these costs will be yours or your insurance company’s responsibility. Pre-authorization will be obtained from you insurance company to cover the costs of this surgery in the same manner that they would cover for the cost of a routine full thickness corneal transplant surgery. DSEK or DMEK are considered to be simply another less invasive form of PK surgery, and is billed in the same manner as routine standard PK surgery, albeit with a billing code that is specifically designated by Medicare for this form of endothelial keratoplasty. Over the long term, because DSEK and DMEK surgery have no corneal sutures or incisions to worry about, it is expected to cost much less in follow-up care than a standard PK surgery. This ultimately saves the patient and his insurance company a substantial amount of money.
Just as is the case with any surgery, you are responsible for the costs of your medical care for injury resulting from treatment; however, these costs may be covered, at least in part, by most major insurance companies or Medicare. Providence Health System and Legacy Health System will not assume financial responsibility for such treatment or provide financial compensation for such injury. Should you suffer any injury as a result of DSEK/DMEK surgery, emergency treatment will be available.