What is DMEK?
Descemet’s membrane endothelial keratoplasty (DMEK) is a surgical procedure that restores corneal clarity in cases where the innermost corneal layer (the endothelium) becomes cloudy due to eye disease or injury.
DMEK involves selective (partial thickness) removal of two of the five corneal layers: the Descemet’s membrane and endothelium layers. These removed layers are replaced by donor tissue that is merely 10-15 microns thick. This is thinner than a human hair.
Watch surgery footage of Dr. Berger performing DMEK
What is the cornea?
The cornea is the transparent front cover of the eye that rests like a dome over the iris, pupil, and anterior chamber. Although it is merely one-half millimeter thick, the cornea protects the eye and is responsible for much of the eye’s optical power.
The endothelium and Descemet’s membrane are thin layers of cells on the inner surface of the cornea. If the cornea becomes damaged through disease or injury, vision will be affected due to the injured cells blocking or distorting light as it enters the eye. It is important to understand that, once these inner cells die, they will not grow back. If a cornea loses too many endothelial cells, it is not able to maintain the proper thickness and visual clarity suffers.
What does DMEK treat?
Descemet’s membrane endothelial keratoplasty (DMEK) is a modern form of corneal transplant – or corneal graft. It is used when the inner cell layer of the cornea stops working properly due to Fuchs’ dystrophy, bullous keratopathy, iridocorneal endothelial (ICE) syndrome, or other endothelial disorders, like trauma to the eye. DMEK selectively replaces only the diseased layer of the cornea, leaving healthy areas intact.
The corneal tissue being used is carefully selected and prepared donor tissue and is only 20-microns thick. This is four times thinner than a sheet of paper!
Dr. Berger performs the procedure by creating a tiny incision at the side of the cornea. Working through an operating microscope, he carefully peels the diseased endothelial layer from the back, innermost section of the cornea and leaves the healthy corneal layers intact. This means that about 95% of the cornea is untouched!
Dr. Berger then places healthy corneal tissue (called a donor disc) inside the eye through a small incision and positions it with a precisely-sized air bubble to hold the disc of donor tissue in place. DMEK usually takes about 30 minutes to complete.
What happens after DMEK surgery?
After the surgery, the eye is patched. There should be no pain – you may experience only minimal scratchiness or slight discomfort. Dr. Berger may give you medications for the eye to reduce discomfort or inflammation, avoid infection and aid in quick healing. You will be instructed to lie down on your back, facing the ceiling for the first 24 hours after surgery.
When you return to see Dr. Berger, sometimes on the same day or the day after surgery, the patch will be removed and your eye will be examined. He will check to make sure that the donor disc is properly positioned. You will then be scheduled for follow-up visits to monitor the healing process.
What are the advantages of DMEK?
DMEK is often preferred over traditional corneal transplant because the postoperative vision recovery is typically faster and better. Because the cornea’s surface is kept intact, there is less risk of infection and refractive changes after surgery. There is also a reduced risk of transplant rejection (around 5%). Because of the larger and more precisely-sized area of donor tissue that is transplanted, DMEK is often chosen over other corneal graft procedures.
Complications of DMEK eye surgery
DMEK is one of the safest and most successful corneal graft surgeries. However, all eye surgeries can have their complications. Although only around 5%, a dislocated donor disc is the most common complication seen with DMEK. If this is the case, Dr. Berger can correct it right there in his office. Increased intraocular pressure and swelling inside the eye are also rare complications but can be managed with eye drops. Eye infection is a possibility and will be monitored and treated as needed by Dr. Berger. Donor tissue rejection is also a rare complication and can result in a second DMEK procedure being needed.
DMEK is a relatively new procedure. Its low risk and success rate have made it a mainstream, preferred treatment for some cornea conditions. Surgeons continue to improve their techniques and tools, so this innovative cornea procedure will only get better and even more successful with time.
What are the differences between PK, DSAEK and DMEK?
(full thickness traditional cornea transplant)
(partial thickness posterior cornea transplant)
|DMEK (Single layer of cells and supporting membrane)|
|Typical time for visual improvement||6-12 months||4-6 weeks||2 weeks|
|Rejection rates at 2 years||17%||9%||.7%|
|Visits for suture adjustment||6-12 visits||2-3 visits||1|
|Time of surgery||45-60 mins.||45-60 mins.||15-20 min.|
|Wound size||7.5 mm diameter circle||3.2 mm linear||Less than 2.4 mm|
|Graft thickness||550 microns||60-100 microns||10 microns|
|Contact lens required||Rigid gas permeable (often)||Not required||None|
|Induced astigmatism||High regular and Irregular astigmatism possible||Minimal to no induced astigmatism||None|
|Indications for surgery||Cornea scar, keratoconus, pellucid marginal degeneration, corneal ulcer||Fuch’s endothelial dystrophy, cornea edema, pseudophakic bullous keratopathy||Fuch’s endothelial dystrophy, cornea edema, pseudophakic bullous keratopathy|
Explore the 3 types of corneal transplants
- Penetrating keratoplasty (PK)
- Descemet’s Stripping Automated Endothelial Keratoplasty (DSAEK)
- Descemet’s Membrane Endothelial Keratoplasty (DMEK)