Corneal transplantation is a common and successful form of tissue transplant, with modern advancements moving toward specialized surgical techniques. The cornea, the clear front window of the eye, is composed of multiple distinct layers. Traditional full-thickness transplants replaced all layers, but contemporary methods focus on selectively replacing only the damaged portion. This evolution has led to less invasive procedures and a quicker return to sight. Descemet’s Membrane Endothelial Keratoplasty (DMEK) is an advanced selective corneal transplant that replaces the thinnest inner layers of the cornea.
Defining DMEK and Its Purpose
DMEK stands for Descemet’s Membrane Endothelial Keratoplasty, a procedure targeting the inner surface of the cornea. The cornea’s innermost layer is the endothelium, supported by Descemet’s membrane. Endothelial cells function like a pump, constantly removing fluid from the cornea to keep it clear and prevent swelling.
When these endothelial cells fail, the cornea swells and becomes cloudy, causing vision loss. Conditions like Fuchs’ dystrophy, an inherited disease, or pseudophakic bullous keratopathy, which is swelling after cataract surgery, are the primary indications for DMEK. The procedure replaces the patient’s damaged endothelium and Descemet’s membrane with healthy donor tissue.
DMEK differs from older transplantation methods, such as full-thickness penetrating keratoplasty (PKP) or Descemet Stripping Automated Endothelial Keratoplasty (DSAEK). PKP replaces the entire cornea, requiring sutures and a long recovery time. DSAEK replaces the endothelium, Descemet’s membrane, and a small amount of supporting corneal tissue, resulting in a graft about 150 microns thick.
The DMEK graft is significantly thinner, measuring only about 10 to 15 microns thick. This ultra-thin graft is composed exclusively of the donor’s endothelium and Descemet’s membrane, making it an almost exact anatomical replacement of the diseased tissue. Replacing only this failing layer while leaving the rest of the healthy cornea intact is associated with a lower risk of tissue rejection and a faster recovery of vision.
The Surgical Procedure
The DMEK procedure begins with preparing the donor tissue, which is delicate due to its minimal thickness. The surgeon or eye bank isolates the donor’s Descemet’s membrane and endothelium. This tissue is then stained with a dye to make it visible and rolled into a tiny scroll for insertion into the patient’s eye.
The patient’s diseased Descemet’s membrane and endothelium are removed through a small incision in a process called descemetorhexis. The surgeon inserts the rolled donor graft through the same incision into the anterior chamber. The entire procedure is performed through small clear corneal incisions, often eliminating the need for sutures.
Once inside the eye, the surgeon manipulates the rolled tissue to uncurl and position it correctly. The graft is positioned with the endothelial cells facing the patient’s cornea. The final step involves injecting a small air or gas bubble, known as a tamponade, into the anterior chamber.
The buoyant force of this bubble pushes the ultra-thin donor tissue against the back of the patient’s cornea. This pressure holds the graft in place until the natural biological forces of the eye allow it to adhere securely. The success of the surgery relies heavily on the bubble providing sufficient and sustained support to the graft.
Post-Surgical Recovery and Outcomes
The period immediately following DMEK surgery requires specific patient cooperation to ensure the graft adheres correctly. Patients are instructed to lie flat on their back, facing the ceiling, for a substantial period (often 4 to 7 days), with breaks only for essential activities. This positioning is necessary because it allows the air or gas bubble to float upward and press the transplanted tissue against the back of the cornea.
Visual recovery with DMEK is often quicker compared to older corneal transplant types. Patients may experience significant blurriness initially due to the large air bubble in the eye, which gradually absorbs over the first one to two weeks. Common post-operative symptoms include a scratchy feeling, mild discomfort, and sensitivity to light.
A potential risk specific to this procedure is graft detachment, where the donor tissue peels away from the patient’s cornea before fully adhering. This complication occurs in a notable percentage of cases and often requires a “re-bubble” procedure. A re-bubble involves injecting a new air or gas bubble into the eye, sometimes in an office setting, to press the graft back into place.
DMEK is associated with high success rates and a lower risk of long-term graft rejection than full-thickness transplants. Patients use topical steroid and antibiotic eye drops for several months to prevent infection and manage inflammation. The meticulous nature of the surgery and patient compliance with post-operative positioning contribute to excellent long-term visual outcomes.