Endothelial Keratoplasty (DMEK / DSAEK)

Endothelial keratoplasty is a partial-thickness corneal transplant for the cornea's failed inner pump layer. Instead of replacing the whole cornea, the surgeon swaps out the diseased endothelium and Descemet's membrane while leaving most of the patient's own cornea in place. The two main versions are DMEK (Descemet's membrane endothelial keratoplasty) and DSAEK (Descemet's stripping automated endothelial keratoplasty). For Fuchs endothelial dystrophy and similar endothelial problems, these procedures have largely replaced full-thickness transplant because recovery is faster, vision is often sharper, and rejection risk is lower.

What the Endothelium Does and Why It Matters

The cornea has five layers from front to back: epithelium, Bowman's layer, stroma, Descemet's membrane, and endothelium. The endothelium is a single layer of cells on the back surface that constantly pumps water out of the cornea, keeping it clear. When enough endothelial cells are damaged or lost, the cornea becomes swollen and cloudy. Symptoms include:

• Blurred vision, often worse in the morning and improving through the day
• Halos around lights
• Glare and contrast loss
• Eye pain or foreign-body sensation if the swelling extends to the corneal surface (bullous keratopathy)

Endothelial cells do not regenerate meaningfully in routine clinical practice. Once enough are lost, drops can sometimes reduce swelling temporarily, but definitive restoration of endothelial pump function usually requires replacing the diseased endothelium.

Indications

Fuchs Endothelial Dystrophy

The dominant indication. A genetic disorder in which endothelial cells progressively die over years to decades, eventually causing corneal swelling and vision loss. Endothelial keratoplasty is offered when symptoms become bothersome, vision drops below the patient's needs, or morning blur becomes intrusive.

Pseudophakic Bullous Keratopathy

Endothelial damage from prior cataract surgery - historically more common before modern small-incision surgery, but still seen.

Post-Surgical Endothelial Failure

After complicated cataract surgery or other intraocular surgery in which the endothelium was damaged.

Failed Prior Corneal Transplant

A previous full-thickness corneal transplant that has lost endothelial function can sometimes be rescued with an endothelial keratoplasty rather than a full repeat transplant.

Iridocorneal Endothelial (ICE) Syndrome

A rare disorder in which abnormal endothelial cells migrate over the iris and angle, with corneal involvement that may need replacement.

When EK Is Not Appropriate

• Significant scarring or thinning of the corneal stroma - needs full-thickness or anterior lamellar transplant
• Severe ocular surface disease - surface stabilization first
• Active inflammation or uncontrolled glaucoma - usually addressed first

DMEK vs. DSAEK

Both are forms of endothelial keratoplasty, but they differ in what is transplanted:

In the past decade DMEK has become the preferred choice for most patients at experienced centers, given the better visual outcomes and lower rejection risk. DSAEK remains widely used and is technically easier, particularly in eyes with complex anatomy (prior glaucoma surgery, vitrectomy, anterior chamber lenses).

How the Procedure Is Done

Donor Tissue Preparation

Donor corneas are obtained from an eye bank. For DMEK, only the back layers are stripped; for DSAEK, a microkeratome or femtosecond laser cuts a thin posterior layer.

Surgery

• Performed in an operating room under local anesthesia with sedation
• A small incision (~3 mm) is made at the corneal edge
• The patient's diseased Descemet's membrane and endothelium are removed (Descemet's stripping)
• The donor tissue is inserted folded or rolled, then unfolded and positioned with a tamponade bubble - usually room air (resolves in 1-3 days) or 20% SF6 gas (resolves in 5-7 days, gives longer tamponade)
• The bubble holds the donor tissue against the back of the cornea while it adheres
• No sutures are needed, or only a small one to close the incision

The procedure typically takes 30-60 minutes per eye.

After Surgery

• The patient lies face up for several hours to days, depending on the gas used, to keep the bubble against the donor tissue
• Eye drops include topical antibiotics and steroids
• Long-term low-dose topical steroids are usually continued for at least a year, sometimes indefinitely, to reduce rejection risk
• Postoperative visits are frequent in the first weeks, less frequent after

What to Expect

Day of Surgery

• Outpatient procedure
• Mild discomfort, usually controlled with acetaminophen
• Vision is hazy from the gas bubble; expect very poor vision for the first 24-48 hours
• Face-up positioning is important - inadequate bubble support is a major contributor to early graft detachment

First Week

• Vision improves as the gas bubble dissolves
• Some patients require a "re-bubble" (an in-office injection of additional air or gas) if the donor tissue has detached
• Pain is usually minimal
• Light sensitivity is common

First Month

• Vision continues to improve as the cornea clears
• Returning to most normal activities is usually allowed
• Avoid heavy lifting, swimming, and rubbing the eye in the first 1-2 weeks

3-6 Months

• Most DMEK patients reach stable, often very good vision by 3 months
• Most DSAEK patients reach stable vision by 3-6 months, with a typical mild hyperopic shift

Risks

Endothelial keratoplasty is generally safe, with most complications either uncommon or manageable.

• Graft detachment - the donor tissue separates from the recipient cornea before adhering. The most common short-term complication; treated with additional air/gas bubble injection in the office.
• Endothelial cell loss over time - donor endothelial cells gradually attrite over years, just as native cells do. Most grafts function for many years.
• Graft rejection - the immune system attacks the donor tissue. Lower risk than full-thickness transplant, but still requires lifelong vigilance and topical steroid drops. Symptoms of rejection: new redness, light sensitivity, decreased vision, foreign body sensation.
• Glaucoma - pressure spikes can occur from the gas bubble or from chronic steroid use; monitoring and dose adjustment manage this.
• Cataract - in patients who have not yet had cataract surgery, the procedure may accelerate cataract formation; many surgeons combine endothelial keratoplasty with cataract surgery in a single operation when appropriate.
• Infection - uncommon
• Late graft failure - some grafts eventually fail and need to be repeated; primary graft failure (the donor tissue does not function from the start) is rare with modern eye-bank tissue

Outcomes

Modern DMEK in an uncomplicated eye gives outstanding results:

• Many uncomplicated DMEK patients achieve 20/25 or better vision, and many reach functional driving-level vision or better
• 5-year graft survival is high in uncomplicated eyes, often in the 90% range in modern series
• Rejection risk is approximately 1-2% at 2 years for DMEK, approximately 5-9% for DSAEK, and 15-20% or higher for full-thickness PKP

DSAEK gives excellent results too, with slightly lower visual ceiling and a typical small hyperopic shift in glasses prescription.

Endothelial Keratoplasty vs. Full-Thickness Corneal Transplant

Penetrating keratoplasty (PKP), the traditional full-thickness transplant, replaces all five layers of the cornea. It is still used when the stroma is significantly damaged (scarring, severe keratoconus, perforation) or when both the front and back of the cornea need replacement. For pure endothelial disease, however, endothelial keratoplasty has substantially replaced PKP because:

• Recovery is months faster
• Few or no corneal sutures and far less suture-induced astigmatism
• Lower rejection risk (the donor tissue volume is smaller and hidden inside the eye)
• Better best-corrected vision in most cases

Frequently Asked Questions

Will I need glasses afterward?

Most patients still benefit from glasses, particularly for reading. The procedure itself is not a refractive surgery; it restores clarity but the eye's overall focusing power is largely set by the cornea's curvature and the lens. After DSAEK, many patients have a small hyperopic (farsighted) shift compared with before surgery; after DMEK, the refractive change is minimal.

How long until I see well again?

Improving vision often begins within days as the cornea clears, and many DMEK patients have good functional vision by 1-3 months. DSAEK usually takes longer, often 3-6 months for stable vision. Some patients see better than they have in years, especially when surgery happens before long-standing corneal damage sets in.

How long does the new tissue last?

Endothelial cells naturally attrite over time, and the same is true of donor cells in the graft. Most grafts function well for many years; some last decades. Late graft failure is possible and can be addressed with a repeat procedure.

Will my body reject the donor tissue?

The risk is real but much lower than with a full-thickness transplant. Modern DMEK series report rejection rates around 1-2% at 2 years, DSAEK around 5-9%, and traditional PKP 15-20% or higher. The reason is that the small volume of donor tissue is inside the eye rather than exposed at the surface, and the corneal endothelium is in a relatively immune-privileged location. Long-term low-dose topical steroid drops further reduce the risk.

Does the donor tissue come from someone who has died?

Yes. Donor corneal tissue comes from deceased donors and is processed by eye banks. Tissue is screened for transmissible disease, and recipients of corneal grafts have an extremely low rate of disease transmission. Donor matching by blood type or HLA is not routinely performed for corneal transplants, in contrast to most solid organ transplants.

Why face-up positioning afterward?

The donor tissue is held against the back of the recipient cornea by an air or gas bubble that floats upward. Face-up positioning keeps the bubble in contact with the donor tissue, allowing it to adhere. Inadequate bubble support or positioning can contribute to graft detachment in the first few days.

References