Descemet's membrane endothelial keratoplasty

What is DMEK?

Descemet’s membrane endothelial keratoplasty (DMEK) is the latest and most advanced option available to treat damaged corneas associated with Fuchs’ Dystrophy and other causes of poor corneal endothelial function. Like DSEK and DSAEK, DMEK is a corneal transplant procedure that replaces only the innermost portion of the cornea, rather than the full thickness of the cornea as in traditional corneal transplants (PKP).

Compared to traditional PKP,  DSEK, and DSAEK options, DMEK is the most anatomically friendly repair possible – utilizing just one cell layer and a thin membrane, all of which is only 15 to 20 microns thick (less than 1/5 the thickness of a human hair).

DMEK leaves the patient’s cornea closer to its original condition than any other transplant technique. DMEK has been shown to offer patients the best chance of achieving 20/25 or better vision, resuming normal activities quickly, and avoiding vision-threatening rejection episodes.

DMEK has provided such a significant improvement in vision with a reduced risk of rejection that we are now advising many patients to have their two eyes affected by Fuchs’ disease operated on 1-2 weeks apart, with or without cataract surgery.

What are the benefits of DMEK?

DMEK shares some similarities with DSEK, but also exhibits several notable differences in donor preparation, intraocular manipulation, and postoperative care.

  • 2.8 mm or smaller corneal incision
  • No increase in corneal thickness
  • No refractive shift from donor graft
  • Ability to pre-operatively plan astigmatism management to reduce or eliminate pre-operative cylinder
  • No changes or guesses for “fudge factors” with IOL calculations

Who is a good candidate for DMEK?

Good candidates for DMEK include:

  • Fuchs’ endothelial dystrophy
  • Posterior polymorphous membrane dystrophy
  • Congenital hereditary endothelial dystrophy
  • Bullous keratopathy
  • Iridocorneal endothelial (ICE) syndrome
  • Failed endothelial keratoplasty

Who is not a candidate for DMEK?

Patients who are not suitable for DMEK include those with:

  • Inability to lie flat
  • Previous glaucoma surgery
  • Scarring of the stroma (small blood vessels near the margin of the cornea)
  • Keratoconus (cone-shaped cornea)
  • Hypotony (low intraocular pressure)
  • Aphakia (absence of a lens inside the eye)
  • Aniridia (significant iris defects)
  • Intraocular lens in the anterior chamber
  • Endothelial failure after traditional corneal transplant

What is the difference between DMEK and DSEK?

Both are procedures to restore vision in an eye with corneal scarring or other conditions.

  • DMEK – defective pump cells are replaced with just the healthy donor cells (tiny), rather than a piece of donor cornea.
  • DSEK – a piece of donor cornea, containing healthy pump cells, is used to replace the defective pump cells.

What are the advantages of DMEK over DSEK?

DMEK:
  • Provides better vision. Large series demonstrate that visual acuity can be 20/25 or better 75% of the time.
  • Provides better vision faster, with the best vision returning sooner than with DSEK.
  • Transplants have a 15 times lower risk of rejection than do DSEK transplants.
  • Steroid drops, with their attendant difficulties, are not needed for as long a time period or in as high a potency as they are after DSEK.
DSEK:
  • Visual acuity after DSEK will be limited to 20/30 or worse in 75% of cases.
  • A transplant with the same number of endothelial cells will be about 5 times larger than a comparable transplant done with DMEK.
  • Requires a larger incision to insert the larger piece of tissue. The extra tissue is actually counterproductive, as it leads to poorer visual outcomes and an increased risk of rejection.

What is the DMEK procedure?

Surgery is performed in an outpatient surgery center conveniently located within our building, eliminating the need for patients to travel to a new location and avoiding hospital admission. Anesthesia is given intravenously and with eye drops (topical anesthesia). The diseased innermost layer of the cornea is removed carefully, and the corresponding thin layer from a healthy donor cornea is put in its place. The transplant is held in place by only an air bubble, requiring patients to lie flat on their backs with their faces directed upwards immediately after surgery to float the bubble into place. The bubble typically dissipates within the first week, and as it does, patients no longer need to lie flat as much. The surgery can be combined with cataract surgery for patients who require both.

What are the risks of DMEK?

Along with the usual risks related to any eye surgery (which your surgeons will go over with you), with DMEK there is a risk of the thin button of endothelium becoming displaced within the first few days or weeks after surgery and requiring a return trip to the operating room to reposition it, or the operation can be repeated with another button of donor endothelium. If the DMEK, either after one or multiple attempts, a traditional corneal transplant operation can still be performed.

Also see:

Corneal Transplant, PKP (Penetrating Keratoplasty) and

DSEK / DSAEK

DMEK
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