DMEK (Desemet's Membrane Endothelial Keratoplasty) Program at Vance Thompson Vision
DMEK TOP LINE
- Descemet's Membrane Endothelial Keratoplasty (DMEK) is a partial thickness corneal graft for endothelial disease.
- Patients with Fuch’s dystrophy or Pseudophakic Bullous Keratopathy can have better vision and less symptoms with a DMEK.
- Patients’ quality of vision is often improved beyond what they test for visual acuity.
- The surgical procedure is very safe and with an experienced surgeon offers improved outcomes compared to full-thickness corneal grafts.
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What is the procedure?
Descemet’s membrane endothelial keratoplasty (DMEK) is a partial thickness cornea transplant that is most commonly used to treat posterior corneal diseases.
In DMEK, the posterior corneal layers, Descemet membrane (DM) and endothelium are replaced by donor DM and endothelium. The term endothelial keratoplasty (EK) encompasses both DMEK and Descemet’s Stripping Endothelial Keratoplasty (DSEK). EK replaced penetrating keratoplasty in 2012 as the most commonly performed keratoplasty in the United States. Endothelial cell disorders remain the most common indication for keratoplasty in the U.S., comprising 40.2% of cases. Fuchs’ dystrophy was the most common indication for keratoplasty in the United States in 2014 (15,013, 21.5%) with post-cataract surgery edema being second (8,529, 12.2%).
WHEN AND WHY DO IT?
EK procedures can be done at various points in the disease process for these suitable patients. There is no magic number for visual acuity or glare acuity that dictates when the procedure should be done. Patient symptoms should be the driver for when to proceed with surgical intervention, an EK. Patients with endothelial disease will often experience blurred vision, glare/halos, trouble driving at night, “watery” or edematous vision, and sometimes pain. As the endothelial disease process worsens the endothelial “pump” cells are unable to maintain dehydration in the cornea and the cornea begins to swell. As the cornea worsens with edema, the fluid can move anterior in the cornea resulting in painful blisters called bullae. Most commonly patients with endothelial disease who are experiencing corneal edema will have the worst symptoms in the morning. These patients often describe, “Vision that is worse in the morning, and then improves as the day goes on.” These patients commonly will have poor vision at night, especially with driving due to glare.
There are many ways to examine and diagnose patients with endothelial disease. Konan Endothelial Cell Count (ECC) allows us to look at cell size and morphology, cell drop out, as well as cell density or count. Corneal pachymetry can tell over time if the cornea is thickening or becoming edematous. Corneal topography/tomography maps corneal irregularities as well as measures corneal thickness. Finally, a slit lamp exam and detailed examination is very important to view and diagnose unhealthy endothelial cells.
EK procedures are not suitable for patients with healthy corneal endothelium, such as patients with stromal scarring or keratoconus. These patients still require a PK.
Good candidates for DMEK
- Fuchs’ endothelial dystrophy
- Posterior polymorphous membrane dystrophy
- Congenital hereditary endothelial dystrophy
- Bullous keratopathy
- Iridocorneal endothelial (ICE) syndrome
- Failed endothelial keratoplasty
How is the procedure done?
The first step in DMEK is to prepare the graft tissue. This is commonly done by the Eyebank under their standard protocol. After preparation the tissue is safely transported to the surgery center and further prepped for the patient.
If the DMEK graft is being performed in conjunction with cataract surgery, the cataract is removed and an intraocular lens is inserted before the corneal graft. Using a laser, a small channel or passage-way (peripheral iridotomy) is made in the host iris to allow aqueous movement in the eye. The host’s endothelium and Descemets membrane is stripped from the posterior cornea and removed from the eye. First the graft is stained with Trypan blue before it is rolled up like a taco into an inserter. The graft is injected into the eye and slowly starts to unfold. The surgeon with gently tap on the cornea, and using fluid mechanics as well as pressure the surgeon can manipulate the graft into place. Once the graft is in position a gas bubble is injected into the eye. After the bubble is safely in place the patients IOP is checked which finishes the surgical process.
Photo shows the gas bubble placed during the DMEK procedure
After the procedure, the patient should lie supine as much as possible with periodic breaks for meals or using the restroom. The amount of time spent supine should gradually decrease over the course of the first week. Patients should avoid heavy lifting and bending at the waist for the first week post-operatively. The patient can shower/wash the eye, but excessive water inside of the eye should be avoided. Patients need to avoid flying until the gas bubble inside their eye has dissolved.
Patients should initially be seen on postoperative (PO) day 1, week 1, month 1, month 3, month 6 and month 12. The graft should be attached and the stroma should be less edematous on each post-operative visit. A significantly edematous stroma may indicate the graft is not functioning well or is upside down. It is very normal for the patient to see very poorly (even hand motion only) while the gas bubble is covering the visual axis.
Drop protocol subject to change
- Durezol/prednisolone acetate 1%: instill 1 drop 4 times per day for 2 months, then 2 times per day for 4 months, then 1 time per day for 6 months.
- Ilevro/Prolensa: instill 1 drop 1 time per day for 1 month or the bottle runs out.
- Vigamox: instill 1 drop 4 times per day for 1 week or the bottle runs out.
Side Effects and Post-op Complications
- Graft detachment: rates are variable and depend on surgeon experience
- Damage to tissue during preparation or surgery
- Upside down grafts
- Epithelial defect or erosion
- Raised intraocular pressure (IOP). In the first week, if a patient has a real soar/achy eye, a bad headache around the eye, or feels nauseated or like vomiting, the surgeon and his/her team should be called immediately.
- Descemet graft folds
- <1% risk of anterior synechiae, hypotony, pupillary block, subepithelial haze, and interface pigment deposits.32
- Cystoid macular edema (CME)
- Graft rejection
- What to look for:
- Decreased vision
- Corneal edema
- Keratic precipitates