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DMEK



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Evaluation

Descemet membrane endothelial keratoplasty (DMEK) procedures can be done at various stages in the disease process for suitable patients. There is currently no definitive guideline regarding visual acuity reduction or glare acuity to dictate when the procedure should be done. Patient symptoms should be the driving factor for proceeding with surgical intervention.

Patients with endothelial disease will often experience blurred vision, glare/halos, trouble driving at night, “watery” or edematous vision, and even pain if the corneal swelling affects the ability of the epithelium to adhere properly. As the endothelial disease progresses, these “water pump” cells are unable to maintain appropriate corneal dehydration and fluid will enter the stroma. As corneal edema worsens, the fluid can move anteriorly into the epithelium, resulting in painful blisters called bullae.

Patients with corneal edema secondary to endothelial disease frequently notice decreased vision quality in the morning. This occurs as a result of increased corneal swelling following an extended period of time spent in a closed-eye state overnight. Patients may also struggle with glare in dim conditions, especially during activities like nighttime driving.

When evaluating a patient with endothelial cell changes, several instruments are used during the examination. We use an instrument that can analyze endothelial cell size, morphology, density, and drop out. We also utilize pachymetry measurements, corneal topography, and tomography to assess corneal irregularity, edema, and endothelial changes. Finally, a detailed slit lamp examination is important to view and diagnose unhealthy endothelial cells.

Endothelial keratoplasty (EK) procedures are not suitable for patients with healthy corneal endothelium, such as those with stromal scarring or keratoconus. These patients still require a full-thickness corneal transplant.

Good candidates for DMEK

  • Fuchs’ endothelial dystrophy

  • Posterior polymorphous membrane dystrophy

  • Congenital hereditary endothelial dystrophy

  • Bullous keratopathy

  • Iridocorneal endothelial (ICE) syndrome

  • Other failed endothelial keratoplasty procedures

Surgery

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 prepared for the patient.

If the DMEK graft is being transplanted in conjunction with cataract surgery, the cataract is removed and an intraocular lens is inserted prior to the corneal transplantation. Using a laser, a peripheral iridotomy is made in the host iris to allow for proper aqueous movement in the eye. Intraocularly, the host tissue endothelium and Descemet’s membrane are stripped from the posterior cornea and removed from the eye. Prior to inserting the endothelial graft, the tissue is stained with Trypan blue before it is rolled up and placed into an inserter. The graft is injected into the eye and it slowly starts to unfold. The surgeon will manipulate and place the graft into an appropriate position by using pressure, fluid mechanics, and gently tapping on the cornea. Once the graft is in position, a gas bubble is injected into the eye to aid in the adherence of the graft tissue to the posterior cornea. After the bubble is safely placed in the patient’s eye, the IOP is checked. This completes the surgical process.


Post Op

Drop protocol is 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 until the bottle runs out.

  • Vigamox: instill 1 drop 4 times per day for 1 week or until the bottle runs out.

Side Effects and Post-op Complications

  • Graft detachment: rates are variable and depend on surgeon experience and donor tissue quality

  • Damage to tissue during preparation or surgery

  • Upside down grafts

  • Epithelial defect or erosion

  • Elevated intraocular pressure (IOP). In the first week, if a patient experiences a significantly sore/achy eye, headache around the eye, feels nauseated, or vomits, the surgeon and his/her team should be called immediately.

  • Descemet’s graft folds

  • <1% risk of anterior synechiae, hypotony, pupillary block, subepithelial haze, and interface pigment deposits

  • Cystoid macular edema (CME)

  • Graft rejection

    • What to look for:

      • Decreased vision

      • Photophobia

      • Corneal edema

      • Keratitic precipitates