DMEK or Descemet’s Membrane Endothelial Keratoplasty is the latest advancement in corneal transplant surgery. It is a newer variant of DSEK corneal surgery. It involves transplanting only the inner 15 microns of the cornea.
It is indicated in Fuchs dystrophy, Pseudophakic Bullous Keratopathy and other corneal diseases limited to the innermost lining of the cornea. A prerequisite is that the rest of the cornea should be healthy. If there is opacity in the center of the cornea than a full thickness graft may be more appropriate. Handling this ultra thin graft requires a high level of dexterity. This behooves a clear view beneath the cornea. The upper layer of the cornea called the epithelium can be removed to improve clarity.
The procedure consists of three parts. Harvesting the graft from the donor cornea is the first step. Next the recipient cornea is prepared to receive the graft. Finally the endothelial graft is introduced into the patients eye and made to stick to the cornea.
STEP 1 OF DMEK
The donor cornea is put endothelial side up in a punch like a Moria disposable punch. A dull instrument is used to separate the descemets from the schwalbes’ line. When approximately 60 percent has been cleaved the corneal button is centered over four holes. It is then stained with trypan blue. It is than punched with a 7.5 mm to 8 mm trephine. The descemets is separated from the rest of the cornea. It is soaked in trypan blue and covered. Attention is than directed to the patient.
Nowadays surgeons are preferring to obtain a precut preloaded prepared graft. This graft already has a mark to determine its orientation.
STEP 2 OF DMEK PROCEDURE
The patients eye is prepped and draped. Some surgeons proceed with topical anesthetic drops. Others prefer to perform a retrobulbar block to prevent eye movements. A speculum is inserted. The center of the cornea is identified. A ring of 8mm is placed over it. The indentation are marked with a marking pen. Two 1 mm paracentesis incisions are made. Viscoelastic is injected in the eye.The main temporal wound is 3 to 5 mm . A reverse sinksy instrument scores the descemets’ and endothelium along the preinked corneal marks. This tissue is than stripped off. A forceps grabs it. It is than placed over the cornea to confirm it is uniform. Also the inner cornea is inspected to detect if there are any strips of the tissue left behind. An opening is made in the iris at 6 or 9 o’clock. If all is fine the viscoelastic is removed. Any residual viscoelastic is an enemy to the donor graft says Dr.Khanna
STEP 3 OF DMEK
Now is the most challenging part. The graft is loaded into a specially designed bulbous glass device attached to a syringe. Hence the graft gets curled with the endothelial side up. This device is introduced into the temporal wound. With gentle pushes the graft is pushed into the anterior chamber of the eye. Then the dance begins as we want the graft to unfold. The cornea is gently tapped and rolling motions executed. An air bubble is introduced under the flap once it opens. The remarked S or F is identified to confirm it is right side up. Air is introduced to raise the pressure of the eye for next 10 minutes. Then some of the air is released. A subconjunctival injection of steroid and antibiotics is given.
Patient is transferred but made to lie flat on their back for the next hour. They are also instructed to do the same at home.
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