NEW ORLEANS — Surgeons are fine-tuning their approach to Descemet membrane endothelial keratoplasty (DMEK) to improve corneal transplant outcomes and allay concerns ophthalmologists have about performing the challenging procedure.
Friedrich Kruse, MD, from the University of Erlangen, in Germany, a leader in the DMEK field, presented new ideas here at the American Academy of Ophthalmology 2013 Annual Meeting.
Although DMEK appears to have several advantages over its predecessor, Descemet's stripping automated endothelial keratoplasty (DSAEK), it is not without risks.
Advantages of the new approach include better visual function and a significant decrease in the likelihood of graft rejection. However, DMEK is also associated with a higher rate of corneal aberration and more rebubbling.
"The DMEK technique is quite complex," Dr. Kruse acknowledged. "We are making modifications to transform the surgery to a technique everyone can do," he said.
Asked by Medscape Medical News to comment on the surgical refinements, Kathryn Colby, MD, a corneal surgeon at the Massachusetts Eye and Ear Infirmary and Boston Children's Hospital, noted that "more and more corneal surgeons are adopting DMEK techniques. We are learning more about the biology of endothelial dysfunction, which, coupled with surgical advances, make it a very exciting time to be a corneal surgeon."
DSAEK requires a relatively thick graft; with DMEK, the graft is thinner, which can cause more problems, Dr. Kruse pointed out. "The main challenge is to insert the graft into the same position. The bubble travels in the roll and you can easily unroll the graft with no additional trauma," he explained. "With surgical refinements, this procedure is ready for clinical use."
Because the challenge of donor preparation is well described in the literature, Dr. Kruse discussed graft control using a technique that ensures orientation based on 3 circular marks — lunar punches — set at the periphery of the graft with a 1-mm trephine.
"It is very important to know whether the graft is upside down or not," he explained. "The success of DMEK depends on unrolling of the membrane. We use an intraocular lens shooter that we have developed to deliver the tissue. The use of a small air bubble inside the Descemet roll offers additional stability and precludes lateral movement of the graft. Therefore, a reproducible insertion becomes possible."
The intraocular shooter is approved for use in Europe but is not yet available in the United States.
Control of donor graft unfolding and attachment is made easier by the small air bubble inside the Descemet roll, Dr. Kruse continued, explaining that the roll can be delivered into the anterior chamber with the air bubble already inside it.
"When the graft is unfolded and centered, the bubble is removed while the anterior chamber becomes shallow. Next, the anterior chamber is filled with air for 60 minutes, and then 50% of the air is removed during the first hour," he said.
The procedure requires an excellent rapport between the surgeon and patient because recovery requires patients to spend the first 2 days after the procedure in bed looking at the ceiling. If graft detachment occurs, it leads to rebubbling," Dr. Kruse noted.
"Using the technique I described with the bubble in the roll and the commercially available intraocular shooter, our rebubbling rate has gone down from 70% to about 5%," he said.
Dr. Kruse has disclosed no relevant financial relationships. Dr. Colby reports financial ties with Novartis.
American Academy of Ophthalmology 2013 Annual Meeting. Presented November 16, 2013.
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Cite this: DMEK Techniques Enhanced for Corneal Transplant - Medscape - Nov 27, 2013.