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STEP UP TO DMEK

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Compared with the rapid adoption of DSAEK (Descemet stripping automated endothelial keratoplasty), corneal surgeons are still struggling with the decision of whether or not to adopt DMEK (Descemet membrane endothelial keratoplasty). Speaking at the 5th EuCornea Congress in London, Sadeer B Hannush MD described how he finally decided to include DMEK in his practice.
He told attendees that he and colleagues are relative latecomers to the community of academic cornea specialists performing DMEK. He explained that they first introduced DMEK in February 2014, and did so only after undertaking an 18-month period of investigation and analysis to gather evidence supporting the decision and to guide their surgical protocol.
“We were early adopters of DSAEK because we were certain it would improve patients’ lives compared with penetrating keratoplasty. However, DMEK brings technical challenges and we were not convinced at first that it offered significant advantages over a well-performed DSAEK with a thin lenticule, less than 100 microns,” said Dr Hannush, Attending Surgeon, Cornea Service, Wills Eye Hospital, Department of Ophthalmology, Sidney Kimmel Medical College at Jefferson University in Philadelphia, US.
“The length of time I spent researching and preparing for DMEK is far longer than that for any other new procedure I incorporated in my practice in the last 26 years since I finished training.”
Ultimately, Dr Hannush and his colleagues concluded that at least for certain patients and in the hands of skilled surgeons, a well-performed DMEK offers significantly faster visual rehabilitation than DSAEK. As another advantage compared with DSAEK, it seemed that DMEK grafts behave consistently once they attach and the cornea clears. 
“The DMEK outcome is predictable once a surgeon gets through the learning curve. Unlike DSAEK, it is not a function of graft thickness or architecture, but simply of good apposition and cell count at the end of the procedure,” Dr Hannush said. 
In addition, Dr Hannush said he was satisfied that the DMEK procedure could be standardised and therefore could be taught well to trainees. Finally, as Wills Eye Hospital is a centre providing consultative services to colleagues for their patients with corneal disease, he felt it was important to be able to choose from the entire armamentarium of keratoplasty procedures in order to offer the best option for each and every patient.

Technical decisions
Aiming to develop a surgical protocol that would minimise the technical challenges of the procedure and optimise outcomes, Dr Hannush and colleagues looked at available evidence and spoke to experts to guide their decisions. In particular, they investigated the following issues: Who should prepare the graft? How should it be inserted and unscrolled? And what should be used for tamponade?
Dr Hannush noted that he needed to review these issues/challenges from the dual perspective of being both a corneal surgeon and medical director of the Lions Eye Bank of Delaware Valley. 
“The methods we chose are not necessarily the right ones for everyone, but they seemed to be best for our situation,” he said. 
The answer to the question of whether the surgeon or eye bank should prepare the donor tissue came easily – it would be done by a trained and certified eye bank technician using the technique developed by Gerrit Melles MD, PhD, Rotterdam, The Netherlands.
“We could not see the surgeon or the institution being responsible for tissue wastage, and so we created a special process for the eye bank to prepare pre-stripped DMEK tissue,” Dr Hannush explained.
While concern over wastage was the major determinant, Dr Hannush told EuroTimes that after a decade of experience as a surgeon performing endothelial keratoplasty, he is also convinced that a well-trained eye bank technician could potentially prepare the graft better and in less time than Dr Hannush could. 
“Using pre-stripped tissue makes the surgeon’s component of the procedure shorter and less stressful,” Dr Hannush said, adding that he still believes there is value for surgeons to learn the stripping technique themselves.
Dr Hannush and colleagues chose to use a modified glass tube (Straiko-Jones) rather than a modified intraocular lens cartridge for introducing the graft into the anterior chamber. He explained that this decision took into account what would be most compatible with the surgical environment at his centre in terms of the personnel involved (nurses, scrubs, residents and fellows) as well as ease of skills transfer in teaching trainees.
For graft unscrolling, the anterior chamber shallowing technique with corneal tapping was selected instead of a small air bubble assisted technique. 
Also, based on a gut feeling and personal communications, including advice from José Güell MD, Barcelona, Spain, use of an isoexpansile concentration of SF6 (20 per cent) rather than air was chosen for tamponade.
“We wanted to ensure graft adherence with the fewest number of rebubbling procedures, and so it made sense to choose the tamponade technique that would provide graft support for the longest period of time,” Dr Hannush told EuroTimes.
Sadeer B Hannush: sbhannush@gmail.com

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