November 2018

NEWS & OPINION

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by Maxine Lipner EyeWorld Senior Contributing Writer


Prestained, preloaded DMEK tissue makes it easier and more efficient for surgeons to perform the procedure, according to Dr. Terry.
Source: Mark Terry, MD

 

Performing DMEK with preprepped and preloaded tissue

When performing Descemet’s membrane endothelial keratoplasty (DMEK) surgeons can attain equally good results with prestained, preloaded donor tissue, without having to do it on their own, according to Mark A. Terry, MD, director of corneal services, Devers Eye Institute, Portland, Oregon. Results from a study published in Cornea indicated that the outcomes were no different than if the surgeons had gone through the trephination, loading, staining, and other steps themselves.1

DMEK obstacles

While the total number of DMEK procedures continues to grow, its predecessor, Descemet’s stripping endothelial keratoplasty (DSEK) remains the preferred procedure, Dr. Terry said. Today, 26% of all endothelial keratoplasties performed are DMEK and 74% are DSEK. “Those numbers should be reversed since the data shows that DMEK gives better visual acuity with faster visual recovery,” Dr. Terry said. Unfortunately, he finds that many practitioners are reluctant to try DMEK since the tissue is only 7–10 mµ thick and very delicate. “It scrolls up like a rug,” he said. “If you touch it directly, you’ll kill the endothelial cells.” On the other hand, even very thin DSEK tissue is easier to manipulate since you can touch this without doing as much damage, he noted.
While DSEK is a good procedure, it still adds tissue to the cornea, Dr. Terry pointed out. “It has a stromal interface, which is not natural, so even if you do a nano-thin DSEK, you’re not going to get the kind of visual results as quickly as you will with DMEK,” he said.
One of the early obstacles with learning to perform DMEK included the fact that surgeons would have to strip the Descemet’s tissue off the donor tissue in the operating room, which came with the risk of tearing and destroying it, Dr. Terry observed, adding that the answer here was having the eye bank prestrip the tissue for surgeons, akin to what happened for DSEK. “DSEK didn’t take off until they had precut tissue from the eye bank,” he said. “DMEK also didn’t climb until there was pre-stripped tissue by the eye banks so surgeons didn’t have to risk damaging this at the time of surgery and canceling the case.”

Considering preloaded tissue

Knowing that many practitioners are put off by the somewhat risky parts of the DMEK process, such as trephinating the tissue, staining with trypan blue, and loading this into an injector, Dr. Terry set out to conquer the issue. “I said to the eye bank, ‘Let’s see if we can preload tissue, where we do everything for surgeons, and all they have to do is take the tube out and inject the tissue,’” he said.
Included in the consecutive case series were 111 eyes with endothelial failure that were treated with donor tissue that was prestripped, prestained, pretrephinated, and preloaded in a Straiko modified Jones tube, Dr. Terry noted. “We found that out of the 111 cases, there were no primary graft failures at all,” he said, adding that in 16 cases it was necessary to place another air bubble and in two others a second rebubble was needed. The endothelial cell loss at 3 and 6 months, respectively, was 26.9% and 30.9%, Dr. Terry reported. “That’s a little less cell loss than we were getting when we were doing our own loading,” he said.
One intriguing finding here was the sense that Dr. Terry had that the preloaded tissue seemed to unscroll easier than previous tissue that had been prepared by the practitioner. “The unscrolling times were much faster with the preloaded tissue,” he said, adding that it was about half the unscrolling time as seen previously. Perhaps having the trypan blue on the tissue for a day or two makes the tissue a little stiffer and allows it to unscroll easier, he theorized.
From a clinical perspective, Dr. Terry views the use of the preloaded tissue as safer than when the surgeon performs all the steps. Also, it saves time in the OR as well as money, he pointed out. “Our operating room charges about $70 a minute,” he said. “Any time you can save will also save money and will allow better efficiency.” He estimated that using preloaded tissue saves about 15 minutes per case, something that will enable more procedures to be done each day, Dr. Terry noted.
The practice also saves money since there is no need to purchase trypan blue, trephines that cost hundreds of dollars, or Straiko injectors, he continued, adding that although the processing fee for the preloaded tissue is greater than traditional tissue, this does not cost the practice more since it is a Medicare pass-through expense.
One pearl for those who opt for the preloaded tissue is to be aware that eye banks will trephinate the tissue to whatever size the practitioner dictates, Dr. Terry explained. If no size is dictated, however, then the eye bank will automatically send an 8 mm stripped area. “In 99% of my cases, I do an 8 mm stripped area, but occasionally I’ll have a small eye and I’ll need a 7 mm stripped area,” he said. “So I have to tell the eye bank in advance that this is what I need.”
Overall, Dr Terry hopes that practitioners come away from the study with the understanding that DMEK surgery has now evolved to the point where many surgeons can incorporate this. “Finally, DMEK is at a point where it is faster, easier, and safer than it has ever been,” he said. “Any surgeon who does endothelial keratoplasty should be able to learn how to do DMEK surgery now that these other problems are taken care of.”

Reference

1. Newman LR, et al. Preloaded Descemet membrane endothelial keratoplasty donor tissue: surgical technique and early clinical results. Cornea. 2018;37:981–986.

Editors’ note: Dr. Terry has no financial interests related to his comments.

Contact information

Terry: mterry@deversseye.org

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