EyeWorld Asia-Pacific March 2011 Issue

29 EW CORNEA March 2011 Bare Descemet’s membrane recipient in DALK; splitting donor corneas may allow surgeons the ability to perform more DALK procedures in more patients DALK; removal of overlying stromal tissue Source: Mark Terry, MD, Devers Eye Institute Novel strategy could help to solve cornea shortage by Faith A. Hayden EyeWorld Staff Writer Split cornea transplantation “doubles” transplant tissue supply W hat’s the most efficient method to instantly double the quantity of something? Take one and split it in two. That’s the thinking behind a novel surgical procedure developed by researchers out of the University of Erlangen-Nuremberg, Erlangen and Nuremberg, Germany, to address the increasing global need for cornea tissue. Although cornea tissue is the most common form of tissue transplanted—on average, 50,000 surgeries are performed in the US alone, according to Eye Bank Association of America (EBAA) statistics—there is an overwhelming need for donor tissue in many parts of the world, including Africa and Asia. Many eye banks try to tackle this problem through education and outreach, but those efforts just aren’t enough to keep up with the demand. Doctors at the Eye Bank Erlangen, University of Erlangen- Nuremberg, found they were facing similar issues. “We have our own cornea bank here in our clinic. Although we’ve made quite a large effort to get more cornea tissue, it’s becoming increasingly more difficult to get enough tissue to serve all of the patients on our waiting list,” said Claus Cursiefen, MD , director, Eye Bank Erlangen, and one of the researchers for the study. “The wait list is getting longer and longer.” Dr. Cursiefen and coworkers knew of a recent, revolutionary development in cornea surgery where instead of replacing a patients’ entire cornea, surgeons replaced only the section that was diseased. “This technique basically allows the cornea being used to be split into two parts,” Dr. Cursiefen said. “We thought maybe we could combine patients in such a way that we could use the anterior portion of the donor cornea for one patient and the posterior portion for the other.” To test this theory, researchers used a combination of deep anterior lamellar keratoplasty (DALK) and Descemet’s membrane endothelial keratoplasty (DMEK) surgeries, two highly complicated procedures, on 12 donor corneas. In DMEK only the corneal endothelial “pump cells” and their basement membrane (<15 microns) are transplanted to patients with isolated diseases of corneal endothelium. In contrast, in DALK surgery, the remaining 98% of the donor tissue is transplanted to patients with healthy endothelium, but scarring of the anterior cornea occurs. The researchers reported a success rate of 83% but have since improved that number to nearly 90%. Two of the 12 cases used in the study had to be converted to penetrating keratoplasty (the current standard technique). Six months after surgery, the mean best spectacle-corrected visual acuity was 20/35 (6/10.5). “Postoperative complications after DALK included Descemet’s folds in three eyes and epitheliopathy in two eyes,” the team wrote in the study. “After DMEK, partial graft detachment occurred in five eyes and was managed successfully with intracameral air reinjection. All corneas remained clear up to six months after surgery.” Although Dr. Cursiefen and coworkers were generally successful and had encouraging results, the method does come with challenges and pitfalls. Before surgeons could even begin to combine the DALK and DMEK techniques, they were faced with a hurdle: The donor cornea had to safely be split in two. The size and thickness of the posterior section of the cornea, which is only 10–15 microns thick and very fragile, made this an especially tricky procedure. Splitting the cornea in two is “very difficult to accomplish without damaging the tissue or creating tears”, Dr. Cursiefen said. Once the donor cornea was successfully split, the two procedures were combined, presenting more challenges and chances for complications. DMEK is a fairly new and highly advanced technique and not an option for all cornea surgery centers yet. “At the moment, only the major cornea surgery centers are performing DMEK,” Dr. Cursiefen said. “But it’s becoming increasingly more popular.” The risk of complications while using the split-cornea method is also higher than with simply transplanting the entire cornea. “If there are complications, we always have the backup of the standard technique,” explained Dr. Cursiefen. “So the patient doesn’t lose anything. In the worst case scenario, the patient has to undergo a second procedure.” On the plus side, however, patients’ vision returns at a much faster rate. “With the standard technique, patients get their full visual acuity back after one and a half years,” Dr. Cursiefen said. “But with DMEK, these patients have good visual acuity after a few weeks.” Currently, the team is making the meeting rounds and presenting the approach to colleagues. They’ve performed about 100 of these split-cornea operations so far and are continuing to follow up with the patients to assess the long-term visual complications. “Split cornea transplantation requires advanced corneal surgical techniques and sophisticated patient logistics, but in the future may become a standard approach to save corneal tissue and reduce transplantation cost,” the researchers wrote. The study, “Split Cornea Transplantation for 2 Recipients”, was published in Ophthalmology in August 2010. EW Editors’ note: Dr. Cursiefen has no financial interests related to his comments. Contact information Cursiefen: claus.cursiefen@augen.med . uni-erlangen.de