A recent innovation in transplanting Descemet’s membrane will make the procedure faster and more predictable, possibly affecting thousands of patients, clinicians say. The first-ever pre-Descemet’s endothelial keratoplasty (PDEK) corneal transplant procedure, performed with an eye bank-prepared, preloaded Descemet’s membrane graft, took place in January, according to LEITR, the Lions Eye Institute for Transplant & Research.
The advance should make PDEK a more “user-friendly” and financially viable procedure, say proponents, including Ahad Mahootchi, MD, of The Eye Clinic of Florida, Zephyrhills, who performed the PDEK with the preloaded graft.
“PDEK can be used for any patient with primary endothelial dysfunction. There are tens of thousands of cases done for this in the United States alone each year, “That's a huge percentage of patients,” Dr. Mahootchi says. Up until now, the surgeon would normally default to DSAEK (Descemet's stripping automated endothelial keratoplasty) due to the obstacles associated with PDEK.
Though surgeons use an air bubble to attach DSAEK, PDEK and DMEK-related grafts, it is perhaps most critical in DMEK grafts, as there is no stroma-to-stroma adherence involved. But PDEK is performed on patients for whom Descemet membrane endothelial keratoplasty (DMEK) is not an option —typically because of prior vitrectomy or prior Yag capsulotomy.
“It is difficult for a surgeon to attach a DMEK graft in an eye that cannot hold an air bubble in the anterior chamber for a significant period of time,” says cornea specialist Marguerite B. McDonald, MD. “Prior vitrectomy patients and prior Yag capsulotomy patients both have a pathway through which the air bubble can possibly dart back into the posterior chamber, thereby making it hard to attach the graft.”
Agreed, says Dr. Mahootchi. With this new procedure, “It’s easy to use in eyes with prior Yag capsulotomy or vitrectomy.”
Dr. McDonald says that cornea surgeons recognize the advantages of transplanting Descemet's membrane with little or no stroma. “Anything to make the surgery faster and more predictable is a great step forward,” says Dr. McDonald, who practices in Long Island, NY.
Traditionally, PDEK grafts are prepared by the surgeon, rather than the eye bank, and require hours of preparation. Additionally, the air-bubble technique and extensive manual manipulation used to create them can damage the endothelium, entailing financial risk to the surgeon — to the tune of $3,000 to $3,500 or more, according to Dr. Mahootchi. “You can't do surgery with torn tissue. And Medicare doesn’t reimburse the tissue if the surgeon doesn't perform the procedure.”
LEITR estimates that the fee for a preloaded (as well as prestained and prestamped) PDEK graft will be $4,450.
The preloaded PDEK graft offers surgeons all the advantages of DMEK, according to Dr. Mahootchi, in addition to saving the surgeon time and money. “That means less steroids, usually an endpoint of steroid use, better final vision and less rejection than DSAEK.”
From bubbles to blisters
The concept of a PDEK graft preloaded into the injector stemmed from a preloaded DMEK that Erkin Abdullayev, MD, senior lab manager at LEITR developed. He first created an alternative to the air-bubble technique — a “blister technique” for DMEK preparation; Dr. Abdullayev prepares the grafts through a “blister” method in which separation of the layers is achieved by a liquid blister rather than by touch. This no-touch technique entails significantly less manipulation of the graft.
In December 2015, LEITR used this technique to start performing preloaded DMEK graft.
“Then I started thinking, this is a procedure that’s definitely attractive for complicated eyes where regular DMEK is not working,” explains Dr. Abdullayev. So he adapted blister technique for PDEK. During preparation, visualization of the graft is enhanced with what LEITR terms “selective staining,” in which only pre-Descemet’s membrane is stained, and not the endothelial cells.
Dr. Abdullayev calls the preloaded grafts an “all in one” option because the grafts are preloaded, stained and marked for orientation (S-Stamp).
Adds Dr. McDonald: “This [all-in-option] clearly shortens the learning curve, it is likely that more cornea surgeons will switch to this from DSAEK." According to LEITR, the learning curve for the procedure will be dependent on the surgeon and his or her experience with DMEK.
Steven M. Silverstein, fellow cornea specialist whose practice is located in Kansas City, sees great value in LEITR’s new advancement. While DSAEK is the gold standard for transplantation for endothelial dysfunction, he says, “DMEK provides more consistently better visual acuity, but has been slow to penetrate the marketplace because of the technical difficulty [involved with] implanting and unscrolling the tissue. The opportunity to use preloaded tissue for this newer procedure is not only optimal for endothelial cell preservation, but for technical ease of use, and I expect that it will become the new standard.”
Dr. Abdullayev will deliver a presentation on preloaded grafts for DMEK at the upcoming 2017 ASCRS meeting in Los Angeles. For more information, e-mail firstname.lastname@example.org. OM