Lamellar techniques have introduced a paradigm shift in corneal transplantation, especially in the United States and other Western countries. Endothelial keratoplasty has undergone rapid advancements in the last decade, becoming the most commonly performed corneal transplantation procedure in the West and relegating penetrating keratoplasty to a minor role.
Endothelial keratoplasty has evolved from deep lamellar endothelial keratoplasty to Descemet’s stripping endothelial keratoplasty to Descemet’s membrane endothelial keratoplasty in just more than a decade.
“The evolution of EK has been astonishingly fast from PK to DLEK to DSEK to DSAEK to DMEK in just 12 short years,” Mark A. Terry, MD, director of corneal services at the Devers Eye Institute and professor of clinical ophthalmology, Oregon Health Sciences University, said. “Even though DLEK proved far superior in patient benefits to the previous standard of PK, it was not widely accepted because it was too difficult a procedure for most surgeons and posed too great a risk of donor damage at the time of surgery. What this showed us is that it takes more than superior patient benefits by a procedure to make surgeons adopt it. The procedure has to be relatively easy and relatively quickly learned.”
In 1997, Gerrit Melles, MD, started with DLEK as the first technique to replace the endothelium.
The evolution from techniques such as PK and DLEK to DSEK and DMEK shows that in addition to patient benefit, cornea techniques needed to become less demanding, easier to learn surgeries, according to Mark A. Terry, MD.
Image: Legacy Devers Eye Institute
“This technique was relatively demanding, so we continued with Descemet’s stripping endothelial keratoplasty in 2001, in which only the host Descemet’s membrane had to be excised instead of a posterior corneal button. However, the corneal graft in both these techniques contains posterior stroma, which seems to somehow degrade the optical quality of a transplanted cornea,” Melles said. “To reach an anatomically ‘normal’ cornea, we worked towards Descemet’s membrane endothelial keratoplasty in 2005, which we thought should eliminate the image degradation caused by the donor stroma, since only Descemet’s membrane is transplanted.”
Today, DSEK, with the variation Descemet’s stripping automated endothelial keratoplasty, and DMEK represent one-third to one-half of the total number of keratoplasty procedures in Western countries, depending on the area. According to a statistical report from the Eye Bank Association of America (EBAA), endothelial keratoplasty was performed more often than PK in the U.S., 23,049 procedures vs. 21,422 procedures, in 2012.
“Penetrating keratoplasty has now been relegated to indications that do not qualify for endothelial transplantation,” Marianne O. Price, PhD, executive director of the Cornea Research Foundation of America, said. “In our practice, 90% of procedures for endothelial dysfunction are DMEK and 10% are DSEK. EK represents about 80% of the 500 transplants the practice performed last year, with anterior lamellars and penetrating grafts for non-endothelial dysfunction each making up 10% of the total.”
According to Massimo Busin, MD, the relative percentage of endothelial procedures in Europe is currently around 30%, but it is much higher for some surgeons.
“Of the 398 transplantations I performed last year, 60% were endothelial, 35% were anterior lamellar and only 5% were penetrating keratoplasty,” he said.
In Asia, numbers are still low, due to the late introduction of the surgery and the high costs of cutting tissues. Donald T.H. Tan, MBBS, FRCSG, FRCSE, FRCOphth, an OSN APAO Edition Board Member, estimated that the relative percentage is around 5% to 10%. However, some centers of excellence, such as in Singapore, are aligning with Western standards.