Cornea: Cornea editor’s corner of the world
January 2013

by Ellen Stodola 
EyeWorld Staff Writer

Advances in endothelial keratoplasty have occurred at a rapid rate considering that less than a decade ago corneal specialists were still performing penetrating keratoplasty for all endothelial replacement. The latest innovation in endothelial surgery is Descemet’s membrane endothelial keratoplasty (DMEK). This technique eliminates the stromal carrier used in Descemet’s stripping automated endothelial keratoplasty (DSAEK) and in theory should result in better vision. However, the DMEK procedure has been slow to be adopted by most corneal surgeons due to the higher complication rate. Complications in DMEK include increased early endothelial cell loss, increased graft detachments, and loss of donor tissue in the preparation of the graft. In addition, the tissue is more difficult to handle once in the anterior chamber, resulting in longer surgical time.

Recently a variation on the traditional DSAEK has been introduced that may provide the benefits of DMEK without the complications. Data has shown that if the donor tissue in DSAEK is cut thinner than in traditional tissue preparation, the visual outcomes are improved. In addition, the newer insertion devices now available make this “thin DSAEK” tissue easier to handle and insert into the eye, reducing trauma to the endothelium. As we continue to strive for better outcomes and reduced complications in endothelial replacement surgery, we need studies to determine if “thin DSAEK” produces similar visual outcomes to DMEK. If it doesn’t and DMEK does result in superior visual outcomes then we need to improve the complications of DMEK such as graft loss during preparation, rebubbling, and endothelial cell loss.

—Edward J. Holland, M.D., cornea editor

When it comes to corneal endothelial disorders, endothelial keratoplasty has become popular with ophthalmologists worldwide, and many choose between Descemet’s stripping endothelial keratoplasty (DSEK) and Descemet’s membrane endothelial keratoplasty (DMEK). DSEK seems to be the current preferred method, with developments in DMEK causing the technique to gain ground.

DSEK involves a transplant of the back layers of a donor cornea into a patient’s eye. This technique offers a certain ease because it has been the procedure of choice for many years. DSAEK is the automated version of this procedure, which uses a machine to cut tissue.

DMEK, on the other hand, uses extremely thin donor tissue, with a better chance of restoring good vision to the patient. However, surgeons using this technique often experience obstacles with handling the donor tissue because of how fragile the grafts can be.

Recently, thin DSAEK has offered an alternative to the other two techniques, utilizing the ease of DSAEK with thinner grafts.

Massimo Busin, M.D., Villa Igea Hospital, Forli, Italy, is one of the surgeons who has been seeing the benefits thin DSAEK can offer, and he compared the advantages and disadvantages doctors see using both DSAEK and DMEK. Similarly, Andrea Ang, M.D., Royal Perth Hospital, Perth, Western Australia, prefers using the thin DSAEK technique, but she also pointed out the advantages of both DSAEK and DMEK. Meanwhile, Francis Price, M.D., Price Vision Group, Indianapolis, favors DMEK and stressed some of its key advantages.

The outcomes of each technique

“Both techniques have developed because the results of the old conventional penetrating keratoplasty were not as satisfactory as one would like them to be,” Dr. Busin said. Advancements were initially made by DSAEK, he said.

However, he said that some physicians felt that there was only a limited number of eyes gaining 20/20 vision after surgery. This prompted the development of DMEK, which was an attempt to increase the number of eyes that would be able to obtain 20/20 vision after surgery.

Dr. Ang agreed with the advantages of DSAEK over penetrating keratoplasty and also with the argument that only a limited number of patients achieve 20/20 vision.

“Recent DMEK studies have shown faster visual rehabilitation and better visual outcomes than the earlier DSAEK studies,” Dr. Ang said. “However, recent studies have shown that the thickness of donor tissue used in DSAEK does influence visual outcome, with newer thin DSAEK techniques demonstrating improved visual outcomes approaching the visual outcomes seen with DMEK and with less complications.”

One of the reasons many surgeons tend to prefer DSAEK to DMEK is simply the ease with which the surgery can be performed. 

“It’s much easier to perform a DSAEK, even with a thin graft, than it is to perform a DMEK,” he said. To back up his point, Dr. Busin said that in the U.S. last year, there were over 21,000 DSAEK procedures, compared to around 343 DMEK procedures.

Dr. Ang said new insertion devices like the EndoSerter (Ocular Systems, Winston-Salem, N.C.), the Busin Glide (Moria, Antony, France), and the Tan EndoGlide (Angiotech, Vancouver, B.C.) help to handle the tissue for insertion. “At the present, thin DSAEK appears an attractive alternative while DMEK techniques continue to improve,” she said.

Complications arising 

Despite DSAEK standing out as the easier technique, there are other factors to consider. DSAEK is often preferred to DMEK because primary failure is more common with DMEK, Dr. Busin said. He said DMEK poses the threat of a significant detachment rate. However, he also said DMEK typically has a lower rejection rate. 

Dr. Ang said “safety in donor preparation and easier manipulation of the tissue in the anterior chamber” is a factor that continues to make the DSAEK technique more popular. “The challenge for thin DSAEK is for the eye banks to come up with techniques to provide reproducible and accurate thin tissue,” she said.

Tissue loss and possibility of endothelial cell loss because of difficulties manipulating the delicate tissue were two possible risks with DMEK that Dr. Ang cited. “Solutions to these problems need to be found in order to make DMEK the procedure of choice for endothelial replacement,” she said.

Technique preferences

Dr. Busin said he is currently seeing a trend toward thin DSAEK, his preferred method. This allows for thinner grafts and thinner incisions with the DSAEK procedure. However, he said that some people may not trust this method yet, which could be why some are leaning toward DMEK. He said in the future he expects to see people favoring thin DSAEK.

“The ease of surgery and the outcome, which is more or less the same, would convince them to move from DMEK back to thin DSAEK grafts,” Dr. Busin said.

Likewise, Dr. Ang also said thin DSAEK is presently her procedure of choice. “This technique results in excellent visual outcomes, is technically less demanding than DMEK, and has fewer complications than DMEK at present,” she said.

Dr. Price said he prefers the DMEK technique, although he still sometimes uses DSAEK. “If it’s a non-complicated case, we recommend DMEK,” he said. After nearly five years using DMEK, there are a number of reasons he favors it. He said better vision results are evident with DMEK. Another reason is rejection rates are significantly lower with DMEK. He said in a cumulative look at DMEK for a two-year period, the rejection rate was less than 1%, compared to about 12% for DSAEK.

He said thin DSAEK does offer some similarities to DMEK. “I think the thinner it gets, the closer you’re going to get to DMEK,” he said. But the question, he said, is how close you can get and how reliable the thin DSAEK would be. Dr. Price said he stopped using thin DSAEK because of significant tissue loss in donor preparation. Currently DMEK donor loss rates are less than 1%; it will be interesting to see if donor loss rates will be that low if all donor preparations for DSAEK are for thin cuts, as there is always some irregularity and unpredictability with microkeratome cuts.

Endothelial replacement future

Endothelial keratoplasty has evolved over the years, Dr. Ang said. “The next phase will be cultured donor endothelial cell seeding of diseased corneas,” she said. “The ability to culture and expand donor endothelial cells will increase the donor supply, especially in countries with limited supply. These cells could be transplanted either as an injection-based therapy or on a carrier.”

---

Editors’ note

Dr. Busin has financial interests with Moria. Drs. Ang and Price have no financial interests related to this article.

Contact information

Ang: angandrea@hotmail.com
Busin: mbusin@yahoo.com
Price: francisprice@pricevisiongroup.net