Glide insertion technique appears to reduce graft failure rate in DSEK

New method rules out the need for folding and unfolding the donor lenticule and is particularly suitable for Asian eyes, surgeon says.

STOCKHOLM — A new glide insertion technique obviates the need for folding and unfolding the donor graft in Descemet’s stripping endothelial keratoplasty. It preserves the donor endothelium and makes transplantation easier and safer in small, shallow Asian eyes, according to one surgeon from Singapore.

“Descemet’s stripping endothelial keratoplasty (DSEK) conventionally requires folding of the donor lamella for insertion and subsequent manipulation in the anterior chamber to unfold it in the eye. This method tends to cause endothelial damage and cell loss,” Donald T.H. Tan, MBBS, FRCRSG, FRCSE, FRCOphth, said in a presentation at the European Society of Cataract and Refractive Surgeons meeting.

Scanning electron microscope and vital dye studies confirmed that folding of the donor lenticule causes extensive endothelial damage, mainly from compression with the folding forceps. Also, in the area of the folding crease, linear streaks of endothelial cell damage are visible, he noted.

Manipulation and unfolding of the donor graft in the recipient eye may be the source of additional problems, “particularly in my part of the world,” Dr. Tan, Ocular Surgery News Europe/Asia-Pacific Edition Editorial Board Member, said.

Asian eyes are smaller, with shallow chambers, a thicker iris and a high rate of angle-closure glaucoma. Unfolding a donor lamella in these small eyes is difficult without causing further damage to the donor and the host.

“In our first 20 cases, using the conventional folding technique, we had a 25% primary failure rate,” Dr. Tan said. “That’s why we developed this new technique, where the donor lenticule is delivered flat and full-diameter to the host bed. By using this method in the subsequent 28 patients, primary failure rate was down to 3.5%.”

Many advantages

The technique is a variation of a sliding technique originated by Massimo Busin, MD.

Donald T.H. Tan

No complicated instruments are needed to guide the donor lamella through the wound – just an ordinary IOL sheet glide, normally available in any operating theater, Dr. Tan said.

Because the wound is normally 5 mm and the diameter of a standard glide is also 5 mm, trim the glide edges by about 0.5 mm on each side to make space and avoid compression of the donor graft during insertion, he said.

The donor lamella is placed, endothelial surface down, on a copious bed of viscoelastic and spread on the plastic glide and on the graft of the endothelial surface. The diameter of the lamella, which is normally 8.5 mm to 9 mm, exceeds the diameter of the glide, Dr. Tan said.

The lamella, kept in place with forceps once it is guided on top of the glide through the incision, will be slightly compressed and narrowed, adapting its shape to the size of the incision, he said.

During the procedure, an anterior chamber maintainer is used to keep a deep chamber.

Because the lenticule is held by forceps during the conventional unfolding process, there is no risk of inverting its position, Dr. Tan said.

“One of the problems with the folding technique is that the lamella, under the pressure of air or [balanced salt solution], may unfold the wrong way up,” he said. “Surgeons use marks to prevent upside-down positioning, but with the glide technique, we avoid the problem entirely. We never had a situation where there was some doubt as to which way the donor graft was facing inside the eye.”

Another intraoperative complication that is avoided with this method is iris prolapse because the glide protects the iris and keeps it in place, Dr. Tan said.

He also noted that the traditional technique could not be performed in the presence of an anterior chamber IOL, especially in Asian eyes.

“If you have an [anterior chamber] IOL present, you cannot unfold the donor lamella without damaging the cornea because the IOL is in the way. What the surgeon has to do normally is remove the IOL, put in a sclera-fixated posterior chamber lens and then do DSEK,” Dr. Tan said.

With the new technique, there is no need to remove the lens. The sheet glide is used over the anterior chamber IOL, and the donor is pulled in without any problem, he said.

A simple procedure

According to Dr. Tan, glide insertion is easier than the folding technique, in which the challenge is to unfold and manage the donor lenticule in the anterior chamber.

“Our technique is simple, with not too much of a learning curve at all. The donor lenticule slides in easily. You need to have coordination of both hands, one holding the donor graft and one holding the glide, but any phaco surgeon can do that,” he said.

Dr. Tan said he taught the technique to many surgeons, and most were able to understand it quickly and were successful from the first attempt.

Complicated cases should be avoided when learning the technique, and the best start is in eyes with fairly big chambers, he said.

“As a matter of fact, we have managed to do glide insertion routinely for every single case since we have abandoned the folding technique,” Dr. Tan said. “This includes vitrectomized eyes, eyes with [anterior chamber] IOLs present and regrafts. So far, we have found no contraindication.”

The technique, however, is still evolving. Because there is still some degree of endothelial damage produced by the insertion, Dr. Tan is working on a different, more specialized inserter, which he said will hopefully reduce endothelial cell loss further.

Quiet eyes

Adopting the new glide insertion technique has dramatically changed the appearance of the eyes in the first day after DSEK surgery, Dr. Tan said. The cornea was swollen with the conventional method, but the eyes appear quiet with glide insertion.

“We do not have, at this point, strong endothelial follow-up data, but this seems to be indicating that we are causing less endothelial damage,” he said.

Dr. Tan used the new glide insertion technique in 28 eyes, with a mean follow-up of 4 months, ranging from 1 to 16 months. The only case of graft failure, so far, was in one eye in which a 400 µm donor lenticule was implanted. Detachment occurred because the donor lenticule was too thick. Therefore, failure had little to do with the insertion technique, he said.

“All patients’ corneas are clear at this point in time. Visual results are reasonably good. Two-thirds of the eyes are 20/40 or better, and just under half of the eyes are 20/30 or better,” Dr. Tan said.

For more information:

• Donald T.H. Tan, MBBS, FRCRSG, FRCSE, FRCOphth, can be reached at the Singapore National Eye Center, 11 Third Hospital Ave., Singapore 168751; +65-6227-7255; fax: +65-6323-1903; e-mail: snecdt@pacific.net.sg.

• Michela Cimberle is an OSN Correspondent based in Treviso, Italy, who covers all aspects of ophthalmology. She focuses geographically on Europe.