Descemet’s stripping technique state-of-the-art in corneal surgery

In this report from the OSN Section Editor Summit, Kenneth R. Kenyon, MD, discusses the recent evolution of transplantation techniques gaining increasing application and acceptance.

Issue: November 1, 2007

ByKenneth R. Kenyon, MD

A note from the editors:

Ocular Surgery News convened its annual Section Editors Summit earlier this year. In this installment from the summit, OSN Cornea/External Disease Section Editor Kenneth R. Kenyon, MD, discussed the recent improvements in corneal transplantation procedures.

Historically, penetrating keratoplasty was the first surgical approach devised for corneal grafting, and then as endothelial rejection and corneal preservation problems needed to be solved, lamellar keratoplasty was created. But because of the limited visual outcomes in these initial lamellar keratoplasty (LK) cases, penetrating keratoplasty (PK) essentially became the transplantation procedure of choice for the past 50 years. Thus it has only been within the current decade that the paradigm shift back to anterior and posterior lamellar keratoplasty (PLK) has afforded a truly extraordinary advance.

I believe Gerrit Melles, MD, PhD, must be credited with the insights facilitating development of the posterior lamellar keratoplasty (PLK) technique and the use of air bubbles to promote attachment of the corneal disc. On the American scene, Mark A. Terry, MD, Thomas John, MD, Francis J. Price Jr., MD, and others have devised deep lamellar endothelial keratoplasty (DLEK) and rapidly advanced to what is now termed Descemet’s stripping endothelial keratoplasty (DSEK).

The basic principle here might be termed: “Where’s the beef?” In a cornea afflicted predominantly with endothelial dystrophy or degeneration, the notion of discarding the surface and stromal tissues that remain viable may be unnecessary. Simply put, if the endothelium alone is bad, then replace it while retaining the rest. So on this theme, let us review the current status of DSEK and Descemet’s stripping automated endothelial keratoplasty (DSAEK).

Sutureless keratoplasty

Basically, the technique involves creating a corneoscleral incision adjacent to the temporal limbus, stripping diseased endothelium and Descemet’s, and then applying a thin lenticule of posterior stroma and endothelium added to the back surface of the recipient. Remarkably, this lozenge of stroma and endothelium adheres without sutures, simply based on the principle that the endothelial pump will cause this tissue layer to adhere spontaneously to the posterior stromal surface. Thus, as with phacoemulsification, we have now entered the age of sutureless corneal transplantation. Moreover, the real afficionados can perform the procedure under topical anesthesia in 15 minutes flat.

Of course, as with phaco, the required instrumentation is considerably more high-tech than the “drill and fill” trephination approaches that we have traditionally used. First, there is the application of an artificial anterior chamber, in conjunction with a modified microkeratome (both by Moria) to excise an anterior corneal cap of about 350 µm in thickness from the usual preserved donor cornea preparation, thereby leaving about 150 µm of posterior stroma and endothelium. This thinned posterior corneal tissue is then placed endothelial side up in a standard punch device, and the typical 8-mm disc of tissue is simply excised in the usual fashion and prepared for insertion.

Through the corneoscleral incision, the stripping of Descemet’s membrane almost in an inverted capsulorrhexis fashion by manual dissectors typically resembling a reversed Sinskey hook appears elegant in its apparent simplicity. Once the central disc of the recipient’s Descemet’s has been removed, the previously prepared donor stromal-endothelial disc is folded, taco-like, with viscoelastic protection and inserted with special folding forceps that do not substantially damage the endothelium. The “taco” is then carefully unfolded and manipulated into its corresponding position.

A big air bubble fills the anterior chamber to tamponade the disc to the posterior corneal surface, or as Dr. John describes it, like sticking a pizza on the ceiling.

Adaptation and complications

The technique requires some mastery of the required skill set, and, in particular, it is necessary to adapt to the paradigm shift of working on the “ceiling” rather than on the “floor.” Most delicate perhaps is manipulating the donor disc into position and utilizing the air bubble to faciliate adhesion. The procedure raises its own set of problems, most commonly intraoperative difficulty in attaining donor disc adhesion and/or postoperative “slipped disc” requiring repositioning. Fortunately, numerous courses, publications and texts afford excellent teaching and management guidance.

Most importantly other complications of conventional PK are avoided, notably all the wound- and suture- related problems as well as big astigmatic shifts and refractive surprises, all related to unpredictable irregularity of the corneal surface contour.

These procedures have now evolved to be within the established realm of the corneal surgeon’s armamentarium. With some additional slights of manual dexterity, the basic DSAEK technique is also adaptable for combination with simultaneous cataract and IOL, IOL exchange and limited anterior segment reconstruction. Now ongoing for more than 5 years, with increasing numbers of surgical converts and cases performed, PLK is recognized as an established keratoplasty procedure. Indeed, many eye banks now even offer pre-cut corneal donor tissue to obviate the need for investment in the artificial anterior chamber and microkeratome, thereby further simplifying and accelerating the procedure.

Postop recovery, costs

Most remarkable is the rapidity and stability of the postoperative visual and anatomical recovery, as PLK-operated eyes recover vision within days to weeks and are structurally stable within a month or 2. For those of us accustomed to the postoperative struggles of traditional keratoplasty with the “suture roulette” of selective suture removals and adjustments ongoing for months, only to struggle anew with unpredictable refractive shifts after sutures are subsequently removed, sutureless PRK is simply miraculous.

On the down side, we as corneal surgeons have to adjust to this initially awkward surgical paradigm of “working on the ceiling.” Then, there is the additional expense of instrumentation, about a $30,000 ticket that needs to be absorbed by your surgical center. Or, alternatively, as previously mentioned, using pre-cut PLK donor discs adds a significant up-charge on the order of $500 for an already costly donor, which is typically a pass-through insurance expense. Yet the offsetting savings of both OR surgical time and postop management time for the surgeon, plus decreased morbidity for the patients, are seemingly more than compensatory.

Indications and results

Clearly, the indications for PLK techniques are limited to endothelial disease or dystrophy, so cases of stromal scarring, keratoconus and the other 50% or so of corneal transplants need to be cared for with either conventional PK or with anterior lamellar procedures that also continue to evolve. Given the improved and accelerated visual outcomes of PLK, many corneal surgeons are more confident to recommend surgery to appropriate patients at an earlier stage of their condition, rather than delaying until visual function and corneal comfort are compromised to the extent traditionally warranted for PK.

Apart from the still somewhat common operative and intraoperative problems, such as the slipped disc, the eventual effects of endothelial cell attrition related to increased operative manipulation of the donor tissue must be ascertained by long-term follow-up.

Some surgeons seem to believe there is a reduced incidence of graft rejection problems. Long-term comparative studies are clearly needed to address this important issue.

For more information:

Kenneth R. Kenyon, MD, can be reached at Eye Health Vision Centers, 51 State Road, North Dartmouth, MA 02747, or Cornea Consultants International, Tal 13, 80331, Munich, Germany; 508-994-1400; fax: 508-992-7701; e-mail: kenrkenyon@cs.com.