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Surgical Techniques for Descemet Stripping Automated Endothelial Keratoplasty


Key Concepts

  • Endothelial keratoplasty allows for selective replacement of diseased corneal endothelium, restoring corneal clarity without full-thickness replacement of the entire cornea.

  • One of the most common forms of endothelial keratoplasty, Descemet stripping automated endothelial keratoplasty (DSAEK) involves preparation and insertion of a thin lamella of posterior stroma, Descemet membrane, and endothelium.

  • DSAEK donor insertion techniques have evolved from simple taco folding with forceps, to the use of donor insertion devices that may be broadly divided into “pull-through” or “inserter” devices mimicking intraocular lens insertion methods—these may enhance donor control and may lead to reduced endothelial cell loss.

  • Improved surgical techniques at all stages of DSAEK result in a reduction in iatrogenic primary graft failure and donor dislocation rates, lower postoperative endothelial cell counts, and potentially, enhanced graft survival rates.

  • Further developments in DSAEK techniques, such as the use of “ultrathin” and “nanothin” donors, and safer donor insertion have led to improved visual outcomes and possibly reduced allograft rejection rates.

Endothelial keratoplasty (EK) is a form of corneal transplantation in which selective replacement of diseased corneal endothelium is achieved. The donor corneal endothelium is transplanted on a carrier consisting of Descemet membrane (DM) and posterior corneal stroma, with the EK technique referred to as Descemet stripping automated endothelial keratoplasty (DSAEK). A variety of names and techniques have been used to describe this selective replacement of diseased corneal endothelium, described later in this book—but this chapter will primarily focus on surgical techniques of DSAEK.

The techniques of EK have evolved since Barraquer first proposed selective replacement of the corneal endothelium for treatment of corneal edema in 1950 using a technique referred to as “queratoplastia laminar posterior,” translated as posterior lamellar keratoplasty (PLK) using an anterior approach. The concept of PLK was reintroduced in laboratory and animal studies, ultimately leading to the first clinical report from Melles and colleagues in 1999 in which the anterior approach was abandoned for a posterior approach. Shortly thereafter, an explosion of variations in EK surgical techniques by various corneal surgeons ensued. Although the techniques of EK significantly contrast to those of penetrating keratoplasty (PK), the goals of EK and PK surgical technique are the same: removal of the corneal pathology, restoration of corneal clarity, improved visual acuity, and minimizing intraoperative and postoperative complications.

The most common form of DSAEK performed at the time involves a thin donor tissue prepared using an automated microkeratome and is referred to as DSAEK. The popularity of this technique was further enhanced by the development of donor preparation techniques at the tissue-processing stage in eye banks, in which eye bank technicians perform donor “precutting” and even “preloading” into DSAEK inserters, before delivering the donor tissue to surgeons.

Intraoperative Considerations

Although most DSAEK surgeries may be performed under local anesthesia, anesthetic choice also depends on case selection and the surgeons’ experience. First, the horizontal and vertical diameters of the eye should first be measured to determine the ideal EK graft diameter during donor tissue trephination. Because the posterior corneal surface is larger in diameter than the anterior corneal surface and more endothelial manipulation occurs with EK than with PK, EK donor buttons are typically larger than PK buttons, measuring 8.5–9 mm in diameter. EK donor buttons that are too large in diameter with extension into the angle can create peripheral iris synechiae and peripheral donor cell loss from iris-cornea touch. After successful donor trephination, a centration point may be determined on the recipient cornea followed by marking the epithelium with the desired corneal trephine blade size, matching the size chosen for the previous donor trephination. The epithelial mark can be made by gentian violet placement on the trephine blade or by simple indention of the epithelium with an unmarked trephine blade. This mark is a useful future reference point during the DM stripping.

Wound Creation

After the epithelium is marked, one to three paracentesis incisions are made as typical for cataract surgery, with either a metal 15-degree blade or 1-mm diamond blade. Paracentesis locations may vary depending on the intraoperative technique and insertion technique chosen. Marking the noncutting edge of the metal 15-degree blade prior to paracentesis creation can aid visualization of the opening later in the procedure. This step is particularly useful for corneas with severe edema or loose epithelium. Some surgeons prefer that the paracentesis remains as peripheral as possible to minimize graft touch or graft dislocation with insertion of a cannula or needle later in the procedure. Other surgeons prefer a slightly more anterior placement of the paracentesis, which affords coverage by the endothelial graft after it is in appropriate position, lowering the potential for wound leakage. At this point, either a cohesive viscoelastic or an anterior chamber (AC) maintainer is used to prevent AC collapse, although some surgeons avoid viscoelastic for the fear that retained viscoelastic may increase interface lubricity and increase risk of postoperative tissue dislocation. ,

After paracentesis placement and appropriate chamber formation, the main incision into the AC is typically created. The incision location can be superior or temporal or along the axis of astigmatism if astigmatism reduction is desired. Incision sizes and types vary among surgeons and may vary from 3 mm to 5 mm, depending on the method of donor insertion or type of inserter device used. Incisions may be scleral, limbal, or clear cornea in location. Advantages of scleral incisions include better intraoperative chamber stability, less risk of postoperative wound leaks, and less induced corneal astigmatism. Disadvantages include more time for conjunctival incision and hemostasis, and the potential for increased donor endothelial damage during donor insertion unless specific donor inserters are used. Advantages of clear cornea and limbal incisions include ease in preparation and closure, and the potential for less donor tissue damage. The main disadvantages of corneal and limbal incisions include greater induced astigmatism, and the need for a shorter tunnel compared with scleral tunnel incisions to avoid extension of the tunnel into the paracentral cornea. A shorter tunnel increases the risk for intraoperative chamber collapse or iris prolapse.

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