DSAEK allograft delivery system enables fold-free, small-incision technique

The device overcomes challenges associated with forceps use and folding donor tissue.

Thomas John

Corneal transplantation has rapidly moved from the traditional full-thickness penetrating keratoplasty to what is now known as selective tissue corneal transplantation. This process has eliminated the corneal wound and corneal sutures found in posterior lamellar keratoplasty procedures.

However, in anterior lamellar keratoplasty procedures, the corneal wound is retained but reduced, from full thickness in PK to partial thickness in anterior lamellar keratoplasty, with retention of sutures for the most part, except in superficial anterior lamellar keratoplasty procedures.

Retaining the patient’s corneal stroma and epithelium in posterior lamellar keratoplasty and retaining the healthy endothelium in deep and total anterior lamellar keratoplasty procedures have their advantages for the patient. Although the interest in posterior lamellar keratoplasty commenced with the more difficult deep lamellar endothelial keratoplasty, it quickly became popular in its simplified form, namely, Descemet’s stripping automated endothelial keratoplasty (DSAEK). The forward movement of progress has taken us to Descemet’s membrane endothelial keratoplasty (DMEK), but due to several technical hurdles with DMEK, DSAEK seems to be the most popular current technique for endothelial replacement.

The donor corneal disc delivery into the recipient anterior chamber through a small entry wound has been challenging, and various techniques have evolved, but no single method has been proven to be superior to other techniques or has been universally accepted.

In this column, Dr. Walter describes the use of an allograft delivery system called the Endosaver (Ocular Systems), which is pending U.S. Food and Drug Administration 510(k) clearance.

– Thomas John, MD
OSN Surgical Maneuvers Editor

A variety of surgical approaches for DSAEK donor graft insertion have been described. These include utilizing large scleral tunnel incisions without donor folding — often using glide devices, sutures and injector devices — or a bi-fold or tri-fold technique through a 3- to 5-mm incision. One of the most challenging steps of small-incision DSAEK is implantation and unfolding of the donor lenticule. A variety of techniques have been described, including fixation sutures, a fixation cannula, and other devices to anchor the graft and facilitate unfolding.

There is significant debate in the ophthalmic literature regarding the DSAEK insertion technique that best preserves donor endothelium. Some report better results with forceps or sutures, and others caution against any folding of the donor disc. Balancing the attractiveness of small-incision DSAEK with the concern for endothelial injury from donor folding and forceps compression, we have developed a novel DSAEK injector device, the Endosaver, which enables fold- and forceps-free tissue insertion through a 4-mm clear corneal incision.

Surgical technique

After a lid speculum is placed, paracentesis wounds are created at the 3- and 9-o’clock positions using a guarded diamond knife. Healon (sodium hyaluronate, Abbott Medical Optics) is injected into the anterior chamber. A superior 4-mm clear corneal incision is then created, and a 90° Moria stripper is used to perform a descemetorhexis. A disposable Sharpoint trephine (Angiotech Pharmaceuticals) is used to prepare the donor lenticule. The Endosaver is then connected to an irrigation tubing and flushed with sterile balanced salt solution.

Figures A-F. Loading the device, graft insertion and unrolling. Image: Walter K

Excess fluid is removed from the carrier platform of the Endosaver using a sterile sponge. A 7- to 8.5-mm donor corneal graft is then placed on the graft carrier with the stromal side down (Figure A) under the operating microscope. Sodium hyaluronate is placed on the endothelial surface of the donor disc. The thumbscrew dial on the Endosaver is rotated to retract the carrier along with the allograft into the insertion sheath (Figure B). While the carrier is retracted, it curves inward so that the donor graft is rolled stromal side out, with the opposite edges of the graft touching when fully retracted (Figure C).

The Endosaver device is rolled 180° so that the donor graft will deploy endothelial side down within the recipient anterior chamber. The sheath is introduced into the incision while simultaneously starting irrigation to stabilize and deepen the anterior chamber (Figure D). The tip of the sheath is advanced to the far edge of the descemetorhexis. The graft remains in the anterior chamber as the sheath is retracted. As the graft is uncovered, it unrolls fully within the anterior chamber (Figures E and F).

Filtered air is then injected to tamponade the graft against the host stromal bed, and high pressure is maintained for a total duration of 10 minutes. If necessary, a Lindstrom LASIK roller is used to massage any fluid out of the donor-recipient interface. After 10 minutes, the air bubble is reduced to approximately 40% by filling the anterior chamber with sterile balanced salt solution and allowing some of the air to escape from the recipient anterior chamber.

The wounds are checked to be watertight, and patients are instructed to lie flat for 1 hour in the recovery room. Occasionally, a 10-0 nylon suture is needed at the clear corneal incision to make it watertight. At 1 hour, patients are examined sitting up to ensure there is no evidence of donor corneal disc detachment or pupillary block. Patients are instructed to lie flat as much as possible until the next day.

References:

• John T, ed. Corneal Endothelial Transplant: DSAEK, DMEK, & DLEK. Panama, Republic of Panama: Jaypee-Highlights Medical Publishers; 2010.
• John T. Selective tissue corneal transplantation: a great step forward in global visual restoration. Expert Rev Ophthalmol. 2006;1:5-7.
• John T, ed. Lamellar Corneal Surgery. New York, NY: McGraw-Hill Companies; 2008.
• Melles GR, Wijdh RH, Nieuwendaal CP. A technique to excise the Descemet’s membrane from a recipient cornea (descemetorhexis). Cornea. 2004;23(3):286-288.
• Price FW Jr, Price MO. Descemet’s stripping with endothelial keratoplasty in 200 eyes: early challenges and techniques to enhance donor adherence. J Cataract Refract Surg. 2006;32(3):411-418.
• Terry MA, Saad HA, Shamie N. Endothelial keratoplasty: the influence of insertion techniques and incision size on donor endothelial survival. Cornea. 2009;28(1):24-31.

• Thomas John, MD, is a clinical associate professor at Loyola University Chicago and is in private practice in Tinley Park and Oak Lawn, Ill. He can be reached at 708-429-2223; fax: 708-429-2226; e-mail: tjcornea@gmail.com.
• Keith Walter, MD, can be reached at kwalter@wfubmc.edu.