Traditionally, graft oedema due to endothelial failure has been treated by full thickness penetrating keratoplasty. While this procedure usually results in a clear cornea with improved vision, there are a number of disadvantages to this approach. Visual recovery is slow, taking up to 1 or 2 years to stabilize, large amounts of induced astigmatism are usual, and the full thickness wound is never as strong as virgin cornea. Graft sutures can loosen and break with the attendant risk of infection or vascularisation. Most patients requiring this surgery are elderly, and these issues, particularly the slow recovery, are a major disadvantage for them.
In recent years techniques for non-penetrating endothelial transplantation have been developed, where only a thin button consisting of posterior stroma, Descemet's membrane (DM) and endothelium is transplanted. These techniques appear to remove many of the disadvantages of full thickness grafting, in particular slow visual recovery, induced astigmatism and poor wound strength. These procedures were pioneered by Gerrit Melles in the Netherlands, whose technique involved a manual dissection of the donor button and manual dissection of a posterior pocket in the host cornea. While results are excellent, this technique is difficult and tedious to perform.
A new technique has been developed which uses an artificial anterior chamber and LASIK-type keratome to cut the donor button. This is variously known as DSEK or DSAEK (Descemet's Stripping Automated Endothelial Keratoplasty) and is simpler and faster to perform than manual dissection.
To harvest the donor button, a full thickness donor corneascleral button is placed in an artificial anterior chamber manufactured by Moria Surgical. An approximately 10mm diameter and 350 micron thick free cap is cut from the anterior corneal surface using an automated keratome - much like a large LASIK free flap without the hinge. An 8.5mm donor button is then trephined from the remaining cornea, consisting of approximately 150 to 200 microns of posterior stroma, DM and endothelium. The host cornea is prepared by scoring an 8mm circle in DM, after which an 8mm diameter piece of DM and endothelium is scraped off the back of the cornea and removed from the eye through a 5mm scleral tunnel incision. A few drops of viscoelastic are placed on the endothelial surface of the donor button and the button is folded in half and inserted into the eye through the tunnel incision, where it will unfold. The donor button is floated up against the bare posterior surface of the host cornea using an air bubble, and allowed to adhere.
The first Australasian case of DSAEK was performed by Dr. Andrew Logan of the Wellington Eye Centre in April of this year. The patient was a 77 year old woman who had had routine phacoemulsification performed 3 years earlier but had subsequently developed endothelial failure and corneal oedema. Prior to DSAEK her best corrected vision was <6/120. Surgery was uneventful and one week after surgery her visual acuity was 6/9 with +.5/-1x90. Prior to her corneal failure her refraction was -1/-1x90. Her subsequent course has been uneventful with no change in acuity or refraction.
DSAEK is a very promising technique for treatment of corneal oedema due to endothelial failure, and avoids many of the problems associated with traditional penetrating keratoplasty.
Slit view at one week post-op: Black arrow indicates posterior surface of graft, white arrow indicates graft/host interface.
Front view one week post-op: Arrows indicate edge of donor tissue.