For the past 50 years, penetrating keratoplasty (PKP) has been the standard of care for patients with corneal endothelial failure. PKP can result in optically clear corneas, but the refractive results are poor. Visual recovery in patients can take between 6-24 months and many series report 50% of patients require contact lenses to achieve useful vision (Muraine et al, 2003, Ing et al, 1998, Tuft & Gregory 1995, Price et al, 1991). Patients with bilateral disease must, therefore, wait a long time for treatment in their second eye until problems in their first eye resolve. In the developing world, these problems are compounded as there is a high rate suture related complications and corneal transplant failure (Dandona et al, 1997). Late rupture of wounds is also a serious risk (Elder & Stack, 2004).
In 1998, Dutch ophthalmologist Gerrit Melles, MD described a technique in which the inside layers of the cornea were manually dissected and selectively replaced (Melles et al, 1998). In 2001, Mark Terry, MD described a modified technique in which the dissection was performed with viscoelastic and termed his technique deep lamellar endothelial keratoplasty, or DLEK (Terry & Ousley 2001). The manual dissection is tedious and involves a steep learning curve. Dr. Melles has since developed a technique that involves stripping of Descemet’s membrane instead of a lamellar dissection, which has been termed Descemet’s stripping endothelial keratoplasty, or DSEK (Melles et al, 2004).
Endothelial transplantation offers several advantages including less postoperative astigmatism, faster visual recovery, and stronger wound integrity (Terry & Ousley 2001). Theoretically, there is less risk of rejection since less of the patient’s tissue is replaced. Finally, there is the potential to make more efficient use of transplant tissue—using the endothelium for DLEK or DSEK in one patient and the stroma for a lamellar graft in another. It is useful in patients with varying types of endothelial dysfunction, including Fuchs dystrophy, Pseudophakic bullous keratopathy (PBK), Aphakic bullous keratopathy (ABK), and Posterior Polymorphous dystrophy (PPMD) (Melles et al, 1998, Terry & Ousley 2001).
The steps of DLEK are described in Table 1. Because DLEK involves dissection of a ledge of tissue on the inner aspect of the cornea, it provides mechanical support that results in less chance of postoperative lenticle dislocation. This allows successful surgery to be performed in apkakia and after glaucoma filtration surgery. In our experience, more advanced cases of endothelial failure with significant corneal edema and pachymetry over 700 microns, the lamellar dissection is much easier than early in the course of endothelial dysfunction.
The disadvantages of DLEK are the technical challenge of the procedure, the risk of perforation, and the need for special designed blades for dissection. Another source of frustration for surgeons is the haze that may form in the interface between the host and donor corneas. Fortunately, we have found that this haze does not correlate with reduced visual acuity and lessens over time (Pramanik et al, 2005).
We use DLEK in patients who cannot lie flat (i.e.-back problems), patients without a true anterior chamber (i.e.-aphakia), and those who have undergone previous glaucoma filtration surgery.
A video of this procedure can be found at:
The steps of DSEK are described in Table 2. DSEK has grown more rapidly in popularity because it is technically easier and faster than DLEK (Price & Price 2005). Our typical operative time for this transplant is 30-60 minutes. It results in a more optically pure interface and has excellent visual recovery.
The disadvantages are that the patient must lie flat for the air bubble to hold the transplant disc in place while the endothelium begins to pump. There is a risk of pupillary block glaucoma, which can be overcome by releasing half of the air from the anterior chamber one hour postoperatively and by dilating the pupil with 1% atropine at the end of the case. Early reports indicated early postoperative dislocation of the transplant disc in 10-15% of the cases (Price & Price, in press, Gorovoy & Price 2005). Modifications of the technique including the scraping of peripheral stroma and removal of fluid from the interface with external massage or stab incisions with a 15-degree blade have resulted in a dislocation rate around 1% (Gorovoy & Price 2005).
We use DSEK in patients with early endothelial failure where the view into the anterior chamber allows adequate visualization of our instruments. It is best in cases where the anatomy of the anterior chamber is good (i.e.-phakia, uncomplicated pseudophakia, and no previous filtration surgery). It is also useful in PKP patients with endothelial failure who had minimal astigmatism before they experienced graft failure.
Future endothelial transplant research will focus on making the procedure more reliable and less surgeon-dependent. Studies are underway to assess the ability of the eye banks to provide pre-cut tissue to reduce intraoperative time and make more effective use of donated corneas. Advances in techniques to minimize trauma to endothelial cells will improve the longevity of these surgeries. Finally, plans are underway to compare endothelial transplantation to penetrating keratoplasty in a prospective trial.
Pramanik S, Goins, KM, Sutphin JE: Corneal Endothelial Transplantation: Descemet's Stripping Endothelial Keratoplasty (DSEK). Eyerounds.org. February 23, 2006; Available from: http://www.EyeRounds.org/cases/54-Descemets-Stripping-Endothelial-Keratoplasty-DSEK.htm
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