EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
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18 EW NEWS & OPINION February 2012 Tools and techniques rePlay online content Ultra-thin DSAEK by Massimo Busin, M.D. P osterior lamellar keratoplasty techniques have truly revolution- ized corneal transplantation. By avoiding a full thickness penetrat- ing keratoplasty, surgeons can offer their patients faster visual recovery and a stronger cornea that can resist the forces of ocular trauma. Deep lamellar endothelial keratoplasty (DLEK) has essentially been replaced with Descemet's membrane auto- mated endothelial keratoplasty (DSAEK). The next evolutionary step in posterior en- dothelial keratoplasty is regarded by many surgeons as the Descemet's membrane endothelial keratoplasty (DMEK) technique. DMEK offers the advantages of faster visual recovery, no hyperopic refractive shift, and little if any induced astigmatism due to the smaller insertion incision size. In addition, Gerrit Melles, M.D., and Frank Price Jr., M.D., have discovered a much lower im- mune rejection rate compared to penetrat- ing keratoplasty and DSAEK. There is still a debate as to whether thinner DSAEK grafts ultimately result in better final post-op visual acuities compared to thicker DSAEK grafts, but the trend among surgeons is to attempt to produce thinner grafts. The main disadvantage of DMEK, as stated in this article by Massimo Busin, M.D., Villa Igea, Forlí, Italy, is that it is tech- nically more challenging, takes longer to perform, and has the potential for greater tissue loss from harvesting the fragile Descemet's graft. In addition, not all patients with endothelial dysfunction are good candidates for DMEK. In this month's column, Dr. Busin describes his technique for producing ultra-thin posterior lamellar grafts for DSAEK. A debate of the advan- tages and disadvantages of ultra-thin DSAEK versus DMEK is inevitable for the future. For surgeons wishing to improve upon their DSAEK technique, but who are not ready to take the plunge into DMEK, ultra-thin DSAEK appears to offer a possible incremental improvement. I personally want to thank Dr. Busin for his work in this field. Richard Hoffman, M.D., Tools & techniques editor Watch this video on your smartphone or iPad using your QR code reader. (Scanner available for free at your app store.) Or view the video of Dr. Busin's procedure at www.eyeworld.org/replay.php. D escemet's stripping auto- mated endothelial kerato- plasty (DSAEK) fulfills the main requirements of the ideal keratoplasty proce- dure, as it is performed under "closed system" conditions and of- fers rapid visual rehabilitation and improved visual outcomes with a low risk of complications. Conse- quently, it has rapidly become the gold standard for surgical treatment of endothelial decompensation, and its indications are quickly broaden- ing to several conditions associated with endothelial decompensation (phakic or aphakic patients, eyes with glaucoma of various types, children, as well as extremely pronounced corneal edema). Three to 6 months post-op, vision of at least 20/40 can be achieved in a percentage of patients that is reported to vary between 38% and 100% (81% in a prospective study conducted at our institution), representing a decisive improvement over post-PK results published in the past.1-2 However, most surgeons agree that 20/20 or better post- DSAEK visual acuity is recorded much less often than expected and have considered the presence of a stromal interface responsible for this. The role of the stromal interface and graft thickness in outcomes In 2006, Gerrit Melles, M.D., the Netherlands, introduced Descemet's membrane endothelial keratoplasty (DMEK), a procedure that foresees the transplantation of only donor Descemet's membrane and endothe- lium, thus eliminating the presence of the stromal interface. However, even with this procedure, the per- centage of patients reported to see 20/20 or better does not exceed 40%, indicating that factors other than the stromal interface play a significant role in determining the final level of post-op visual acuity. In addition, there are a number of disadvantages to DMEK. It re- quires considerable surgical skills and prolonged surgical time, and unlike DSAEK, it is not suitable for all eyes, such as those with a shallow or poorly visualized anterior cham- ber, or those with communication between anterior chamber and vitre- ous cavity, through which the donor Figure 2. Modified Busin glide with side platform allowing scooping of UT-DSAEK graft Source: Massimo Busin, M.D. endothelium may easily dislocate posteriorly. Finally, a high rate of tis- sue loss (up to 16% in some reports) with DMEK, an unacceptably high detachment rate (up to 63%), and a relatively high failure rate (up to 8%), have discouraged most sur- geons from adopting this procedure in their clinical practice. Recent evidence has shown that DSAEK grafts thinner than 131 mi- crometers allow 20/20 post-op vision in a number of patients much larger than thicker grafts do.3 However, to date neither surgeons nor eye banks have addressed the issue of final DSAEK graft thickness when prepar- ing tissue to be transplanted, and no standardized method has been de- veloped to consistently obtain donor tissue of a particular thickness. For this reason, until recently, it was also impossible to prospectively evaluate a possible correlation between DSAEK graft thickness and visual outcomes. A procedure to obtain reproducible results In 2009, at the annual meeting of the Cornea Society in San Francisco, I presented a new approach to DSAEK surgery aimed at utilizing what I named "ultra-thin" (UT) DSAEK grafts. In this procedure, the surgical technique differs substan- tially from conventional DSAEK, both in the preparation and in the manipulation and delivery of the graft. In fact, the UT graft is created with two microkeratome passes, the first one to debulk the donor tissue and the second one to cut down the final thickness to about 100 mi- crometers. This is an easy-to-perform and widely applicable procedure to obtain reproducible results with the Figure 1. Anterior OCT image of a donor cornea after preparation for UT-DSAEK. The white arrows indicate the site of the first cut, the yellow arrows the site of the second pass