Because of the potential for better vision with thinner EKs, is the continued effort to overcome the tissue and endothelial cell loss associated with DMEK still warranted?

DMEK offers the best visual outcomes and lowest graft rejection risk

Marianne O. Price

Yes. Fortunately, it is possible to have one’s cake and eat it too. DMEK provides the thinnest possible EK, and DMEK techniques have already evolved to match the low rate of tissue loss (less than 1%) and moderate endothelial cell loss seen with standard DSAEK. In fact, the attempt to obtain thinner and thinner grafts has recently led to some increased DSAEK tissue loss, because microkeratome cuts are inherently variable.

DMEK provides patients with the best possible vision because it eliminates the stromal interface as well as posterior corneal surface higher-order aberrations that can degrade visual clarity with DSAEK. Residual stroma increases higher-order aberrations two ways. First, DSAEK grafts rarely, if ever, have a perfectly uniform thickness. Furthermore, folds can develop in the donor tissue as it conforms to the recipient cornea, because the curvatures rarely match perfectly. The thicker the graft, the more such folds degrade vision.

DMEK also dramatically reduces the risk of immunologic graft rejection by completely eliminating stroma, which recent studies suggest is more antigenic than endothelium.

Overall, DMEK is the best option for patients, because it provides the best possible vision, lowest risk of graft rejection and best prognosis for long-term graft survival.

Marianne O. Price, PhD, is executive director of the Cornea Research Foundation of America, Indianapolis. Disclosure: Dr. Price has no relevant financial disclosures.

Reference:

• Anshu A, Price MO, Price FW. Risk of corneal transplant rejection significantly reduced with Descemet’s membrane endothelial keratoplasty [published online ahead of print Jan. 2, 2012]. Ophthalmology. doi:10.1016/j.ophtha.2011.09.019.

DSEK with thin EK is currently the most consistent, reliable technique

Edward J. Holland

Until DMEK is further refined, DSEK is currently the most reliable EK method. Visual acuity with the standard DSEK procedure was quite good but often did not achieve the 20/25 or 20/20 level. The thought was that the stromal tissue accompanying the transplanted Descemet’s membrane and endothelium reduced visual acuity. Efforts to improve the visual outcomes of EK led to the development of DMEK. Visual outcomes with DMEK have been excellent, but the technique has significant drawbacks. The tissue harvesting with DMEK is much more challenging and leads to a higher rate of lost corneas. In addition, the tissue is much more difficult to handle with possibly more long-term endothelial cell loss. Attachment rates have been reported to be significantly lower with the DMEK procedure, requiring a higher rate of re-bubbling and potential additional cell loss.

Over the last few years we observed that our DSEK patients with thinner donor tissue had better visual outcomes than our patients with thicker tissue. A retrospective study on our DSEK patients confirmed this observation. We have since been striving for thin DSEK tissue in the range of 80 µm to 100 µm. With this “thin EK” technique, coupled with new insertion devices such as the EndoSerter (Ocular Systems), we have achieved an even higher rate of visual outcomes in the 20/20 to 20/25 level while still retaining the advantages of traditional DSEK: ease in tissue handling, excellent attachment rates and less endothelial trauma. Graft rejection rates are very low with all endothelial keratoplasty techniques.

Theoretically, DMEK should give the best visual outcomes of all the EK procedures. We should continue to strive for an improvement in DMEK techniques to better our outcomes. However, until DMEK achieves this success, I encourage surgeons to evaluate thinner DSEK tissue as I believe at present this is the most consistently reliable method to achieve the best visual outcome. Ultimately, future studies comparing endothelial cell loss and visual outcomes will give us the answer as to what is the safest and most effective procedure for endothelial transplantation.

Edward J. Holland, MD, is an OSN Cornea/External Disease Board Member. Disclosure: Dr. Holland has no relevant financial disclosures.

Reference:

• Neff KD, Biber JM, Holland EJ. Comparison of central corneal graft thickness to visual acuity outcomes in endothelial keratoplasty. Cornea. 2011;30(4):388-391.