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52 EW CORNEA May 2012 Donor characteristics not primary in graft survival by Rich Daly EyeWorld Contributing Editor U.S. have been endothelial kerato- plasty—primarily Descemet's strip- ping endothelial keratoplasty—procedures, which have become the standard of care for Fuchs' dystrophy and other cases of uncomplicated endothelial dys- function. "The cause of death does not matter for any of the grafts, as long as the cause and related problems are not excluded in general by the eye banks," said Dr. Price about other CDS analyses of donor age impacts on graft survival. The newest form of EK, De- An example of a corneal graft Source: Jonathan H. Lass, M.D. Research indicates limited impact from baseline factors of cell loss, but emerging surgical techniques are seen as more important T he search for factors affect- ing graft survival continues, with one study indicating effects from specific donor characteristics. But sur- geons caution these effects are small and do not apply to newer tech- niques. In published analyses of data from the Cornea Donor Study (CDS) Investigator Group it was found that following penetrating keratoplasty for endothelial dysfunction, larger donor grafts, younger donors, and female donors were associated with higher endothelial cell density over 5 years. The study, "Baseline Factors Related to Endothelial Cell Loss Following Penetrating Keratoplasty," was published in the November 2011 issue of the Archives of Ophthal- mology. It examined a subset of 567 CDS participants and found median endothelial cell loss at 5 years was 68% for grafts larger than 8-9 mm in diameter, 75% for grafts 7 mm to smaller than 8 mm in diameter, and 74% for grafts 8 mm in diameter. Additionally, grafts from female donors experienced a 67% cell loss compared with a 72% cell loss among grafts from male donors. No significant associations with cell loss were found from the method of tissue retrieval, donor cause of death, history of diabetes, and either time from death to preservation or to surgery. One of the study's authors, Alan Sugar, M.D., professor of ophthal- mology and visual sciences, Kellogg Eye Center, University of Michigan, Ann Arbor, warned that the effect it found was small. "We follow all graft patients closely, but the slightly higher cell loss risk in the situations docu- mented in the CDS does not trans- late into any evidence that closer follow-up or any specific post-op treatment has any utility," said Dr. Sugar. Efforts to minimize cell loss in such patients continue to be frus- trated by a poor understanding of the specific reasons for cell loss within the first 6 months and poor options for treatment other than for rejection, said Dr. Sugar. Another author of the study, Francis Price Jr., M.D., director, Price Vision Group, Indianapolis, and chairman, Cornea Research Foundation of America, Indianapo- lis, pointed out that the standard treatment for such patients has rap- idly evolved beyond the study's focus on penetrating keratoplasty. Specifically, for the last 3 years, over 40% of all corneal transplants in the scemet's membrane endothelial ker- atoplasty (DMEK), which involves just the transplantation of the en- dothelial cells and Descemet's mem- brane, has produced better results from older patients since thickness of the membrane increases with age. Similarly, David R. Hardten, M.D., director of research, Min- nesota Eye Consultants, Minneapo- lis, and adjunct associate professor of ophthalmology, University of Minnesota, Minneapolis, has moved from penetrating keratoplasty to endothelial keratoplasty as the pre- ferred technique in most patients. The main criteria, Drs. Hardten and Price agreed, is healthy endothe- lial cells, rather than gender, dia- betes, or age as a risk factor for poor performance of the corneal tissue. "Interestingly we have success- fully been using eyes from donors into their 70s and occasionally with a history of past cataract surgery if the cell count is adequate," said Dr. Price. Recipient health key Dr. Hardten has seen recipient char- acteristics as more likely to increase the risk for post-op endothelial cell loss, including patients who have pseudophakic or aphakic corneal edema with peripheral anterior synechiae, corneal neovasculariza- tion, glaucoma tube shunts, anterior chamber IOLs, or those with silicone oil in the eye. "I typically follow patients who have had prior transplant rejection, who have difficulty perceiving changes in their eyes, or [who have] other risk factors a little closer, depending on the clinical situation," said Dr. Hardten. Among recipient characteristics associated with loss of endothelial cell density, Dr. Sugar highlighted patients with pseudophakic bullous keratopathy, rather than those with Fuchs' dystrophy. Surgical modifications There are a few circumstances where surgeons modify their donor im- plant technique. For instance, Mark A. Terry, M.D., director, Corneal Services, Devers Eye Institute, Portland, Ore., and professor, clinical ophthalmol- ogy, Oregon Health & Science University, Portland, modifies his Descemet's stripping automated endothelial keratoplasty technique when an anterior chamber IOL is present. That modification includes constricting the pupil and closing all peripheral iridotomies before tissue insertion. That is followed by insert- ing the tissue eccentrically, unfold- ing it carefully, and leaving a larger-than-usual air bubble. In recipients with tubes and trabeculectomies, Dr. Terry avoids elevating the pressure too high and at the end of the case leaves the chamber filled with air, which is usually gone the next day. Dr. Terry uses only a DMEK in cases of Fuchs' dystrophy with a clear enough cornea to visualize the tissue easily. And he does not per- form a DMEK in eyes with anterior chamber IOLs, tubes, or aphakia. Treatment modifications used by Dr. Price include higher doses of topical corticosteroids for African American patients due to their greater risk for immunologic graft rejections. In eyes with tubes, Dr. Price trims the tubes to prevent them from contacting the cornea and sometimes repositions them to keep them away from the cornea. In patients with anterior cham- ber IOLs, Dr. Price typically replaces them with posterior chamber lenses through a pars plana vitrectomy, if vitreous is encountered. EW Editors' note: The doctors mentioned have no financial interests related to this article. Contact information Hardten: 612-813-3632, drhardten@mneye.com Price: 317-844-5530, francisprice@pricevisiongroup.net Sugar: asugar@umich.edu Terry: 503-413-6223, mterry@deverseye.org