Eyeworld

EW CORNEA 42 June 2014 W hen it comes to graft success, donor age is not an issue; it is only a "number" in the majority of cases, new 10-year study results show, accord- ing to Jonathan H. Lass, MD, Charles I. Thomas professor, Case Western Reserve University Depart- ment of Ophthalmology and Visual Sciences, and University Hospitals Eye Institute, Cleveland, Ohio. The results published in the December 2013 issue of Ophthalmology indicate that most of the tissue that is offered is equivalent in graft success irre- spective of age, Dr. Lass said. "With approximately 75% of donors available in the United States ranging from age 34 to 71, they were equivalent in terms of graft success," Dr. Lass said. Tissue from donors in this age range resulted in a 10-year success rate of 75% for patients undergoing penetrating keratoplasty for an endothelial dysfunction condition including Fuchs' dystrophy and pseudophakic/aphakic corneal edema for the first time, he reported. Old school thinking These results are contrary to the pre- vailing thinking in the mid 1990s when the Cornea Donor Study (CDS) was first conceived. Back then there was a prejudice against using older tissue, Dr. Lass said. "We would attempt to match age—if someone was 40 then you would expect tissue from [a donor] 40 or below," he said. The study was conceived by Edward Holland, MD, and Mark Mannis, MD, and Dr. Lass later joined in the planning. "We wanted to see the range of tissue and the equivalence in terms of success of the transplant and what would happen to the endothelial cells after the transplant in terms of cell loss," Dr. Lass said. The randomized study, initiated in 2000 and funded by the National Eye Institute, included corneal tissue from 43 eye banks, with donors ranging in age from 12 to 75. The 1,090 recipients all underwent pene- trating keratoplasty. When donors were in the 34 to 71 age range, in- vestigators found that the 10-year success rate was relatively constant at 75%. "The transplants from (donors) 65 and below had a success rate of 77% in 10 years, and the ones above 65 had a 71% success rate," Dr. Lass said. The difference was not statisti- cally significant. This means that for the majority of donor tissues avail- able in the U.S., there was an equiva- lence in terms of graft success. However, some differences at the age extremes were noted. Tissues from donors in the 72 to 75 age range did not fare as well. "There was a cut point that established there was a clear difference over (age) 71," Dr. Lass said. For those in this age range, success decreased to 62%. Meanwhile, when tissue do- nated by those 33 years old and below was considered, a marked improvement was seen, with a 96% success rate. Dr. Lass theorized that the difference seen at the extremes is a function of cell resiliency changes with age. "Metabolically the older cells cannot withstand the stress of (donor) death, preservation, and the trauma of the surgery as well as these young cells," Dr. Lass said. New wisdom Despite the differences at the extremes, the study drives home the point that the majority of donor tissue is the same. "The take-home message is that most of the tissue that you're going to get offered is equivalent," he said. "If you had the uncommon situa- tion of a younger recipient with endothelial disease like Fuchs' dystrophy who needed a transplant, you would not consider a donor over age 72." Dr. Lass views the fact that there is equivalency in the majority of tis- sue as good news. The fact is, there is a scarcity of young donors: "The [percentage] of donors younger than 32 is less than 8%," he said. The Cornea Donor Study was conducted on PK patients. Nowa- days, however, this is no longer the prevailing surgery performed. Dr. Lass cited 2013 Eye Bank Association of America statistics that in 2008, domestic use of PK tissue was at 32,524 grafts but by 2013 had decreased to 20,954. Meanwhile, during this same period, domestic use of EK tissue had grown from 17,468 to 24,987 grafts. "Over the last 5 years PK has been virtually replaced by DSAEK for the management of endothelial dys- function conditions," he said. "We think that many of the principles regarding age will apply to the new surgeries, but we now have another study going on—the National Eye Institute-sponsored Cornea Preserva- tion Time Study (CPTS)." That study will consider whether corneas preserved beyond 8 days are as successful for Descemet's stripping endothelial keratoplasty (DSEK) as those preserved for less time. "Another major issue is that corneas can be stored up to 14 days at 4 degrees C, but the majority of surgeons are unwilling or have got- ten in the habit of not using tissue beyond 7 or 8 days," Dr. Lass said. "The eye bank may not be able to place that tissue and they're having to export it out of the country." While the main goal of this new study will be to consider how long corneas can be successfully stored, information on donor age will be available as well. "They're random- ized on the basis of preservation time, but we'll have all the informa- tion on donor age because the sur- geons are masked as to the age of the donor (when doing the proce- dure)," Dr. Lass said. Overall, Dr. Lass stressed the need to continue to study the donor pool so that there is an adequate amount of excellent quality donor tissue available to meet the needs of the aging Baby Boomer population. He also said that the donor pool is under continued threat from infec- tions such as West Nile virus as well as social history, with increasing drug addiction becoming a factor. "The question of the tissue suit- ability is always there," Dr. Lass said. "We're going to need maximum flexibility on the part of surgeons and patients in accepting tissue that we believe is suitable for the proce- dure and we'll be successful." In addition, while with PK the prejudice may have been against older tissue, the same may not hold true for newer procedures, he said. "With the latest endothelial keratoplasty procedure, Descemet's membrane endothelial keratoplasty (DMEK), being performed more fre- quently, there's an interest in using older tissue because the procedure is easier to accomplish when the en- dothelium/Descemet's complex is stiffer; that stiffness increases with age," Dr. Lass said, adding that the Cornea Donor Study was helpful in showing that the majority of older tissue ultimately fares well. EW Reference Writing Committee for the Cornea Donor Study Research Group, Mannis MJ, Holland EJ, Gal RL, Dontchev M, Kollman C, Raghinaru D, Dunn SP, Schultze RL, Verdier DD, Lass JH, Raber IM, Sugar J, Gorovoy MS, Sugar A, Stulting RD, Montoya MM, Penta JG, Benetz BA, Beck RW. The effect of donor age on pen- etrating keratoplasty for endothelial disease: graft survival after 10 years in the Cornea Donor Study. Ophthalmology. 2013 Dec: 120(12): 2419–27. Editors' note: Dr. Lass has no financial interests related to his comments. Contact information Lass: Jonathan.Lass@UHhospitals.org by Maxine Lipner EyeWorld Senior Contributing Writer In the maturing transplant zone Penetrating keratoplasty for Fuchs' dystrophy Source: Jonathan H. Lass, MD 42-44 Cornea_EW June 2014-DL_Layout 1 6/3/14 12:34 PM Page 42

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