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The success rate for cornea transplant patients has less to do with the age of the donor than it does the quality of the tissue, according to a study published recently in Ophthalmology magazine. The findings are encouraging news to Central Florida eye surgeons, who predict it will necessarily expand the donor pool following last year’s changes in federal regulations that require more rigorous screening and record-keeping procedures.

“This is a significant breakthrough,’’ said Dr. Lewis Groden about the Cornea Donor Study, a five-year, multi-centered examination of 1,100 patients. The study was funded by the National Eye Institute, which is one of the National Institutes of Health, and it was coordinated by the Jaeb Center for Health Research in Tampa.

The study showed that five years after receiving a transplant, the already favorable success rate of 86 percent was the same for a patient who received tissue from a donor younger than 65, as it was for a patient who received tissue from a donor aged 66 to 75. This is noteworthy because many retinal specialists have long believed that younger corneal tissue was superior to older tissue.

“Surgeons for many years have felt that younger is better,’’ said Groden, 56, who, in the past 27 years, has transplanted thousands of corneas, which is the part of the eye, with the lens, that refracts light to the retina. Groden explained each person is born with a certain number of corneal endothelial cells that naturally die off as the person ages. “Since a corneal transplant is, in effect, transplantation of those cells, the feeling has been ‘Let’s pick young corneas with lots of cells, and they will be better than older corneas with fewer cells.’ It stands to reason and it is what corneal surgeons have believed for many years,’’ Groden said.

“What this study was designed to answer was ‘Is that assumption true?’ And we know now it isn’t true,’’ he said. “Older donors do as well.’’

Even more important, Groden said, is that the “results of the study are being supported by real-world experience, which is not always the case.’’ Groden, in addition to being associate professor in the Department of Ophthalmology at the University of South Florida Medical School in Tampa, also is medical director of the Central Florida Lions Eye and Tissue Bank, which is the largest eye bank in the U.S., harvesting more than 4,000 tissue donations per year. “We don’t find, at the eye bank level, that the failure rate (of transplants) has been adversely affected by using older corneas,’’ he said.

That is primarily because all donor tissue is screened and an eye bank won’t release a cornea for transplant unless the standards are met, Groden said, and “That’s what this study showed: If the standard is met, age isn’t a factor.’’

But not all cornea specialists are as enthused by the study’s findings. Dr. Naazli Shaikh, is section chief of surgery at the Orlando Veterans Administration Medical Center. “I would classify this as important information, but it is just telling me that there’s no difference between a 65-year-old and a 75-year-old cornea. I have no objection to allowing (older) tissue into the donor pool, but in my practice I would limit the use of 75-year-old tissue to cases where you really have no other choice,’’ she said.

“I still prefer to give a younger cornea to an older patient because you cannot predict how long someone is going to live,’’ Shaikh said. “This was only a five-year study; it doesn’t mean anything because a good transplant can last up to 20 years and a bad transplant can fail at 6 years. We really won’t know anything until we give it a 10- or 15-year follow-up,’’ she said. “I have a feeling that down the line they are going to find a difference … We don’t have enough long-term (data) to reach a conclusion.’’

That information is forthcoming because the NEI has extended funding for the CDS study five more years.

Even though the number of cells in a donor cornea must meet a minimum standard, Shaikh remains concerned about the quality of cells in older corneas. “The number of cells doesn’t necessarily correlate to the quality,’’ she said. “You have to look at size and shape. When they’re all the same, that’s a good cornea.
But the more polymorphism (in older corneas) means it is not that good.’’

Newer transplant procedures like the DSEK (Descemet’s Stripping Endothelial Keratoplasty) make “the endothelial cell count even more important, said Shaikh, 35. “These are corneal transplants of just the endothelial cell layer – the inner layer – of the cornea. And when you handle the tissue during the transplant you lose quite a few of the cells. So, you want to start with the maximum number of cells of the best quality,’’ she said.

Still, Shaikh sees no downside to the Cornea Donor Study. “It’s good to add more people to the pool, as long as the standards are good,’’ she said. “Doctors will continue to select the best tissue from the batches they get, but that tissue will always be the younger donors.’’

Groden elaborated on that point. “No one is going to make a surgeon take anything. Surgeons are offered tissue with (the appropriate information) as to donor age, cell count, cause of death, time from death to preservation, et cetera. Then it’s up to the surgeon to accept it or not,’’ he said. “We surgeons are inherently pretty conservative. My sense is that while we now will use tissue that is older, we’ll look very hard at medical history to make sure our patients get good tissue.’’

But what this study hopefully will do, Groden said, “is educate surgeons as to the acceptability of (older) tissue.’’



July 2008

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