Donor Age Not Factor in Corneal Transplant Success

By John Gever
CINCINNATI, April 1 -- Corneas from eyes up to 75 years old may be transplanted without sacrificing long-term success rates, researchers said in a finding that could swell the corneal donor pool by 20% to 35%.There was no significant difference (P=0.11) in the five-year transplant success rate in a large prospective study when donors were 66 to 75 as when they were younger, reported Edward J. Holland, M.D., of the University of Cincinnati, and colleagues in the April issue of Ophthalmology.Dr. Holland and colleagues found that 86% of transplants in both groups lasted five years (difference 0%, upper limit of one-sided 95% CI 4%).
The Cornea Donor Study, the investigators wrote, was predicated on the practice of many U.S. eye banks to arbitrarily set the upper age limit for donor eligibility at 65 or younger because some surgeons are reluctant to use corneas from older donors.
"This reluctance is not based on scientific evidence, as prior studies have not demonstrated that donor age is an important factor in determining transplant success if the quality of the donor cornea, including the endothelial cell density, is controlled for," the researchers wrote. But these studies may have been inadequately designed or were too small for definitive conclusions.
"The significance of this study is that we now have scientific evidence showing that older donors can be used reliably in corneal transplantation," said Dr. Holland in a telephone press briefing.
"We believe this will expand the donor pool available for many eye banks and persuade surgeons to use corneas from older donors," he said. He estimated that the number of donors could increase 20% to 35% as a result of the study.
According to Mark J. Mannis, M.D., of the University of California Davis, who co-chaired the study with Dr. Holland, there has been a myth -- held by many surgeons as well as patients -- that younger equals better when it comes to cornea donors.
He said he was satisfied that there is no increase in risk from older donor corneas.
The publication comes at a critical moment, the investigators wrote. Although donor corneas have not been in short supply, FDA regulations issued last year are expected to shrink the number of eligible donors by imposing stricter requirements for infectious disease screening, recordkeeping, and quarantining.
In addition, the exploding popularity of refractive surgery is cutting into the long-term supply of corneas. Corneas modified by such surgery are ineligible for full-thickness transplant, said Dr. Holland, who is chairman of the Eye Bank Association of America.
Janine A. Smith, M.D., of the National Eye Institute, which helped fund the study, said it was the largest of its kind and a landmark in understanding the effect of donor age on cornea transplantation.
The study involved 1,090 transplant recipients, who obtained corneas from 43 eye banks nationwide. Patients with Fuch's dystrophy, pseudophakic or aphakic corneal edema, or certain other causes were included. Patients with keratoconus were excluded.
In explaining the exclusion, Dr. Holland said the graft failure rate with keratoconus is much lower than for the other conditions. Finding a significant difference in failure rates in keratoconus patients would thus have required a much larger study, he said.
Corneas from donors 12 to 75 years old were screened according to each eye bank's current standards and then assigned randomly. To be eligible, corneas had to have endothelial cell densities of 2,300 to 3,300 cells/mm2. Transplant surgeons were unaware of the donor's age.
The researchers defined graft failure as corneal cloudiness lasting at least three months or undergoing a repeat transplant. They also classified graft failures into categories of primary failure, rejection, refractive, or miscellaneous causes.
In addition to finding no difference in overall five-year failure rates, there was not a significant relationship between donor age and graft survival when age was treated statistically as a continuous variable, the researchers said.
On the other hand, the researchers found an advantage for younger donors when the dichotomy point was set at age 40. The graft survival rate for donors up to 40 was 93% (95% CI 89% to 98%) versus 85% (95% CI 83% to 88%) for donors 41 and older.
There are about 33,000 corneal transplants are performed annually in the United States. Dr. Holland said that with corneas from donors up to 75 years old now proven to be suitable for transplant, attention could now turn to even older donors.
"In the future, [donors older than 75] may be another group we want to look at," he said.
The study was funded by the National Eye Institute, Eye Bank Association of America, Bausch & Lomb, Tissue Banks International, Vision Share, San Diego Eye Bank, The Cornea Society, Katena Products, ViroMed Laboratories, Midwest Eye-Banks (Michigan Eye-Bank, Illinois Eye-Bank), Konan Medical Corp., Eye Bank for Sight Restoration, SightLife, Sight Society of Northeastern New York (Lions Eye Bank of Albany), and Lions Eye Bank of Oregon.
Potential conflicts of interest were not disclosed.
Primary source: OphthalmologySource reference:Gal R, et al "The effect of donor age on corneal transplantation outcome results of the cornea donor study" Ophthalmology 2008; 115: 620-26.