WASHINGTON - Older corneas seem to transplant as well as younger ones, says a major new study that promises to expand the age of cornea donation to 75.
It may sound surprising. After all, when it comes to most types of transplants, younger organs and tissue are more coveted -- and there has been controversy among corneal surgeons about using older eye tissue, too.
But government-funded researchers randomly assigned cornea recipients to get either younger or older tissue and found the corneas of both groups survived just as well five years later. The study was published Tuesday in the journal Ophthalmology.
"We now have scientific evidence showing that older donors can be used reliably in corneal transplantation," said Dr. Edward Holland of the University of Cincinnati and one of the study's lead researchers.
The cornea is the clear covering for the front of the eye, crucial for helping it focus light. More than 39,000 corneal transplants were performed last year, according to the Eye Bank Association of America.
The nation has had an adequate supply so far. But specialists say there are international shortages, and eye banks fear U.S. supplies will tighten as a result of tougher Food and Drug Administration donor-safety rules that began last summer, increasing interest in older donors.
Transplant surgeons decide how old a cornea they'll accept. Some surgeons, Holland included, have worked with eye banks that accept corneas from donors older than 65. Others banks set younger limits, although age isn't the most important factor. Donors must be in good health, free of various infections -- and the corneas must contain enough of a particular cell type, endothelial cells that balance fluid to keep the cornea clear, not cloudy.
To see whether age mattered, the National Eye Institute funded the new work at 80 medical centers. Researchers recruited about 1,000 people who needed new corneas because of two conditions -- a swelling known as Fuch's dystrophy and a complication of cataract surgery -- that together account for almost half of corneal transplants. Most were in their 60s and 70s, although 12 percent were in their 50s and 3 percent in their 40s.
Participants were divided into two groups, getting corneas either from donors ages 12 to 65 or from those 66 to 75. Then researchers tracked how often the transplant failed, because the cornea was rejected or turned cloudy. Five years later, 86 percent of both groups still had successful transplants.
"There was a bias against older tissue," said co-author Dr. Jonathan Lass of University Hospitals Case Medical Center in Cleveland. "This is going to change our view of that."
There are two caveats:
- The study focused on older adults with conditions that put them at medium risk of transplant failure. But about 20 percent of corneal transplants are in younger adults with lower-risk conditions whose transplants seldom fail. The study doesn't address whether a 20-year-old would be OK with a 75-year-old cornea.
Holland, however, contended the study results should apply to all ages.
- Also, Lass led a closer look at the fate of those endothelial cells that keep corneas clear. Those cells normally die slowly with age, at a rate of about half a percent a year during adulthood, he said. For unknown reasons, transplanted corneas rapidly lose many of those cells in the first year before the rate of loss slows again.
Using a special camera to count the cells, Lass found that older transplanted corneas did lose slightly more endothelial cells -- 75 percent loss in older corneas over five years and 69 percent loss in younger ones. The difference wasn't statistically significant, nor was there any difference in cloudiness between the two groups, Lass stressed. Still, the researchers will track patients for five more years to watch for late differences.
