The Hindu : Front Page : Age no bar for corneal donation

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Wednesday, Apr 02, 2008
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Age no bar for corneal donation

Study finds transplants with older corneas are good enough

Eye banks set age limit for donors at 65
There are some caveats, and studies continue

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. In most types of transplants, younger organs and tissue are more coveted.

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 is published on Tuesday in the scientific journal Ophthalmology.

“There was a bias against older tissue,” said Jonathan Lass of University Hospitals Case Medical Centre in Cleveland, one of the authors of the study. “This is going to change our view of that.”

The cornea is the clear covering for the front of the eye, important for helping it focus light. Enough corneas have been available so far for those seeking transplants in some countries like the U.S. But there are international shortages. More than 39,000 corneal transplants were performed last year in the U.S. alone, according to the Eye Bank Association of America.

Eye banks typically set the age limit for cornea donors at 65 or younger, although age is not the most important criterion. Donors must be in good health, free of various infections, and the corneas must contain enough of a particular cell type that is responsible for keeping it clear, not cloudy.

To see whether age mattered, the National Eye Institute funded the new work at 80 medical centres around the country. Researchers recruited about 1,000 people in their 60s and 70s who needed new corneas because of two conditions that destroyed their own — a swelling known as Fuch’s dystrophy and a complication of cataract surgery — that together account for almost half of corneal transplants.

Participants were divided into two groups, getting corneas either from donors ages 12 to 65 or from those 66 to 75. Researchers tracked how often the transplant failed, because the cornea was rejected or turned cloudy. Five years later, 86 per cent of both groups still had successful transplants.

Two caveats

There are two caveats. One is that the researchers only tested people 60 and older with conditions that put them at medium risk of transplant failure. But about 20 per cent of corneal transplants are in younger adults whose transplants seldom fail. The study does not address whether a 20-year-old would be all right with a 75-year-old cornea, just that the age did not matter to older patients.

Endothelial cells

Also, Dr. Lass led a closer look at the fate of those endothelial cells responsible for preventing corneas from turning cloudy. The average 30-year-old has about a million of those cells on his or her cornea, but the cells die at a rate of about half a percent a year, he said. For unknown reasons, transplanted corneas rapidly lose more than half their endothelial cells before the density plateaus.

Older transplanted corneas did lose slightly more endothelial cells than did those from younger donors, but the difference was not statistically significant — nor was there any difference in cloudiness, Dr. Lass said. Still, the researchers will continue to track these patients for five more years to see whether the cell loss eventually makes a practical difference. — AP

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