By Andrew M. Seaman
NEW YORK (Reuters Health) - Despite concerns that corneas from older donors might not last, a new U.S. government study finds transplant success up to 10 years later is not significantly affected by donor age.
About 75 percent of corneal transplants from donors between ages 34 and 71 were successful after 10 years. The findings may lead to more donor tissue becoming available both for transplants in the U.S. and export of corneas to other countries, according to the study's lead author.
"By expanding the range of donor tissue, we'll be able to provide more donor tissue for the vast majority of the world," Dr. Mark Mannis said. He is chair of ophthalmology and vision science at the University of California, Davis.
"Over the past several decades, corneal transplantation - which is a restorative operation - has become more successful and common," he said. "The problem is that corneal blindness worldwide far outstrips the availability of corneal transplant tissue."
There were about 46,000 corneal transplants performed in the U.S. in 2012, according to Mannis and his colleagues in the journal Ophthalmology.
The cornea is the eye's outermost layer. It helps protect the eye from germs and dust and is also partly responsible for focus and the entry of light.
Corneal tissue for transplantation comes from deceased donors and tissue from donors younger than 31 years old made up less than 10 percent of the donor pool last year, the researchers note in their report.
Previously, Mannis told Reuters Health, some surgeons would only accept corneal tissue from donors younger than 65, or in some cases, 50.
"The purpose of this study is to determine if the success of corneal transplant is in any way related to the age of the donor," Mannis said.
For the study, the researchers recruited 1,090 people ranging in age from 40 to 80 years old to receive donor corneas. The people were recruited from 80 U.S. medical centers and needed transplants for endothelial disorders, which result in the loss of cells from the central portion of the cornea.
In a previous study published in 2008, the researchers found the success rate of corneal transplants was 86 percent regardless of donor age five years after the surgery. They noticed, however, that corneas from older people had more cell loss, which was tied to a higher likelihood that the transplant would fail.
For the new study, the researchers continued to track 663 transplant recipients for another five years.
They found that corneas donated by people 12 through 65 years old were about as successful as those donated by people 66 through 75 years old - between 71 percent and 77 percent were still viable 10 years after transplantation.
When the study team looked at transplant success by narrower donor age groups, however, they did find some differences.
For example, the success rate after 10 years increased to 96 percent for corneas donated by people between ages 12 and 33 years old, and fell to about 62 percent for donor corneas from people between 72 and 75 years old.
But the success rate of donations from people between ages 34 and 71 was consistently about 75 percent.
Mannis said the results will help reassure corneal tissue recipients they're getting good tissue, encourage surgeons to use tissue from older donors and increase the number donors.
He cautioned, however, that the results pertain to people with endothelial disorders of moderate severity.
"It's not entirely generalizable to people with all kinds of corneal disease," he said.
In a separate analysis, the researchers confirmed that corneas from younger donors lose fewer cells after transplantation, though they still can't say whether a certain amount of cell loss can predict a transplant failure.
Mannis said the study is completed but analysis of the data is continuing.
"We're going to look at this data and see what other things we can learn," he said.
SOURCE: http://bit.ly/1il615S and http://bit.ly/1il68hO Ophthalmology, online November 15, 2013.