Case Western Reserve University and its research partners have completed a first-ever study that bolsters findings of a national study confirming the viability of older corneas for transplant.
The unique five-year Specular Microscopy Ancillary Study (SMAS) conducted by the Case Western Reserve School of Medicine and Case Medical Center, a partnership between the School of Medicine and University Hospitals, and carried out in Cleveland analyzed 347 patient images from 80 sites across the United States. The images were of patients who had not experienced graft failure after corneal transplantation.
The results were analyzed at the Specular Microscopy Reading Center (SMRC) located at Case Western Reserve that uses specialized microscope and techniques to count cells. The Cleveland study, which complements the recent news of the NIH/NEI decade-long Cornea Donor Study (CDS), measured a key layer of cells (endothelial cells) in the back of the cornea responsible for keeping the cornea clear by drawing out water.
SMRC also was the central reading center involved in the national CDS that followed recipients of cornea transplants.
Jonathan Lass, medical director of the reading center, as well as professor and chair of the Department of Ophthalmology and Visual Sciences at Case Western Reserve and his team found a trend; both groups experienced similar loss of cells over 5 years as was previously observed in other studies, however this was the first time to definitively show this trend. The pivotal study was designed to check not only the clarity of the cornea transplant but also the number of corneal endothelial cells lost at measured periods of time following transplantation. The study analyzed the number of cells at six-months post transplant, then again at one year intervals for the next five years determined by analyzing pictures of these cells taken from an instrument called a specular microscope.
"If the number of cells falls below a certain range, the cornea swells and the patient may need another corneal transplant," said Lass, who led SMAS. "This measurement becomes a significant indicator of the long-term success of the cornea transplant," he said. "The question we tried to answer was if more endothelial cells were lost in corneas from older donors, over the age of 66, compared with younger donors".
Lass and his team found only a slight association between the age of transplanted corneas and their cell loss over a five-year period. They found that although the older donor corneas (from 66 to 75 years of age) lost somewhat more cells than the younger donors (12 to 65 years of age), the five-year transplant success rate for recipients was the same—86 percent.
However, the difference is enough for the NEI to extend the Cleveland study for another five years to confirm that transplant success does not differ between the two age groups.
As a result of the SMAS and CDS findings, the donor age pool—currently limited to donors 65 and younger—may be expanded by as much as 20 to 35 percent to include donors up to 75 years of age. "Besides expanding the donor cornea pool, the scheduling of transplant procedures could become easier for both surgeons and patients, since there will be more corneas readily available," Lass added.
The availability of donor corneas has been adequate for the past 10 years in the United States, where more than 33,000 corneal transplants are performed each year. However, recent changes in Food and Drug Administration regulations will likely cause a decrease in the supply of donated corneas. These new regulations require additional screening and testing of potential donors for contagious diseases, registration of eye banks, more detailed records and labels and stricter quarantine procedures. In addition, many eye banks previously set the age limit for donors at 65 years or younger because some surgeons have been reluctant to use older corneas. The findings from the new study could lessen these restrictive policies. In addition, as any tissue that is not used is then exported to eye banks around the world, this will add to the international supply as well.
As a national leader in eye health care the Department of Ophthalmology and Visual Sciences continues its longstanding tradition of excellence in eye care and specialization in corneal transplantation. With advanced clinical, teaching, and research in the management of eye diseases and surgery in conjunction with the Visual Sciences Research Center at UHCMC and Case, the Center ranks 10th in the country in funding from the National Eye Institute.
Additional support for CDS was provided by: Eye Bank Association of America, Bausch & Lomb, Inc., Tissue Banks International, Vision Share, Inc., San Diego Eye Bank, The Cornea Society, Katena Products, Inc., ViroMed Laboratories, Inc., Midwest Eye-Banks (Michigan Eye-Bank, Illinois Eye-Bank), Konan Medical Corporation, Eye Bank for Sight Restoration, SightLife, Sight Society of Northeastern New York (Lions Eye Bank of Albany), and Lions Eye Bank of Oregon.
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