How Storing Corneas Affects Transplantation Success
The cornea is the eye’s clear outer covering. Certain diseases can cloud the cornea, causing reduced vision and even blindness. Replacing a cloudy cornea with a healthy cornea from a donor can restore vision. Last year, nearly 50,000 corneal transplantations were performed in the United States. The supply of donor corneas is currently sufficient for U.S. patients; however, demand is expected to increase with the aging population.
The U.S. Food and Drug Administration has approved the use of solutions to preserve donated corneas for up to 14 days before transplantation. However, surgeons in the United States generally prefer not to use corneas stored for longer than seven days.
To investigate how long corneas can be safely stored, a team of researchers led by Dr. Jonathan Lass of Case Western Reserve University School of Medicine and University Hospitals Eye Institute compared success rates of transplantation for corneas stored for seven days or less to those stored for eight to 14 days. The study was funded by NIH’s National Eye Institute (NEI). Two reports on the study’s results appeared online in JAMA Ophthalmology on November 10, 2017.
The researchers evaluated three-year corneal transplantation success rates from 1,090 patients who had surgery on one or both eyes (1,330 eyes total) to restore vision loss from corneal disease. Patients were randomly assigned to receive corneas that had been either stored up to seven days or stored between eight and 14 days. The eye surgeries were performed by 70 surgeons across the United States.
The three-year success rates for corneas stored up to seven days was 95% and for those stored between eight and 14 days was 92%. However, the success rate for corneas stored between 12 and 14 days was 89%. The success rate for those stored between eight and 11 days was 94%. Thus, most of the difference in success rates between the two main groups could be attributed to a lower success rate for corneas stored between 12 and 14 days.
In the second study report, the research team analyzed cell loss among 769 participants in the innermost layer of the cornea three years after transplantation. Cell loss in the innermost layer is related to long-term failure of transplanted corneas. Three years after transplantation, corneas stored up to seven days had a 37% loss of cells, and those stored between eight and 14 days had a 40% loss. The effect of storage time on the loss of cells at three years was comparable for corneas stored between four and 13 days.
Taken together, the studies support the use of corneas that have been stored up to 11 days. The results suggest that more patients would have access to vision-saving transplantations if surgeons expand the window in which donor tissues can be considered suitable.
“The current practice of surgeons to use corneas preserved for no longer than seven days is not evidence-based,” Lass says, “but rather a practice based on opinion, which hopefully will change with this new evidence.”