About a third of the corneal transplant surgeries in the United States involve people with diabetes who donate their corneas after death.
The number of corneal transplants has grown over the last decade, but through continuous research, the medical community has learned that not all corneal tissue from diabetics may be suitable for the procedure, known as keratoplasty.
In a new study, supported by a five-year, $6.4 million grant from the National Eye Institute of the National Institutes of Health, researchers from Case Western Reserve University, University Hospitals and the Jaeb Center for Health Research, aim to finally determine which diabetic individuals can successfully donate their corneas for keratoplasty (and which should not).
"This is an important question that should be answered," said Jonathan Lass, the Charles I Thomas Professor and vice chair for academic affairs in the Department of Ophthalmology and Visual Sciences at the Case Western Reserve School of Medicine and director of University Hospitals Eye Institute Eye Image Analysis Reading Centers.
Doing so will have a major impact on eye-banking and keratoplasty practices."
Jonathan Lass, Charles I Thomas Professor and Vice Chair for Academic Affairs, Department of Ophthalmology and Visual Sciences, Case Western Reserve School of Medicine
The question about which donors are suitable takes on increasing urgency, as recent eye-bank data suggests diabetic donors comprise 30% to 35% of the cornea donor pool--a 50% to 72% increase in just over a decade.
The numbers are rising simply because there are more people with diabetes in this country, said Lass, principal investigator and chair of the new study. And because the population is aging, so is demand for this kind of surgery.
Corneal transplant numbers increasing
The cornea is the clear outer layer at the front of the eye that helps focus light to see clearly. The number of corneal transplants nationally declined 20% in 2020 because of the pandemic, but is now recovering, with elective surgeries back to pre-2020 levels, according to the Eye Bank Association of America.
The number has steadily increased since the association began tracking the procedure in 1991. Just over 51,000 corneal transplants were performed in the United States in 2019, up 17% from the 10 years before and a 30% jump from 1991.
Although the standard approach for all types of keratoplasties is to use corneas from diabetic donors, some eye banks and surgeons are increasingly avoiding them for a procedure known as "Descemet membrane endothelial keratoplasty," or DMEK.
The researchers are focusing on DMEK for this study because it's the most common procedure high-volume corneal-transplant surgeons are performing (which will help recruit patients for the study), and because previous research found that eye-bank technicians had more problems preparing donors with diabetes for the DMEK surgery.
The need for corneal transplants is mostly caused by the failure of corneal endothelial cells from diseases such as Fuchs Dystrophy or after cataract surgery with complications. These cells keep the cornea clear and thin. With the DMEK procedure, these cells are replaced with normal endothelial cells that are attached to the Descemet membrane from the donor provided by the eye bank.
Focus of the new research
The study will focus on DMEK to examine transplant success and the loss of endothelial cells after surgery and determine the impact of donor and recipient diabetes on these outcomes.
The goal: help inform the eye-banking and surgical communities about the safety and effectiveness of transplanting donor corneas from donors with diabetes.
The new Diabetes Endothelial Keratoplasty Study (DEKS) will involve about 16 eye banks and 30 clinical sites around the country. University Hospitals will be one of the clinical sites and will be led by Ahmed Omar, an assistant professor at the CWRU School of Medicine and director of the Cornea Service at University Hospitals Eye Institute.
"We are really excited that UH will be a clinical site of this huge study, which will shape the future for DMEK surgeries and address some of the important questions surrounding tissues from diabetic donors," Omar said. "This study could also help identify some of the reasons why 2 to 3% of donated corneas fail for no apparent reason, which is a reason for frustration among patients and surgeons."
The study will involve 1,420 donors and over 1,000 patients. Two-thirds of the donors will be non-diabetic and one-third diabetic. Diabetes in the recipient will also be monitored to understand how that may influence the success of transplants.
The study will:
- Compare the one-year keratoplasty-success rate following DMEK with corneas from donors with and without diabetes.
- Compare the one-year loss of endothelial cells in the central cornea after DMEK with corneas from donors with and without diabetes.
- Explore how the severity of a donor's diabetes affects outcomes one year after DMEK surgery.