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Study finds corneal donor tissue can be safely stored for longer

New research led by Dr Jonathan Lass of Case Western Reserve University School of Medicine and University Hospitals Cleveland Medical Centre has found that corneal donor tissue can be safely stored for 11 days before transplantation surgery to correct eye problems in people with diseases of the cornea. This is four days longer than the current conventional maximum of seven days in the US.

"Over the past 20 years, corneal transplant specialists have gotten comfortable only using corneas up to one week after they are stored. But our findings show they can safely use them up to 11 days after first being stored," said Lass, Charles I Thomas professor in the department of ophthalmology and visual sciences at Case Western Reserve School of Medicine, member of the University Hospitals Eye Institute, and lead investigator of the national Cornea Preservation Time Study, which produced the results. "This will help to meet the expected future demand for corneas in this country as well as in patients overseas today, who now receive as many as thirty percent of corneas donated by US citizens."

Patients who need corneal transplants are typically age 50 and older. According to projections by the US Census Bureau, that population will grow from about 109m currently to about 133m by 2030 in this country.

The cornea, the eye's clear outer covering, helps focus light so people can see clearly. When it is damaged, incoming light can become distorted, harming quality of vision and often resulting in blindness. Damage can arise from scarring due to previous surgery, injury or infection; corneal ulcers; swelling or thinning of the cornea; and inherited diseases and conditions of the eye, such as Fuchs' Dystrophy. When the blurred vision and/or pain are serious enough, transplantation of a new cornea may be necessary.

Transplanted corneas come from people who chose to donate them when they died.

In the study, 70 eye surgeons at 40 surgical sites nationwide performed a corneal transplant called a Descemet stripping automated endothelial keratoplasty (DSAEK) on 1,090 people (1,330 eyes). In this procedure, doctors or the eye bank take a slice from the back of a healthy donated cornea, open a small slit in the patient's eye, scrape out the diseased endothelial cells and replace them with the donor cells. The majority of the patients underwent transplantation for Fuchs' dystrophy, which causes a gradual decline in vision due to corneal swelling and clouding. Patients were randomly assigned to one of two treatment groups: those who received corneas preserved for up to seven days and those who received corneas preserved for eight-14 days.

Lass and the surgeons found that three-year graft success rates were 92.1% for corneas preserved for eight-14 days and 95.3% for corneas preserved up to seven days. Probing further, they discovered that there was no statistically significant difference between patients who received corneas preserved up to seven days and those who received ones preserved eight-11 days. Rather, much of the difference between the groups was attributed to those who received corneas preserved 12-14 days.

"It's important to note that patients who received corneas preserved 12-14 days still had high success rates of 89.3%," said Lass. "This means that if individual circumstances require it, these longer-preserved corneas may be used with a high degree of success."

Currently, the supply of donated corneas is sufficient to meet the demand in the US. In fact, more than a third of donated US corneas are sent to patients in need internationally. But while US eye banks provided about 28,000 corneas for use by patients in other countries in 2015, there are 10m cornea-blind individuals worldwide.

Although results of the study directly apply only to the use of donor corneas used for this specific operation and these conditions, researchers hope that results could be extended to donor corneas used for other types of transplants and other eye diseases.

Separately, the investigators assessed the degree of corneal endothelial cell loss, which typically occurs after transplantation. The endothelium is a single layer of cells lining the inner surface of the cornea; among its functions, it helps keep the cornea clear and from not swelling.

The surgeons found that in corneas preserved up to seven days, there was a 37% loss of cells versus a 40% loss in corneas preserved eight-14 days. Again, probing further, they discovered a comparable rate of loss in corneas preserved four-13 days. "This finding also supports the use of corneas stored up to and including 11 days," said Lass.

Importance: Demonstrating that endothelial cell loss following Descemet stripping automated endothelial keratoplasty (DSAEK) is independent of donor cornea preservation time (PT) could increase the pool of corneal tissue available for keratoplasty.
Objective: To determine whether endothelial cell loss 3 years after successful DSAEK is related to PT.
Design, Setting, and Participants: A multicenter, double-masked, randomized clinical trial included 40 clinical sites (70 surgeons) in the United States, with donor corneas provided by 23 US eye banks. A total of 945 eyes of 769 participants were included in the Cornea Preservation Time Study that had not experienced graft failure 3 years after DSAEK, performed primarily for Fuchs endothelial corneal dystrophy (96% of the cohort). The study was conducted from April 16, 2012, to June 5, 2017.
Interventions: DSAEK with random assignment of a donor cornea with PT of 0 to 7 days (0-7d PT) or 8 to 14 days (8-14d PT).
Main Outcomes and Measures: Endothelial cell density (ECD) at 3 years determined by a central image analysis reading center from clinical specular or confocal central endothelial images.
Results: Nine hundred forty-five eyes of 769 participants (median age, 70 years [range, 42-90 years], 60.8% women, 93.0% white) in the Cornea Preservation Time Study that had not experienced graft failure 3 years after DSAEK were included. At the initial eye bank tissue screening, mean (SD) central ECD was 2746 (297) cells/mm2 in the 0-7d PT group (n = 485) and 2723 (284) cells/mm2 in the 8-14d PT group (n = 460). At 3 years, the mean (SD) ECD decreased from baseline by 37% (21%) in the 0-7d PT group and 40% (22%) in the 8-14d PT group to 1722 (626) cells/mm2 and 1642 (631) cells/mm2, respectively (mean difference, 73 cells/mm2; 95% CI, 8-138 cells/mm2; P = .03). When analyzed as a continuous variable (days), longer PT was associated with lower ECD (mean difference by days, 15 cells/mm2; 95% CI, 4-26 cells/mm2; P = .006). Endothelial cell loss (ECL) was comparable from 4 to 13 days’ PT (n = 878; 36%-43% when tabulated by day). Available extension study ECD results at 4 years mirrored those at 3 years in the 203 eyes in the 0-7d PT group (mean [SD] ECD, 1620 [673] cells/mm2 and mean [SD] ECL, 41% [23%]) and 209 eyes in the 8-14d PT group (mean [SD] ECD, 1537 [683] cells/mm2 and mean [SD] ECL, 44% [23%]) (mean difference, 112 cells/mm2; 95% CI, 5-219 cells/mm2; P = .04).
Conclusions and Relevance: Although ECL 3 years after Descemet stripping automated endothelial keratoplasty is greater with longer PT, the effect of PT on ECL is comparable from 4 to 13 days’ PT.

Jonathan H Lass, Beth Ann Benetz, David D Verdier, Loretta B Szczotka-Flynn, Allison R Ayala, Wendi Liang, Anthony J Aldave, Steven P Dunn, Tyrone McCall, Shahzad I Mian, Lisa C Navarro, Sanjay V Patel, Sudeep Pramanik, George O Rosenwasser, Kevin W Ross, Mark A Terry, Craig Kollman, Robin L Gal, Roy W Beck

[link url=""]Case Western Reserve University material[/link]
[link url=""]JAMA Ophthalmology abstract[/link]

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