EXPANDING DONOR POOL

Donor age is not an important factor in graft survival for most penetrating keratoplasty procedures performed for endothelial disease, suggest the 10-year data from the Cornea Donor Study.

Mark J Mannis MD, Co-Principal Investigator, presented the findings on behalf of the Cornea Donor Study Research Group at the 5th EuCornea Congress in London, UK.

Sponsored by the National Eye Institute and representing the largest and longest multicentre study of corneal disease, the Cornea Donor Study was a double-masked, multicentre study that enrolled 1,090 patients with a moderate risk condition.

The transplanted corneas were from donors aged 12 to 75 years, met Eye Bank Association of America criteria, and had an endothelial cell density between 2,300 and 3,300 cells/mm2. The corneas were randomly assigned to participants without respect to recipient factors, and both the participants and surgeons were masked to graft donor age.

The primary analysis compared 10-year success rates in procedures performed with corneas from donors aged 12 to 65 years versus from donors aged 66 to 75 years, and found there was no statistically significant difference in the outcomes.

An analysis of donor age as a continuous variable did show a significant association between higher donor age and lower graft survival rate beginning at five years post-transplantation, reported Dr Mannis, professor and chair, University of California Davis Eye Center.

When 10-year success rates were then analysed with the cohort divided into three groups based on donor age, the results showed evidence of a donor age effect at the extremes of age range. While the 10-year success rate of grafts from donors aged 12 to 33 years (n = 80) was 96 per cent, it was only 62 per cent for grafts from donors aged 72 to 75 years (n = 130), and 75 per cent for donors aged 34 to 71 years (n = 880). The latter group represents the vast majority of donors.

“Approximately 75 per cent of corneas available for transplant in the United States are from donors aged 34 to 71 years, and the 10-year success rate of grafts from donors in that age group was fairly constant at 75 per cent,” said Dr Mannis.

“In addition, transplants from donors 34 to 71 years and those from donors 72 to 75 years had similar survival through six years, and even after 10 years the difference in survival between those two groups was modest.”

Other prognostic factors

In analyses examining the prognostic significance of other variables, no other donor-related characteristics predicted graft failure. However, several recipient-related features were associated with the outcome.

The data showed the 10-year cumulative probability of graft failure was significantly lower among patients with a diagnosis of Fuchs’ dystrophy compared with those whose indication for surgery was pseudophakic/aphakic corneal oedema (20 per cent versus 37 per cent).

In addition, existing glaucoma at the time of transplantation independently predicted increased risk of graft rejection. The 10-year cumulative probability of graft failure was 58 per cent among patients with a history of glaucoma surgery and who were using IOP-lowering medications at study entry, but 22 per cent among those with no history of glaucoma surgery or medication use.

The results also showed trends for recipient age, race, and smoking status to be associated with graft survival. Specifically, success rates were lower in recipients aged 70 years and above versus those less than 60 years old (71 per cent vs 81 per cent).

Success rates were also lower in African-Americans compared with white/non-Hispanic patients (62 per cent vs 76 per cent), and in individuals who were smokers relative to those who were non-smokers (65 per cent vs 76 per cent).

Dr Mannis also presented data on long-term endothelial cell loss that showed it continued over time, but at a much slower rate after the first five years.

“Donor age slightly influenced endothelial cell density over the long-term, but that was driven by the youngest donors with the least cell loss and best graft survival. For the vast majority of corneas from our donor pool, age was not a factor in long graft survival,” Dr Mannis said.

Mark J Mannis: mjmannis@ucdavis.edu