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Objective:
In order to evaluate the effect of donor age on cornea graft survival, the Cornea Donor Study (CDS) was originally designed to determine whether the graft-survival rate over a 5-year follow-up period is similar with corneal tissue from donors older than 65 years of age compared with that from younger donors. As measurement of corneal endothelial cell density by specular microscopy can serve as an indicator of the health of the cornea, the Specular Microscopy Ancillary Study (SMAS) was developed in order to evaluate the effect of donor factors, specifically donor age, on endothelial cell loss following penetrating keratoplasty.
The study was extended through 2012 to determine the overall 10-year survival rate for moderate risk grafts and to determine whether the graft-failure rate is equivalent with corneal tissue from donors older than 65 years of age compared with that from younger donors.
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Results:
The 5-year cumulative probability of graft survival was 86% in both the <66.0 donor age group and the ≥66.0 donor age group (difference = 0%, upper limit of one-sided 95% confidence interval = 4%). In a statistical model with donor age as a continuous variable, there was not a significant relationship between donor age and outcome (P=0.11). Three graft failures were due to primary donor failure, 8 to uncorrectable refractive error, 48 to graft rejection, 46 to endothelial decompensation (23 of which had a prior, resolved episode of probable or definite graft rejection), and 30 to other causes. The distribution of the causes of graft failure did not differ between donor age groups.
As at 5 years, there was not a significant difference comparing the 10-year survival curves of the 12 to 65 and 66 to 75 years old donor age groups. The 10-year success rate was 77% for 707 corneas from donors 12 to 65 years old compared with 71% for 383 donors 66 to 75 years old (difference = +6%, 95% confidence interval = -1% to +12%, P=0.11). At 11 years post-keratoplasty, the difference between groups was similar (difference = +5%, 95% confidence interval = -2% to +12%). In contrast to the findings at 5 years, after 5 years the association of continuous donor age with graft success was significant. Relatively constant 10-year success rates were observed within three data-derived (not pre-specified) groupings according to donor age: 96% (95% confidence interval 89% to 99%) among the 80 study eyes (7% of the 1,090 eyes) that received a cornea from a donor 12 to 33 years old, 75% (95% confidence interval 71% to 78%) among the 880 eyes (81% of the 1,090 eyes) that received a cornea from a donor 34 to 71 years old), and 62% (95% confidence interval 51% to 72%) among the 130 eyes (12% of the 1090 eyes) that received a cornea from a donor 72 to 75 years old.
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Conclusions:
Although the primary analysis did not show a significant difference in 10-year success rates comparing donor ages 12 to 65 and 66 to 75 years, there was evidence of a donor age effect at the extremes of the age range. Since we observed a fairly constant 10-year success rate for donors age 34 to 71 years, which account for approximately 75% of corneas in the United States available for transplant, the Cornea Donor Study results indicate that donor age is not an important factor in most penetrating keratoplasties for endothelial disease.
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