Drs Fajgenbaum and Hollick indicate an important difference between donor corneas used in corneal transplantation in the United Kingdom and the United States: the age at cornea donation.

Further supporting their observation, UK data for donor age in 2013-14, which were reported more recently, indicate that the proportion of donors under 60 years was 27% and under 70 years 55%. Comparable data from the United States quoted by Drs Fajgenbaum and Hollick were 50% under 60 years and 18% over 70 years. While donor age in endothelial keratoplasty patients across the United States may not be uniformly as low as published in reports from single large centers in the US, the data from the Eye Bank Association of America indicate that donor age is likely to be significantly lower than in other countries. Moreover, while repeatability of donor endothelial cell density counts might be uncertain in any setting, about donor age there can be no uncertainty.

We thank Drs Fajgenbaum and Hollick for raising this additional point, which is very likely to further explain differences in corneal transplant outcome in the 2 countries, whether penetrating or endothelial keratoplasty.