Among study participants with a clear graft at 10 years , the 125 who received a cornea from a donor 12 to 65 years old experienced a median cell loss of 76 % , resulting in a 10-year median ECD of 628 cells/mm ( 2 ) ( interquartile range [ IQR ] , 522-850 cells/mm ( 2 ) ) , whereas the 51 who received a cornea from a donor 66 to 75 years old experienced a cell loss of 79 % , resulting in a median 10-year ECD of 550 cells/mm ( 2 ) ( IQR , 483-694 cells/mm ( 2 ) ; P adjusted for baseline ECD = 0.03 ) .