Eleven corneas from 10 patients scheduled for PK for Fuchs dystrophy were recruited from the cornea service at Mayo Clinic, Rochester, Minnesota; the mean (SD) age was 70 (7) years (range, 62-78 years). Corneas were examined by slitlamp biomicroscopy, and central thickness was measured by an ultrasonic pachymeter (DGH 1000; DGH Technologies, Inc, Frazer, Pennsylvania). Best-corrected visual acuity was measured using the electronic Early Treatment of Diabetic Retinopathy Study protocol15 and expressed as a logarithm of the minimum angle of resolution (logMAR). Patients with a history of contact lens wear, glaucoma, previous ocular trauma, or surgery (except for cataract surgery), diabetes mellitus, or use of medications known to affect the cornea were excluded. Five control corneas from 5 patients who were scheduled for enucleation for choroidal melanoma were also recruited to serve as controls with histologic data; the mean (SD) age was 63 (15) years (range, 40-80 years). Twenty control corneas from 20 subjects enrolled in a previous study16 were used as additional controls for estimates of keratocyte density by confocal microscopy in vivo. This group was age-matched to the subjects with Fuchs dystrophy and had a mean (SD) age of 70 (5) years (range, 61-80 years). This study adhered to the tenets of the Declaration of Helsinki and was approved by the Mayo Clinic Institutional Review Board. Written informed consent was obtained from all subjects after explanation of the study.