title: Long-term graft survival in penetrating keratoplasty: the biexponential model of chronic endothelial cell loss revisited.
abstract: OBJECTIVE
  To present a novel interpretation of the biexponential nature of chronic endothelial cell loss after penetrating keratoplasty (PK). We hypothesize that the fast component of endothelial cell loss reflects the endothelial cells of graft origin. The slow component might just reflect cell loss of the recipient endothelium. We investigate herein whether this hypothesis is in line with long-term survival in bullous keratopathy (BK: almost no endothelium in the recipient bed) and keratoconus (KK: recipient bed with plenty of endothelium).
  
  
  METHODS
  We reviewed endothelial graft failures in PK for BK (n = 88) and KK (n = 87). Patients with immune reactions or a history of glaucoma were excluded. We built a statistical model to predict graft failures from biexponential endothelial cell loss and compared this data to the actual outcomes.
  
  
  RESULTS
  After 15 years, the incidence of late endothelial failures was 8% in KK and 33% in BK. The 95% confidence intervals of the simulated outcomes corresponded completely to the actual outcomes during follow-up.
  
  
  CONCLUSIONS
  Our novel interpretation of the biexponential model is in line with long-term data of PK for BK and KK. Our findings highlight the importance of the recipient bed endothelial reservoir on the long-term prognosis in PK.
authors.affiliation: University Eye Hospital Freiburg, Germany. daniel.boehringer@uniklinik-freiburg.de
authors.forename: Daniel
authors.initials: D
authors.lastname: Böhringer
authors.forename: Stefan
authors.initials: S
authors.lastname: Böhringer
authors.forename: Katharina
authors.initials: K
authors.lastname: Poxleitner
authors.forename: Florian
authors.initials: F
authors.lastname: Birnbaum
authors.forename: Johannes
authors.initials: J
authors.lastname: Schwartzkopff
authors.forename: Philip
authors.initials: P
authors.lastname: Maier
authors.forename: Rainer
authors.initials: R
authors.lastname: Sundmacher
authors.forename: Thomas
authors.initials: T
authors.lastname: Reinhard
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002452:Cell Count; D002648:Child; D002908:Chronic Disease; D055954:Corneal Endothelial Cell Loss / Q000503:physiopathology*; D004728:Endothelium, Corneal / Q000473:pathology; D005500:Follow-Up Studies; D006085:Graft Survival / Q000502:physiology*; D006801:Humans; D015948:Keratoplasty, Penetrating; D008875:Middle Aged; D015233:Models, Statistical; D012189:Retrospective Studies