title: Regional variation in the refractive-index of the bovine and human cornea.
abstract: OBJECTIVE
  Given the refractive importance of the human cornea, surprisingly little attention has been directed to the study of local variation in corneal refractive-index. This in vitro and in vivo study measures the refractive-index of different portions of the bovine and human cornea.
  
  
  METHODS
  Fifty fresh bovine corneas (obtained from an abattoir) and 10 human subjects were used for the study. The refractive-index of the central, nasal, and temporal corneal epithelium was measured with a bench-top Abbe refractometer in the case of bovine corneas and with a hand-held refractometer with humans.
  
  
  RESULTS
  The mean (+/-standard deviation) refractive-indices of the central, nasal, and temporal bovine corneal epithelium were 1.3760 (+/-0.003), 1.3757 (+/-0.002), and 1.3746 (+/-0.002), respectively. Refractive-indices of the anterior and posterior bovine corneal stroma were 1.3731 (+/-0.002) and 1.3708 (+/-0.004), respectively. The mean (+/-standard deviation) refractive-index in the central, nasal, and temporal periphery of the human cornea epithelium were 1.3970 (+/-0.001), 1.3946 (+/-0.001), and 1.3940 (+/-0.001), respectively.
  
  
  CONCLUSIONS
  There are small local differences in the refractive-index of the bovine and human corneal epithelium and the refractive-index of the epithelium is higher than that of the anterior and posterior stroma of the bovine cornea.
authors.affiliation: School of Optometry, University of Waterloo, Waterloo, Ontario, Canada.
authors.forename: Balamurali
authors.initials: B
authors.lastname: Vasudevan
authors.forename: Trefford L
authors.initials: TL
authors.lastname: Simpson
authors.forename: Jacob G
authors.initials: JG
authors.lastname: Sivak
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D000818:Animals; D002417:Cattle; D003315:Cornea / Q000502:physiology*; D003319:Corneal Stroma / Q000502:physiology; D019573:Epithelium, Corneal / Q000502:physiology; D006801:Humans; D066298:In Vitro Techniques; D009666:Nose; D012031:Refractometry; D013701:Temporal Bone; D055815:Young Adult