title: The theory and implications of the biaxial model of corneal birefringence.
abstract: OBJECTIVE
  A theoretical model of biaxial optical anisotropy is derived and its structural, biomechanical and developmental implications are discussed with reference to known corneal anatomy. METHODS A concise review of the theory of optical crystallography is followed by the derivation of a theoretical model of the optical anisotropic properties of a dome of biaxial birefringent crystalline material. The model is then applied to parameters relevant to the biaxial model of human corneal birefringence.
  
  
  RESULTS
  Theoretical distributions of refractive indices and vibration directions for transmitted monochromatic light are derived for the central and paracentral zones of a model human cornea. Contours of equal refractive index (equirefringence curves) are found to have orthogonal confocal spheroconic geometry.
  
  
  CONCLUSIONS
  A novel model of corneal structure is proposed in which discrete uniaxial positive birefringent fibre-like elements conform to the derived spheroconic geometry. Biomechanical implications and the relationship of the birefringent elements to known corneal anatomy are discussed. The crystallographic conventions are proposed as a standard for further investigations of corneal birefringence.
authors.affiliation: Department of Ophthalmology, Warwick Hospital, South Warwickshire NHS Trust, Warwick, UK. g.misson@warwick.ac.uk
authors.forename: Gary P
authors.initials: GP
authors.lastname: Misson
mesh_terms: D016880:Anisotropy; D001696:Biomechanical Phenomena; D001718:Birefringence; D003315:Cornea / Q000502:physiology*; D019781:Corneal Topography / Q000379:methods; D003461:Crystallography / Q000379:methods; D006801:Humans; D008954:Models, Biological; D012031:Refractometry