title: Changes in the refractive index of lens fibre membranes during maturation--impact on lens transparency.
abstract: OBJECTIVE
  Local variations in refractive index are the physical cause of light scattering in a material or tissue and also induce phase changes of propagating light waves. The goal of this study was to analyse local differences in refractive index by phase contrast microscopy of sections of human lenses.
  
  
  METHODS
  Refractive index was estimated by immersion refractometry. Cryo-sections of quick-frozen human donor lenses were embedded in a graded series of bovine serum albumin solutions, and in immersion oil, ranging in refractive index from 1.34 to 1.52.
  
  
  RESULTS
  Fibre membranes in the lens cortex prove to have a refractive index considerably above that of fibre cytoplasm at the same location. Fibre membranes in the lens nucleus have a refractive index approximately the same as that of fibre cytoplasm at the same location.
  
  
  CONCLUSIONS
  In the lens cortex, transparency is obtained by a high spatial order of the lens fibre lattice to compensate for the light scattering caused by differences in refractive index between fibre membranes and cytoplasm. In the lens nucleus, high spatial order is less important, because the minor differences in the refractive index between fibre membranes and fibre cytoplasm lead only to minimal scattering.
authors.affiliation: The Netherlands Ophthalmic Research Institute, KNAW, Amsterdam, The Netherlands. ralph.michael@web.de
authors.forename: Ralph
authors.initials: R
authors.lastname: Michael
authors.forename: Jan
authors.initials: J
authors.lastname: van Marle
authors.forename: Gijs F J M
authors.initials: GF
authors.lastname: Vrensen
authors.forename: Thomas J T P
authors.initials: TJ
authors.lastname: van den Berg
mesh_terms: D015925:Cryopreservation; D006801:Humans; D007904:Lens Cortex, Crystalline / Q000502:physiology; D007907:Lens Nucleus, Crystalline / Q000502:physiology; D007908:Lens, Crystalline / Q000502:physiology*; D008858:Microscopy, Phase-Contrast; D012029:Refraction, Ocular; D012031:Refractometry