title: The variation in transparency of amniotic membrane used in ocular surface regeneration.
abstract: OBJECTIVE
  Scant consideration has been given to the variation in structure of the human amniotic membrane (AM) at source or to the significance such differences might have on its clinical transparency. Therefore, we applied our experience of quantifying corneal transparency to AM.
  
  
  METHODS
  Following elective caesarean, AM from areas of the fetal sac distal and proximal (ie, adjacent) to the placenta was compared with freeze-dried AM. The transmission of light through the AM samples was quantified spectrophotometrically; also, tissue thickness was measured by light microscopy and refractive index by refractometry.
  
  
  RESULTS
  Freeze-dried and freeze-thawed AM samples distal and proximal to the placenta differed significantly in thickness, percentage transmission of visible light and refractive index. The thinnest tissue (freeze-dried AM) had the highest transmission spectra. The thickest tissue (freeze-thawed AM proximal to the placenta) had the highest refractive index. Using the direct summation of fields method to predict transparency from an equivalent thickness of corneal tissue, AM was found to be up to 85% as transparent as human cornea.
  
  
  CONCLUSIONS
  When preparing AM for ocular surface reconstruction within the visual field, consideration should be given to its original location from within the fetal sac and its method of preservation, as either can influence corneal transparency.
authors.affiliation: School of Pharmacy, University of Reading, Rm 108, Hopkins Building Whiteknights, PO Box 228, Reading RG6 6UB, UK. c.j.connon@reading.ac.uk
authors.forename: C J
authors.initials: CJ
authors.lastname: Connon
authors.forename: J
authors.initials: J
authors.lastname: Doutch
authors.forename: B
authors.initials: B
authors.lastname: Chen
authors.forename: A
authors.initials: A
authors.lastname: Hopkinson
authors.forename: J S
authors.initials: JS
authors.lastname: Mehta
authors.forename: T
authors.initials: T
authors.lastname: Nakamura
authors.forename: S
authors.initials: S
authors.lastname: Kinoshita
authors.forename: K M
authors.initials: KM
authors.lastname: Meek
mesh_terms: D000650:Amnion / Q000033:anatomy & histology* / Q000502:physiology; D001684:Biological Dressings; D003315:Cornea / Q000502:physiology*; D005612:Freeze Drying; D006801:Humans; D012031:Refractometry; D012542:Scattering, Radiation; D014021:Tissue Preservation / Q000379:methods