title: The effect of vitamin C deficiency and chronic ultraviolet-B exposure on corneal ultrastructure: a preliminary investigation.
abstract: OBJECTIVE
  In the visually debilitating condition of climatic droplet keratopathy, corneal transparency is progressively lost. Although the precise cause of the disease and the mechanism by which it progresses are not known, a lifetime exposure to high solar radiation and a vitamin C-deficient diet may be involved in its development. This study examines the effect of dietary ascorbate levels and ultraviolet (UV)-B exposure on corneal stromal structure.
  
  
  METHODS
  Eight guinea pigs were divided into four treatment groups (A, B, C, and D). For 15 weeks, Groups A and C were fed an ascorbate-rich diet (2 mg/100 g bodyweight/day), while Groups B and D received an ascorbate-deficient diet (0.07 mg/100 g bodyweight/day). For the last 12 weeks of the study, Groups C and D also experienced chronic UVB exposure (0.12 J/cm² for 40 min/day). Following euthanasia, the corneas were enucleated and their stromal ultrastructure examined using X-ray scattering and electron microscopy.
  
  
  RESULTS
  UVB exposure resulted in an increased corneal thickness (p<0.001), but this was not accompanied by a widespread expansion of the collagen fibrillar array, and in the case of ascorbate-deficient animals, stromal thickening was associated with the compaction of collagen fibrils (p<0.01). Neither UVB exposure nor ascorbic acid deficiency caused any change in the average diameter or D-periodicity of the stromal collagen fibrils.
  
  
  CONCLUSIONS
  UVB-induced changes in the corneal ultrastructure were most pronounced in animals fed an ascorbic acid-deficient diet. This suggests that ascorbic acid may play a vital role in protecting the corneal stroma from the harmful effects of UVB.
authors.affiliation: School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom.
authors.forename: Sally
authors.initials: S
authors.lastname: Hayes
authors.forename: Thamara A
authors.initials: TA
authors.lastname: Cafaro
authors.forename: Patrycja J
authors.initials: PJ
authors.lastname: Boguslawska
authors.forename: Christina S
authors.initials: CS
authors.lastname: Kamma-Lorger
authors.forename: Craig
authors.initials: C
authors.lastname: Boote
authors.forename: Jonathan
authors.initials: J
authors.lastname: Harris
authors.forename: Robert
authors.initials: R
authors.lastname: Young
authors.forename: Jennifer
authors.initials: J
authors.lastname: Hiller
authors.forename: Nicholas
authors.initials: N
authors.lastname: Terrill
authors.forename: Keith M
authors.initials: KM
authors.lastname: Meek
authors.forename: Horacio M
authors.initials: HM
authors.lastname: Serra
mesh_terms: D000818:Animals; D001206:Ascorbic Acid Deficiency / Q000473:pathology*; D001835:Body Weight; D003315:Cornea / Q000473:pathology / Q000528:radiation effects* / Q000648:ultrastructure*; D003319:Corneal Stroma / Q000473:pathology / Q000528:radiation effects / Q000648:ultrastructure; D006168:Guinea Pigs; D008297:Male; D008853:Microscopy; D053838:Scattering, Small Angle; D014466:Ultraviolet Rays; D014961:X-Ray Diffraction