The effect of vitamin C deficiency and chronic ultraviolet-B exposure on corneal ultrastructure: a preliminary investigation.

Abstract

PURPOSE:

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: Sally Hayes, Thamara A Cafaro, Patrycja J Boguslawska, Christina S Kamma-Lorger, Craig Boote, Jonathan Harris, Robert Young, Jennifer Hiller, Nicholas Terrill, Keith M Meek, Horacio M Serra
• Journal: Molecular vision (Mol Vis) Vol. 17 Pg. 3107-15 ( 2011) ISSN: 1090-0535 [Electronic] United States
• PMID: 22171156 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Topics

• Animals
• Ascorbic Acid Deficiency (pathology)
• Body Weight
• Cornea (pathology, radiation effects, ultrastructure)
• Corneal Stroma (pathology, radiation effects, ultrastructure)
• Guinea Pigs
• Male
• Microscopy
• Scattering, Small Angle
• Ultraviolet Rays
• X-Ray Diffraction