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Mol Vis. 2011;17:3107-15. Epub 2011 Nov 26.

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

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1
School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom.

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.

PMID:
22171156
PMCID:
PMC3235536
[Indexed for MEDLINE]
Free PMC Article
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