When vitamin A deficiency occurs, the integrity of epithelial barriers and
the immune system are compromised before the visual system is impaired.
This leads to increased severity of some infections and risk of death,
especially among children. When vitamin A depletion is sufficient to
affect the visual system, nightblindness occurs first, followed by
xerophtalmia which can affect both the conjunctiva and cornea, and may
lead to irrreversible partial or total blindness (see: WHO. Global
Prevalence of Vitamin A Deficiency. MDIS Working Paper no. 2. 1995
(WHO/NUT/95.3)).
Interestingly, in most populations where VAD is now prevalent, a word
exists in their language or dialect to depict, for example nightblindness!
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