Vitamin A deficiency (VAD) is a lack of vitamin A in humans. It is common in poorer countries but rarely seen in more developed countries. Nyctalopia (night blindness) is one of the first signs of VAD. Xerophthalmia, keratomalacia, and complete blindness can also occur since Vitamin A has a major role in phototransduction. Approximately 250,000 to...
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http://en.wikipedia.org/wiki/Vitamin_A_deficiency
(from the article `nutritional disease`) ...of children become blind each year due to a deficiency of the vitamin. Even a mild deficiency can impair immune function, thereby reducing ... Defective vision under reduced illumination may reflect the congenital or hereditary condition known as retinitis pigmentosa or may be acquired as a .....
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http://www.britannica.com/eb/a-z/v/30
A nutritional condition produced by a deficiency of vitamin a in the diet, characterised by night blindness and other ocular manifestations such as dryness of the conjunctiva and later of the cornea (xerophthalmia). Vitamin a deficiency is a very common problem worldwide, particularly in developing countries as a consequence of famine or shortages ...
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http://www.encyclo.co.uk/local/20973
Vitamin A deficiency: A lack of vitamin A. Vitamin A deficiency (VAD) occurs where diets contain insufficient vitamin A for meeting the needs associated with growth and development, physiological functions, and periods of added stress due to illness. Infections such as measles may precipitate a child into clinical VAD. In VAD areas, women of childb...
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http://www.medterms.com/script/main/art.asp?articlekey=11211
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