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Vitamin A deficiency is the leading cause of preventable childhood blindness worldwide and is a major cause of childhood mortality. [1] Each year, approximately 250,000 to 500,000 malnourished children in the developing world go blind from a VAD, with about half of whom dying within a year of losing their sight. [ 2 ]
The causes are vitamin A deficiency during pregnancy, followed by low transfer of vitamin A during lactation and infant/child diets low in vitamin A or beta-carotene. [ 4 ] [ 5 ] The prevalence of pre-school age children who are blind due to vitamin A deficiency is lower than expected from incidence of new cases only because childhood vitamin A ...
A major cause of Bitot's spots is vitamin A deficiency (VAD). [4] Rarely, pellagra due to deficiency of vitamin B 3 (niacin) may also cause Bitot's spots. [5] They can also be caused by Colestyramine , which is a bile acid sequestrant which can reduce the absorption of fat soluble vitamins (Vitamins A, D, E, K)
Keratomalacia is an eye disorder that results from vitamin A deficiency. Vitamin A is required to maintain specialized epithelia (such as in the cornea and conjunctiva ). The precise mechanism is still not known, but vitamin A is necessary for the maintenance of the specialized epithelial surfaces of the body.
The causes are vitamin A deficiency during pregnancy, followed by low transfer of vitamin A during lactation and infant/child diets low in vitamin A or β-carotene. [ 22 ] [ 19 ] The prevalence of pre-school age children who are blind due to vitamin A deficiency is lower than expected from incidence of new cases only because childhood vitamin A ...
No vitamin A toxicity has ever been reported from ingestion of excessive amounts. [24] Overconsumption of beta-carotene can only cause carotenosis, a harmless and reversible cosmetic condition in which the skin turns orange. Preformed vitamin A absorption and storage in the liver occur very efficiently until a pathologic condition develops. [21]
Vitamin A is supplied through the diet, and a deficiency often results from poor dietary intake of Vitamin A-rich foods. [19] Low dietary levels of Vitamin A can be worsened by infections that cause inflammation in the gastrointestinal tract, which prevent the body from fully absorbing Vitamin A available within digested food.
There are many diseases known to cause ocular or visual changes. Diabetes , for example, is the leading cause of new cases of blindness in those aged 20–74, with ocular manifestations such as diabetic retinopathy and macular edema affecting up to 80% of those who have had the disease for 15 years or more.