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Vitamin A plays a major role in phototransduction, so this deficiency impairs vision, often presenting with nyctalopia (night blindness). [1] In more severe VAD cases, it can progress to xerophthalmia, keratomalacia, and complete blindness. [1] Vitamin A deficiency is the leading cause of preventable childhood blindness worldwide and is a major ...
Hypervitaminosis A results from excessive intake of preformed vitamin A. Genetic variations in tolerance to vitamin A intake may occur, so the toxic dose will not be the same for everyone. [23] Children are particularly sensitive to vitamin A, with daily intakes of 1500 IU/kg body weight reportedly leading to toxicity. [21]
Treatment of the deficiency can be accomplished with a vitamin A or multivitamin supplement or by eating foods rich in vitamin A. Treatment with supplements and/or diet can be successful until the disease progresses as far as corneal ulceration, at which point only an extreme surgery can offer a chance of returning sight.
The Mayo Clinic diet was created by weight management practitioners at the Mayo Clinic and was designed as a lifestyle change program to promote gradual and sustained weight loss, says Melissa ...
An early sign of vitamin A deficiency is night blindness. [6] Vitamin A in the form of retinoic acid is essential to normal epithelial cell functions. Severe vitamin A deficiency, common in infants and young children in southeast Asia causes xerophthalmia characterized by dryness of the conjunctival epithelium and cornea. Untreated ...
Night blindness may exist from birth, or be caused by injury or malnutrition (for example, vitamin A deficiency). It can be described as insufficient adaptation to darkness. The most common cause of nyctalopia is retinitis pigmentosa , a disorder in which the rod cells in the retina gradually lose their ability to respond to the light.
Hypervitaminosis is a condition of abnormally high storage levels of vitamins, which can lead to various symptoms as over excitement, irritability, or even toxicity. Specific medical names of the different conditions are derived from the given vitamin involved: an excess of vitamin A , for example, is called hypervitaminosis A .
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