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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 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 ...
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.
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 ...
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 ...
Alcohol-induced liver disease can also exacerbate other health conditions that contribute to retinopathy, such as hypertension [39] and hyperglycemia. [39] [40] Metabolic pathway of vitamin A. Alcohol consumption leads to abnormalities in the metabolism pathways of several essential nutrients for eye health such as vitamin A and zinc.
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The predominant cause of nutritional optic neuropathy is thought to be deficiency of B-complex vitamins, particularly thiamine [2] (vitamin B 1), cyanocobalamin (vitamin B 12) and recently copper. [3] Deficiency of pyridoxine (vitamin B 6), niacin (vitamin B 3), riboflavin (vitamin B 2), and/or folic acid also seems to play a role. Those ...