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  2. Vitamin A deficiency - Wikipedia

    en.wikipedia.org/wiki/Vitamin_A_Deficiency

    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 ...

  3. Xerophthalmia - Wikipedia

    en.wikipedia.org/wiki/Xerophthalmia

    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 ...

  4. Vitamin A - Wikipedia

    en.wikipedia.org/wiki/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 ...

  5. Nyctalopia - Wikipedia

    en.wikipedia.org/wiki/Nyctalopia

    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.

  6. Hypervitaminosis A - Wikipedia

    en.wikipedia.org/wiki/Hypervitaminosis_A

    Hypervitaminosis A is believed to have occurred in early humans, and the problem has persisted throughout human history. Toxicity results from ingesting too much preformed vitamin A from foods (such as liver), supplements, or prescription medications and can be prevented by ingesting no more than the recommended daily amount.

  7. Keratomalacia - Wikipedia

    en.wikipedia.org/wiki/Keratomalacia

    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.

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  9. Bitot's spots - Wikipedia

    en.wikipedia.org/wiki/Bitot's_spots

    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)