Xerophthalmia keratomalacia

Health is unquestionably compromised by abnormal vitamin A nutriture at the extremes of too little (xerophthalmia/keratomalacia/irreversible blindness) or too much (toxicity). However, the health and social consequences of subclinical or marginal nutritional states are yet to be fully delineated. This section considers the criteria used to define a public health problem, the geographic distribution of hypovitaminosis A at varied levels of severity, and programs initiated for its control. Consideration is then given to hypervitaminosis A. 

The principal physiological functions of tins vitamin include growth, production of visual purple, maintenance of skin and epithelial cells, resistance to infection, gluconeogenesis. mucopolysaccharide synthesis, bone development, maintenance of myelin and membranes, maintenance of color and peripheral vision, maintenance of adrenal cortex and steroid hormone synthesis, Specific vitamin A deficiency diseases include xerophthalmia, nyctalopia, hemeralopia, keratomalacia, and hyperkeratosis. 

Two retinoids, retinoic acid and retinal, appear to have most of the biochemical functions attributed to vitamin A Retinoic acid is required for cell differentiation and is the ligand for two families of nuclear receptors, RAR . y and RXR 0 y. These receptors are part of a family of superreceptors that include the steroid hormones and cholecalciferol. Vitamin A deficiency can lead to a variety of symptoms depending on the age of the deficient person. The most serious syndrome is keratomalacia, which results in desiccation, ulceration, and xerophthalmia of the cornea and conjunctiva. It is one of the leading causes of blindness in infants and children. 

A Dermatitis, night blindness, keratomalacia, xerophthalmia Serum vitamin A Teratogenic effects, liver toxicity with excessive intake alcohol intake, liver disease, hyperlipidemia, and severe protein malnutrition increase susceptibility to adverse effects of high intake , 6-carotene supplements recommended only for those at risk of deficiency (fat malabsorption)... 

Nutritional vitamin A deficiency causes xerophthalmia, a progressive disease characterized by night blindness, xerosis (dryness), and keratomalacia (comeal thinning), which may lead to perforation xerophthalmia may be reversed with vitamin A therapy. However, rapid, irreversible blindness ensues once the cornea perforates. Vitamin A also is involved in epithelial differentiation and may have some role in corneal epithelial wound healing. There is no evidence to support using topical vitamin A for keratoconjunctivitis sicca in the absence of a nutritional deficiency. 

At the end of the last century, a new child s disease was observed for the first time in Japan during a period of depression. It was called Hikan and was characterized by hemeralopia, xerophthalmia, and keratomalacia. Untreated, the victims soon died, but they could be cured almost instantly by the administration of cod liver oil. 

Critical (clinical horizon) <150 <5 10 Xerophthalmia night blindness xerosis-conjunctiva (Bitot s spots) xerosis-comeal and comeal ulceration/ keratomalacia... 

Table XIV Oomen, 1971 McLaren era/., 1965a Sommer era/., 1975a, 1976). Measles, though prevalent in developed countries, is not reported to be a blinding disease in such countries. There is substantial literature that documents the association shown in Table XIV between malnutrition and xerophthalmia. A controversy has developed in the medical literature, therefore, as to whether vitamin A deficiency is the primary cause of keratomalacia, with intercurrent measles as a precipitating factor (Oomen, 1971 Sauter, 1976 Franken, 1974), or whether measles can cause blinding corneal disease in a malnourished child in the absence of vitamin A deficiency (Frederique et aL, 1969).

Sommer, A. (1982a). Nutritional Blindness. Xerophthalmia and Keratomalacia. Oxford Univ. Press, London and New York. 

Apart from this, carotenoids are also important in immune system activity and intercellular communication [64, 65]. Deficiency of carotenoids results in clinical signs of conjunctiva and corneal aberrations including xerophthalmia, night blindness, and keratomalacia [66]. The increasing requirement of carotenoids in the food, cosmetic, and pharmaceutical industries makes them ideal candidates for enhancement and manipulation. The carotenoids market has reached, in 2010, an estimated US 1.2 billion, but it is expected to reach 1.4 billion in 2018, with a compound annual growth rate of 2.3 [67]. 

Vitamin A is transported from the gut to the liver in chylomicrons, and from the Hver to the tissues bound to a specific retinal-binding protein or pre-albumin. Deficiency of vitamin A is usually associated with poor protein diets. It is not necessarily reversible by administration of vitamin A alone since the synthesis of retinolbinding protein is affected by the deficiency and therefore so is vitamin A absorption. Deficiency may cause night blindness, xerophthalmia and keratomalacia. Vitamin A toxicity is unUkely with a normal diet but can cause dermatitis, hair loss, and hepatic dysfunction. In pregnancy it can cause teratogenicity if taken in... 

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