An eye disorder in which vitamin A deficiency causes the conjunctiva and cornea to become abnormally dry. Without treatment, xerophthalmia may progress to keratomalacia, a condition in which severe damage is caused to the cornea.
This is a blinding eye disease, almost exclusively of infants and young children, which results from vitamin A deficiency, associated with protein-calorie-malnutrition. Xerophthalmia literally means ‘dryness’ of the conjunctiva.
n. a progressive nutritional disease of the eye due to deficiency of *vitamin A. The cornea and conjunctiva become dry, thickened, and wrinkled. This may progress to *keratomalacia and eventual blindness.
A fat-soluble vitamin essential for normal growth, for the formation of bones and teeth, for cell structure, for night vision, and for protecting the linings of the respiratory, digestive, and urinary tracts against infection.
Vitamin A is absorbed by the body in the form of retinol. This is found in liver, fish-liver oils, egg yolk, dairy produce, and is added to margarines. Carotene, which the body converts into retinol, is found in various vegetables and fruits.
Vitamin A deficiency is rare in developed countries. In most cases, it is due to malabsorption. Vitamin A deficiency may also result from long-term treatment with certain lipid-lowering drugs. Deficiency is common in some developing countries due to poor diet. The first symptom of deficiency is night blindness, followed by dryness and inflammation of the eyes (see xerophthalmia), keratomalacia, and eventually blindness. Deficiency also causes reduced resistance to infection, dry skin, and, in children, stunted growth.
Prolonged excessive intake of vitamin A can cause headache, nausea, loss of appetite, skin peeling, hair loss, and irregular menstruation. In severe cases, the liver and spleen become enlarged. Excessive intake during pregnancy may cause birth defects. In infants, excessive intake may cause skull deformities, which disappear if the diet is corrected.
The drug tretinoin (a derivative of vitamin A) is used to treat severe acne.... vitamin a
See entries:– CONJUNCTIVITIS, CONTACT LENS FATIGUE, GLAUCOMA, IRITIS, PALMING, RETINITIS, RETINITIS PIGMENTOSA, RETINOPATHY, SCLERITIS AND EPISCLERITIS, XEROPHTHALMIA (dryness of the eyes). ... eyes
Many eye disorders are minor, but some can cause loss of vision unless treated. (See also cornea, disorders of; retinal detachment.)
Squint is sometimes present at birth. Rarely, babies are born with microphthalmos. Other congenital disorders that affect the eye are nystagmus, albinism, and developmental abnormalities of the cornea and retina.
Conjunctivitis is the most common eye infection and rarely affects vision. Trachoma or severe bacterial conjunctivitis can impair vision. Corneal infections can lead to blurred vision or corneal perforation if not treated early. Endophthalmitis (infection within the eye) can occur as a result of eye injury or infection elsewhere in the body.
Narrowing, blockage or inflammation of the blood vessels of the retina may cause partial or total loss of vision.
Malignant melanoma of the choroid is the most common cancerous tumour of the eye. Retinoblastoma is a cancerous tumour of the retina that most commonly affects children.
Various vitamin deficiencies (particularly of vitamin A) can affect the eye. This may lead to xerophthalmia, night blindness, or, ultimately, keratomalacia.
Uveitis may be caused by infection or an autoimmune disorder such as ankylosing spondylitis and sarcoidosis.
Macular degeneration of the retina is common in the elderly, as is cataract.
Glaucoma, in which the pressure inside the eyeball becomes raised, can lead to permanent loss of vision. In retinal detachment, the retina lifts away from the underlying layer of the eye.Ametropia is a general term for any focusing error, such as astigmatism, myopia, or hypermetropia. Presbyopia is the progressive loss with age of the ability to focus at close range. Amblyopia is often due to squint.... eye, disorders of
(nyctalopia) the inability to see in dim light or at night. It is due to a disorder of the cells in the retina that are responsible for vision in dim light (see rod), and can result from dietary deficiency of *vitamin A. Vitamin A deficiency may progress to cause *xerophthalmia and *keratomalacia. Night blindness may be caused by other retinal diseases, e.g. *retinitis pigmentosa. Congenital stationary night blindness is characterized by poor night vision from early childhood that does not get worse, in association with *nystagmus. Compare day blindness.... night blindness
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