night blindness


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night blindness,

inability to see normally in subdued light. It is usually a result of vitamin A deficiency. The rod cells, one of two light-sensitive areas of the retina of the eyeeye,
organ of vision and light perception. In humans the eye is of the camera type, with an iris diaphragm and variable focusing, or accommodation. Other types of eye are the simple eye, found in many invertebrates, and the compound eye, found in insects and many other
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, are impaired in their capacity to produce a chemical compound called rhodopsin, or visual purple, that is necessary for the perception of objects in dim light. Consequently, the visual threshold, or the minimum intensity of light necessary for sight, is greatly increased. Folk medicine has long recognized the role of the ingestion of liver in alleviating the condition, but it was not until the first quarter of the 20th cent. that vitamin A was identified as the crucial element. Treatment of night blindness consists of the oral or intravenous administration of vitamin A.

night blindness

[′nīt ‚blīnd·nəs]
(medicine)
Reduced dark adaptation resulting from vitamin A deficiency or from retinitis pigmentosa or other peripheral retinal disease. Also known as nyctalopia.
References in periodicals archive ?
Oguchi disease is a very rare form of congenital stationary night blindness in which patients usually present with non progressive nyctalopia and Mizuo-Nakamura phenomenon.
Association between gestational night blindness and serum retinol in mother/newborn pairs in the city of Rio de Janeiro, Brazil.
Indeed, a drop in visual acuity and night blindness were the main reasons for consultation in our study.
Kamran Ahsan, Obaid Khan and Abdul Salam of the Federal Urdu University of Arts, Science and Technology, in Karachi, explain how night blindness, nyctalopia, afflicts millions and may be present at birth as a genetic disease, arise in childhood through malnutrition or injury or be a symptom of numerous eye diseases.
Women suffering from night blindness become dependent on their families, and their risk of accidents, personal injury, and death increases (Christian, Bentley, et al.
Benefits of vitamin A: May protect against night blindness and dry eyes.
It costs so little but, in a country where night blindness is a major problem, two eggs a week in a child's diet can make the difference to them being able to see properly.
Ranga Rohantha Silva has poor vision during the day and has been suffering from night blindness for a long time, one of the first symptoms of retinitis pigmentosa (RP).
RP typically manifests in young adulthood as night blindness or a loss of peripheral vision and, in many cases, progresses to legal blindness by age 40.
Features include adjustable neck strap and reflector, three bright LED's that light up two pages for reading, four standard 120-hour batteries, and a clip-on red night vision filter that minimizes night blindness when switching from light to dark.
Congenital stationary night blindness, an inherited condition that affects one's ability to see in the dark,AaAa is caused by a mutation in a calcium channel protein that shuttles calcium into and out of cells.
The official noted that the Cuban-Venezuelan Mission Miracle eye-care program has helped Guyana "mop up the backlog" of 40,000 pending procedures for cataracts, pteridium and night blindness.