night blindness


Also found in: Dictionary, Thesaurus, Medical, Acronyms, Wikipedia.

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
..... Click the link for more information.
, 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 ?
Table 2: Association of night blindness with vitamin A status.
Based on the prevalence of night blindness in preschool children, some studies have positively shown that the overall rate of deficiency in Bangladesh improved from 3.6% in 1982-83 to 1.78% in 1989 and 0.6% in 1996.
The campaigns have reportedly slashed the rate of night blindness to 0.04 percent now in the country from the figure of 3.76 percent in 1982.
Indeed, a drop in visual acuity and night blindness were the main reasons for consultation in our study.
Women suffering from night blindness become dependent on their families, and their risk of accidents, personal injury, and death increases (Christian, Bentley, et al., 1998; Christian et al., 2000).
Editor's note: Retinitis pigmentosa is a disease that begins with night blindness in adolescence and progresses to side vision loss, tunnel vision, and eventual blindness in some men and women.
Elderly cats may also experience night blindness or deafness, both of which may contribute to nighttime yowling.
Benefits of beta-carotene: May protect against night blindness and dry eyes.
One note on handheld spot lights: They can cause temporary night blindness. Aim them away from yourself and other persons on the vessel, and avoid pointing them into the white walls of your gunnels.
Didem Yucel Yilmaz, two researchers in metabolism unit at Hacettepe University's Child Health Institute, Child Health and Diseases Department, have discovered a new gene that causes retinitis pigmentosa, publicly known as night blindness. "Almost 1.5 million people in the world suffer from this problem," Ozgul told AA correspondent.
Vitamin A supplementation was associated with a reduced incidence of diarrhoea (0.85, 0.82 - 0.87) and measles (0.50, 0.37 - 0.67) and a reduced prevalence of vision problems, including night blindness (0.32, 0.21 - 0.50) and xerophthalmia (0.31, 0.22 - 0.45).