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 ?
To understand if barriers to use of health services led women to live with night blindness, we examined whether women considered distance to health facility, cost of care, and quality of health facility as barriers to use health services (see Table 1 for details).
In a very few cases, night blindness is idiopathic, meaning it is a disease that develops without an apparent known cause.
Hidden in the genetic composition of all men, it remains largely recessive in the 20th century, but like night blindness or schizophrenia, it can't be ignored when it surfaces.
Later they learned that lack of vitamin A was the major cause of night blindness, damage to eye tissues, blindness, and even death, particularly in children.
When retinitis pigmentosa progresses, patients suffer progressive night blindness, where it becomes difficult to see in dim light, or visual field constriction and then deterioration of vision.
CHM is an X-linked inherited retinal dystrophy which manifests in affected males in childhood as night blindness and a reduction of visual field, followed by progressive constriction of visual field, ultimately leading to complete blindness.
The term retinitis pigmentosa (RP) comprises a heterogeneous group of inherited retinal disorders characterized by a progressive bilateral degeneration of rod and cone photoreceptors that causes night blindness and eventually progressive visual field impairment leading to blindness.
ly/1wDf1ue), the authors state that the disruption to the supply of vitamins and micronutrients caused by such surgeries could affect the optic nerve and visual system, leading to a range of ophthalmic complications, including night blindness, corneal xerosis, and corneal ulceration.
Fully shielded lighting fixtures prevent glare which can cause night blindness in drivers and sky glow, which prevents us from enjoying a starry night sky.
KARACHI -- Director General of National Accountability Bureau (NAB) Sindh Wajid Durrani has lauded the efforts for launching an awareness campaign about night blindness.
The FAO also stated that the cost of micronutrient deficiencies such as the deficiency of Vitamin A that causes night blindness is estimated at 2 to 3 per cent of global economic output that comes to be around 1.
If his was not a case of chronic night blindness, then what was it?