Symptoms And Causes Of Nyctalopia

Symptoms And Causes Of Nyctalopia
Nyctalopia - Night blindness or difficulty in seeing at night. Symptom of vitamin A deficiency.

Night blindness is an eye disorder in which vision is abnormally impaired in dim light

or at night. It is caused by a deficiency of visual purple (rhodopsin) in the

light-sensitive rod cells of the retina at the back of the eye. Night blindness most

commonly occurs as a result of retinitis pigmentosa, a degenerative condition of the

retina. Visual purple may also decrease if there is a dietary deficiency of vitamin A -

its principal component. Exposure to bright lights may cause the supply of visual purple

to be temporarily depleted. Night blindness may also occur in choroidoretinitis and

glaucoma.

Individuals suffering from night blindness not only see poorly at night, but also

require some time for their eyes to adjust from brightly lit areas to dim ones. Contrast

vision may also be greatly reduced.

Xerophthalmia is a more advanced form of the effect of Vitamin A deficiency on our

eyes. In that disease, the eyes become excessively sensitive to light, and in addition

production of tears is markedly decreased, which prevents the normal lubrication of the

eye. This leads to ulceration and infections of the eye.

Night blindness caused by vitamin A deficiency can be treated with therapeutic dosages

of the vitamin. Some types of damage to the retina, such as retinitis pigmentosa, are

usually irreversible.

Vitamin A maintains the skin and mucous membranes. Promotes growth, strong bones,

healthy skin, hair, teeth and gums. Builds up resistance to respiratory infections and

shortens the duration of diseases. It counteracts night blindness and aids in the

treatment of many eye disorders. Night blindness is an early symptom of a deficiency of

vitamin A.

Vitamin A is one of the few vitamins in which excess produces definite and severe

effects. Toxic symptoms can occur with intake exceeding 100 000 IU's daily.

Hypervitaminosis A leads to loss of appetite, a dry, itchy skin often with peeling,

intense headaches and an enlarged liver. Recovery is fairly rapid when intake is

reduced.