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Night blindness (nyctalopia) is the inability to see well at night or in poor light. It is not a disorder in itself, but rather a symptom of an underlying disorder or problem, especially untreated nearsightedness.
Nyctalopia (Greek for “night blindness”) is a condition making it difficult or impossible to see in relatively low light. It is a symptom of several eye diseases. Night blindness may exist from birth, or be caused by injury or malnutrition (for example, a lack of vitamin A).
Causes:
Night blindness is due to a disorder of the cells in the retina that are responsible for vision in dim light. It has many causes, including:
- Nearsightedness
- Glaucoma medications that work by constricting the pupil
- Cataracts
- Retinitis pigmentosa
- Vitamin A deficiency
The most common cause of nyctalopia is retinitis pigmentosa, a disorder in which the rod cells in the retina gradually lose their ability to respond to the light. Patients suffering from this genetic condition have progressive nyctalopia and eventually their daytime vision may also be affected. In X-linked congenital stationary night blindness, from birth the rods either do not work at all, or work very little, but the condition doesn’t get worse.Another cause of night blindness is a deficiency of retinol, or vitamin A, found in fish oils, liver and dairy products. In the Second World War misinformation was spread by the British to cover up the reason for their pilots’ successful night time missions. Their success was, in the misinformation, attributed to improved night vision and pilots flying night missions were encouraged to eat plenty of carrots, which contain carotenoids and can be converted into retinol. The actual reason for their success was their use of advanced radar technologies.
The opposite problem, known as hemeralopia, is much rarer.
The outer area of the retina is made up of more rods than cones. The rod cells are the cells that enable us to see in poor illumination. This is the reason why loss of side vision often results in night blindness. 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.
In order to determine what is causing night blindness, the eye doctor will perform a thorough eye exam and may order any of a number of specialized exams .
Historical usage
Aulus Cornelius Celsus, writing ca. 30 AD, described night blindness and recommended an effective dietary supplement: “There is besides a weakness of the eyes, owing to which people see well enough indeed in the daytime but not at all at night; in women whose menstruation is regular this does not happen. But success sufferers should anoint their eyeballs with the stuff dripping from a liver whilst roasting, preferably of a he-goat, or failing that of a she-goat; and as well they should eat some of the liver itself.”
Historically, nyctalopia, also known as moonblink, was a temporary night blindness believed to be caused by sleeping in moonlight in the tropics.
Treatment:
Treatment for night blindness will depend upon its cause. Treatment may be as simple as a new prescription for your eyeglasses or switching glaucoma medications, or it may require surgery in cases of cataracts.
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Disclaimer: This information is not meant to be a substitute for professional medical advise or help. It is always best to consult with a Physician about serious health concerns. This information is in no way intended to diagnose or prescribe remedies.This is purely for educational purpose
Resources:
http://en.wikipedia.org/wiki/Night_blindness
http://www.medicinenet.com/script/main/art.asp?articlekey=43325
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