Lack of vitamin A, first causes night blindness or inability to see in dim light. The mother herself can detect this condition when her child cannot see in late evenings or find her in a darkened room. Night blindness is due to impairment in dark adaptation. Unless vitamin A intake is increased, the condition may get worse, especially when children also suffer from diarrhea and other infections.

Night blindness, officially known as nyctalopia, is inability to adapt to dark lighting conditions. When a person can't see well enough to discern contrasting images under low lighting conditions, blindness can result.

The retina is well supplied with an important chemical substance called rhodopsin, or “visual purple”. Light falling on the retina brings about certain chemical changes in the rhodopsin and other substances present in the rods and cones. These changes occur very rapidly, but large quantities of vitamin A are needed to bring this about. If there is any marked deficiency of vitamin A, night blindness may occur. This can usually be corrected by administering suitable amounts of vitamin A in the diet.

Vitamin A deficiency also contributes to development of night blindness because of the nutrient's importance in maintaining the health of the eye's retina. One study reported in Journal of Nutrition (October 2004) effectively used tests detecting night blindness in pregnant women to determine whether mothers-to-be lacked vitamin A considered crucial for healthy development of their babies.

Retinitis Pigmentosa is characterized by night blindness and black dotting of the fundus. The Optic Nerve becomes pale white, called Optic atrophy. 

Types of Night Blindness

What are the causes of night blindness?

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,

• Lack of vitamin A, which can cause a disorder of the retina and make the eyes very dry
• Cataracts, which are cloudy areas in the lens of the eye
• Some forms of retinal degeneration, like retinitis pigmentosa
• Trouble adjusting from low levels of light to high levels of light
• Certain medications
• Birth defects

Some risk factors for night blindness include:

• Age: older people are more likely to have cataracts
• Diet: people who don’t eat enough sources of vitamin A, such as green leafy vegetables, eggs, and whole milk products (vitamin A deficiency is very rare in the US, but still occurs in certain less developed countries)

Disorders that affect the ability of the body to absorb vitamin A:

What are the signs and symptoms of night blindness?

Symptoms are difficulty or inability to see in low light or darkness. While driving, this may also occur a few seconds after the bright headlights of an oncoming car have passed.

Associated symptoms include:

• Dry eyes
• Blurred vision

Treatment

Treatment for night blindness will depend upon its cause . Treatments generally include:

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