• Night Blindness

    (Nyctanopia; Nyctalopia; Day Sight; Nocturnal Amblyopia)

    Definition

    Night blindness means having difficulty seeing in the dark or in low light. One of the most common issues with night blindness is difficulty driving in the evening or at night.
    The Retina of the Eye
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    Causes

    There are several common causes of night blindness:
    • 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, such as retinitis pigmentosa
    • Trouble adjusting from low levels of light to high levels of light
    • Certain medications
    • Birth defects

    Risk Factors

    A risk factor is something that increases your chance of getting a disease or condition. Some risk factors for night blindness include:
    • Age: elderly people are more likely to have cataracts
    • Genetics: retinitis pigmentosa
    • 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:
      • Liver disorders
      • Surgery on the pancreas or liver
      • Intestinal conditions
      • Bowel surgery for obesity

    Symptoms

    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.

    Diagnosis

    A doctor will give you a medical examination to determine the cause of your night blindness. Some of the things a doctor might do are:
    • Ask detailed questions about your experience of night blindness
    • Test the levels of vitamin A in your blood
    • Give you an eye exam
    • Ask about your medical history, including:
      • Diet
      • Medications
      • Use of corrective lenses
      • Family history of diabetes

    Treatment

    Depending on the reason for your night blindness, treatment will address the specific cause. Treatments generally include:

    Prevention

    If you experience night blindness, it is important to take safety precautions, like not driving in the evening or at night. Also, eating a diet with adequate amounts of vitamin A may help prevent night blindness.

    RESOURCES

    National Eye Institute http://www.nei.nih.gov/

    Retina International http://www.retina-international.org/

    CANADIAN RESOURCES

    Canadian Ophthalmological Society http://www.eyesite.ca/

    Health Canada http://www.hc-sc.gc.ca/index%5Fe.html/

    References

    Beers, MH, Fletcher AJ, Jones TV, et al. The Merck Manual of Medical Information. 2nd ed. Whitehouse Station, NJ: Merck Research Laboratories; 2003.

    Herse P. Retinitis pigmentosa: visual function and multidisciplinary management. Clin Exp Iptom . 2005;88:5:335-350.

    Retina International. Night blindness. Retina International website. Available at: http://www.retina-international.org/index.php?menuid=42 . Accessed November 10, 2010.

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