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

Night blindness is caused by a disorder of the cells in the retina that are responsible for vision in dim light (cones). There may be several common causes:
  • Lack of vitamin A, which can cause a disorder of the retina
  • Cataracts , which are cloudy areas in the lens of the eye
  • Some forms of retinal degeneration, such as retinitis pigmentosa
  • Certain medications
  • Birth defects

Risk Factors

Factors that may increase your chance of night blindness include:
  • Age—Elderly people are more likely to have cataracts.
  • Genetics
  • Dietary deficiencies—Not getting adequate amounts of vitamin A, which come from 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
  • Glaucoma
  • Diabetes
  • Trouble adjusting from low levels of light to high levels of light

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

Your doctor will ask about your symptoms and medical history. An eye exam will be done. A blood test can be used to test the amount of vitamin A in your blood.

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Treatment

Treatment depends on the cause of night blindness. Options may include:Night blindness may require taking extra safety precautions when necessary. This may mean avoiding driving in the evening or at night.

Prevention

To help reduce your chance of night blindness:
  • Follow treatment plans for chronic conditions that may contribute to night blindness
  • Eating a diet with adequate amounts of vitamin A

RESOURCES

American Optometric Association
http://www.aoa.org

Eye Smart—American Academpy of Ophthalmology
http://www.eyesmart.org

CANADIAN RESOURCES

Canadian Ophthalmological Society
http://www.cos-sco.ca

Health Canada
http://www.hc-sc.gc.ca

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.

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

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