Night blindness, also called nyctalopia, is not itself a disorder. Instead, it is a symptom of other disorders, according to the Cleveland Clinic. When in dim light, the eye dilates the pupil. When there is brighter light, the pupil needs to contract to adjust.
People who have an underlying disorder that causes night blindness have dysfunctional cells in the retina involved in dim light vision. Night blindness may also occur when driving at night: this occurs for a few seconds after bright headlights pass by and the eyes need to readjust, noted the NYU Langone Medical Center.
Night blindness causes can be either treatable or non-treatable. For example, while rare, a deficiency in vitamin A can cause night blindness, according to MedlinePlus. Someone may have a deficiency in vitamin A if she does not consume enough foods with vitamin A, such as eggs and green leafy vegetables.
Certain conditions can affect vitamin A absorption, such as liver disorders. A doctor will test the level of vitamin A in the blood and if it is found to be the cause of the night blindness, the doctor will recommend vitamin A supplements.
Side effects of certain drugs may cause night blindness. For people who suspect that their medication is causing night blindness, they should talk to their doctors and not alter their dosage before doing so.
Other treatable causes of night blindness include cataracts and nearsightedness. If the cause is cataracts, in which the person has cloudy areas in the lens of her eye, her doctor may recommend surgery to remove the cataracts. People who have night blindness and nearsightedness may need to get a new eyeglass prescription.
Non-treatable causes of night blindness include birth defects and retinitis pigmentosa. With retinitis pigmentosa, a genetic disorder, the retina is damaged, causing night blindness. Patients may also have a loss of peripheral vision and a loss of central vision, with the loss of central vision occurring in advanced cases of the disease.
MedlinePlus noted that one in 4,000 people in the United States have retinitis pigmentosa. Unfortunately, there is no effective treatment for this eye condition.
References
Texas Department of Insurance. Night Blindness. Web. 21 November 2011
http://www.tdi.texas.gov/pubs/videoresource/t5nightblind.pdf
Cleveland Clinic. Night Blindness. Web. 21 November 2011
http://my.clevelandclinic.org/disorders/night_blindness/hic_night_blindness.aspx
NYU Langone Medical Center. Night Blindness Web. 21 November 2011
http://www.med.nyu.edu/content?ChunkIID=96907
MedlinePlus Medical Encyclopedia. Vision – Night Blindness. Web. 21 November 2011
http://www.nlm.nih.gov/medlineplus/ency/article/003039.htm
MedlinePlus Medical Encyclopedia. Retinitis Pigmentosa. Web. 21 November 2011
http://www.nlm.nih.gov/medlineplus/ency/article/001029.htm
Reviewed November 22, 2011
by Michele Blacksberg RN
Edited by Jody Smith