People with night blindness (also called impaired dark adaptation) see poorly in the darkness but see normally when adequate amounts of light are present. The condition does not actually involve true blindness, even at night.
Checklist for Night Blindness
| Rating | Nutritional Supplements | Herbs |
|---|---|---|
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Zinc (for deficiency) |
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Reliable and relatively consistent scientific data showing a substantial health benefit. Contradictory, insufficient, or preliminary
studies suggesting a health benefit or minimal health benefit. For an herb, supported by traditional use but
minimal or no scientific evidence. For a supplement, little scientific support and/or minimal
health benefit. |
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Symptoms include difficulty seeing when driving in the evening or at night, poor vision in reduced light, and feeling that the eyes take longer to “adjust” to seeing in the dark.
Over the counter treatment typically consists of oral supplementation with vitamin A.
Therapy includes management of any underlying medical condition.
Night blindness may be an early sign of vitamin A deficiency. Such a deficiency may result from diets low in animal foods (the main source of vitamin A), such as eggs, dairy products, organ meats, and some fish. Low intake of fruits and vegetables containing beta-carotene, which the body converts into vitamin A, may also contribute to a vitamin A deficiency. Doctors often recommend 10,000 to 25,000 IU of vitamin A per day to correct a deficiency. Beta-carotene is less effective at correcting vitamin A deficiency than is vitamin A itself, because it is not absorbed as well and is only slowly converted by the body into vitamin A.
Dietary zinc deficiency is common, and a lack of zinc may reduce the activity of retinol dehydrogenase, an enzyme needed to help vitamin A work in the eye. Zinc helps night blindness in people who are zinc-deficient;1 therefore, many physicians suggest 15 to 30 mg of zinc per day to support healthy vision. Because long-term zinc supplementation may reduce copper levels, 1 to 2 mg of copper per day (depending on the amount of zinc used) is usually recommended for people who are supplementing with zinc for more than a few weeks.
Bilberry, a close relative of the blueberry, is high in flavonoids known as anthocyanosides. Anthocyanosides speed the regeneration of rhodopsin, the purple pigment that is used by the rods in the eye for night vision.2 Supplementation with bilberry has been shown in early studies to improve dark adaptation in people with poor night vision.3 4 However, two newer studies found no effect of bilberry on night vision in healthy people.5 6 Bilberry extract standardized to contain 25% anthocyanosides may be taken in capsule or tablet form. Doctors typically recommend 240 to 480 mg per day.
1. Anonymous. Zinc-responsive night blindness in sickle cell anemia. Nutr Rev 1982;40:175–7.
2. Alfieri R, Sole P. Influencedes anthocyanosides admintres parvoie parenterale su l’adaptoelectroretinogramme du lapin. CR Soc Biol 1964;15:2338 [in French].
3. Jayle GE, Aubry M, Gavini H, et al. Study concerning the action of anthocyanoside extracts of Vaccinium myrtillus on night vision. Ann Ocul 1965;198:556–62 [in French].
4. Belleoud L, Leluan D, Boyer YS. Study on the effects of anthocyanin glycosides on the nocturnal vision of air controllers. Rev Med Aeronaut Spatiale 1966;18:3–7.
5. Zadok D, Levy Y, Glovinsky Y. The effect of anthocyanosides in a multiple oral dose on night vision. Eye 1999;13:734–6.
6. Muth ER, Laurent JM, Jasper P. The effect of bilberry nutritional supplementation on night visual acuity and contrast sensitivity. Altern Med Rev 2000;5:164–73.
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The information presented in Healthnotes is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over-the-counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires December 2005.