Night Vision Problems

Night Vision Problems: Halos, Blurred Vision, and Night Blindness

Are you having problems with night vision? Millions of Americans do. Poor night vision can be an early sign of progressive vision problems such as cataracts. But problems with night vision -- or at the extreme, night blindness -- is often treatable.

What causes poor night vision?

Difficulty with night vision can stem from a number of different problems ranging from exposure to the sun and vitamin deficiencies to a chronic disease such as diabetes:

Cataracts. The lens of the eye is located behind the pupil. Over a lifetime, the process of cell turnover inside the lens produces debris that gradually builds up. This creates a cataract. Painless and progressive, cataracts slowly cloud the lens.
The first symptom of cataracts is usually decreased night vision. The light distortion caused by cataracts also frequently produces halos around lights -- again, mostly at night. Blurry vision is also common.

Vitamin A deficiency . Vitamin A is an essential vitamin that's found in carrots and yellow or green leafy vegetables. It helps keep the retina -- back of the eye -- healthy. Vitamin A deficiency is a rare cause of night blindness in the U.S. It occurs mostly in people with problems absorbing nutrients from the gut. This might occur as a result of different diseases and conditions such as Crohn's disease, celiac disease, cystic fibrosis, or pancreatic insufficiency.
Zinc deficiency. Zinc works in the eye as a partner to vitamin A. Without zinc, the vitamin A that's present may not be as effective, and night blindness could result. Beef, poultry, beans, and nuts are rich sources of zinc. Dietary deficiency is uncommon in this country.
Retinitis pigmentosa . Retinitis pigmentosa is an uncommon genetic disorder. It affects young people, usually before age 30. Worsening night vision is often the earliest symptom. Variable amounts of vision loss follow, although most people retain some vision.
Sunlight exposure. If your night vision seems temporarily worse after a trip to the beach, it probably is. Sustained bright sunlight can impair night vision for up to two days. Wear your sunglasses regularly to avoid this cause of poor night vision.
LASIK surgery problems. Complications after LASIK surgery are uncommon. However, some people do experience night vision problems after LASIK. The most common complaint is distorted vision in the form of glare and halos around objects. Distorted vision may be present during the day, too. It becomes more noticeable and bothersome, though, at night. Some people are more prone to developing night vision problems after LASIK. Those who are can be identified before the surgery based on characteristics of their eyes. Ask about your own chances of complications if you're considering LASIK.

Diabetes. People with diabetes are at higher risk for night vision problems. Over years, high blood sugar is toxic to the blood vessels and nerves in the eye. The retina -- the back of the eye where images are focused -- is gradually damaged (retinopathy). Two early signs of retinopathy from diabetes are poor night vision and taking a long time to see normally after coming indoors from bright light outside.

How are night vision problems diagnosed?
Blurry vision or poor night vision are good reasons to schedule an appointment with an eye doctor, also known as an ophthalmologist.

A simple examination and conversation at an ophthalmologist's office will uncover virtually any serious cause of night blindness. The doctor will dilate your eyes with drops and examine your eyes with a slit-lamp, a sort of upright microscope with a bright light mounted on it.

How is night blindness treated?
The most common cause of poor night vision -- cataracts -- is also one of the most treatable. Cataract surgery replaces the clouded natural lens with a clear plastic lens. Vision is immediately improved, often dramatically, although many people will still need to wear glasses for good night vision.

Diabetic retinopathy can be prevented by tightly controlling blood sugar levels with medicines and diet. One treatment for advanced diabetic retinopathy uses a laser to destroy tiny budding blood vessels that threaten vision. Called panretinal photocoagulation, this laser procedure preserves vision overall. But night vision can be even worse afterward.

Although vitamin A and zinc deficiency aren't common causes of night blindness, it's worthwhile to eat a diet rich in these nutrients if you're having night vision problems.

SOURCES:

Yanoff, M. Ophthalmology, 2nd edition, Mosby, 2004.

Ophthalmology, 1983; vol 90: pp 126-131.

Office of Dietary Substances: "Zinc."

Christian, P. American Journal of Clinical Nutrition, 2001; vol 73: pp 1045-1051.

Reviewed by Louise Chang, MD on August 05, 2008
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