Most of us take it for granted that we can see at night, but millions of Americans have problems with night vision. Having night blindness can be a sign of untreated myopia (nearsightedness) or progressive cataracts, or it could be a congenital problem such as retinitis pigmentosa, which has no treatment, so far. Most of these diseases cause degeneration of the rods of the retina, which are responsible for vision in dim light.

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The Causes of Night Blindness

There’s a range of causes that can lead to night blindness. These include:

Myopia: Someone with nearsightedness has difficulty focusing his or her eyes, so objects may appear blurry. The person will also have difficulty adapting to darkness.

Glaucoma medications: These work by constricting the pupil.

Diabetic retinopathy: People with diabetes are at a higher risk for night vision problems. High blood sugar is toxic to the blood vessels and nerves in the eye, and the retina is gradually damaged. Two early signs of retinopathy are poor night vision and taking a long time to see normally after coming indoors from bright light outside.

Cataracts: The first symptom of cataracts is usually decreased night vision. The light distortion caused by cataracts also frequently produces halos around lights, usually at night. Blurry vision is also common in those with cataracts, a disease that clouds the eye.

Retinitis pigmentosa: This is an uncommon genetic disorder, usually affecting people before the age of 30. Worsening night vision is often the earliest symptom. Variable amounts of vision loss follow, although most people retain some vision.

Vitamin A deficiency: Vitamin A, in carrots and yellow or green leafy vegetables, keeps the retina healthy. It’s a rare cause of night blindness, but can occur in people with problems absorbing nutrients. Conditions that can cause this are Crohn’s disease, celiac disease, cystic fibrosis, and pancreatic insufficiency.

Xerophthalmia: This is a more advanced form of the effect of Vitamin A deficiency. With xerophthalmia, the eyes become excessively sensitive to light and production of tears is markedly decreased, which prevents the normal lubrication of the eye. This leads to ulceration and infections of the eye.

Zinc deficiency: Zinc – found in beef, poultry, beans, and nuts – works in the eye as a partner to Vitamin A. Without zinc, night blindness could result.

Sunlight exposure:  Sustained bright sunlight – after a beach trip, for instance – can impair night vision for up to two days. Wear your sunglasses regularly to avoid this.

LASIK surgery problems: While complications are uncommon, 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, but it becomes more noticeable and bothersome at night.

Treating Night Blindness

Treatment for night blindness will depend upon its cause. It may be as simple as getting a new eyeglass prescription or switching glaucoma medications, or it may require surgery if the night blindness is caused by cataracts. Make sure to schedule an appointment with your doctor to find the cause.
If the cause is cataracts, surgery will immediately improve your vision, often dramatically. If the cause is diabetic retinopathy, vision can be helped by controlling blood sugar levels through medicine and diet. There are also laser procedures that destroy budding blood vessels, although the treatment itself may also reduce night vision.
Finally, having a diet rich in Vitamin A and zinc will help keep your eyes healthy.

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Sources:
http://my.clevelandclinic.org/disorders/night_blindness/hic_night_blindness.aspx
http://www.webmd.com/eye-health/night-vision-problems-halos-blurred-vision-night-blindness
http://www.medicinenet.com/script/main/art.asp?articlekey=197