Dry eyes are caused by a lack of adequate tears. Your tears are a complex mixture of water, fatty oils and mucus. This mixture helps make the surface of your eyes smooth and clear, and it helps protect your eyes from infection.

      Causes are:

1. Decreased tear production

Dry eyes can occur when you're unable to produce enough tears. The medical term for this condition is keratoconjunctivitis sicca (ker-uh-toe-kun-junk-tih-VY-tis SIK-uh). Common causes of decreased tear production include:

• Aging

• Certain medical conditions, including diabetes, rheumatoid arthritis, lupus, scleroderma, Sjogren's syndrome, thyroid disorders and vitamin A deficiency

• Certain medications, including antihistamines, decongestants, hormone replacement therapy, antidepressants, and drugs for high blood pressure, acne, birth control and Parkinson's disease

• Laser eye surgery, though symptoms of dry eyes related to this procedure are usually temporary

• Tear gland damage from inflammation or radiation

2. Increased tear evaporation

Common causes of increased tear evaporation include:

• Wind, smoke or dry air

• Blinking less often, which tends to occur when you're concentrating, for example, while reading, driving or working at a computer

• Eyelid problems, such as out-turning of the lids (ectropion) and in-turning of the lids (entropion)

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Signs and symptoms, which usually affect both eyes, may include:

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• -A stinging, burning or scratchy sensation in your eyes

• -Stringy mucus in or around your eyes

• -Sensitivity to light

• -Eye redness

• -A sensation of having something in your eyes

• -Difficulty wearing contact lenses

• -Difficulty with nighttime driving

• -Watery eyes, which is the body's response to the irritation of dry eyes

• -Blurred vision or eye fatigue

Risk factors

Factors that make it more likely that you'll experience dry eyes include:

• Being older than 50. Tear production tends to diminish as you get older. Dry eyes are more common in people over 50.

• Being a woman. A lack of tears is more common in women, especially if they experience hormonal changes due to pregnancy, using birth control pills or menopause.

• Eating a diet that is low in vitamin A, which is found in liver, carrots and broccoli, or low in omega-3 fatty acids, which are found in fish, walnuts and vegetable oils

• Wearing contact lenses

Complications

People who have dry eyes may experience these complications:

• Eye infections. Your tears protect the surface of your eyes from infection. Without adequate tears, you may have an increased risk of eye infection.

• Damage to the surface of your eyes. If left untreated, severe dry eyes may lead to eye inflammation, abrasion of the corneal surface, corneal ulcer and vision problems.

• Decreased quality of life. Dry eyes can make it difficult to perform everyday activities, such as reading.

Prevention

If you experience dry eyes, pay attention to the situations that are most likely to cause your symptoms. Then find ways to avoid those situations in order to prevent your dry eyes symptoms. For instance:

• Avoid air blowing in your eyes. Don't direct hair dryers, car heaters, air conditioners or fans toward your eyes.

• Add moisture to the air. In winter, a humidifier can add moisture to dry indoor air.

• Consider wearing wraparound sunglasses or other protective eyewear. Safety shields can be added to the tops and sides of eyeglasses to block wind and dry air. Ask about shields where you buy your eyeglasses.

• Take eye breaks during long tasks. If you're reading or doing another task that requires visual concentration, take periodic eye breaks. Close your eyes for a few minutes. Or blink repeatedly for a few seconds to help spread your tears evenly over your eyes.

• Be aware of your environment. The air at high altitudes, in desert areas and in airplanes can be extremely dry. When spending time in such an environment, it may be helpful to frequently close your eyes for a few minutes at a time to minimize evaporation of your tears.

• Position your computer screen below eye level. If your computer screen is above eye level, you'll open your eyes wider to view the screen. Position your computer screen below eye level so that you won't open your eyes as wide. This may help slow the evaporation of your tears between eye blinks.

• Stop smoking and avoid smoke. If you smoke, ask your doctor for help devising a quit-smoking strategy that's most likely to work for you. If you don't smoke, stay away from people who do. Smoke can worsen dry eyes symptoms.

• Use artificial tears regularly. If you have chronic dry eyes, use eyedrops even when your eyes feel fine to keep them well-lubricated.

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