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

• A stinging, burning, scratchy or gritty 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
  

When to see a doctor

See your health care provider if you have any of the signs and symptoms of dry eye above, including red, irritated, tired or painful eyes. Your provider can take steps to determine what's bothering your eyes.

Dry eyes are caused by a variety of reasons that disrupt the healthy tear film. Your tear film has three layers: fatty oils, aqueous fluid and mucus. This combination usually keeps the surface of your eyes lubricated, smooth and clear. Problems with any of these layers can cause dry eyes.

Reasons for tear film dysfunction are many, including hormonal changes, autoimmune disease, inflamed eyelid glands or allergic eye disease. For some people, the cause of dry eyes is decreased tear production or increased tear evaporation. Additional Causes and further clarification below.

• Low Blink Rate
• Meibomian Gland Disfunction
• Decreased function of the Lacrimal Glands
• Lagophthalmos (incomplete eyelid closure)
• Contact Lens misuse
• Medications (antihistamines, decongestants, antidepressants)
• Environmental Conditions (smoke and wind)
• Refractive surgery

Tear glands and tear ducts

Tear glands, also called lacrimal glands, located above each eyeball continuously supply tear fluid that's wiped across the surface of the eye with each blink of the eyelids. Excess fluid drains through the tear ducts into the nose.

Decreased tear production

Dry eyes can occur when you're unable to produce enough liquid tears, also called aqueous fluid. 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 Sjogren's syndrome, allergic eye disease, rheumatoid arthritis, lupus, scleroderma, graft vs. host disease, sarcoidosis, thyroid disorders or vitamin A deficiency
• Certain medicines, including antihistamines, decongestants, hormone replacement therapy, antidepressants, and medicines for high blood pressure, acne, birth control and Parkinson's disease
• Corneal nerve desensitivity caused by contact lens use, nerve damage or laser eye surgery, though symptoms of dry eyes related to this procedure are usually temporary

Increased tear evaporation

The oil film produced by small glands (meibomian glands) on the edge of your eyelids might become clogged. Blocked meibomian glands are more common in people with rosacea or other skin disorders.

Common causes of increased tear evaporation include:

• Posterior blepharitis (meibomian gland dysfunction)
• Blinking less often, which tends to occur with certain conditions, such as Parkinson's disease; or when you're concentrating during certain activities, such as while reading, driving or working at a computer
• Eyelid problems, such as the lids turning outward (ectropion) and the lids turning inward (entropion)
• Eye allergies
• Preservatives in topical eye drops
• Wind, smoke or dry air
• Vitamin A deficiency

Risk factors

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

• Tear production tends to diminish as you get older. Dry eyes are more common in people over 40.
• 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 a diet low in omega-3 fatty acids, which are found in fish, walnuts and vegetable oils.
• Wearing contact lenses or having a history of refractive surgery.