Dry eyes occur when your tears aren’t able to provide adequate moisture for your eyes. Tears can be inadequate for many reasons. For example, dry eyes may occur if you don’t produce enough tears or if you produce poor-quality tears.
Dry eyes feel uncomfortable. If you have dry eyes, your eyes may sting or burn. You may experience dry eyes in certain situations, such as on an airplane, in an air-conditioned room, while riding a bike, or after looking at a computer screen for a few hours.
Treatments for dry eyes may make you more comfortable. These treatments can include lifestyle changes and eyedrops. For more-serious cases of dry eyes, surgery may be an option.
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.
For some people, the cause of dry eyes is an imbalance in the composition of their tears. Other people don’t produce enough tears to keep their eyes comfortably lubricated. Eyelid problems, medications and other causes, such as environmental factors, also can lead to dry eyes.
Poor tear quality
The tear film has three basic layers: oil, water and mucus. Problems with any of these layers can cause dry eyes symptoms.
- Oil. The outer layer of the tear film, produced by small glands on the edge of your eyelids (meibomian glands), contains fatty oils called lipids. These smooth the tear surface and slow evaporation of the middle watery layer. If your oil glands don’t produce enough oil, the watery layer evaporates too quickly, causing dry eyes. Dry eyes are common in people whose meibomian glands are clogged. Meibomian dysfunction is more common in people with inflammation along the edge of their eyelids (blepharitis), rosacea and other skin disorders.
- Water. The middle layer is mostly water with a little bit of salt. This layer, produced by the tear glands (lacrimal glands), cleanses your eyes and washes away foreign particles or irritants. If your eye produces inadequate amounts of water, the oil and mucous layers can touch and cause a stringy discharge.
- Mucus. The inner layer of mucus helps spread tears evenly over the surface of your eyes. If you don’t have enough mucus to cover your eyes, dry spots can form on the front surface of the eye (cornea).
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-VIE-tis SIK-uh).
You may not produce enough tears if you:
- Are older than 50. Tear production tends to diminish as you get older. Dry eyes are common in people older than 50.
- Are a postmenopausal woman. A lack of tears is more common among women, especially after menopause. This may be due in part to hormonal changes.
- Have a medical condition that reduces your tear production. Dry eyes are also associated with some medical conditions such as diabetes, rheumatoid arthritis, lupus, scleroderma, Sjogren’s syndrome, thyroid disorders and vitamin A deficiency.
- Have had laser eye surgery. Refractive eye surgeries such as laser-assisted in-situ keratomileusis (LASIK) may cause decreased tear production and dry eyes. Symptoms of dry eyes related to these procedures are usually temporary.
- Have tear gland damage. Damage to the tear glands from inflammation or radiation can hamper tear production.
Blinking spreads a continuous thin film of tears across the surface of your eyes. If you have an eyelid problem that makes it difficult to blink, tears may not be spread across your eye adequately or your tears may evaporate too quickly, causing dry eyes. Eyelid problems can include an out-turning of the lids (ectropion) or an in-turning of the lids (entropion).
Medications that cause dry eyes
Medications that can cause dry eyes include:
- Some drugs used to treat high blood pressure
- Antihistamines and decongestants
- Hormone replacement therapy
- Certain antidepressants
- Isotretinoin-type drugs for treatment of acne
Other causes of dry eyes include:
- Dry air
- Tasks that require enough concentration that you blink less often, such as working at a computer, driving or reading
Signs and symptoms, which usually affect both eyes, may include:
- A stinging, burning or scratchy sensation in your eyes
- Stringy mucus in or around your eyes
- Increased eye irritation from smoke or wind
- Eye fatigue
- Sensitivity to light
- Eye redness
- A sensation of having something in your eyes
- Difficulty wearing contact lenses
- Periods of excessive tearing
- Blurred vision, often worsening at the end of the day or after focusing for a prolonged period
When to see a doctor
See your doctor if you’ve had prolonged signs and symptoms of dry eyes, including red, irritated, tired or painful eyes. Your doctor can take steps to determine what’s bothering your eyes or refer you to a specialist.