Dry eye syndrome is a chronic lack of sufficient lubrication and moisture in the eye and a common source of discomfort. Tears are necessary because they keep the eye surface smooth and clear and protect the eye from infection. A lack of tears results in stinging, burning, dryness, and redness. Although the main result of dry eyes is discomfort, dry eyes can lead to infection and corneal scarring if left untreated. There is no known cure, but the symptoms can be alleviated. One of five people suffers from dry eyes, making it the most common eye problem, especially in people over age 40.
Dry Eye Symptoms
- A stinging, burning or scratchy sensation in the eyes
- A sensation of sand or debris in the eyes
- Stringy mucus in or around the eyes
- Eyelids sticking together in the morning
- Sensitivity to light
- Difficulty wearing contact lenses
- Blurred vision, often worsening as the day progresses or after visually focusing for a prolonged period on a nearby task
- Increased eye irritation from smoke or wind
- Excessive tear production
Tears are a complex mixture of water, fatty oils, proteins, electrolytes, and bacteria‐fighting substances that regulate various cell processes. This mixture helps make the surface of your eyes smooth and clear. Without tears, good vision is impossible.
There are two types of tears. The first, known as watery tears, moisten the eye in response to injury. These are also the tears produced when a person becomes emotional and cries. But healthy eyes are continuously covered by a tear film — a constant layer of fluid designed to remain stable between blinks. A stable tear film prevents dry eyes and maintains clear, comfortable vision. This tear film protects your eyes and lubricates them. It reduces the risk of eye infection and, with each blink of your eyelids, helps clear your eyes of any debris. When eyes become irritated by dust, smoke or fumes, extra tears form to help wash away the foreign material.
Decreased production of fluids from tear glands can destabilize the tear film, allowing it to break down and leave dry spots on the clear front surface of the eye (cornea). This can cause irritation and diminished vision. An imbalance in the substances that make up the tear film can also lead to dry eyes. Treatment of dry eyes is aimed at restoring a more normal tear film to minimize dryness and its consequences, including blurred vision and discomfort.
The tear film has three basic layers: mucus, water, and oil. Problems with any of these layers can cause dry eye symptoms.
Mucus. The inner layer of mucus allows tears to spread evenly over the surface of your eyes. Dry spots form easily in any part of the cornea that experiences a loss of the mucus layer.
Water ‐ The middle layer, which makes up about 90% of tears, is mostly water and a small amount of salt. This layer, produced by the tear glands (lacrimal glands), cleanses the eyes and washes away foreign particles and irritants. A shallow water layer can predispose eyes to an unstable tear film. If the eye produces only small, inadequate amounts of water, the oil and mucus layers can touch, which causes the stringy discharge familiar to people with dry eyes.
Oil ‐ The outer layer, 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. When the oil layer is abnormal, the watery layer evaporates too quickly. Dry eye problems are common in people whose meibomian glands are clogged. Meibomian dysfunction is more common in people with inflammation along the edge of their eyelids such as in (blepharitis), rosacea and other skin disorders.
Dry Eye Causes
An imbalance in the composition of tears causes dry eyes in some cases. In other cases an insufficient amount of tears is produced to keep eyes comfortably lubricated. Eyelid problems, medications and other causes, including environmental factors, can also cause dry eyes.
The most common cause of dry eyes is a lack of tears. Tear production decreases with age leaving delicate eyes exposed to an irritating environment. 75% of people over age sixty‐five suffer from some form of dry eye syndrome. Although dry eyes can affect both men and women at any age, the condition is more commonly found in women. Menstruation, pregnancy, lactation, the use of oral contraceptives, or menopause can trigger the condition.
Dry eyes can also be caused by a number of diseases including rheumatoid arthritis, diabetes, thyroid abnormalities, and asthma. Chronic use of ocular medications, as in glaucoma, can also exacerbate dry eyes. Vitamin A deficiency can also reduce the secretion of tears. Medications such as anti‐depressants, decongestants, antihistamines, blood pressure medications, oral contraceptives, diuretics, ulcer medication, tranquilizers, and beta‐blockers can cause dry eyes. Environmental factors such as sun, wind, smoke, fluorescent lights, air pollution, heaters, air conditioning, and dry climates can increase the evaporation of tears and cause dry eyes. Certain activities which require intense long‐term focusing of vision such as computer use, reading, or driving can cause less frequent blinking and deplete the eye of moisture. Finally, some people have an exceptionally large punctum, or drainage canal, and their tears drain away more rapidly, causing dry eyes.
Refractive eye surgeries such as laser‐assisted in‐situ keratomileusis (LASIK) also may cause decreased tear production and dry eyes. Symptoms of dry eyes related to these procedures usually resolve within several months.
Some common medications, both prescription and over‐the‐counter (OTC), that can cause dry eyes include:
Diuretics, drugs commonly used to treat high blood pressure
Antihistamines and decongestants
Isotretinoin‐type drugs for treatment of acne
Birth control pills
Dry Eye Diagnosis
Dry eyes can be diagnosed using the Schirmer Test. (Filtered paper strips are placed inside the patient's lower eyelid for about 5 minutes to measure the rate of tear production). Other tests may use special dyes in eye drops to determine the surface condition of eyes. The dye allows the doctor to look for staining patterns on the cornea and measure how long it takes tears to evaporate. The punctum may also be temporarily closed to see if the amount of tears present in the eye increases. A tiny implant about the size of a sesame seed is placed inside the drainage canal. This implant, which prevents most the tears from leaving the eye, is absorbed by the body in a few days. It allows the patient and doctor to see if an increased amount of moisture in the eye is effective.
Dry Eye Treatment
Effective treatment begins with a thorough exam to determine which factors may be causing the symptoms. The goal of treatment is to keep your eyes moist.
Managing lid problems. Eyelid conditions, such as an anatomic abnormality or an incomplete blink can aggravate dry eyes. The eye care provider may refer a patient with such disorders to an eye surgeon who specializes in plastic surgery of the eyelids (oculoplastic surgeon). For eyelids inflamed due to blepharitis, the doctor may recommend a special cleaning regime. The doctor may also prescribe a short‐term, nightly treatment with antibiotic drops or ointment or treatment with an oral antibiotic such as tetracycline or doxycycline.
Adding Tears ‐ Mild cases of dry eyes are often treated with over‐the‐counter artificial tears. The eye doctor may suggest which drops might be best for the patient. Lubricating drops can be used as needed, even several times an hour, to provide relief. Using drops proactively, before beginning an activity that tends to aggravate dry eye symptoms, also helps. If using drops frequently, preservative‐free eye drops are the best choice to avoid an allergic or toxic reaction to preservatives. Ointments may also be used to ensure lubrication. These ointments can blur vision, and are usually recommended for use at bedtime.
Conserving Tears ‐ Partially or completely closing tear ducts, which normally serve to drain tears away, can help conserve the tear film and alleviate dry eyes. The tear ducts can be plugged with tiny silicone plugs. Silicone plugs can be removed or left in. A more permanent option is thermal cautery. In this procedure the doctor numbs the area with an anesthetic and then applies a tiny hot wire that shrinks the tissues, causes scarring, and closes the tear duct. People with severe dry eyes also may benefit from a special customized contact lens (Boston Scleral Lens). This lens rests on the white part of the eye (sclera), creating a fluid‐filled layer over the cornea that keeps it from drying out.
Medications ‐ Cyclosporine (Restasis) is the only medication approved by the Food and Drug Administration (FDA) for chronic dry eyes. Restasis decreases inflammation on the eye surface and helps increase production of healthy tears. Some people experience a burning sensation in their eyes when using this drug. Don't use Restasis if you currently have an eye infection or if you have a history of herpes viral infection of your eye. When people experience intolerable irritation from dry eyes despite the frequent use of lubricating eye drops, doctors may prescribe steroid drops. A slow‐ release medication can be inserted inside the eyelid to release moisture throughout the day. Patients who have difficulty opening their eyes in the morning may be prescribed an ointment available for use at bedtime to help alleviate the problem.
More than one variable may contribute to symptoms. Work with your eye care professional to devise a plan to address the factors that appear to be contributing to the problem. This process often takes time and requires patience and a trusting relationship with your doctor. Left untreated, dry eyes can lead to more serious conditions including corneal ulcers, infection, and conjunctivitis.