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What are dry eyes? | Tears and their function | Causes | Symptoms | Diagnosis | Treatment | Complications

What are dry eyes?

One of five people suffers from dry eyes, making it the most common eye problem, especially in the older population. Tears normally keep the eyes moist and lubricated. 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.

Tears and their function

Tears cover the eyes constantly, bathing and lubricating them. Every time a person blinks, new tears are spread across the eyeballs. Tears are important because they keep the eye surface smooth and optically clear. They also contain a substance called lysozyme that acts as an antibacterial agent protecting the eye from infection.

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. The lacrimal gland located above the eyeball produces watery tears.

The tarsal glands, which are found in the eyelids, produce a tear film containing three layers that moistens and lubricates the eye constantly. The purpose of the outer, oily layer is to reduce the evaporation of tears. The middle watery layer cleanses the eye and washes away foreign particles and irritants. The inner mucus layer stabilizes the tear film, coating the surface evenly and allowing tears to adhere to the surface of the eye.

Both types of tears drain out of the eye through a small opening in the lower eyelid know as the punctum. First they drain into a tear sac and then into the nasal passages.

Causes

The main cause of dry eyes is the lack of tears. Tear production decreases with age leaving delicate eyes exposed to an irritating environment. It affects seventy-five percent of people over age sixty-five.

Dry eyes are 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, asthma, cataracts, glaucoma, and lupus. 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.

Many computer users don't blink often enough while staring at the screen. As a result, they don't produce adequate tears and experience dry eyes.

Finally, a few people have an exceptionally large punctum, or drainage canal, and their tears drain away rapidly causing dry eyes.

Symptoms

The eyes of a person who suffers from this disease feel gritty, itchy, or dry. People may also experience burning, stinging, redness, stringy mucus in their eyes, and sensitivity to light. Sometimes they feel as if their eyelids are sticking together in the morning.

People who have dry eyes may have difficulty wearing contact lenses because the contacts normally float on top of the tear layer, and there isn't enough moisture available to float the lens.

As strange as it may sound, watering eyes may also be a symptom because excess tears are produced as a result of irritation. However, the watering tears are the same as crying tears. There isn't enough oil to stop their evaporation, so they don't lubricate the eye sufficiently, and the eyes remain irritated and dry.

If you are experiencing some of the symptoms described here, it does not necessarily mean you have dry eyes. However, if you experience one or more of these symptoms, you should contact your eye doctor for a complete exam. Click here for information on emergency or immediate care.

Diagnosis

Dry eyes can be diagnosed using the Schirmer Test. Filtered paper strips are placed inside the patient's lower eyelid to measure the rate of tear production.

The punctum can 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.

Treatment

Dry eyes can't be cured, but they can be treated. Artificial tears are the most common treatment. Synthetic tears in the form of eye drops are used to lubricate the eyes and replace missing moisture. However, prolonged use of artificial tears can disrupt the eye's natural tear production. Artificial tears can wash away the natural infection-fighting film found in real tears which can lead to further aggravation.

A slow-release medication can be inserted inside the eyelid to release moisture throughout the day. If patients have difficulty opening their eyes in the morning, an ointment is available for use at bedtime to help alleviate the problem.

Another form of treatment is to prevent the evaporation of tears. Dry eye sufferers can use a humidifier to add moisture to the air. They should avoid smoke, wind, and other irritating conditions.

Some sufferers have found relief by using soft contact lenses. Although the soft contact lenses absorb water and other fluids, they act as a bandage to protect the cornea.

For many patients, the most effective treatment for dry eyes is blocking the punctum (the natural canal that drains tears from the eyes) with a plug. Initially, the ophthalmologist inserts a temporary plug in the punctum to prevent the patient’s tears from draining out of the eye. Most patients experience immediate relief of their symptoms. The temporary plug is absorbed by the body within a few days. If the temporary plug gives the patient relief, the doctor will insert a permanent silicon plug in the drainage canals. If necessary, the silicon plugs can be removed easily. This simple procedure is covered by most insurance companies.

Complications

Untreated dry eyes can lead to more serious conditions including corneal ulcers, infection, and conjunctivitis.