Dry, stinging, burning eyes caused by improper lubrication or lack of tears
Dry eyes, a common eye problem, is caused by a lack of tear production. Tears normally keep the eyes moistened and lubricated. However, stinging, burning, dryness, and redness will result if enough tears are not produced to keep the eyes wet and comfortable. While discomfort is the primary result of dry eyes, infection and corneal scarring may occur if left untreated.
What Is Tear Film?
Tear film, which constantly covers the eye, is made up of three layers. The oily outer layer reduces evaporation of the tears. The watery middle layer cleanses the eye and washes away foreign particles or irritants. The inner layer consists of mucus, which coats the surface evenly and allows the tears to adhere to the surface of the eye.
Two Types of Tears
The lacrimal glands, which are located above the eyeball, produce watery tears to moisten the eye and "crying tears" in response to injury and emotion. The smaller tarsal glands in the eyelids produce a tear film which constantly moistens and lubricates the eye. Both types of tears drain from the eye through the punctum, located in the eyelid. The tears then travel through a canal into the tear sac and finally into the nasal passages.
Tears are important to the maintenance of good vision. The tear film, which is spread over the eye by blinking, keeps the surface of the eye smooth and optically clear. Tears also protect the eye from infection, since they contain a substance called lysozyme, which acts as an antibacterial agent.
What Are the Symptoms of Dry Eyes?
Patients with dry eyes often complain that their eyes feel gritty, itchy and dry. Other common symptoms include burning, stinging, redness, stringy mucus, and sensitivity to light. Some patients may experience their eyelids sticking together in the morning. Patients with dry eyes may also have difficulty wearing contact lenses, which normally float on top of the tear film. If not enough tear film is produced, irritation and redness may result from the contact lens rubbing against the surface of the eye.
Surprisingly, watering of the eyes is also a symptom of dry eyes, as excess tears are produced in response to irritation. However, these excess tears are "crying tears" which consist mostly of water. The excess tears lack the oil necessary to keep them from evaporating and, therefore, do not function to lubricate the eye.
What Causes Dry Eyes?
The causes of dry eyes are numerous. Normally, tear production decreases with age, leaving the delicate eye tissues exposed to the irritating effects of the environment. Dry eyes are more common with women, especially during change of life or pregnancy.
Dry eyes often occur in patients with arthritis. Medications and vitamin A deficiency may also cause dry eyes by reducing tear secretion. In addition, environmental factors such as sun, wind, and smoke contribute to the occurrence of dry eyes. Finally, an overly large punctum (drainage channel) or abnormal eyelid location may cause dry eyes.
How Are Dry Eyes Diagnosed?
Dry eyes are often diagnosed with a simple eye examination. The Schirmer Test, which measures tear production, may be used. In the Schirmer tear strip test, filtered paper strips are placed just inside the lower eyelid to measure the rate of tear production.
In some cases, temporary closure of the punctum may be performed to determine if eye discomfort is due to dry eyes. A tiny collagen implant, about the size of a grain of rice, is painlessly placed in the tear drainage canals. The implants permit only a small percentage of tears to pass into the nasal passages, thus building up a layer of tears on the surface of the eye. The implants are absorbed by the body in 3 to 5 days, giving the patient and doctor time to evaluate the effectiveness and comfort provided by an increase in the amount of tears on the surface of the eye.
How Are Dry Eyes Treated?
Artificial tears are the most common treatment for dry eyes. Eye drops, which are available without a prescription, are used to lubricate the eyes and replace missing moisture. Slow-release medicine that gradually releases moisture during the day can be inserted just inside the lower lid. Difficulty opening the eyes in the morning may be treated with an ointment at bedtime.
Patients who suffer from dry eyes can also take steps to prevent the evaporation of tears. Using a humidifier to add moisture to the air and avoiding smoke, wind, and other irritating conditions may provide relief.
If artificial tears alone fail to provide sufficient relief from dry eyes, soft contact lenses may be used to keep moisture on the surface of the eye. Soft contact lenses have a tendency to absorb water and other fluids and act as a bandage that protects the cornea. When used to treat dry eye, soft contact lenses trap artificial tears and medicine drops on the surface of the eye, thus providing needed moisture and lubrication.
In some cases, the punctum must be permanently narrowed or sealed to keep the tears from draining out of the eye quickly. The punctum may be blocked by the insertion of permanent punctum plugs. Unlike the dissolvable type used in testing, these plugs remain in place unless removed. The punctum can also be narrowed or blocked using surgical techniques or lasers. This procedure can usually be performed in the office and is painless, as a local anesthetic is administered before the treatment. Although it is possible to reopen the punctum once it has been closed, the need to do so is rare.
If you are suffering from dry eyes or other eye discomforts, you should obtain a complete eye examination.