Diagnosing Dry Eye Syndrome
Dry eye syndrome is a condition in which the eyes do not produce enough tears, resulting in dryness of the eyes and discomfort. At NYU Langone, our ophthalmologists are skilled at identifying the cause of dry eye syndrome and determining the best treatment for you.
Dry eye syndrome occurs when the tear film, which is a natural layer of water, oil, and mucus that coats the surface of the eyes, does not adequately lubricate them. This can cause damage to the cornea and other parts of the eye’s surface, preventing them from functioning correctly. The cornea, which is the transparent, dome-like structure on the front of the eye, is lined with a protective layer of cells called the corneal epithelium. The epithelium prevents any foreign particles from entering the eye, with the help of the tear film.
The tear film has several important functions: to keep the eye moist, to keep the cornea clear for light to pass through, and to wash dust and debris away from the eye. Tears also help protect the eye from bacteria and other pathogens.
If there isn’t enough oil, water, or mucus in the tear film, the eye is not lubricated properly, potentially damaging the epithelial cells on the surface of the cornea. If left untreated, this can lead to discomfort and, over time, breakdown and loss of the protective layer of epithelial cells. The damage is usually reversible, but sustained loss of the epithelial cells can cause discomfort, vision loss, increased risk of infection, and possible permanent scarring of the cornea.
Symptoms of Dry Eye Syndrome
Most people feel like their eyes are dry from time to time. Long periods of looking at a computer monitor or TV screen or being inside a heated room can lead to dry eyes. But if you begin to experience dry eyes frequently, and they do not resolve with rest or conservative measures, dry eye syndrome may be the cause of your symptoms.
If you have dry eye syndrome, you may feel constant or intermittent dryness in your eyes. You may also notice frequent stinging, burning, itching, or irritation of the eyes. They may seem to tire easily, and it may become increasingly uncomfortable to wear contact lenses. Chronic redness of the eye is also a common symptom, as is occasional blurred vision. A lack of tears can affect the clarity of eyesight.
Another common symptom of dry eye syndrome is frequent bouts of excessive tearing, which is the body’s response to the lack of moisture in the eye. These so-called “reflex tears” do little to actually lubricate the eye.
Causes of Dry Eye Syndrome
One of the most common causes of dry eye syndrome is blepharitis, an inflammation of the oil glands along the rim of the eyelid. The inflammation prevents proper oil secretion to the eye, which leads to more rapid evaporation of the tear film. The oil glands, called meibomian glands, may become blocked by eye makeup and other cosmetics, by natural oils if your skin tends to be oily, or by flaky skin from conditions such as dandruff and seborrheic dermatitis. Exposure to dusty environments, or to areas where debris or chemical irritants are present, can also put you at risk for dry eye syndrome.
Other conditions associated with dry eye syndrome include diabetes; thyroid disorders; and autoimmune disorders, such as Sjogren’s syndrome and systemic lupus erythematosus, which can cause inflammation of the lacrimal gland, the gland that produces the watery component of tears.
When taken for long periods, certain medications—such as antihistamines, prescription pain medications, and some acne medications—can cause eyes to become dry. Dryness may also occur because of vitamin A deficiency or hormonal changes.
Dry eye syndrome is exacerbated by activities such as watching television or working at a computer. When performing these tasks, you don’t blink as much as usual, so the tear film evaporates more rapidly than normal. Also, wearing the same pair of contact lenses for too long puts stress on the surface of the eye, which can compromise the tear film.
If your eyes often feel dry or irritated, an ophthalmologist can perform several tests during a routine eye exam to determine the cause. These tests are meant to determine whether you have dry eye syndrome and, if so, whether it has damaged the epithelial layer protecting the cornea, which may cause further eye irritation.
In Schirmer’s test, an ophthalmologist numbs both eyes with drops and places a special strip of filter paper on the inside of both lower lids. After five minutes, the doctor gauges how much moisture each eye produced based on indicators on the paper. If your eyes produce less than a certain amount of moisture, this indicates you may have dry eye syndrome.
Epithelial Staining Test
An epithelial staining test offers the most accurate way to diagnose dry eye syndrome. Your ophthalmologist administers a painless drop into each eye that stains any abnormal, or devitalized, epithelial cells in the cornea and conjunctiva, which is a protective membrane that lines the eyelids and covers parts of the sclera, or white of the eye. Using a microscope, the doctor can then closely examine the epithelial cells for signs of damage.
After your doctor determines the severity of dry eye syndrome and whether there is damage to the epithelium, he or she can establish the best treatment for you. It is important to treat dry eye syndrome as soon as possible, especially if there is damage to the epithelium, because repeated epithelial scarring can lead to irreversible vision loss. Proper lubrication of the eyes can prevent this pattern.