The function of your eye can be compared to a camera. Just as a camera focuses light rays onto film to record a picture, the cornea and lens focus light onto your retina to form an image. While the lens is extremely important in the proper focusing of light rays, the front surface of the cornea is actually responsible for two-thirds of the total focusing power of your eye. Your tear film is present on the front of your cornea and provides the smooth, clear surface required for good visual function. In addition, the tear film provides lubrication for eyelid movement over the cornea, nutrition for the external surface of your eye, and also anti-bacterial substances to maintain the health of your eye.
This tear film is more than just salt water. It is composed of three layers—oil, water and mucous. Dry eye disease is an irritating and occasionally painful condition involving a reduction of (or imbalance between) one or more of the tear film layers.
Mucous forms the innermost layer of the tear film. It is made by special cells in the conjunctiva (the thin, delicate membrane that covers the white part of your eye). Mucous helps the overlying water layer adhere to the eye.
Water composes the middle and largest of the three tear layers. It is produced by the main and accessory tear glands. This layer provides lubrication; washes debris away from the surface of your eye; and contains oxygen, sugar and protein to nourish the cornea. In addition, it contains antibodies and enzymes that help protect your eye from infection.
Oil forms the last and outer layer and is secreted by glands present near the base of your eyelashes. The oil layer stabilizes and retards evaporation of the tear film layer.
Dry scratchy, irritated eyes are a very common problem that affects all ages, especially older adults. It is hard to determine the exact number of dry eye disease sufferers because of the wide range of causes; however, it is known that at least 60 million people worldwide use artificial tear products to treat dry eye symptoms.
For most people, it is uncomfortable but not vision-threatening. In some cases, however, a faulty or diminished tear film can affect the cornea's focusing ability and increase the risk of infection.
Estrogen can inhibit the function of oil-producing glands. This is thought to affect a gland in the eyelid that produces an oily substance needed as a component of a normal tear film. A Harvard study showed a substantial link between hormone replacement therapy and dry eye disease. Of the 25,000 women age 49 and older, those participants taking estrogen were about 70% more likely to have dry eye syndrome than women not taking the hormone. And, women taking both estrogen and progesterone had a 30% increased risk of dry eye syndrome.
Dry eye disease is a frustrating problem that usually affects both eyes and can range from a mild annoyance to severe discomfort. You should arrange for an evaluation of your condition, if one or more of the following symptoms significantly bother you:
A medical history and detailed description of your symptoms is essential to properly diagnosing dry eye disease. Your eye care specialist will also conduct a thorough eye examination, including one or more of the following tests:
Schirmer's Tear Strips: After numbing your eyes with drops, these small paper strips measure the amount of tears your eyes produce.
Rose Bengal Staining: These rose-colored drops are used to highlight areas on the front of your eye that are dry and irritated.
Fluorescein Staining: These yellow-colored drops reveal areas where the cornea (the transparent front portion of the eye) and conjunctiva (a membrane that lines the eyelids) are damaged. They also outline the tear pool and give an estimate of its volume.
Tear Break-Up Time: This test estimates the time required for your tear film to evaporate before blinking. Generally, a break-up time of less than 10 seconds indicates an abnormality in your tear film.
Slit Lamp Examination: The doctor uses a special microscope to evaluate your eyelids' health and check for mucous filaments and/or debris in the tear film.
Dry eye disease is a life-long condition. Although it is rarely cured, proper treatment can achieve control and comfort.
The most common treatment for dry eyes is use of non-prescription artificial tear substitutes, such as Refresh, Thera Tears, Tears Naturale and other products with no preservatives and nothing "to take the red out" (which can cause a "rebound" effect that exacerbates problems). To be effective, these drops must be used frequently—sometimes as often as every hour.
As just explained, the common treatment for dry eyes is to alleviate symptoms by adding moisture with artificial tears or retaining moisture with punctal plugs. There is, however, another option: Restasis®, an FDA-approved prescription eye drop that treats the cause (rather than symptoms) of dry eyes by increasing tear production in patients who don't produce enough tears.
Why is Restasis® "revolutionary?"
Its creation came from a major change—in viewing dry eye not as a nuisance, but as a disease. As with rheumatoid arthritis treatment (which changed from relieving symptoms to attacking related immune alterations to prevent later disability), Restasis® researchers realized the need to shift from relieving the symptoms of dry eyes to treating the inflammatory process that causes the condition.
What is this inflammatory process?
Dry eye disease occurs when the surface of the eye becomes irritated by any of a number of environmental or physical factors, including aging, diseases, contact lenses, computer work, allergens, smoke and medications. In a normal functioning eye, there is an anti-inflammatory component that keeps the disruptive effect of this irritation to a minimum. However, when this component is lacking and the irritation is not controlled, the eye does not produce adequate tears. This irritation causes the body's immune system to activate its troops of inflammatory cells, including T-lymphocytes. Thinking that the eye is under attack, these T-cells release special proteins called "cytokines." The ensuing inflammation—of both the eye's surface and the glands that produce tears—results in abnormal tears and symptoms of dry eye. Since the tears are abnormal, the irritated eye is not properly nourished or lubricated. This encourages the cycle of inflammation and symptoms to repeat again and again.
How does Restasis® treat the problem?
Restasis® was created to treat the underlying inflammation that causes dry eye disease and to thus alleviate its symptoms. It regulates the eye's immune reaction to dry eye stimuli by reducing the number of inflammatory cells that are activated and blocking the production of destructive inflammatory chemicals.
How safe is Restasis®?
Restasis® is a .05% concentration of Cyclosporin A formulated as an eye drop used twice a day. This dosage is miniscule compared to its more common therapeutic use in reducing the risk of organ transplant rejection. Safety studies show that Restasis® does not pass into the bloodstream or cause side effects to the body.
Who can use Restasis®?
Anyone who suffers from dry eye symptoms or already uses artificial tears without relief may be a candidate for Restasis®. Beneficial effects (like decreased artificial tear use) take about three months to occur. If you are interested in Restasis®, your eye care specialist can conduct tests to determine if a prescription is right for you.
It is important to remember that dry eyes are often a life-long condition that can fluctuate in severity. Dry eyes can usually be controlled, but rarely cured. The following measures may help you to alleviate much of your discomfort, fear and frustration:
Since 1985, Eye Care Specialists has provided comprehensive medical, surgical and laser care for virtually every eye condition to more than 130,000 people in southeastern Wisconsin. If you would like detailed booklets/handouts on the information contained in this section or other eye-related topics, please contact our Communications & Education Department at 414-321-7035. To schedule a comprehensive eye evaluation, call one of our three convenient Milwaukee-area locations directly.