Dry eye syndrome (also known as keratoconjunctivitis sicca or KCS) is one of the most common ocular conditions. It is characterized by decreased production of natural tears. Most cases are mild, but it often can affect your comfort and ocular health. Despite greater understanding of tear film production, the underlying cause of dry eyes is usually unknown. However, various treatments are available to afford some relief from their chronic ocular problem.
The Normal Tear Film
The tears form a moist layer over the surface of the eye, including the cornea and conjunctiva. Since the tear layer is the outermost surface of the eye, it acts as an interface between the eye and the outside environment. There are several important functions of the tear film. It moistens and protects the surface cells (epithelium). Without that moisture, the cells can harden and look more like the skin over the rest of your body. The tear film also provides a smooth, transparent surface that helps focus light entering the eye, and is necessary for sharp, clear vision. Our tears also serve as a vehicle for oxygenation and nourishment of the ocular surface. Finally, the tear film contains several substances that help protect the ocular surface against infection.
The film is comprised of three layers, each essential to maintaining the health of the eye (FIG. 1). Abnormalities of any of these layers can cause a tear dysfunction problem. The innermost layer is made of mucin produced by cells in the conjunctiva, and helps the tears spread smoothly over the ocular surface (wettability). The thick middle layer is composed primarily of water, and is produced by the lacrimal gland. Finally, the outer lipid layer, produced by the meibomian glands, enhances the stability of the middle aqueous layer by retarding tear film evaporation.
What Are The Symptoms of Dry Eye?
The most common symptoms are dryness, burning, irritation, a sandy or gritty feeling, redness, and blurred vision. These symptoms usually affect both eyes, but only one can be affected. The eyes typically get worse as the day progresses, and can become more pronounced when reading or watching TV. Some patients may be especially sensitive to dry or irritating environments, such as dry heat, warm or smoke-filled rooms, and wind. Sensitivity to light may also be reported.
HOW IS DRY EYE DIAGNOSED?
How is Dry Eye Diagnosed?
The signs of dry eye are often subtle, and the eye doctor may not make the diagnosis unless he or she specifically tests for it. The following are often used and can be very helpful in detecting dry eyes.
Vital Dry Stains
Rose bengal (rose colored) and lissamine green dyes adhere to the ocular surface where it is dry or irritated. The amount and pattern of staining can tell the doctor what is causing your symptoms.
Test of Tear Production
These tests involve placing a small strip of paper or a thread under the lower lid and measuring how much tears it absorbs over a small period of time. These tests are simple and make the diagnosis if the result is low. However, they often miss mild cases of dryness.
Tear Break-up Time (BUT)
The tear break-up time (BUT) is a direct measure of the stability of the preocular tear film. A normal tear film with sufficient lipid, aqueous, and mucinous layers begins to break up, or show signs of discontinuity, after approximately 10 seconds. This process is generally accelerated in patients with dry eyes.
What is Sjogren's Syndrome?
Sjogren’s syndrome is the combination of dry eyes and dry mouth or dry eyes and a systemic autoimmune disease, such as rheumatoid arthritis or lupus erythematosis. The combination of dry eyes and dry mouth alone is called primary Sjogren’s syndrome, and can be associated with inflammation elsewhere in the body. A thorough general physical examination and some blood tests are necessary to make the diagnosis of primary Sjogren’s syndrome. In most cases the only treatment is of the ocular and mouth dryness.
Treatment of Dry Eyes
At present, there is no cure for dry eyes; there is no way to restore your tear production to normal. However, there are a number of ways to ameliorate the symptoms. In general, patients suffering from dry eyes will benefit from a moist, humid environment. A warm, dry room can be made more tolerable by using a home humidifier and by avoiding smoke or dust. Swimmer's goggles or even side shields with spectacles increase the humidity in the environment immediately around the eye, and delay the evaporation of tears.
Artificial Tear Preparations
Artificial tears remain the primary treatment for mild to moderately dry eyes. They are made to simulate the aqueous (liquid) layer of your natural tears. Most artificial tears also have a thickening agent to improve lubrication and help them last longer by retarding evaporation. The most common thickening agents are derivatives of cellulose or polyvinyl alcohol. Unfortunately, placing a drop of tears in your eye cannot replace the natural constant flow of tears over the eye. Before long, the artificial tear drops evaporate or drain from the eye (through the natural tear drainage ducts that lead from the eye to the nose). Therefore, you may need to instill the drops frequently (as often as every 15 minutes) to keep the eyes moist.
There are a large variety of commercially made artificial tear preparations. They generally can be divided into three types:
Tear Solutions With Preservatives
The available tear solutions vary widely and change every year. No one type is best for everyone. You have to try several and find the one that provides you the most relief. All of these drops come in a small bottle and contain preservatives so that the bottle does not become contaminated while you are using it. Unfortunately the preservatives can cause irritation and injury to the surface cells, particularly if the drops are used very frequently or if the eyes are very dry. New, less-irritating, preservatives are constantly being developed, so some products are safer to use than others, but any can cause problems.
Tear Solutions Without Preservatives
For this reason many preservative free preparations have been made available. Since there is no preservative these products are packaged in very small plastic dispensers that must be discarded the day they are opened. Although much less convenient and more expensive than tears in larger bottles, they are the best products for people requiring drops every 2 hours or more or who are sensitive to a preservative.
Lubricating Ointments And Gels
These are more viscous so they lubricate better and stay in the eye longer, however they often blur your vision. Therefore most people use them at bedtime or when their symptoms are especially severe. In general the gels are in-between drops and ointments.
Restasis (cyclosporine ophthalmic emulsion 0.05%) is an exciting new treatment for dry eyes. Unlike artificial tears, Restasis is the first drug proven to increase tear production in some patients with dry eyes. Researchers have found that inflammation in the surface cells contributes to dry eyes. Restasis quiets this inflammation.
Restasis is most likely to benefit patients with moderate dry eyes (as opposed to mild or severe). It is an eyedrop that is instilled twice daily in addition to your usual artificial tears. If the restasis works your comfort will improve and most likely your need for artificial tears will lessen.
The most common side effect of Restasis is a temporary burning sensation. Many patients see an improvement in 1 month. However, you may not see the effect of Restasis until you have been using it for 3 months, and it takes about 6 months to get the maximum effect. You have to keep using the drops to maintain the effect. Keep in mind that Restasis is a treatment, not a cure.
Tear Conservation By Punctal Occlusion
Conserving existing tears by reversible (punctal plugs) or irreversible (punctal cautery) punctal occlusion can be of tremendous benefit to dry eye patients with severe tear deficiency. Punctal occlusion prolongs the action of artificial as well as natural tears by retaining them longer on the eye. One method of occlusion is to place a silicone punctal plug into the tear drainage holes of the lids. The advantage of this type of punctal occlusion is its reversibility. If punctal plugs appear to relieve the symptoms of dry eyes with few or no problems, then permanent punctal occlusion via cautery may be considered.
Partial Or Total Tarsorrharphy
In severe cases of dry eye it is appropriate to consider partial or total surgical closure of the eyelids. This is known as a tarsorrhaphy. This procedure decreases the surface area that the eye needs to keep lubricated.
It appears that a high dietary intake of omega-3 essential fatty acids decreases the risk of dry eye. A recent study found that there was a relationship between omega-3 fatty acids in the diet and the likelihood of dry eyes. Using the Women’s Health Database at the Harvard School of Public Health, the investigators examined the dietary intake of essential fatty acids in 32,470 female health professionals. They found that the higher the dietary ratio of omega-3 to omega-6 essential fatty acids, the lower the likelihood of dry eye, and the higher the dietary omega-3 intake, the lower the likelihood of dry eye. Conversely, they found that the lower the ratio of omega-3s to omega-6s the higher the likelihood of dry eye.
Based on this finding, doctors have tried omega-3 supplements to treat dry eye. In some patients the supplements appear to lessen their symptoms. Treatment is started at 2-4 capsules twice daily. If it is going to help you will see a response in 4 to 8 weeks.
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Copyright © 2009 Robert C. Arffa, M.D., 1370 Washington Pike, Bridgeville, PA 15017