Your Natural TearsYour tears play an important role in keeping you healthy. Tears keep the surface of your eyes clean and moist, and help protect your eyes from debris and bacteria. Although they may appear to be nothing more than water, your tears are actually quite complex. They are composed of water, carbohydrates, lipids, electrolytes, lysozymes (enzymes that act like natural antibiotics to kill bacteria and viruses), lactoferrin (proteins that prevent or slow bacterial growth), binding proteins and vitamins. A model of the tear film that scientists have adopted is a basic three layer film that consists of a mucus layer, water layer and a lipid or oily layer.
Purpose of Artificial TearsAlthough it is impossible for over-the-counter artificial tears to substitute perfectly for natural tears, manufacturers of artificial tears try to simulate the natural tear film or at least one of the three layers to improve where natural tears are lacking. Because there are so many different brands of artificial tears, it's sometimes confusing to figure out which one is best for your eyes.
Artificial Tears and HydrogelsSome artificial tears are thin like water and some are thick, almost like gel. Most artificial tears contain hydrogels, or particles that work to increase the moisture in your eyes for a longer period of time. Some artificial tears may seem to work better for your eyes since some brands of artificial tears contain more hydrogels than others.
Artificial Tears and Added PreservativesSome artificial tears contain preservatives and some don't. While preservatives will not cause harm to most of us, people with severe dry eye syndrome that require frequent instillation of artificial tears can have a toxic or sensitivity reaction to them that can actually worsen their symptoms. A particularly well-known preservative called BAK or benzalkonium chloride should be avoided for particularly sensitive individuals.
Artificial Tears That Change Your TearsSome artificial tears have ingredients that change the chemical make-up of your tears to decrease negative or pathological changes that can occur to your eye as a result of having dry eyes for long period of time. One school of thought is that if you change the composition of the tear film, the symptoms of dry eye will be reduced. Artificial tears that decrease that change the composition of your tears include Optive, Hypotears, Akwa Tears and Thera Tears.
Artificial Tears That Coat Your EyeSome artificial tears have ingredients that promote healing of the surface cells of the eye. Artificial tears that contain HP-guar are much more likely to improve the moisture content of cells that have more damage due to dryness. HP-guar is a molecule that forms a gel layer that protects the damaged cells. This gel layer also increases the likelihood of the water component of your tears to "stick" to your eye. Artificial tears that work by coating the eye include Systane Ultra and BLINK Tears.
Artificial Tears That Stabilize Natural OilsSome artificial tears aim to stabilize the oil part of the tear film. The oil part of the tear film can be disrupted if conditions are present such as blepharitis or meibomian gland dysfunction. If the oil part of the tear layer is disrupted, your natural tears will evaporate at a much faster rate than normal, leaving your eyes feeling dry and gritty. These artificial tears actually contain oily ingredients such as castor oil or mineral oil. Examples of these artificial tears are Refresh Endura, Systane Balance and Smooth XP artificial tears.
Artificial Tears That Last LongerA few brands of artificial tears attempt to increase contact time with the eye simply by being much more viscous. Refresh Liquigel contains a higher concentration of carboxymethylcellulose that makes it more difficult for the lubrication effect to wear off. Celluvisc is another artificial tear that is similar to Refresh Liquigel but is really more of a gel than a liquid and is extremely viscous. Although the thickness of this eye drop may cause temporary blurry vision, it is a side effect that severe dry eye patients are willing to put up with.
What You Should Know About Artificial TearsIt is important for you to take a few moments to discuss with your eye doctor the origin of the dry eye condition you may have. Your doctor may recommend a specific artificial tear that may be a better alternative for the type and level of severity of your dry eye condition.
The Eye Digest, The University of Illinois, Eye & Ear Infirmary, Chicago, Illinois. Artificial Tears: Too Many Choices. Page reviewed 19 May 2009.