The eye depends on the flow of tears to provide constant moisture and lubrication to maintain vision and comfort. Tears are a combination of water, for moisture; oils, for lubrication; mucus, for even spreading; and antibodies and special proteins, for resistance to infection. These components are secreted by special glands located around the eye. When there is an imbalance in this tear system, it can cause a condition known as dry eye syndrome or DES. DES occurs when your tears aren't able to provide adequate moisture for your eyes. Tears can be inadequate for many reasons. For example, dry eyes may occur if you don't produce enough tears or if you produce poor-quality tears.
Have you ever heard someone say, “I’m so hungry, I could eat a horse”? Of course, there is no way that one person could actually eat that much, and, without being able to store what was not eaten immediately, the rest would spoil. Strangely enough, one of the most common symptoms of DES is excessive tearing. If you have DES, why would you have too many tears? Although it does not seem to make sense at first, this is often the case. With DES, your eye becomes slightly dry and irritated; therefore, it produces an enormous amount of tears all at once to try to get moist and comfortable again.
Unfortunately, just like our hungry person could eat only so much and the rest was wasted, your eye can only handle so many tears at any one time; the rest pour over your eyelids and down your cheeks. Those tears that pour down your cheeks do not help your eyes and are wasted. Also, just like our hungry person will eventually get hungry again, your eyes will become slightly dry and irritated again, and the whole process repeats. You may also experience the following symptoms:
- Dry, gritty/scratchy, or filmy feeling
- Burning or itching
- Blurred vision
- Foreign body sensation
- Light sensitivity
Dry eye syndrome is most commonly caused by situations that dry out the tear film. This can be due to dry air from air conditioning, heat, or other environmental conditions. An eye infection along the eyelids or the eyelashes, called blepharitis, can contain bacteria that may breakdown the oil in the tears. In addition, DES can also be caused by any of the following:
Aqueous (watery) tear deficiency is caused by either poor production of watery tears or excessive evaporation of the watery tear layer.
- Poor production of tears by the tear glands may be a result of age, hormonal changes, or various autoimmune diseases, such as primary Sjögren syndrome, rheumatoid arthritis, or lupus.
- Evaporative loss of the watery tear layer is usually a result of an insufficient overlying lipid layer.
- Some medications, such as antihistamines, antidepressants, beta-blockers, and oral contraceptives, may decrease tear production.
If blinking is decreased or if the eyelids cannot be closed, the eyes may dry out because of tear evaporation.
- When you read, watch TV, or perform a task that requires close attention with your eyes, you do not blink as often. This decreased blinking allows excessive evaporation of the tears.
- Certain conditions, such as stroke or Bell palsy, make it difficult to close your eyes on your own. As a result, your eyes may become dry from tear evaporation.
If the conjunctiva is producing an abnormal amount of mucin.
- This can result from chemical (alkali) burns to the eye or because of different autoimmune diseases, such as Stevens-Johnson syndrome and cicatricial pemphigoid.
- This abnormal production leads to poor spreading of the tears over the surface of the eye. The surface of the eye can dry out and even become damaged, even though more than enough watery tears may be present.
Insufficient lipid layers are the result of meibomian gland dysfunction, as with rosacea or following oral isoretinoin medication.
- Meibomian glands are the oil glands in the eyelids that produce the lipid layer.
- If the oil glands become blocked or if the oil is too thick, there may not be enough oil to cover the watery tear layer to prevent its evaporation.
Most clinicians diagnose and treat Dry Eye Syndrome based on the symptoms alone. Assessment of symptoms has been determined to be the single most important test for dry eye syndrome diagnosis. However, there are some basic tests that may be performed like tear film break-up time, Schirmer test and fluorescein staining.
Although no cure exists for DES, many treatments are available. Treatment is dependent on the severity of DES; you may only require a humidifier or occasional eyedrops, or you may require surgery to help decrease DES. If you notice your eyes are dry mainly while you are reading or watching TV, taking frequent breaks to allow your eyes to rest and become moist and comfortable again is helpful. Closing your eyes for 10 seconds every five to 10 minutes will increase your comfort, as will blinking more frequently.
Over-the-counter lubricating eyedrops, commonly referred to as artificial tears, may help relieve your dry eyes. Some examples of these products include Refresh, Genteal, Soothe and Tears Naturale. Medications as well as surgical options are also available. These are best discussed with your ophthalmologist after a thorough exam.