What is dry eye?
When you blink, a film of tears spreads over the eye, making the surface of the eye smooth and clear. Without this tear film, good vision would not be possible.
Sometimes people don't produce enough tears or the right quality of tears to keep their eyes healthy and comfortable. This condition is known as dry eye.
The tear film consists of three layers:
- An oily layer;
- A watery layer;
- A layer of mucus.
Each layer has its own purpose. The oily layer, produced by the meibomian glands, forms the outermost surface of the tear film. Its main purpose is to smooth the tear surface and reduce evaporation of tears.
The middle watery layer makes up most of what we ordinarily think of as tears. This layer, produced by the lacrimal glands in the eyelids, cleanses the eye and washes away foreign particles or irritants.
The inner layer consists of mucus produced by the conjunctiva. Mucus allows the watery layer to spread evenly over the surface of the eye and helps the eye remain moist. Without mucus, tears would not stick to the eye.
Normally, the eye constantly bathes itself in tears. By producing tears at a slow and steady rate, the eye stays moist and comfortable.
The eye uses two different methods to produce tears. It can make tears at a slow, steady rate to maintain normal eye lubrication. It can also produce a lot of tears in response to eye irritation or emotion. When a foreign body or dryness irritates the eye, or when a person cries, excessive tearing occurs.
It may not sound logical that dry eye would cause excess tearing, but think of it as the eye's response to discomfort. If the tears responsible for maintaining lubrication do not keep the eye wet enough, the eye becomes irritated. Eye irritation prompts the gland that makes tears (called the lacrimal gland) to release a large volume of tears, overwhelming the tear drainage system. These excess tears then overflow from your eye.
How is dry eye treated?
Adding tears
Eyedrops called artificial tears are similar to your own tears. They lubricate the eyes and help maintain moisture. Artificial tears are available without a prescription. There are many brands on the market, so you may want to try several to find the one you like best.
Preservative-free eyedrops are available for people who are sensitive to the preservatives in artificial tears. If you need to use artificial tears more than every two hours, preservative-free brands may be better for you.
You can use the artificial tears as often as necessary — once or twice a day or as often as several times an hour.
Conserving your tears
Conserving your eyes' own tears is another approach to keeping the eyes moist. Tears drain out of the eye through a small channel into the nose (which is why your nose runs when you cry). Your ophthalmologist may close these channels either temporarily or permanently with punctal plugs. This method conserves your own tears and makes artificial tears last longer.
Other methods
Tears evaporate like any other liquid. You can take steps to prevent evaporation. In winter, when indoor heating is in use, a humidifier or a pan of water on the radiator adds moisture to dry air. Wraparound glasses may reduce the drying effect of the wind.
A person with dry eye should avoid anything that may cause dryness, such as an overly warm room, hair dryers or wind. Smoking is especially bothersome.
Some people may find dry-eye relief by supplementing their diet with omega-3 fatty acids, which are found naturally in foods like oily fish (salmon, sardines, anchovies) and flax seeds. Ask your Eye M.D. if you should take supplements of omega-3 fatty acids and, if so, in what form and dosage.
If other methods do not give you adequate relief from dry eye, your ophthalmologist may suggest that you use a prescription medication. One such medication, cyclosporine, works by stimulating tear production. Steroid eyedrops may also be used, but are generally not recommended for long-term treatment. Other treatment options may include ointments, gels and inserts.
Dry eye due to lack of vitamin A in the diet is rare in the United States but is more common in poorer countries, especially among children. Ointments containing vitamin A can help dry eye if it is caused by unusual conditions such as Stevens-Johnson syndrome or pemphigoid. Vitamin A supplements do not seem to help people with ordinary dry eye.
Source American Academy of Ophthalmology,
Last reviewed and updated in March 2010
