Dry Eye-A Closer Look
What is dry eye?
Normally, the eye constantly bathes itself in tears. By producing tears at a slow and steady rate, the eye stays moist and comfortable.
Sometimes people do not produce enough tears or the appropriate quality of tears to keep their eyes healthy and comfortable. This condition is known as dry eye.
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 large quantities 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.
What are the symptoms of dry eye?
The usual symptoms include:
- Stinging or burning eyes
- Stringy mucus in or around the eyes
- Excessive eye irritation from smoke or wind
- Excess tearing
- Discomfort when wearing contact lenses
Excess tearing from "dry eye" may sound illogical, but it can be understood 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.
What is tear film?
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.
The tear film consists of three layers:
- Oily layer
- Watery layer
- 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. It's main purpose is to smooth the tear surface and reduce evaporation of tears.
The middle watery layer makes up most of what we think of as tears. This layer produced by the lacrimal glands in the eyelids, cleanses the eye and washes away foreign particles of 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.
What causes dry eye?
Tear production normally decreases as we age. Although dry eye can occur in both men and women at any age, women are most often affected. This is especially true after menopause.
Dry eye can also be associated with other problems. For example, people with dry eyes, dry mouth and arthritis are said to have Sjogren's syndrome.
A wide variety of common medications - both prescription and over-the-counter - can cause dry eye be reducing tear secretion. Be sure to tell your ophthalmologist the names of all the medications you are taking, especially if you are using:
- Sleeping pills
- Medications for "nerves"
- Pain relievers
Since these medications are often necessary, the dry eye condition may have to be tolerated or treated with eyedrops called artificial tears.
People with dry eye are often more prone to the toxic side effects of eye medications, including artificial tearms. For example, the preservatives in certain eyedrops and artificial tear preparations can irritate the eye. These people may need special preservative-free artificial tears.
How is dry eye diagnosed?
An ophthalmologist is usually able to diagnose dry eye by examining the eyes. Sometimes tests that measure tear production are necessary.
One test, called the Schirmer tear test, involves placing filter-paper strips under the lower eyelids to measure the rate of tear production under various conditions. Another test uses a diagnostic drop to look for certain patterns of dryness on the surface of the 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.
Source: American Academy of Ophthalmology