What Are Dry Eyes?
Do your eyes ever sting, burn, or feel scratchy? To be comfortable, your eyes need to be lubricated, or bathed, with tears. Normally, there is always a film of tears on the surface of your eyes. But if your eyes don't produce enough tears, the surface gets irritated. This is known as "dry eyes."
Not Enough Lubricating Tears
When you cry, your eyes make reflex tears. Each time you blink, another kind of tears, called lubricating tears, spread over the surface of your eyes. These tears keep the eyes moist and comfortable. You aren't aware of these tears because they stay on the surface of the eyes. But without them, your eyes get dry. Then they burn or sting and feel scratchy. They may also water. This doesn't relieve the dryness, however, because the eyes water with reflex tears, not lubricating tears.
What Causes Dry Eyes?
Heaters and air conditioners
Wind, smoke, or dry weather
Allergies such as hay fever
Eyelid problems, injuries to the eye, or diseases like rheumatoid arthritis
How Lubricating Tears Flow
Lubricating tears flow from glands in the upper eyelid over the surface of the eye. From the eye, the tears drain into canals that lead to the nose.