Dry eye is a condition where you either don’t produce a sufficient volume of tears, or your tears are poor quality. As a result, your eyes are always dry, itchy, and irritated. Dry eye can also cause excessive tearing if your tear glands try to overcompensate for your lack of quality tears.
Your tears have oily, watery, and mucus layers. Each layer performs a critical function in keeping your eyes moist and healthy. The oily layer is on the outside of your tears and prevents the tears from evaporating. The middle, watery layer washes debris out of your eye. The mucus center layer of your tears spreads your tears over your eyes and helps them stick to your eyes.