Sometimes people cry when they are sad. Other times people cry tears of joy. But your eyes make tears all the time, whether you are crying or not. Do you know the tears help keep your eyes healthy? They keep your eyes from drying out. A special area of the eye drips (滴) all the time. It keeps the eye humid.
If you look in a mirror, you can see tiny holes in the corners of your eyes. Each hole leads to a small tube that runs to your nose. Tears run slowly into this tube drip by drip. Day and night the holes drain (流走) the tears away. If they didn't, you would always look as if you were crying.
If you begin to cry, there are many more tears. The holes can't drain all of them. Then extra tears run out onto your face.
Tears help keep eyes safe. If there is something harmful in the air, the eyes fill with tears. These tears coat your eyes. They keep the harmful air out.
Contact lenses (隐形眼镜) can make the eyes too dry. Some people have to add tears to their eyes.
They buy bottles of eye drops to keep their eyes wet.
