When your eyecare professional says you have dry eyes they are talking the surface of your eyes has dry spots on it. When you then blink the lid will drag across your eye  - this leads to the eye becoming irritated and it’s reaction is to tear up more..... The downside of this type of tear is that it has a lot less oil in it and therefore doesn’t lubricate. The artificial tears have the perfect combination of oils / lubricants and surface conditioners to help rehydrate those patches and leads to less watering.