Usually that's due to any type of eye irritation - allergies, infection, cold, something in the eye, overnight dryness- and the artificial tears should wash them away. Maybe you can try a different brand of tears and see if that helps? Even if they are preservative free, your eyes just might not like them. Genteal is another brand - I use them and really like them. Systane, B&L Moisture Eyes are other ones my eye doc recommended. Drugstore.com also lists Tears Naturale and TheraTears.