The most important thing to know is that overusing artificial tears may make your problem worse.

Remember that in addition to lipids (oily stuff that retards evaporation), aqueous (watery stuff) and mucin (sticky stuff) there are also all kinds of other goodies in your natural tears that nourish your epithelium (eye surface). If each week you generate a small mountain of empty single-use vials thinking that because they are unpreserved they are also harmless, not only will you get tired of spending all that money but you may wash all the good stuff out of your tears — like stuff that prevents infections! If your tears are perfectly healthy, this will make them less healthy or even unhealthy. And if as is the case with most of us, you are already somewhat deficient in lipids (oily stuff), and/or have a mucin layer (sticky stuff) problem, you may make those problems even worse.

It sounds contradictory — the more tears you use, the drier you get. But think about it. If the only thing keeping your tears from evaporating faster than you can make them or supplement them is oily stuff that your eyes secrete, and you don’t even make all that much oily stuff, and you over-dilute the tears so that there’s almost no oily stuff left, what’s going to happen? They’re going to evaporate faster, ergo, your eyes will be drier. This is why some patients report that when they stopped using artificial tears altogether, they actually saw an improvement in their symptoms.

Anyway, to answer the question, if you’re using normal off-the-shelf artificial tears, please try to avoid using them more than once every couple of hours. If the only way you can keep your eyes comfortable is dosing every 15 minutes, you’re probably going to make your tear film more and more unstable. You may need to get some more effective eyedrops, and you should be looking into things like lid therapy to boost your lipid supply. If you are truly aqueous deficient, punctal plugs may be in order. Please have a look at our dry eye treatment pages for other strategies.