How Often Should Latisse Be Used?

You apply Latisse on the upper eyelash line (not in the eye) at night before you go to bed. You just use a tiny bit daily. 

While it probably would not hurt anything, since Latisse is really Lumigan and this is used for glaucoma treatment as a drop, it is best not to get Latisse in your eye. For one thing there is a chance of darkening your iris if you do, and for another, it is not advisable in general. That being said, you probably do not have to worry about this if you follow the manufacturers recommendations of applying with the applicator that comes packaged with the Latisse to just the lash base at bedtime. A tiny amount is all that is required, and enough will transfer from the upper to the lower lashes to work on those as well. More is not better and in this case less is more!

For optimimum results Latisse should be applied at bedtime every night. Most people see results in 8 weeks with full effects occuring at 16 weeks. It is best to apply it every day until this time, and then it may be possible to switch to a maintenance therapy such as once every other day depending on your physiology and response.
As far as your question regarding the eye, it is best to avoid getting the drug into the eye by applying it sparingly outside to the base of the lashes and dabbing excess fluid with a tissue. This helps minimize ocular side effects and irritation.