Latisse was, and still is, used for many years as a treatment for glaucoma in the form of eye drops.  Patients and doctors noticed eyelash growth as a side effect. Allergan, the company who owns the patent, then got it FDA approved for eyelash growth.  Latisse is put in a thin line along the upper lash margin (like an eyeliner), NOT in the eye. 

It is very safe as long as a few precautions are observed.  Our office has a short medical questionaire that we go over with our patients before we prescribe it.  Every patient we have treated has been happy with the difference in their eyelashes.  A few of our patients developed eyelid irritation and had to stop using it.   Hope this helps.  Dr. I