Well, when dilated pupils occur, the black part of the eye will be bigger than normal one. And you will feel painful in some cases. To treat it, the first thing you can do is to make sure you wash your eyes frequently. Also, it is also important to apply cleansing eye drops to get rid of any foreign particles. For the home remedies, you can try some cool teabags, and just put them on your eyes, maybe it can be effective. Of course, cool cucumbers can be used too. By the way, you should know that when you suffer dehydration, your body will be disordered. So at that moment, you may suffer high blood pressure too. And then it is possible to lead to dilated pupils. Also, some factors, such as high blood pressure and anxiety, drug use, illness, and trauma can lead to it. Anyway, just be careful.