Well, first, I think you need to check your eyes to see if your eyes have been hit. And if your eyes have some hit, it can be normal to have this kind of symptom. And you should know that in some degree, it is a sign of black eye. Of course, it all depends if your eyes are hit and how hard the slap was. Generally speaking, when your eyes are hit, it will make the blood around your eyes flow not so smoothly. And then it will turn black spots in your eyes. For your situation, you can put on ice on your eyes so that it can cool them. And remember that you should do this for several times. Anyway, just be careful about it. And you can also go and see the eye doctor too.