Well, first, you should know that dilated pupils occur, when the pupils, the black part of the eye are bigger than normal. Also, we can say that dilated pupils look like a big black circle. And according to the experts, there are many different factors which can cause pupils to be dilated. For example, high blood pressure and anxiety can lead to it in some degree. Besides, drug use, illness, and trauma are other causes. So you should pay attention to them. And for the sake of safety, you can go and have a test in the hospital.
Well, as far as I know, people will have dilated eyes during critical or dangerous situations, and dilated eyes will be seen before an eye exam because the doctor will apply some special eye drops to dilate their eyes to better examine. And when eyes are dilated, the center of the eyes will shrink, because the nervous system dictates the muscles to shrink. So, that is the basic picture. Anyway, it is not harmful.
The dilated eyes will be bigger than the normal eyes from the visual side. The eyeballs will be extruded which will show the amazing look. When you are scared or surprising, you may show the dilated eyes. After a while, the eyes will come back to the formal state and keep the normal size.