Well, in some degree, it can lead to dilated eyes. Generally speaking, when you have concussion, it can just lead to some changes in your body, such as high blood pressure in your brain. And then that can affect your eyes, leading to some eye problems, such as dilated pupils. And when that occurs, the black part of the eye is 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, anxiety can lead to it in some degree. Besides, drug use, illness, and trauma are other causes. For your situation, just have the doctor check your eyes carefully and have some treatments.