Well, yes, when you have a panic attack, it is possible for your eyes to have dilated pupils. First, you should know that high blood pressure can lead to dilated pupils. So when you have a panic attack, it will just make you have high blood pressure. And then in that situation, it can just affect your eyes, leading to dilated pupils. Also, you should know that anxiety can be the cause too. So just be careful about it.
Pupil are the black circle in eyes working as camera aperture, which let light get into eyes. It can change size just like the aperture. When you are in a bright environment, the pupil shrinks to let less light in, so that you won't feel blinding. When you are in a dark place, the pupil dilate to let more light in so that you could see clearer. Other than light, pupil changes size in response to emotions too. According to researches, pupil dilates when people are angry, terrified or excited, because the muscle of irises is controlled by nervous system. It is the involuntary response to different stimulation to nervous system. This is why panic attack causes pupils dilate.
It is true that sometimes our pupils would be dilated if we are panicked or surprised by something unexpected you know? And as you are panicked, your brain would give signal to your pupil muscle to make them dilated. But it is not a serious problem if dilated eyes are not generated by other causes.