Yes, when you are scared, your eyes may get dilated. It is the stimulation of the eye nerves that will cause the eyeballs change suddenly. However, it will get released after a while. In addition, when you find something you have an interesting, you may also get the dilated eyes. After calming down, your eyes will come back to the normal state.
Well, I have to say that it is normal for you to have dilated pupils. Dilate pupils are often caused by high blood pressure. When you are scared, your blood pressure can be very high, and then it can lead to high eye pressure in your eyes. In that way, it can affect your eyes, and then lead to dilate pupils. So that is way you have dilate pupils, when you are scared. So to treat it, you should calm down, and then it will be fine. Also, you should know that there are also many other factors, which can causes dilated pupils too, such as hyperventilation, muscle tensions, which are the most common causes to dilated pupils. Anyway, just be careful about them.
There are lots of reason for pupils dilate ,being scared is one of them.Because the nervous system controls the muscles of the irises, the response of the nervous system to different stimuli results in involuntary pupil dilation. Another commonly cited reason the pupils dilate is in response to excitement or sexual arousal. When a person sees something or someone he finds very attractive, his eyes may dilate.
Plus natural light swift ,drug use and other reasons makes pupils dilate as well.