There must be some reasons for the dilated eyes which you may not find on the surface. Maybe you have the high blood pressure suddenly which will also cause the dilated eyes. Or you may see something that you have great interest in. All these could make your eyes become bigger.
Well, it seems that you are quite into this particular question, I quite understand your curiosity. Actually, I used to have the same puzzle. So, as a matter of fact, it is quite normal to see that , because you should know that our pupils will automatically change its size in order to adjust to different levels of light intensivity. So, with modest lights, our eyes will be dilated. However, sometimes, eye problems could lead to dilated eyes. If you do not feel right, you should consult a doctor.
I'm very sorry to hear about it. Your eyes dilate primarily for controlling the amount of light that enters your eyes. There are many reasons that lead to it together. Firstly, your eyes dilate maybe for the purpose of physiological stimuli like being charmed to somebody. Under this condition, it's your focus on something switching suddenly that gives rise to it. Secondly, your eyes dilate maybe indicate that your head have injury or other symptoms of your body such as your eyes dilate awkwardly and no repercussion to the light. On this occasion, you'd better see a doctor and take medical help. Thirdly, it may means that you have something very happy or in love. As we know, people in the excited state, the eyes will dilate for some time. I think there must be some other reasons that lead to your eyes' dilation. Take it easy, it doesn't matter!