It is really noraml to suffer it. Inf act, almost everyone has such experience. Because our eyes are too sensitive to the flash light from camera, so our eyes closed themslves to protect the eyes from damages from the harsh flash light. The only thing you can do is try your best to keep your eyes open when you take a picture. If you can't do it, you can shield your eyes by sunglasses.
It is a natural reaction for human beings to close eyes when facing the flash light from camera. In fact, the sharp and harsh flash light is harmful for the eyes. And our eyes can feel uncomfortable to the flash light that closing the eyelids to protect the eyes. But to get a bueatiful pictures, we have to do everything to keep our eyes open when take pictures.