Tunnel vision is caused by loss of peripheral vision. Usually it is normal to get tunnel vision if you stand up quickly. I don't know how to explain it, but most of people suffer it. It is not a serious problem and the tunnel vision will recover soon about several seconds. Also, i heard that blood loss to parts of the bran can also cause tunnel vision. However, if you often suffered from tunnel vision, you shall pay attention to it. It is said that tunnel vision can also be caused by retinitis pigmentosa and glaucoma. So, you'd better check your eyes if you suffered from it.
