Seeing two of something, when you know there is only one is called double vision. The double vision can be up and down, or side to side. It can be visible all the time, part time, or always on the verge of double which causes head aches, dizziness, and an uneasy feeling. Double vision can be caused by serious, life threatening disease, or you might have been born with it. Tumwater Eye Center will help you understand why you have double vision and what can be done to help.