As the term implies, “double vision” (diplopia) is the simultaneous perception of two images of a single object all or some of the time. These double images may be overlapping, or each may stand distinctly on its own. Causes of double vision may range from something as simple as a case of dry eye to conditions as serious as diabetes and brain tumors. For this reason, double vision is not something to be overlooked. If you are experiencing double vision, have an eye professional make a diagnosis of the cause. If double vision cannot be reversed, there are treatments that can help people live with the condition, including special prism glasses to minimize the effect of double vision. Double vision that's new or unexplained needs urgent medical attention. With so many potentially serious causes for double vision, it's important to discover the reason without delay. Double vision in one eye may be caused by astigmatism, cataracts, or age-related macular degeneration.