Diplopia, also known as double vision, is the simultaneous perception of two images of a single object that may be displaced horizontally or vertically in relation to each other. It is a loss of visual focus under regular conditions and can be caused by a diverse range of ophthalmologic, infectious, autoimmune, neurological, and neoplastic conditions. Diplopia can be diagnosed mainly by information from the patient, and doctors may use blood tests, physical examinations, computed tomography (CT), or magnetic resonance imaging (MRI) to find the underlying cause. There are two main types of diplopia: monocular and binocular. Monocular diplopia occurs when someone sees double vision with only one eye open, and the causes are typically confined to the eye and less likely to be neurological. Binocular diplopia occurs when someone sees double vision only when both eyes are open, and the causes may be serious conditions, neurological or otherwise. The outlook for diplopia is generally positive, and it doesnt have a long-term effect on most people. Depending on the underlying cause, treatment options may include surgery, medication, or adjusting eyeglass or contact lens prescriptions.