What does diplopia mean?
Diplopia means double vision. It is usually caused by a misalignment between the two eyes when the image of the object you are looking at falls on different areas of the retina in each eye. As a result the object is perceived in two different places and therefore is seen double. However, it can also be caused by a structural problem in one eye - for example if a cataract is present, leading to diplopia in one eye only.