Double vision, also known as diplopia, is the simultaneous perception of two images of a single object – the patient sees two images of a single thing either all the time, or some of the time.
Normal sight depends on multiple areas of the vision system working together seamlessly.
How An Image is Perceived
From the front to the back of the eye:
• The cornea is the clear window into the eye. It does most of the focusing of incoming light.
• The lens is behind the pupil. It also helps focus light onto the retina.
• The retina is like the film inside a camera – images falling onto the retina stimulate light-sensitive cells and create signals that are sent via the vision (optic) nerve to the brain to allow us to see.
• The vision (optic) nerve carries visual information from the eyes to the brain.
• Muscles of the eye — extraocular muscles — normally move both eyeballs in a coordinated manner
• The brain is where several areas process visual information from the eyes.
• Problems with any part of the vision system, from front to back, can lead to double vision.