Binocular eye movements in humans: from optimal binocularity to strabismus

Binocular vision and stereopsis is one of the major characteristics of frontal eyed species, such as humans. Binocular vision results from the projection of 3D-objects on corresponding area's of the retina's of the two eyes. An individual with. binocular vision perceives one single image of the object containing depth information (binocular vision). The minute differences between the' left and the right image (disparity) ideally give rise to stereoscopic vision. This entity of the binocular system has been used for artificial stereopsis in 3-D pictures and movies. The importance of binocular vision in daily life becomes clear when individuals with optimal binocular coordination are forced to use mostly one eye (e.g. because of an eye infection). Their loss of binocular visual information causes difficulties with simple tasks, like shaking hands. Individuals who have sub-optimal binocularity for a longer period can function very well due to adaptive mechanisms and the use of nonstereoscopic depth cues. Many people are unaware of their slight sub-optimal binocularity which only a stereopsis test reveals. People with low vision in one of their eyes, have less binocularity but the use of both eyes can still be very useful for the detection of large moving objects such as approaching cars. They usually have no impairments in their daily tasks. Individuals with vision in one eye only adapt mainly by making more head movements. With this adaptation they have no difficulties, even with tasks like driving a car.