Sight is the ability to see clearly, vision is the ability to take what you see and do something with it. Each eye on its own provides 10% of all information. Both eyes working together provide the remaining 80%
Thanks to the close side-by-side positioning, each eye takes a view of the same area from a slightly different angle. These two separate images are sent to the brain for processing and when the two images arrive simultaneously in the back of the brain, they are united into one picture. The brain combines the two images by matching up the similarities and interpreting the small differences. These small differences between the two images add up to a big difference in the final perceived picture! The combined image is a three-dimensional ‘stereoscopic’ picture – stereoscopic refers to the vision’s ability to make objects appear firm and solid through the added perception of depth. With stereoscopic vision, we can see where objects are in relation to our own bodies with much greater precision – especially when those objects are moving towards or away from us. We can see a little bit around solid objects without moving our heads and we can even perceive and measure ‘empty’ space using our eyes and brains.
Here are just a few examples of general actions that depend heavily on stereoscopic vision:
- Throwing, catching or hitting a ball
- Driving and parking a car
- Planning and building a three-dimensional object
- Threading a needle and sewing
- Reaching out to shake someone’s hand
- Pouring into a container
- Stepping off a curb or step
- Writing and drawing
This ability of combining the two visual images from each eye requires accurate binocular vision. Binocular vision is achieved by both eyes working as a team and is dependent on accurate alignment of the eyes and appropriate unification of the two images by the brain. If the views of the two eyes vary too much the brain will not be able to match them up and will be forced to make a choice and it will reject all or part of the information from one eye. When both eyes work together smoothly, accurately, equally and simultaneously we can both enhance our quality of life and increase life choices. Every attempt should be made to develop this ability in a person.
Vision and balance are closely related
As with the hearing system vision is intricately linked with the vestibular system. Vision allows the brain to orient the location of the head or body by sight.
- When the head turns to the left your eyes typically follow around to the left
- Once your eyes settle on a target your brain uses this information as a reference for your balance system
- Reduced visual acuity affects the ability of the eyes to locate an appropriate visual reference and therefore can reduce accuracy impairing proper balance