Only a small part of what the eye 'sees' is in focus. To turn the image on the retina into complete vision the eye needs help from the brain.
- The brain processes the raw information coming from the eye in a number of ways.
- The brain combines multiple partially focused images to give the illusion that everything is in focus.
- The brain combines the information from both eyes into a single image.
- The eye's lens projects images on to the retina upside down, so the brain must flip it the right way up again.