We take it for granted that we see with our eyes. If our vision is bad we go to “the eye doctor.” But the eyes make up only one part of the system that creates what we see and what we think of as “vision.” The primary function of our visual system is not to recreate the physical reality of the world as exact images. Vision’s primary function is to support our interactions with the environment in:
- Recognizing the nature of the objects around us.
- Moving through and acting on that environment.
We’ll begin with an overview and then explore aspects of the system in some more detail…
Light is bouncing off objects all around you. When you look at something:
- Light bouncing off that object passes through your pupil and lens and is focused onto the retina (Optical stage)
- The retina’s light-sensitive cells (photoreceptors) convert the image formed by the light rays into nerve impulses–messages that your brain understands. The optic nerve, composed of the axons of the retina’s ganglion cells then transmits these impulses from the eye to the brain where neural processing begins. (Retinal stage)
- The brain receives these impulses and then makes sense of these impulses, assembling them into an image that you “see.” (Neural stage)
We will look at each of the three stages of vision.