The human eye is a complex organ that allows us to see. In order to process information, parts of the eye receive visual cue and other parts transmit that information to our brains. While it might sound simple, the process is actually quite complex.

Read on to learn about vision and optics and to get information on how we see.

How the Eye and Brain Perceive Images

In order for us to see, numerous components of the eyes and brain must work together. In order for this to happen, the following occurs:

1. Light enters the eye through the pupil.
2. From the pupil, the light passes through the lens and is focused on the retina.
3. Next, the rods and cones within the retina transform the light into electrical signals.
4. The optic nerve transmits the electrical signals to the brain.

Once the signals reach the brain, they are processed in a large section devoted solely to processing visual information. Since the brain is actually responsible for transforming the electrical signals into visual cues, some vision theory experts claim that the brain, not the eye, is actually responsible for sight.

Aspects of Vision

There are many aspects of vision, including:

• Color Vision: In order to see in color, the brain must be able to distinguish different wavelengths of light. Wavelength information is typically transmitted to the brain from the cones in the retina.
  
  When a person can't distinguish certain colors, he is said to be colorblind. Most people who are colorblind have problems distinguishing reds and greens..
  
  
• Depth Perception: Without depth perception we would live in a two-dimensional world. Being able to perceive depth makes the world 3-D and allows us to gauge our distance from an object.
  
  Perceiving depth requires motion parallax. This is the ability to distinguish stationary objects on a background as we move through space. Motion parallax can be illustrated when you are driving in a car. As the car moves forward, close objects pass by quickly but far-away objects seem to remain in the same place..
  
  
• Motion Perception: Motion perception is the process of inferring the speed and direction of motion in a visual scene given some visual input.

Vision Theory

How the eyes and brain perceive images and how we see has fascinated people for hundreds of years. This fascination has led to the formulation of several vision theories. Vision theory attempts to explain how visual processing creates what people actually see.

Hermann von Helmholtz, a 19th century German physician and physicist, is often credited with founding the scientific study of visual perception. Helmholtz believed that vision was a form of unconscious inference. In other words, he believed that people used prior assumptions about the world in order to process visual information.

In processing visual information, von Helmholtz thought people used the following assumptions:

• that light comes from above
• that objects are viewed from above and not below.

In order to learn what assumptions the visual system makes, researchers often use visual and optical illusions. When viewing optical illusions, some researchers believe that the system for processing visual information makes the wrong assumptions, making a person see something that isn't really there.

In addition to Hermann von Helmholtz's vision theory, there are other vision theories, including:

• The Bayesian Inference Theory, a theory that expands on von Helmholtz's vision theory.
• The Gestalt Theory, which states that people use six factors (proximity, similarity, closure, symmetry, common fate and continuity) to process visual information.