The Main Functions of the Eye

Close-up of a young woman's eye
A close-up of a woman looking into the camera. (Image: Jack Hollingsworth/Blend Images/Getty Images)

Eyes are the body's camera. In addition to vision, your eyes also provide depth perception and contribute to your balance. These functions are made possible by multiple components in your eye, including rods, cones, retinas and lens.

Light Detection

Every object reflects light. The human eye is only able to pick up on a small range of this light, called the visible spectrum. Some insects only see the infrared spectrum. There are tools to make other forms of light visible, but without aid, the eye can only see the colors of the rainbow. Inherited disorders of the eye causes people to confuse one color for another -- a condition commonly called color blindness. It is very rare for someone to be completely color blind. The most common type of color blindness is the inability to distinguish red from green.

Night Vision

The less light there is, the less the items will reflect for the eyes, making nighttime or darkness harder to see. The human eye has specialized cells called rods that allow for night vision. The human eye has a 20 to 1 ratio of rods over cones -- daylight cells. The rods are there to create extra focus on each object that radiate less light. Without these numerous rods, the eye would not be able to see at night.

Focus

The eye, like a camera, has a lens. This lens allows for light to be focused on a light receptor, the retina. In a camera, the light receptor is the film. The lens is what allows for a sharp, clear focus. Defects in the lens will cause vision to be blurry at certain distances. Corrective glasses, or additional lenses, can be added to overcome the deficit.

Depth Perception

The human body has two eyes located on the front of the body. This close positioning of the eyes allows them to see the same object from a slightly different view -- stereo vision. Each different view of the eye allows the eye to see a little around the object. Two eyes allows the body to not only be able to tell the size of an object but where it is in relation to other objects. Having this type of vision is necessary for driving, throwing, catching and building a 3-D object. Loss of vision in one eye can lead to a loss of depth perception.

Balance

The eye is a small part of the vestibular system -- the balance system of the body. Most of the information for the vestibular system is provided by the inner ear, but uses the visual system and the joints, muscles and receptors in them to give information to the body about where it is in relation to other objects. If balance is correct, walking down the street upright will make buildings and other objects appear upright. The visual system is responsible for providing information to the brain about where the body appears in relation to the horizon. Loss of vision can alter balance. This is quickly tested by standing on one leg with eyes open and eyes closed. As soon as the eyes are closed, balance becomes more difficult.

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