Vision: Not Only the Work of Eyes

Answer: When the images created by light and dark hit the eye for visual interpretation, they first meet the cornea that directs its view through the pupil to the lens which focuses the visual material onto the retina. The retina sits in the back of the eye, and its purpose is to take the images that pass through the cornea and lens, in the front of the eye, turning the light and shapes into signals. This information is sent through the optic nerve into the brain for interpretation.

When the function of the eye is likened to a camera the retina is described as the film. It has rods that are sensitive to black and white in dim light, and cones which provide color vision and predominately work in the daylight. The cones are made to see the color wavelengths that register red, green, and blue. Variations of those basic colors make up all the full range of colors people see when interpreted by the cortex in the brain. Another feature on the retina is photosensitive ganglion that deals with bright sunlight.

Visual information is sent to the cortex for interpretation, but it also goes to the thalamus; a part of the brain that takes in the sensory information of sight, touch, sound, and taste. In addition to sending images to the brain for interpretation, the brainstem also receives information from the eye. One area of the brainstem that receives information is the pretectum and it tells the pupils how to respond to the amount of light the eye is seeing; the less light the larger the pupil opening. Two, the superior colliculus allows the eye to scan the view and see it a smooth sweep of the panorama.

There are four lobes in cerebral cortex: the frontal lobe, the temporal lobe, the parietal lobe, and the occipital lobe. This is the gray matter that processes the information our senses tell us. Particularly involved with vision is the occipital lobe located in the back of the head. The occipital lobe is behind the temporal lobe and its main purpose is making use of visual information. Within this lobe is the visual cortex that receives its information from the retina, the lobe is used in color perception as well. Behind the frontal lobe and above the temporal lobe is the parietal lobe, and its purpose is to help understand the sensory information we receive through vision, hearing, touch and taste. This area of the brain recognizes objects, allows speech, interprets the bodies position in relationship to objects around it, reading, tasks involving numbers, and some visually perception. These events occur when the eyes work properly.

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