Vision is the dominant human sense. The eye admits light and focuses it onto the light-sensitive cells of the retina. These cells, the rods and cones, contain chemicals that break down when struck by light. ‘Vhe breakdown of chemicals triggers the sending of messages to the brain along the optic nerve. The cones, which are packed together in the center Of the retina, are the color receptors.
The rods, which spread to the outer edges Of the retina, are not sensitive to color bur are more sensitive than the cones to light. Color vision results from the stimulation Of three types of cones, each Sensitive to light of a different wavelength. The cones pass information on opponent cells, which relay information to the brain. Defects in cones result in colorblindness, which may be dichromatic (only two of the three types of cones are functioning), or monochromatic (none of the cones is functioning).
What Is Vision;What Does It Do In Eyes
Depth perception is the ability to determine where an object is located in three- dimensional space. Pictorial depth cues such as overlapping, relative size, and perspective help us to perceive depth, even when we view a picture. Binocular vision, in which the brain combines information from the two eyes, provides the most precise information about depth. Experiments with the visual c/ifflndicate that depth perception may be innate.
Information received through our eyes is carried by the optic nerve to the brain for processing, In the primary visual cortex at the back of the brain, highly specialized cells called feature detectors respond to specific visual patterns. 8 Different areas of the brain seem to specialize in different aspects of an image. Neurons in one brain pathway perceive shapes and colors and recognize objects. Neurons in another brain pathway specialize in detecting motion and in deter- mining the relative position of objects.