Because of the brain’s ability to organize information about the relative intensity of these three primary colors-in essence, mixing them-from such a simple palette we can distinguish millions of colors. Some react primarily to red, some to green, some to blue light. There are three kinds of cones, each “tuned” to different parts of the light spectrum. The retina contains nerve cells as well as a layer of 120 million rods and cones, receptor cells that respond to light. The lens changes shape to allow us to see both near and far objects clearly. World onto the retina in the back of the eye. In the front, the cornea and lens focus light reflected from objects in the The eye is roughly spherical and about an inch in diameter. The sense organ for vision is an exquisitely evolved biological instrument for turning light into the brain’s language of electrical signals. The brain devotes more space to vision than to all other senses combined. Barring vision-impairing conditions, we walk (or drive, or ride) safely through the world, recognize friends (and enemies), read, write, and otherwise learn what’s happening by the power of sight.Īccordingly, the physical apparatus for gathering visual information-the eye-and the brain circuits that process this information are more complex than corresponding systems for the other senses. All of our senses give us vital information about our surroundings, but the one we rely on most is vision.
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