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Sensation and Perceptio6

Sensation and Perceptio6 - Sensation and Perception Eye...

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Sensation and Perception Eye Trouble Nearsightedness is the inability to clearly see distant objects. Farsightedness is the inability to clearly see close objects. A cataract is a lens that has become opaque, resulting in impaired vision. Rods and Cones The retina has millions of photoreceptors called rods and cones. Photoreceptors are specialized cells that respond to light stimuli. There are many more rods than cones. The long, narrow cells, called rods , are highly sensitive to light and allow vision even in dim conditions. There are no rods in the fovea, which is why vision becomes hazy in dim light. However, the area just outside the fovea contains many rods, and these allow peripheral vision. Because rods are so sensitive to light, in dim lighting conditions peripheral vision is sharper than direct vision. Example: People can often see a star in the night sky if they look a little to the side of the star instead of directly at it. Looking to the side utilizes peripheral vision and makes the image of the star fall onto the periphery of the retina, which contains most of the rods. Cones are cone-shaped cells that can distinguish between different wavelengths of light, allowing people to see in color. Cones don’t work well in dim light, however, which is why people have trouble distinguishing colors at night. The fovea has only cones, but as the distance
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