46. Ever wonder how your pretty little eyes work? Light goes through the pupil, which is the black hole in the center of your eye. The light becomes an image on the retina, which converts the image into nerve impulses. Your brain reads these impulses and "tells" you what you are seeing. The image that the retina receives is upside down, but your brain reverses it to right‐side up. That's it, in a nutshell—or, in an eyeball, if you'd prefer.
In an experiment years ago, a brave researcher wore special lenses that turned everything upside down. He had no idea if his brain would be able to reverse everything after he stopped wearing the special lenses. After stumbling around for a while, he became used to the lenses because his brain corrected the images. To conclude his experiment, he stopped wearing the lenses. After a while, to his great relief, his brain returned his vision to normal.
Your pupils get bigger as a light source gets dimmer, but they also get bigger if you see something, like a delicious meal, that interests you. "Your eyes are bigger than your stomach" is an expression parents use when a child fills his plate with more food than he can eat.
People with vision problems are usually near‐sighted or far‐sighted. Near‐sighted people see clearly only objects that are near; far‐sighted people see clearly only objects that are far away. Both groups of people need corrective lenses (glasses or contacts).
People whose near and far vision is good have "20/20" vision. People with poor eyesight might have 20/40 vision or worse. That is, a person with good vision can see an object from 40 feet away as clearly as a person with poor vision can see the object from 20 feet away. No matter how good their vision is when they are young, most people will need reading glasses when they get old. And we can thank an Italian for inventing glasses and an American for inventing bifocals.
Just as there are only seven colors in the rainbow, there are only six basic colors for people's eyes: amber, blue, brown, gray, green, and hazel. Brown is by far the most common color, with blue a distant second. Sometimes people mistakenly say that their eyes are black, but only their pupils are black, not their irises. Occasionally you will meet a person whose eyes are two different colors! 7.8, 411
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