原版英文小故事 45. Your Eyes

Light goes through the pupil, the dark hole in the center of your eye. The

light becomes an image on the retina, which converts these images into

nerve impulses. The brain reads these impulses and “tells” you what you

are seeing. The image that the retina receives is upside down, but the

brain reverses it to right-side up.

In an experiment years ago, a brave researcher wore special lenses that

turned everything upside down. After stumbling around for awhile, he

became used to the lenses because his brain corrected the images. To

conclude his experiment, he stopped wearing the lenses. After awhile, his

brain returned his vision to normal.

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 your vision is when you are young, you will need reading glasses

when you get old.

Your pupils get bigger as a light source gets dimmer, but your pupils 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.