Photo: imagesthai.com
If the eye is not exactly the right shape or the lens can't form a clear image on the retina. In this case you may need to wear glasses to correct your vision. A short sighted person can see nearby objects very clearly. A long sighted person can see things in the distance while nearby objects are blurred.
Contact lenses are an alternative to wearing glasses and many people prefer these. They are thin plastic discs that rest on the surface of the cornea. They act like the lenses are made from very soft material that does not cause any discomfort to the eye.
Some lenses are only worn for just one day and then they are thrown away. It can be difficult to get used to wearing contact lenses and to putting them in the eye without scratching the delicate cornea. However, many people now prefer them to wearing glasses.
Film and television images consist of a series of rapidly changing still images, yet we see them as continues motion. There is a slight delay between each of the images that appear on the screen. However, because this delay is so short, our brain is able to fill in the gaps and provide a complete picture of what is happening.
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