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Theory:

We have eyelids to protect our eyes from foreign particles such as dust, chemicals, etc. It also shuts out the light when not required.
  • Eyes can see distant objects as well as nearer objects clearly.
  • The minimum distance that the eye can see distinctly varies with age.
  • A person with normal eyes can read most comfortably from a distance of \(25\) \(cm\).
  • Some people can see the objects close to them clearly, but they cannot see the farther objects clearly, and some can see the farther objects clearly, but they can not see the nearer objects clearly. These defects are corrected by using suitable lenses.
  • In some cases the lens of the eye become cloudy or foggy. This condition is called a cataract, which results in loss of vision. This develops with ageing, and it can be rectified by replacing the old lens with an artificial lens.
Intumescent_cataract.jpg
Cloudy layer on eye
 
How to protect our eyes?
We know that eye is a sensitive organ so the following steps to be taken to keep it safe.
  • One should go for a regular eye check-up.
  • Persons with eye defects should wear spectacles regularly.
  • Excess or insufficient light both can lead to problems. So always study or watch tv in a sufficient light.
  • Do not look at the sharp sources of light like the sun directly. Excess of light can damage the eyes.
  • If dust enters into the eye, one should not rub them and rather wash them gently.
  • Food is also an important factor; lack of nutrients in the food may cause defects in vision. Take a balanced diet to ensure that you get the right nutrients.
shutterstock_166163204 (1).jpg
Healthy foods
Reference:
https://commons.wikimedia.org/wiki/File:Intumescent_cataract.jpg