Why do we need glasses or contact lenses?
People who are short sighted or myopic have much focusing power,so need to wear a negative power lens in front of the eye in order to bring image into focus on the retina.People who are long sighted do not have enough focusing,so in order to bring the image into focus on the retina,they need to wear a plus lens in front eye.Lastly,astigmatism is a condition where eye rather being completely circular has an oval shape to it and requires an oval shape or what is called a toric lens to be worn in front of the eye to bring the world into focus.
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