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Question
Write a short note on Presbyopia.
Solution
The focusing power of the eye lens decreases with age. The muscles near the lens lose their ability to change the focal length of the lens. The near point of the lens shifts farther from the eye. Because of this old people cannot see nearby objects clearly.
Sometimes people suffer from nearsightedness as well as farsightedness. In such a case bifocal lenses are required to correct the defect. In such lenses, the upper part is the concave lens and corrects nearsightedness while the lower part is a convex lens which corrects farsightedness.
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