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प्रश्न
Write a short note on Presbyopia.
उत्तर
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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संबंधित प्रश्न
A person needs a lens of power -5.5 dioptres for correcting his distant vision. For correcting his near vision he needs a lens of power +1.5 dioptre. What is the focal length of the lens required for correcting (i) distant vision and (ii) near vision?
Anuja’s father cannot see nearby objects clearly.
(a) What is the eye defect he is suffering from?
(b) How is it corrected?
Bifocal lens is required to correct _______ defect.
Write the name.
The defect of eye occurring due to ageing
Write scientific reason.
Presbyopia effect is more common in people over 40 years of age.
Distinguish between:
Myopia - Presbyopia
The eye defect ‘presbyopia’ can be corrected by
Complete the correlation:
Farsightedness : Convex lens : : Presbyopia : ______
