What is presbyopia? Which part of the bifocal lens contains the concave and convex lens?

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Solution

The power of accommodation of the eye usually decreases with ageing. For most people, the near point gradually recedes away. They find it difficult to see nearby objects comfortably and distinctly without corrective eye-glasses. This defect is called Presbyopia.

It arises due to the gradual weakening of the ciliary muscles and diminishing flexibility of the eye lens. Sometimes, a person may suffer from both myopia and hypermetropia.

Such people often require bifocal lenses. A common type of bi-focal lenses consists of both concave and convex lenses. The upper portion consists of a concave lens. It facilitates distant vision. The lower part is a convex lens. It facilitates near vision.

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Similar questions

Q. Can't we use concavo-convex or convexo-concave instead of bifocal lens for presbyopia patient?

Q. The bifocal lens used in the correction of presbyopia has a ___ lens on upper side and a convex lens on lower side.

Rewrite the following table so as to match second and third column with first column

Column		Column II	Column III
(1)	Myopia	Old age problem	Convex lens
(2)	Hypermetropia	Near-sightedness	Bifocal lens
(3)	Presbyopia	Long sightedness	Concave lens

Match the defects of vision in Part A with an appropriate remedy in Part B.

$\begin{matrix} PART A & PART B 1)Myopia & a) Convex lens 2)Hypermetropia & b) Surgery 3)Presbyopia & c) Concave lens 4)Cataract & d) Bifocal lens \end{matrix}$

Q. Match the elements of table I and II.

Table I	Table II
a) Myopia	i) Bifocal len
b) Hypermetropia	ii) Cylindrical lens
c) Presbyopia	iii) Concave lens
d) Astigmation	iv) Convex lens

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