What is presbyopia ? State its cause. How is it corrected ?
Answers
The power of accommodation of the eye usually decreases with ageing. It would be difficult without corrective eye glasses.It arises due to gradually weakening of the ciliary muscles and diminishing flexibility of eye lens.
It can be corrected by using bifocal lenses. The upper portion consists of concave lenses of suitable power. The lower portion consists of convex lens of suitable power.
What is presbyopia ?
Presbyopia is an abnormal condition of the eye in which our eye lens become hard and we cannot see the objects which are far away from us hence leading to some sort of short-sightedness.
This is common in people who are old. People cannot see objects about more than 25 cm distance clearly .
State its cause
The causes of presbyopia are as follows :-
(i) The lens becomes opaque and non-functional.
(ii) The ciliary muscles become defective.
(iii) Lens becomes hard .
How is it corrected ?
The problem is corrected by using a bi-focal contact lens or a bi-focal spectacle.
Hope it helps !