Presbyopia


 
 
Concept Explanation
 

Presbyopia

Presbyopia: In old age,  after the age of 40 or more noticably after the age of 45, the ciliary muscles become weak and are not able to contract enough to decrease the focal length adequately. In this case also, objects at the normal near point are not focused on the retina.When far-sightedness occurs due to this reason, it is called presbyopia.

A person may have any of the above defects or a combination of these defects. Among the elderly, the combination of near-sightedness and far-sightedness is common. Such people need converging glasses (convex lens) for reading and diverging glasses (concave lens) for seeing at a distance. They either keep two sets of spectacles or use bifocal lenses whose upper portion is for distant vision and lower portion is for reading. In many cases, both parts of the bifocal lens are concave. The upper part is highly divergent to correct near-sightedness and the lower part is kept less divergent to aid reading.These days, it is also possible to correct the refractive defects using surgical interventions.

Sample Questions
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Question : 1

In a bifocal lens the lens is divided ______________.

Right Option : B
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Question : 2

The inability among the elderly to see nearby objects clearly because of the weakening of the ciliary muscles is called ____________

Right Option : C
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Question : 3

In a bifocal lens the upper part is  _________to correct near-sightedness and the lower part is kept _________________ to aid reading.

Right Option : A
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