Write the importance of ciliary muscles in the human eye. Name the defect of vision that arises due to gradual weakening of the ciliary muscles. What types of lenses are required by the person suffering from this defect to see the objects clearly?
Akshay, sitting in the last row in his class, could not see clearly the words written on the blackboard. When the teacher noticed it, he announced if any student sitting in the front row could volunteer to exchange his seat with Akshay. Salman immediately agreed to exchange his seat with Akshay. He could now see the words written on the blackboard clearly. The teacher thought it fit to send the message to Akshay's parents advising them to get his eyesight checked.
In the context of the above event, answer the following questions:
(a) Which defect of vision is Akshay suffering from? Which type of lens is used to correct this defect?

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Solution

Ciliary muscles adjust the focal length of the eye lens. This property is known as power of accomodation.
Presbyopia arisis due to gradual weakening of the ciliary muscles and diminishing flexibility of eye lens as increasing age of human.
A common type of bi-focal lens consists of both concave and convex parts required to see objects clearly.
(a) Since Akshay could see only nearby objects but not the far objects, thus he is suffering from myopia. Concave lens is used to correct this defect.

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