Question

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 in old age. What type of lenses are required by the persons 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 ? (b) State the values displayed by the teacher and Salman. (c) In your opinion, in what way can Akshay express his gratitude towards the teacher and Salman ?

Answer 1

Sometimes, the eye may gradually lose its power of accommodation. In such conditions, the person cannot see the objects distinctly and comfortably. The vision becomes blurred due to the refractive defects of the eye. There are mainly three common refractive defects of vision. These are (i) myopia or near-sightedness, (ii) Hypermetropia or farsightedness, and (iii) Presbyopia. These defects can be corrected by the use of suitable spherical lenses. We discuss below these defects and their correction.

Answer 2

ciliary muscles hold the eye and change the curvature of the eye thereby changing the focal length of the eye

the defect is called presbyopia or old age hypermytropia
akshay is suffering from myopia
concave lens is used to correct the defect.