Question

Presbyopia can be corrected with the help of _______
A. Bifocal lens
B. Diverging lens
C. Convex lens
D. All of the above

Answer 1

Hint: Presbyopia is a condition of the eye which occurs due to the gradual decrease in the power of accommodation of the eye due to ageing. The signs of presbyopia will start at the age of mid 40s. some of the main symptoms are blurred vision at normal reading distance, eyestrain, headache etc.

Complete step by step answer:
A person who suffers from both myopia and hypermetropia is said to suffer from presbyopia.
Myopia is a condition of the eye in which the parallel rays are focused in front of the retina and due to this the person will not be able to see objects which are far away. i.e. a person with myopia can only see nearby objects. Hence it is also called nearsightedness.
Hypermetropia is another condition where the image of the nearby objects will be formed behind the retina and thus the person will not be able to see the nearby object. i.e. the person with hypermetropia can only see far objects and hence it is also called as long sightedness.
A person with presbyopia will have both these abnormalities and he/she will gradually decrease the power of the eye. Presbyopia becomes noticeable mainly after the age of 40s and will become worse around 60s, i.e. it becomes worse on ageing.
Since these people have both myopia and hypermetropia, they require a bifocal lens to correct it.
Hence the correct answer is option A.

Note:
A bifocal lens consists of both convex and concave lenses. We know that the concave lens is used for the correction of nearsightedness or myopia. A concave lens will diverge the rays from distant objects and form the image at the retina thus making the vision of distant objects possible. Whereas a convex lens is used to correct long-sightedness. A convex lens will converge the rays from near objects and make the rays converge on the retina of the eye and thus makes the vision of nearby objects possible.
In a bifocal lens the upper portion has a concave lens and the lower has a convex lens.