Question

Myopia is due to:
A. Elongation of eyeball
B. Irregular change in focal length
C. Shortening of eyeball
D. Older age

Answer 1

Hint: In humans, there are different types of eye defects. These defects are due to refractive error. These errors are caused when the light instead of directly focusing on the retina of the eye, either focusses at the front of the retina or behind the retina. These defects can be corrected using specific lenses like concave, convex or bifocal. Different types of eye defects include myopia, hypermetropia, presbyopia, etc.

Complete answer:
Myopia is an eye defect in which light coming from an object gets focused slightly in front of the retina instead of directly falling on the retina. In this defect, a person cannot see distant objects, but can see the objects closer to him clearly. It is also known as Nearsightedness or Short Sightedness.
Myopia is caused due to the variation in the distance between the eye lens and retina. This distance increases when the eyeball gets elongated along its axis. This results in the object at a distance to appear blurry.
Thus, myopia is due to elongation of the eyeball.

Hence, the correct answer is option A i.e. elongation of eyeball.

Note:
There is no cure for these eye defects. But, using a lens can prevent the increase of these defects. Myopia can be corrected using a concave lens. Concave lens diverges the light coming from the object so that it falls on the retina instead of falling in front of the retina. Hypermetropia is a defect which can be corrected using a convex lens, A bifocal lens is used to correct presbyopia. Hypermetropia is due to shortening of eyeball while Presbyopia is due to older age.