Explain the eye defect myopia. How can it be corrected with the help of a lens?

Myopia : This eye defect is also called short sightedness or near sightedness. It occurs when the image of a distant object is focused in front of the retina. This may be due to one of the following
reasons:
(a) Lengthening of eyeball from the front of the back, (b) Due to increased convexity of the lens.
It can be corrected by using appropriate biconcave lenses.