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Myopia :A myopic eye is able to see nearby objects but far off objects appear blurred. The point beyond which the objects cannot be seen clearly is called far point.

Causes of myopia

Myopia can be due to :

(i) Elongation of the length of the eye ball, when the eye ball elongates, the distance between the eye lens and the retina increases, this results in the image being focused in front of the retina. So it is blurred.

(ii) Shortening of the focal length of the eye lens. 

Correction of Myopia : In this case, the ciliary muscles of the eye become weak and are not able to increase its focal length by suitable thinning the lens. So the eye lens will have small focal length which will converge the distant rays in front of the retina. To focus these rays at the retina, the rays must be diverged suitably. This is done by using a concave lens of suitable focal length (as spectacles) in front of the eye.