The power of accomodation of the eye decreases with ageing.For most people,the far point gradually comes closer and the near point recedes.This defect is known as presbyopia.
It arises due to the gradual weakning of the ciliary muscles and diminishing flexibility of the eye lens.Such a person may suffer from both myopia and hypermetropia.
This defect is then corrected by using bi-focal lenses of suitable focal lengths.The upper part of lens is concave lens which corrects myopia while the lower part is convex lens to correct hypermetropia.
