● Astigmatism : This defect arises due to the difference in the radius of the curvature of the cornea in the different planes. ◦ The cylindrical lens is used by the people suffering from Astigmatism. ● Myopia : A person suffering from myopia can see the near objects clearly while far objects are not clear. ◦ A Concave lens (diverging lens) is used by people suffering from myopia. ● Hypermetropia : A person suffering from hypermetropia can see the distant objects clearly but not the near objects. ◦ People suffering from hypermetropia uses a convex lens.