An eye that suffers from myopia as well as from hypermetropia is said to suffer from presbyopia. A person with this defect cannot see objects distinctly placed at any distance from him as well as near objects clearly. This occurs commonly in old people.

To correct this defect, a person is prescribed bifocal lens that has both types of lenses convex lens to correct hypermetropia and concave lens to correct myopia.

Hence, we use bifocal which is a combination of concave and convex lenses