Myopia, hypermetropia, and presbyopia are three significant defects of vision. Myopia refers to nearsightedness due to which a person can see nearby objects. A person who has myopia cannot see far objects clearly. This defect could be resolved with the help of a concave lens. In hypermetropia, a person cannot see near objects clearly and is corrected by using a convex lens. In presbyopia, a person is difficult to see both nearby and far objects. It is treated with the use of bifocal lenses.