PRESBYOPIA

Age related loss of accomodation is called presbyopia. With age lens of eye hardens and its focusing power reduces. So approximately at 40 years of age a person needs near glasses which have magnifying effect. 

Roughly at 40 years age +1 diopter, at 45 years age +1.5 diopters and at 50 years age +2 diopters is used. After cataract surgery with monofocal lens which cannot focus of near, usually +2.5 diopters of near refraction is given