Bifocal Lens

Bifocal Lens it is called a bifocal. The term bifocal means literally "Two Focuses". It is meant to describe eyeglass lenses that enable the user to see clearly at two different distance ranges through one lens. Benjamin Franklin is credited with inventing the first bifocal lens by gluing two lens halves from different prescriptions together. Bifocals are used for many reasons, but the main reason is Presbyopia, a condition that affects every adult above the age of 40 years. Presbyopia is when the human near focus system gradually becomes unable to focus on objects that are closer in. At that point, the prescription that helps people to see objects clearly at distance is no longer sufficient to see close objects also.