Bifocal lenses: Bifocals are eyeglasses with two distinct optical powers. Bifocals are most commonly prescribed to people with presbyopia who also require a correction for myopia, hyperopia, and/or astigmatism.These lenses provide assistance to old age people with both close work and long distance vision. The upper part of the lens is used for correcting the short-sightedness. On the contrary, the lower half of the lenses help in reading or doing other close work. Original bifocals were designed with the most convex lenses (for close viewing) in the lower half of the frame and the least convex lenses on the upper.