what is bifocal glasses

Bifocal glasses are a type of eyeglasses that feature two different optical powers in one lens. The top part of the lens corrects distance vision, while a smaller portion at the bottom of the lens corrects near vision. The lenses are split into two parts, offering different prescriptions for various distances. When looking closely at bifocal lenses, you can see a line where these different viewing zones meet. The first bifocal was invented by Benjamin Franklin, who glued the top half of one lens to the bottom half of another and created what we now call an “Executive” bifocal. Bifocal glasses are commonly used to help the eye adjust vision to focus on objects that are close once it begins to lose the ability to transition focus due to age-related conditions like presbyopia. Bifocal glasses are most commonly prescribed to people over the age of 40 to help compensate for the natural degradation of vision due to the aging process. The most modern bifocal lenses are called “No-line” or “Progressive” lenses, which have a smooth change in focus from the top of the lens (distance), through the middle (arm’s length), to the bottom of the lens (reading distance) .