The first pair of glasses in modern times was depicted in a 14th century painted portrait of Cardinal Hugh de Provence although history texts have mentioned glasses as far back as the 9th century. Official sales of spectacles can be traced back to 15th century Italy. These glasses contained lenses for single vision only so the people of the time with both near and far-sightedness were out of luck. It took a few hundred years but Renaissance man Benjamin Franklin, a popular American statesman and inventor, eventually designed what is now known as the executive bifocal in 1784.
Ben Franklin suffered from not only near-sightedness, the inability to see objects clearly in the distance, but also Myopia, a condition in which fine print appears indistinct or blurry. Both conditions combined made him Presbyopic. He was forever switching between two pairs of eyeglasses, depending on the task at hand and finally got tired of doing it. Mr. Franklin developed the first bifocal which was basically two different lenses bonded together with the top part of the lens addressing his near-sightedness and the bottom part of the lens addressing his Myopia. He just had to tilt his head. Today, this bifocal style is called the executive bifocal or the Ben Franklin style bifocal. The entire bottom portion of the lens is for close up; it is quite noticeable and not so cosmetically appealing to the eye. This type of lens is heavier than other types of lenses.
Defining the Bifocal
The bifocals of today have a small extra window at the bottom of your lenses which allows you to accommodate your eyes for reading. This extra window is not the same for every pair of bifocals. In fact, your vision requirements dictate the strength of the magnification as well as the positioning of it on the lenses.
There are several styles of bifocals and the executive or E style is just one of them. All styles perform the same fundamental purpose. The bifocal provides you with clear sight for viewing in the distance as well as clarity for fine print and close up tasks. Bifocals may come in different shapes, sizes and materials, particularly the part of the lenses that serve long distance viewing. The lenses are segmented and the magnified part for fine print is typically a little thicker and therefore easy to see. This thicker, magnified area may not always be centered at the bottom of the lens and stretch across the entire frame like the executive bifocal. Rather, the center point of this magnified portion may be positioned anywhere, depending on your own range of vision and pupil distances.
Purchasing the Glasses
If you already have near-sighted (prescription glasses) but find that you need a boost for reading, the bifocal can be specially prescribed to suit your vision needs. However, if your eyesight has always been 20/20 but you find that Presbyopia is creeping up due to the aging process, you should be able to get by with over the counter bifocals, particularly the executive style as the magnified portion stretches all the way across the lens. The material for bifocal lenses typically is either glass or plastic, although there is photochromic glass or plastic, which darken in bright light and lighten in dim light along with hi-index materials as well.
The executive bifocal is quite handy for simple vision problems. However, if your eyes require a little finer tuning, there are other multi-focal styles for eye glasses such as the trifocal, flat top bifocal, the round bifocal, and no-line bifocals.