Bifocals And Trifocals 101: Everything You Need To Know
It is truly amazing when you consider just how many technologies were invented centuries ago that are still in use today. A perfect example of this is the bifocal. According to legend, they were invented by Benjamin Franklin sometime during the 1760′s. This bit of history has come under fire over recent years as many wonder if Franklin really did put together the first pair of bifocals, but there can be no denying that millions of people from around the world still rely on these glasses, as well as trifocals, as part of their daily life. Here is a basic primer for bifocals and trifocals for those folks who may be considering getting their first pair.
Bifocals
A bifocal lens is defined as a lens that features two distinctive prescriptions in it. Almost all bifocals are by prescription, but you can find ones at your local corner store that you can buy over-the-counter, however these likely won’t provide the vision help you need. When Benjamin Franklin put together the first set of bifocals, he took one very convex lens and one not so convex lens and put them together. This was the style for creating bifocals for years until the early 19th century when a doctor figured out how to fuse the two separate pieces of glass without destroying them. Now, thanks to modern technology, most bifocals are created by moulding one piece of lens inside another and then fitting it for a frame. This was the biggest technological advancement to happen to bifocals for years until the invention of the no-line bifocal. With a no line bifocal, the line where one lens transfers to the other was removed and the popularity of these types of glasses increased dramatically. Today, progressive lenses have taken the mantel first put forth by Benjamin Franklin to create eyeglasses that allow you to see two (or even three) different optical powers in one lens.
While there can be no denying that bifocals changed the way people looked at, and looked through, eyeglasses, they haven’t been without their criticism. For many people, headaches and other issues crop up soon after they begin using them for the first time. This is often because of the constant back and forth from one prescription to the other. The introduction of progressive lenses has helped to significantly reduce this from happening, however. There has also been problems with some computer monitors, as well since people often have to change how they look at a monitor or a television set so that they use the proper part of the lens.
Trifocals
While the origin of the bifocal may be up for some debate, the origin of the trifocal is not. The lens came to be in 1824 thanks to the hard work of one Dr. John Hawkins. As the name suggests, a trifocal lens has three optical strengths in it instead of two. There is often a strength for objects that are far away, a second strength for things that are at arms length and a final length that is for reading. While strengths of the various lenses depend on what your prescription would be, in general, the medium strength is often half way between the two other strengths.
While some of the problems outlined above that seem to hamper bifocal wearers do crop up with people who wear trifocals, the more gradual change from one strength to the other tends to make getting used to these types of glasses easier than what you may find with bifocals. There may also be a cost issue at work here, as well, since trifocals are likely going to be a bit more expensive than bifocals.
As much as bifocals have felt the sting from the advancement of progressive lens technology, trifocals are now becoming difficult to find at all due to the popularity of progressive lenses. In fact, some areas have completely stopped selling them in favour of the progressive lens, which is now easier to make and often times cheaper or at least competitively priced compared to old fashion trifocals. You can bet that by 2020, it will be almost impossible to find old-style trifocals anywhere in the Western world.
As you can see, bifocals and trifocals have been an indispensible part of history for centuries. Without the innovations put forth by both bifocals and trifocals, you can bet that today’s progressive lenses wouldn’t exist. For generations, bifocals and trifocals provided a cost effective way for people to essentially own two pairs of eyeglasses for the price of one. Bifocals have helped to make the legacy of Benjamin Franklin even more impressive than what was previously thought and throughout the world today, both bifocals and trifocals continue to play a pivotal role in helping people see better for less cash.
