Do You Need Bifocal Glasses?
What Are Bifocal Glasses?
Bifocals are an invention by Benjamin Franklin. Franklin was a person who suffered from near-sightedness as well as far-sightedness. This means he had difficulty in reading or seeing close-up things, as well as problems in clearly seeing far away objects. Thus, he had two pairs of glasses. A pair of reading eye glasses, which would help him with reading and concentrating on close objects, and another pair of eyeglasses to correct his distance vision.
As with most people who had such vision problems, Franklin too was fed up of having to repeatedly remove and change between his reading eyeglasses and his distance vision glasses. He wanted an easier way of correcting his vision and wished to have just one pair of eyeglasses that would help with his near and far sightedness. He came upon a bright idea to cut into half the lenses on both his eyeglasses and fitted one half of each type of lens into one singular eyeglass frame. Thus were born the bifocals.
How Do Bifocals Work
Bifocal glasses have two types of lens in each eye. The lens of each eye of bifocals consists of a lower and an upper lens. One lens (the bottom one) is made to correct the near vision and enable reading, whereas the other lens (the top one) corrects distance vision. The top lens may not have any type of correction in it, for those who do not have a distance vision problem, but only need vision correctness for nearby objects.
Earlier, the bifocal eye glasses that were available had a distinct line on each lens, where the two lenses were joined. These are known as Franklin Glasses, Executive or E style bifocals. With advances in technology, now you can find progressive bifocal lenses where there is no visible line in the lens.
Bifocal reading glasses have a lower part that has near vision correction and is useful while reading, as well as to concentrate on close things.
The near vision correction part of bifocal glasses can be one of four types:
- A round segment in the lower part of the lens.
- A semi-circle kind of segment, which is also referred to as the flat top, half moon, or the D segment.
- A very narrow area in a rectangle shape in the lower part of the lens in bifocals. This area is also known as the ribbon segment.
- And lastly, the cut half of a near vision correction lens, where the dividing line between the two parts of the lens is apparent.
Irrespective of what type of bifocal reading glasses that you go in for, all of them work on the same basic principle. The lower part of the bifocal lens is for near vision correction, so when you look down to read something, you are looking through that part of the lens. To see into the distance, a person has to look up and straight. While doing so, you look through the upper portion of the bifocal lens, which is made for distance vision correction. Thus, you can use bifocal glasses to correct both types of vision problems.