There is no doubt that as we grow older, our bodies gradually start to deteriorate. As we age, there comes a time when our eyesight becomes weak, and we require prescription glasses to see clearly.
However, even with glasses, what if you start to see some objects blurred while others are crystal clear. Well, this is the time you need to get prescription bifocal glasses, which will help you to solve your eyesight problems.
The word Bifocal means having two focal lengths. In other words, bifocals are glasses having a single lens with two distinct sections, each for vision at a different distance.
The Invention of the Bifocal
The bifocal glasses were invented in the 1700s by Benjamin Franklin. As he got older, he started having trouble seeing objects both close and far away.
He had to use two different pairs of glasses, each with different lenses, one for objects near and the other for things far. He decided to make a single pair of glasses that had both types of lenses fit into the frame.
Today almost all eyeglass stores such as Overnight Glasses, Eye Buy Direct, Lensabl, and most others provide bifocal lenses to their customers.
The Need for Bifocal Glasses
For us, to see correctly, the light rays from the object must pass through the eye lens and converge right at the retina. For this to happen, the cornea (the transparent layer forming in front of the eye), the eyeball, and the eye lens must be correctly positioned.
However, as we grow older, our eye lens loses its focusing ability and causes objects near to appear blurred. This condition is called Presbyopia.
Presbyopia is an example of refractive vision error that is the bending of light rays in the wrong direction, resulting in impaired vision. Bifocal glasses are used to treat people suffering from Presbyopia.
Difference between Standard Prescription Glasses and Bifocals
Many people suffering from presbyopia also suffer from an additional refractive vision error. That refractive vision error can be either Hyperopia (Farsightedness) or Myopia (Nearsightedness).
Hyperopia is where the light rays converge after the retina, causing the person with this condition to see objects farther away clearly, but things near him blur.
On the other side, myopia is where the light rays adjoin in front of the retina, making the person suffering from this condition see objects near him clearly but farther away objects blurred.
One thing to note here is that hyperopia and presbyopia are not the same. Presbyopia, as stated before, occurs when the eye lens loses its focusing capability, whereas hyperopia occurs due to the eyeball being too short.
On the other hand, myopia occurs due to the eyeball being too big.
Standard prescription glasses help eliminate hyperopia or myopia as they use a single lens, either convex in case of hyperopia or concave for myopia.
The convex lens focuses the light rays on meeting at the retina instead of after it, whereas the concave lens diverges the light rays to meet at the retina rather than before it. Hence, prescription glasses are a good choice until the user becomes a victim of presbyopia.
Without Bifocals, the person with the glasses would clearly see objects at one length, whereas things at another length obscure, requiring him to remove the glasses to see them correctly.
The constant need to wear and remove the glasses can become tiresome. Hence the bifocals are a much better option instead.
Bifocals, as stated before, have a single lens with two sections, one section to see far away objects clearly and the other section to see things near clearly, allowing good vision for all distances regardless of myopia, hyperopia, or presbyopia.
Further Developments on the Bifocal Glasses
The bifocal was later surpassed by the trifocal and the progressive lens. The trifocal is made of a lens with three sections, each for a specific distance categorized as far, intermediate, and near.
This feature provides more depth to the varying lengths that objects can be viewed from compared to the bifocal.
Both the bifocal and trifocal have visible lines in the lenses indicating the border where one section ends and the other begins.
As we make the transition from one area of the bifocal and trifocal to the other, there is a noticeable distinction between focusing power of the different sections, making it uncomfortable for some users.
The progressive lens, on the other hand, also consisting of 3 distinct areas, is designed so that as the user makes transitions between the different sections, the difference in focusing power is unnoticeable hence providing a natural vision for the user.
Also, the progressive lenses do not use visible lines to indicate the different sections of the lens, making them more aesthetically pleasing.
The bifocal glasses were an essential invention that has helped people with vision problems conduct day-to-day tasks conveniently.
If you are also suffering from presbyopia and are also burdened by the need to wear and remove your glasses constantly, then the bifocals, the trifocals, or the progressive lenses can be the solution to your problems.