Some people over the age of forty may have experienced that when they tried to purchase a pair of reading glasses, the seller or retailer recommended a relatively expensive pair of bifocal reading glasses. In fact, these bifocal reading glasses have been widely used for many years. A large number of older adults have to rely on these devices for some of their daily activities, including recreational activities. However, there are still probably many users who do not know or have little understanding of two things about these glasses. One is the origin and the other is the exact function.
The origin of the most widely known bifocal reading glasses is that they were invented in 1794 by Benjamin Franklin, one of the founders of the United States. This great statesman was getting old and had difficulty seeing both near and far. For a long time, he had to regularly use two pairs of prescription glasses, one for near vision and the other for distance vision. This was, of course, very inconvenient when he wanted to switch his visual range on a daily basis. A great man is always more likely to be driven to develop an alternative to an unsatisfactory, current solution. Benjamin was also a great inventor in his time. He created the first pair of bifocal reading glasses, putting both lenses in one frame.
This is also the design of bifocal reading glasses widely seen today. Their basic design has never changed significantly in the last two centuries. Up to now, the function of these amazing glasses is quite clear, i.e. they allow the wearer to see both near and distant objects clearly. This is achieved by combining positive and negative power in one lens. The lower part of the lens is usually made for close viewing and the upper part is made for distant viewing.
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