Bifocal glasses are not a recent invention. As the story says, Benjamin Franklin had two sets of glasses, one for faraway objects and the other for close reading. He reluctantly shifted from the two separate glasses, which is very inconvenient. After quite a period of this bother, the great forerunner designed a pair of bifocal glasses that allow him to see both distant and near things clearly. This was the initial form of bifocal reading glasses. He just cut the two pairs of glasses in half and used half of each lens for each eye so that the bifocal glasses were invented.

Science and technology always advance at a rapid pace, but the basic principle of bifocal reading glasses has remained the same since its invention. The lens of modern bifocal glasses has two parts: the lower part for close reading and the upper for distant vision. This design principle of bifocal reading glasses is based on the common sense that people generally use bifocal glasses in certain ways. They look downwards the bifocal reading glasses when reading or looking at close objects and look up when looking at distant things.

Bifocal glasses are truly useful for a large population that develops prysbiopia on earth. In the US alone, almost 4 million people suffer from it each year, most of which are between thirty to fifty years of age. Bifocal glasses have become a necessary part of their lives. Bifocal reading glasses eliminate the switch between separate glasses.

Bifocal glasses also perform as the pioneer of multifocals, followed by trifocals and progressive glasses. After the invention of bifocal reading glasses, multifocal glasses are natural.

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