What is the advantage of bifocal lenses?

[Abby Eyeglasses]

I found so many old people love to buy bifocal glasses, what is the advantage of bifocal lenses, please?

[Daniel Glasses]

advantage of Bi-focal lens, it contain two prescriptions, the top part of the lens will be used for your distance vision and the bottom part will be used for reading, there is a line separating distance and reading sections.

The reading section is in the shape of a D on it’s side, the bifocal has a flat top and a curved bottom.