bifocals are glass lens that you place upon your nose & push up. they help you see better & / read
A bifocal (bi means two) is a lens that has two different prescriptions cut in it.
Benjamin Franklin
Benjamin Franklin did.
No, you cannot change the bifocal prescription on glasses without changing the lens. The lens is what is prescribed by your eye doctor. The frame, however, can be changed.
Two focal lengths in one lens.
a bifocal lens
Bifocal is a type of corrective lens. Bifocal lenses are divided into two sections, usually the top for seeing far away objects and the bottom for seeing nearby objects.
It means you are using a bifocal contact lens that has a bifocal power of about +1.25 to +1.50. A high add would have the bifocal power of about +2.50.
The root word in bifocal is "focal," which refers to the point at which light rays converge after passing through a lens. The prefix "bi-" in bifocal means two, indicating that bifocals have two distinct areas for different vision correction needs.
I used my bifocals to watch the television
a bifocal (using both eyes) disecting microscope. probably with zoom lens
Bifocal
it is possible for a person to have both myopia and hypermetropia(hyperopia).The defect can be corrected by using bifocal lens.