Three kinds of lenses that can seem similar are bifocal lenses, progressive lenses, and transition lenses. The difference between these three lenses are:
Bifocal lenses contain two different prescriptions. These prescriptions are divided by a visible horizontal line across the lens.
Progressive lenses also have two different prescriptions. However, in progressive lenses, the horizontal line used in bifocals is not present; instead, the two areas are blended smoothly.
Transition lenses darken when exposed to sunlight, but become clear when you’re inside. […]
