Single vision lenses have the same focal power throughout (top to bottom) and can be used to correct nearsightedness, farsightedness, astigmatism, or a combination of these disorders.

Bifocal lenses have two parts: the upper part normally used for distance vision and the lower part used for near-vision tasks such as reading. Until recently, bifocal eyeglasses had a line going across the entire length of the lens. Now there are a number of variations on the theme. (you can delete the blue text if it is too much to fit on the page)

Progressive/Trifocal lenses have three different focus areas: the top for distance vision, the center for intermediate vision, and the bottom for near vision.