Single vision lenses provide correction for a single focal length over the entire area of the lens. It is commonly used for distance, intermediate, or reading glasses.
Bifocal lenses corrects for distance vision on the top and reading vision on the bottom. The two areas of vision are divided by a segment line that runs horizontally across the lens.
Intermediate/ Computer lenses refers to specifically designed lenses to provide optimum vision range for specific jobs or hobbies such as artists, musicians, electricians and those that work with computers. Intermediate can have near and intermediate (computer distance), or intermediate and distance. Unlike the bifocal, there is not visible line on the lenses where the powers change.
Progressive lenses, also known as no-line bifocals, provide a smooth continuous field of vision at near, intermediate and distance focal ranges. Progressives eliminate unsettling image jumps, that occur on bifocal or trifocal lenses. It is also more cosmetically appealing having no line through out the lenses