Single vision lenses are designed to correct sight at one distance only, with a single prescription covering the entire surface of the lens.
They are usually prescribed for people who are either longsighted or shortsighted, and who need glasses just for things like reading, driving or working at a computer.
Opting for single vision lenses may mean you also need a separate pair of glasses for different activities.
Bifocal lenses allow the wearer to see at two different focal points. The top section of the lens is for distance i.e driving or tv and the lower segment is for reading. Although not usually as expensive as varifocal lenses, which invisibly blend prescriptions, bifocals do have a visible line where the two different sections meet.
Varifocal lenses work by offering a gradual change in lens strength from the top of the lens to the bottom. Unlike bifocals, varifocal glasses have no specific area of lens strength, but progressive lens zones.
The lack of a dividing line make varifocals more visually appealing and remove the need for multiple pairs of glasses.
The way to look through varifocals depends on what you want to look at. If you’re looking into the distance, you look through the top of the lens. To view things at a closer distance gradually move your eyes lower through the lens to keep the object in focus. For the best close-up focus, you need to look through the bottom of the lens.