A word about different types of spectacle lenses:
Single Vision - These spectacle lenses have the same prescription over the entire area of the lens. They can be used for either distance or near vision.
Multifocals - These lenses are used where the wearer has a separate distance and near prescription. There are two types of multifocal lenses: the bifocal and the varifocal.
- The bifocal - In this lens, the distance prescription is at the top of the lens and the reading prescription is in a segment in the lower half of the lens. The two prescription areas are separated by a visible line running across part of the lens.
- The varifocal - These lenses are designed to provide a gradual, controlled increase in focussing ability between the distance and near vision. Outwardly they appear as single vision lenses. Varifocal lenses often additionally allow their wearer good intermediate distance vision e.g. when using a computer.