Contact Lens Types
Single Vision Lenses
Single vision lenses are prescribed if you need correction for one field of vision, either for distance, intermediate (computer), or items up close (near vision). Single vision has the same optical focal point or correction over the entire area of the lens.
Bifocal contacts lenses have two prescriptions in the same lens. Multifocal contact lenses have a range of powers (similar to progressive eyeglass lenses) in each lens.
The term, 'multifocal contacts' is used as a catch-all term for all contact lenses with more than one power, including bifocal contacts.
How Multifocal Contact Lenses Work
Bifocal and multifocal contact lenses work in several different ways, depending on the design of the lens. The designs fall into two basic groups:
Alternating vision (translating) lenses are so named because your pupil alternates between the two powers, as your gaze shifts upward or downward.
Simultaneous vision lenses require your eye to be looking through both distance and near powers at the same time. Although this might sound unworkable, your visual system learns to select the correct power choice depending on how close or far you're trying to see.