In a bifocal lens prescription, what is the purpose of the Addition value?

The Addition value in a bifocal lens prescription is specifically intended to improve near vision. Bifocal lenses are designed to assist individuals who have presbyopia, a condition associated with aging that affects the ability to focus on close objects. The Addition value represents the strength needed to help with near tasks such as reading, sewing, or other activities that require focused vision at a closer range.

In bifocal lenses, there are typically two different prescriptions in one lens: one portion for distance vision and another for near vision. The Addition is the difference in power between these two segments, providing the necessary increase in magnification to enable clear vision at close distances. This is particularly important for people who find it difficult to see small print or perform other intricate tasks up close due to the effects of presbyopia.

The other choices relate to different aspects of vision correction. Distance vision is handled by the main prescription in the upper segment, enhancing peripheral vision is not a function of bifocal lenses, and astigmatism correction is usually addressed separately with cylindrical lenses rather than via the Addition in bifocal lenses. Thus, the purpose of the Addition value is indeed focused on facilitating improved near vision for activities requiring close focus.