bifocali

Bifocals are eyeglasses that contain two distinct lens powers, one for distance vision and one for near vision. This type of lens is prescribed for individuals who have presbyopia, an age-related condition that makes it difficult to focus on close objects. The upper portion of a bifocal lens typically corrects for distance vision, while the lower portion contains a segment for reading or other near tasks.

The distinct line separating the distance and near segments is a characteristic feature of traditional bifocals. This line, often visible to the wearer and others, signifies the transition between the two optical powers. The placement and size of the near segment can vary depending on the wearer's specific needs and the design of the bifocal lens.

Bifocals were first developed in the late 18th century, with Benjamin Franklin often credited with their invention, though historical evidence suggests earlier rudimentary forms. Over time, lens technology has advanced, leading to various types of multifocal lenses beyond basic bifocals, including trifocals and progressive lenses, which offer a smoother transition between different focal lengths. Despite the availability of newer options, bifocals remain a popular and effective solution for many people experiencing presbyopia.