BIFOCAL LENS Meaning and
Definition
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A bifocal lens refers to an optical lens with two distinct optical powers that allow the wearer to see objects clearly at different distances. It is typically used to correct presbyopia, a condition that affects people as they age and causes difficulty in focusing on near objects.
The bifocal lens is divided into two sections, each with a different lens power. The upper portion of the lens is designed for distance vision, while the lower part is intended for near vision. The separation between these sections is usually demarcated by a visible line, which allows the wearer to easily switch their gaze between near and far objects.
The higher portion of the bifocal lens is usually made for normal sight, addressing any issues related to farsightedness or astigmatism. It is commonly ground from convex lenses. In contrast, the lower portion of the lens is specifically crafted to assist in reading or other close-up tasks. It is typically ground from concave lenses.
Bifocal lenses are commonly used in eyeglasses or visual aids prescribed by optometrists or ophthalmologists. They offer a convenient solution to individuals experiencing age-related vision changes. By providing two focal lengths in a single lens, bifocals eliminate the need for individuals to switch between different pairs of glasses when transitioning between near and far distances.
Etymology of BIFOCAL LENS
The word "bifocal" is derived from the Latin words "bi" meaning "two" and "focalis" meaning "related to a focus". This term was coined by the American inventor, Benjamin Franklin, who is credited with inventing the bifocal lens in the 18th century. The etymology of "lens" comes from the Latin word "lentil" because the shape of a lens resembles a lentil seed. So, the combination of "bifocal" and "lens" refers to a lens that has two different focal lengths.
