Bifocals


Benjamin Franklin was frustrated by his need to switch glasses because he was both near-sighted and far-sighted, and so he invented bifocals. He took the lenses from the two different types of glasses, cut them in half, and put them back together, using one half of each in one frame. Thus, the bifocal lens was born. The term “bifocals,” or bifocal lenses, refers to the use of two different strength lenses in the same pair of glasses.

Need for Bifocals

Individuals who are near-sighted, far-sighted, or have an astigmatism before they begin to have vision problems associated with aging will experience the same frustration that Benjamin Franklin had – the need to switch glasses for different types of visual situations – unless they wear bifocals. Presbyopia is a condition brought on by aging, where the eye has more difficulty accommodating and can be corrected with so-called reading glasses, as it manifests itself by the inability to read small print, etc. Those who have worn glasses for prior conditions will require bifocals to deal with their multiple visual problems.

Bifocal Types and Usages

Traditional bifocals feature a lens with a visible line across the middle, and later on, the moon-shaped bifocal was developed. Wearing bifocals while working on computers has produced different concerns because reading a computer screen is different than reading a book; computer users need to tilt their heads upwards to work comfortably. Thus, the occupational progressive lens was developed to address such issues.

Computer glasses are also available that clip on to one's regular glasses. Occupational lenses are not only beneficial for alleviating presbyopia as it affects computer use, but are also beneficial for reducing glare and eyestrain in the workplace, which reduces work performance. Trifocals also allow for additional visual accommodation as they have three options: far, intermediate, and near. People who are driving who need to see in the distance, their dashboard, and perhaps a map – though this may be unsafe – would benefit from using trifocals, as all three viewing distances are required. Progressive lenses are multi-focus lenses that have no visible lines between the segments.

Seeing With Bifocals

Since bifocals operate on the principle of having different segments of the lens used for different situations, the wearer has to learn how to use the bifocals, which may take some patience. The usual configuration requires the wearer to look toward the top of the lens when they want to see something at a distance. For viewing at distances of less than 18 inches, and for detailed work, the viewer looks through the lower portion of the lens.

Bifocal Innovations

Advances in optometry are forthcoming with the potential development of so-called “electro-active” glasses that refocus automatically, similar to the function performed by a camera. This process would be achieved by using chemistry and electrical current applied through the use of a microchip. However, until such time as this technology is refined, bifocals rely on the curvature of the lens, and physically providing two or three different levels of refraction.

Developing the electro-active lens will prove to be a challenge as cost and cosmetic feasibility are consumer driven concerns. Until such time as these high-tech lenses are available, bifocal, trifocal, and progressive lenses are the only options available to those with more than normal age-related vision problems.

By Eve Visconti           


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