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Purpose of Bifocals

[Summary]Bifocals Bifocals with separate lenses Bifocals are eyeglasses with two distinct optical powers. Bifocals are commonly prescribed to people with presbyopia who also require a correction for myopia, hyperopia, and/or astigmatism. 4 Bifocals in the ani

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Bifocals

Bifocals with separate lenses

Bifocals are eyeglasses with two distinct optical powers. Bifocals are commonly prescribed to people with presbyopia who also require a correction for myopia, hyperopia, and/or astigmatism.

4 Bifocals in the animal world

5 References

7 External links

History[edit]

Benjamin Franklin is generally credited with the invention of bifocals. Historians have produced some evidence to suggest that others may have come before him in the invention; however, a correspondence between George Whatley and John Fenno, editor of The Gazette of the United States, suggested that Franklin had indeed invented bifocals, and perhaps 50 years earlier than had been originally thought.[1] Since many inventions are developed independently by more than one person, it is possible that the invention of bifocals may have been such a case. Nonetheless, Benjamin Franklin was among the first to wear bifocal lenses, and Franklin's letters of correspondence suggest that he invented them independently, regardless of whether he was the first to invent them.[1]

A Trial of Bifocals in Myopic Children With Esophoria

About 25 percent of all persons in the United States are myopic. The most common form of myopia is childhood myopia, which begins after age 6 and progresses rapidly until age 16. Myopia progression results from excessive growth of the eye, primarily by enlargement of the vitreous chamber. Excessive elongation of the eye is a major risk factor for retinal detachment.

What are Bifocals? (with pictures)

Though most people who require bifocals have difficulty focusing on objects both up close and far away, they have always been designed with the corrective lens for close range focusing at the bottom and the corrective lens for distance vision at the top. While this design once made sense, because close range focusing was generally required for reading and writing, activities traditionally preformed while looking down, more and more people find it awkward to use such lenses with a computer. Since the computer monitor is directly in front of the user, the up close corrective lens seems out of place on some glasses.

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