Saturday, October 15, 2011

Bifocal Lenses

[article contributed by Richard Johnson]

Bifocals were invented by Benjamin Franklin over 250 years ago. Franklin cleverly cut two pairs of lenses in half and placed the stronger reading segments in the bottom half of a small metal frame and the weaker segments on top. For the next 130 years bifocals were essentially the same until rimless eyeglasses (pince-nez) and spectacles became very popular. The fact that one needed only a small reading segment was long obvious to make bifocals less of an annoyance. The solution came in the cemented bifocal lens which was revolutionary at the time and worked well since lenses were the flat, thin, non-toric type. The reading segment was either a small circle or oval.

The invention of the toric or curved lens in the early 1900’s was followed by the invention of the Kryptock bifocal lens in which the two segments were fused together creating a far less visible appearance of two distinct lenses. The kryptock bifocal lens was much more expensive but gained steadily in popularity during the 1915 to 1930 period. The 1930’s to early 1950’s saw some variations in the shape of the reading segment… a flat top to the circular reading segment was created… this type eventually by the 1980’s became the most popular type of bifocal lens.

Interestingly a return to the Franklin type of bifocal lens became popular in the 1960’s it was called the executive bifocal lens. The big problem is that the successful use of bifocals means that the wearer must be able to almost make the reading segment disappear when not doing close work… the individual must be able to see around the reading segment…this can’t be done if the reading segment takes up the entire bottom half of the lens.

Often those who say they can’t wear bifocals have either not given them a chance or continue to fuss with two pairs of glasses…. It can take as long as two weeks of great frustration to get used to them but with patience the wearer discovers suddenly that he or she is unaware of the previous annoyance.

Just as many people have had problems with progressive lenses and despite trying them just can’t wear them.. period. This seems to be the case with most people who have worn traditional bifocals. Progressives are often three times the cost of traditional bifocal lenses.

Whichever type you choose be aware that there will remain times when they are frustrating.

For those of us who wear a pince-nez it’s extremely important that a hoopspring or oxford type pince-nez stays attached to the nose bridge in the same position each time it is clipped on: if the lenses droop or slope down, serious problems can arise. This isn’t a problem with the fingerpiece or astig clip pince-nez.

Friday, October 7, 2011

Progressive Lenses

No, not as in Flo the Progressive spokesperson. She is mighty cute and LeDandy likes her. This post is about progressive lenses. Lenses with different levels of correction blended together for us older folks. The Wikipedia article referenced above is quite informative.

LeDandy recently had a set made for his fingerpiece. I was concerned that the lenses of my fingerpiece would be too small for progressives. The lenses are the traditional classic size (one and a half inches wide, one and three sixteenths of an inch tall) and I was not going to alter the size of my lenses for something as frivolous as vision.

There was a period of adjustment for about two weeks as my vision adjusted to the lenses. Progressive lenses were a wise choice for me.


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