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Finn Bowyer -October 04, 2019
With so many different lenses on the market today it’s no wonder that manypeople are asking “What are Bifocals?”
Bifocals help those that require vision correction for myopia(short-sightedness) and presbyopia (long-sightedness). The lenses allowclear vision at either distance within one pair of spectacles.
They can be thought of as ordinary prescription lenses with an additionalreading segment. The reading segment is usually positioned towards the lowerpart of the lens.
Brief History Of Bifocal Lenses
It is thought that Benjamin Franklin invented Bifocal lenses in thelate 1760s. However, evidence now suggests that others may have worn“Split Bifocals” before him. As he aged, Franklin required separateglasses for distance and near use. Growing tired of constantlychanging his spectacles, he decided to do something about it. Hissolution was to cut the lenses from each pair in half. He then splitthe lens into two halves. Distance lenses at the top. Reading at thebottom. Franklin could now use one pair of glasses for clear vision atboth distances. He originally named them “Double Spectacles”.
Modern technology has certainly helped to improveBifocals. They are now more durable and stylish. As well as morewidely available. But despite these technological advances, they stillwork largely in the same way. As he aged, Franklin required separateglasses for distance and near use. Growing tired of constantlychanging his spectacles, he decided to do something about it.
His solution was to cut the lenses from each pair in half. He then split thelens into two halves. Distance lenses at the top. Reading at the bottom.Franklin could now use one pair of glasses for clear vision at bothdistances. He originally named them “Double Spectacles”.
Modern technology has certainly helped to improve Bifocals. They are nowmore durable and stylish. As well as more widely available. But despitethese technological advances, they still work largely in the same way.
Different Types Of Bifocal Lenses
Many variations of Bifocal have since been designed to suit various uses.Opticians are likely to recommend one of the following types of Bifocals.
D Seg Bifocals
The reading area of the D Seg Bifocal looks like a letter D positionedon its side. They may be referred to as a Flat Top Bifocal. The D Seg isthe easiest Bifocal design for a wearer to adapt to. Because of this,it’s the most popular type on the market today.
The readingsegment is available in various types. The most widely used lenses are D28 and D 35. The D 28 segment is 28mm wide and the D 35 is 35mm wide.
Round Bifocals
As the name suggests, the round bifocal is round at the top. They wereoriginally designed to help wearers reach the reading area more easily.However, this reduces the width of near vision available at the top ofthe segment. Because of this, round bifocals are less popular than the DSeg.
The reading segment is most commonly available in 28mm and 25mm sizes.The R 28 is 28mm wide at the centre and the R25 is 25mm wide.
Executive Bifocals
The Executive Bifocal is similar to the original Split Bifocal worn byBenjamin Franklin. The entire top portion of the lens is dedicated fordistance use whilst the bottom portion is for reading. They offer a muchwider reading area than other types of bifocal.
It’s not all good news, however. As mentioned earlier, the entire bottomhalf of the lens is dedicated to reading. This prevents the edge profilefrom being uniform, meaning the lenses are more difficult to glaze. Thiscan lead to lenses looking unsightly when mounted into frames. Thosewith higher prescriptions and a taste for exotic styles or semi-rimlessframes will want to avoid executive bifocals.
Curve Top Bifocals
The Curve Top Bifocal, or the C Bifocal, is almost identical to the DSeg. A slight curve at the top of the lens is the only difference. Oncemore, the near vision segments are available in different widths. The C28 is the most popular size available.
Double D Bifocals
Double D Bifocals are designed for those that require an intermediate orreading segment at both the top and bottom of the frame.
At first, you may think, why on earth would you need near visionavailable at the top of your glasses? However, there are some situationswhere this would be very beneficial. Think of an electrician wiring alight near a ceiling or a decorator cutting in around the coving. Inthese cases, a near or intermediate segment at the top of the framewould be very useful.
Need a new pair of Bifocals? Discover a huge range offashionable glassesavailable at Spex4Less including 100% satisfaction guarantee and 12 monthswarranty.
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