What are bifocal lenses?

Bifocals were the original lens developed for those of us that can not see up close to read and or at a distance.  Originally it was considered a modern marvel in engineering developed by Ben Franklin in the 1700.  With the advent of computer age, while they are no longer considered the modern marvel they once were, there are many people who still wear them, and they do serve a purpose!

A bifocal lens, as it implies gives you two visions.  Up-close or near for reading and distance vision. This eliminates the need for two pairs of glasses to see at both distances. The lens style comes with a visible line in the lens that mark the distinction between the near vision and distance vision.   

The vision in the bifocal that LensFactory makes is illustrated below. At LensFactory we do a half-moon — also known as a flat-top, straight-top or D segment bifocal.

To use a bifocal all you need to do is look through the correct area of the lens to see what you want to see, near or distance.  Most people look down to read so the near vision is in the lower portion of the lens that is shaped like the letter D on its belly. The bottom part of the lens, or near vision can be tricky because it acts just like a magnifying glass.  This makes objects seem closer to the viewer than they really are.

This can make going downstairs challenging as you need to look through the top of the lens or the distance portion of the lens for that task vs your natural inclination, which is to look down and use the bottom portion of the lens.  With time and practice and wearing your bifocals full time, your eyes will start to naturally go to where they need to go for you to see things clearly.

Did you know, in some instances, bifocals are even prescribed for children who are having trouble seeing while reading. It helps them with their focus while reading and assists with eye strain.  Speaking of reading, what about those reading glasses you can get at the local drugstore? Those are a single vision and work as a magnification just like the near vision in a bifocal or trifocal lens.  They work well for some people, and others not so much. They are inexpensive and easy to get and great for people who always lose their glasses. 

At LensFactory we can make you a pair of readers with no prescription required.  We will need to understand what power you want in the lens and whether you want the power in the full lens or power in the bottom of the lens and clear on top.  Please contact us to get further information on how to place the order for this type of lens.

When you are transitioning from the near vision to the distance vision your eyes need a split second to adjust, and you will experience something called a “jump”.  This is perfectly normal and is to be expected with a bifocal.  This can be unsettling and may cause the wearer to feel off balance because your brain is quickly adjusting to the different vision strengths of near vs distance.  But, with time and with consistent wear this will go away as your eyes and brain learn to adjust to the lens.

Some examples of activities that people find bifocals useful for are needlepoint or up-close work while watching TV or working on an engine in a car or any other type of task wear you want to be able to see up close and in detail and then look up and see at a distance as well.

Some of the disadvantages to wearing a bifocal is there is no intermediate vision.  This can make it hard to read the dashboard of your car or your computer screen.  Therefore, some people prefer a progressive lens or a trifocal which have the intermediate lens.

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