Multifocal vs. Unifocal
There seem to be many different types of lenses, but generally this difference can be reduced to multifocal or unifocal. A progressive lens incorporates multiple strengths and therefore corrects at multiple distances, unifocal glasses only correct vision for either near, or far and do nothing for the intermediate distances. If you also know that varifocal, multifocal, and progressive lenses are all names for one and the same type of product, there are already a lot fewer question marks. However, there are still different types of progressive lenses, more on that in the next paragraph.
What are multifocal lenses?
Multifocal lenses are ground to multiple strengths, which allows you to use them as reading glasses as well as regular glasses. The predecessor of these lenses are the bifocal lenses: in these glasses, the reading area is clearly identifiable by the indented surface. This area allows you to read properly, while the rest of the glasses are for “normal” viewing. Meanwhile, technology has advanced and the transition of strength is gradual, allowing you to see well into the distance through the top and read with the bottom.
The advantages and disadvantages
Because the glass is ground to multiple strengths, you will often have to get used to looking through the glass a certain way to see something sharply. Because the glass is ground to multiple strengths, you will often have to get used to looking through the glass a certain way to see something sharply. Also, the lenses sometimes distort a little to the side, although very good progressive lenses are available today that minimize that distortion. The advantages: you no longer have to switch between reading and normal glasses, and once you get used to them you have sharp vision at all distances, without having to strain to do so.
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