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The bifocals have a shape at bottom portion of the lens called a segment for reading. Varifocals do not have a shape or line - look like a normal lens.

Common bifocal shapes are crescent or semi circle. Some can have a line going all the way across lower portion called an executive bifocal.


The near prescription is in the lower segment shape of the bifocal. The top area above has the distance prescription.


Whilst the reading portion of bifocal is not as large as separate single vision reading glasses, it is of generous size and larger than a varifocal.


However the reading segment shape is quite visible and so can be noticed by other people as well the bifocal wearer.  So its cosmetic appearance is not as nice as varifocals.

It can show away the age of someone over 40 as that is when reading glasses are often required.


There is a jump in vision between the segment shape and distance portion of the bifocal and so have to be careful going up and down any steps or kerbs.


There is no intermediate prescription for computer users.

The position of the lower segment of bifocal is designed for reading books or paperwork lower down than a computer screen which tends to be bit higher up.


It may be possible to use the computer screen with a bifocal when stood up in certain situations like a sales assistant stood at the tills and so the screen is relatively lower.


Some people are very happy to use bifocals despite the limitations as the larger area and convenience suits them better than varifocals. The lower cost is a benefit too. For others, solutions is to use a varifocal :





The varifocal is a multifocal  lens that does not have any visible lines - and so looks like a normal lens - no tell tale signs of age and cosmetically nicer.


The varifocal works by gradually blending distance prescription into near prescriptions - from the top of the lens towards the bottom of the lenses - and so the prescription changes  gradually from top to bottom - rather than an abrupt change like with bifocals.


This means the varifocal has intermediate prescriptions - and so its ideal to view the computer screens and music sheets on piano.


The prescription  tends to be near the middle portions of the varifocal lenses called the corridor of progression.

Since the lens has been blended, the areas to sides have some distortion if try to view through the varifocal. Therefore have to use the central areas of the lens in order to get the best vision


It can seem strange at first - as have to point nose to look at objects - and then perhaps move chin up or down slightly to get the area into focus.



The disadvantage of varifocal is the smaller reading area than a bifocals.

Sometimes this can cause difficulties if need to have wide area to read - like with drawing plans - but it does not mean that they wont do the job.

There are limits to varifocals - like with edge distortion if try to look through sides of the lenses - as there are blended areas here.


So if aware of varifocal limits. then most people can adapt to it - and learn how to use them.


Of course, there are occasions that varifocals are not suitable - e.g. a person may feel dizzy with them or needs a large area for close work.

Also if have been wearing bifocals for many years, it can be difficult to adapt to varifocals - and vice versa.


Varifocals can be that more expensive than bifocals but offer more features.


There are many different brands of varifocals - some give less side distortion or perhaps give more reading area

Some varifocals are designed to maximise intermediate areas to help with computer but there may be a trade off with less reading or distance portions.

Varilux is a brand of varifocal and sometimes varifocals may be referred to as varilux as it was a popular brand in the early days.