Varifocals or Bifocals?

12th May 2017

Many of those who need glasses have probably asked this question at some point. So what is the difference between varifocal and bifocal lenses?

They are known by a variety of different names depending on where you are in the world, but the base functions allow relatively clear-cut distinctions to be made, so that the decision-making process may be that bit easier for you.

Bifocal Lenses

A bifocal lens actually incorporates two separate lenses of different focal length,  hence its name. The basic principle is that the focal length of one lens, usually the top one, allows you to focus on and discern objects in the distance, while the bottom lens offers a shorter focal length, useful for reading and other close-in tasks.

This short focal lens can be tailored to the user’s needs, so that it provides optimum clarity for either reading, using a computer screen or for other tasks as desired.

While the bifocal lens offers dual focus depending on the wearer's direction of vision, the presence of two different lenses in front of the eye results in a noticeable line that can take some time to acclimatise to, as well as potential blind spots.

Varifocal Lenses

Varifocal lenses, or multifocal lenses as they are sometimes referred to, are a more advanced option than bifocals.

Varifocal lenses differ in two key ways. The line between the two focal points that is visible in a bifocal lens is blended, offering a seamless transition between far and near objects. This reduces strain on the eye when focusing on objects in the plane immediately in front of the wearer.

The disadvantage, however, is the reduction of peripheral clarity. Images at the edge of the lens tend to be blurred as a result of the lens construction, and users need to incorporate more neck movement to view objects clearly in these regions.

This can take some time to acclimatise to, with images initially seeming to swim or blur. As the brain adapts, vision becomes normal,  though there will still be the need for greater neck movement for a wide field of vision.

Varifocals or Bifocals?

Each lens type offers the wearer a flexible approach to catering for their visual needs. It is best to discuss precise requirements with an optician if in doubt, as they can advise on the best lens based on your desired field of vision. Then all that remains to do is select a fashionable set of frames.

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