Customers oftentimes ask us if someone still buys bifocal lenses today or if they are even obsolete? No, they are not obsolete because they are still a great alternative to progressive lenses.
What a lot of people do not know as far as progressive lenses have evolved over the years when it comes to the actual size of the clear field of view bifocals provide you with the biggest field of view. Depending on what reading segment you choose the size for the reading zone and the shape will vary.
In most cases when people rely on progressive lenses or bifocal the Add value is set around 2 diopters. This value is one of the big drivers for the actual size of the reading zone in progressives. What you get is a reading zone that is only a few millimeters wide. With bifocal lenses, you can choose how wide the reading zone should be.
In most cases, the reading segment is 25-28mm wide. This means with bifocals you can get 10x size when it comes to the reading zones. And yes this includes high-end progressive lenses in comparison. So you can actually perform eye movements from the left to the right with bifocals. This is something you can not do with progressives.
This is why you will always see bifocals here and there. Because people do like them. In the periphery, in the lower half of the lenses, you have indeed zero blur. This is simply not possible with progressive lenses.
What About the Aesthetics With Bifocal Lenses?
Sure normal progressive lenses look like they are made for old people. And most customers do not want that. A good alternative here is blended bifocals. They provide you with two separate segments but for the person in front of you, no visible line is observable.
They are also called free form bifocal lenses. The reading zone with this kind of bifocals can get as big as 42mm. This is unheard-of with progressive lenses. The good thing with bifocals, in general, is the field of view does not get minimized over time. You know what you get before you order.
Here in the picture below you can see a variety of bifocal designs available. The manufactures come up with new ideas to market bifocals in a new way. Although all of them are marketed as bifocals what you get can be very different. Here in the picture below I hold a Freeform (blended) bifocal lens in front of my face.
No person could tell if I wear bifocals, progressives, or single vision lenses. As soon as you hold the lenses further away from your eyes and you look through them the different zones get observable.
In the paragraphs, before I mentioned the Add value is one of the biggest drivers when it comes to the size of the reading zones in progressives. This also means the size changes depending on how good your eyes can still adapt to the reading distance.
Typically the older you are the lesser your eyes are able to adapt to the reading distance. So you can plan to have a smaller reading zone with each incremental addition of lens power in the Add value. This inconsistency is nothing the wearer of bifocals has to deal with.
But there is one exception to this rule. The Shamir Duo is branded as a bifocal lens that has no visible line. Yet the reading zones vary with an increased or decreased Add value. I do not want to get too much into detail but ask the optician if the reading zone will be exactly as wide as what you saw on the dummy lenses to get more security about what you buy.
Here in the picture above you can see a Shamir Duo on the left without a visible line. On the right, you can see a classic bifocal lens design with its typical big reading segment and of course the visible line.
The visible line in classic bifocal lenses also becomes more dominant as the Add value increases as well as the width of the reading segment. Of course, this leads to a ledge that can be big as you can see in the picture below.
This type of lens design (Franklin Lens) was the very first bifocal lenses and it still gets manufactured today. In fact, in recent years they got positive press in studies. The topic around myopia management is big today and will become more relevant in the future.
Franklin lenses are one of the more effective spectacle lens designs to help younger people to slow down the progression of myopia. (Depending on the individual condition)
Despite the Size of the Reading Zones, You Get Even More Benefits With Bifocals
- Better Control of prismatic side effects
- faster adaption process
- less misshaped objects
One big problem with progressive lenses is side effects that deviate the picture differently for each eye when the wearer looks down up. Of course with progressives, this is the only way to use the different zones. And in some cases, the distances between those zones leads to problems.
Because each eye can not be optimized in a independently to address this problem. I am writing here about prismatic side effects. Although this can be a problem with bifocals too the problem can be addressed differently.
Let us dive a little deeper into this topic. The only way to reduce this side effect in progressives is to shorten the distance between the point you look through to enjoy the best distance vision and the point you look through for full reading support. This brings the downside of smaller fields of view with it and more blur in the periphery.
With bifocals however you can choose to set these points individually. The result is less prismatic side effects while the width of the field of view maintains its size. The periphery also has no increase in terms of the mentioned blur.
Those are some big benefits to bifocals you can use when progressives fail. And this is why bifocal lenses will never obsolete. As you can see even the oldest bifocal lens designs are still relevant today.
If you liked this article about bifocals you may be interested in an article in which I describe how bifocals can look like in-depth. Here is the mentioned article. Depending on if you like to choose plastic or glass for your next pair of lenses you can get different options. But you will get this information in the other article.
I hope you found the information you were looking for.
I wish you a great day.