A lot of wearers wish to have adjustable focus glasses. Currently on the market are those you can manually adjust by turning a nob on the side and the focus of the lenses changes (aka Alvarez variable-power spectacles).
This means those adjustable focus lenses can e used by multiple people as a backup solution although they have different prescriptions or for one person that actually needs glasses for distance vision and reading glasses as well.
But those possibilities do not come with their own limitations. For example due to the way the lenses are made your vision becomes slightly less clear.
This comes from little lines crossing the whole lens which are needed to produce prismatic effects. While this works for a short time this is not an adequate replacement for normal glasses as they can give 100% clarity in combination with antireflective coatings which are not even available with adjustable focus glasses.
- Visual experience is less clear compared to normal glasses
- Can not be adjusted to your pupilary distance
- Field of view is limitetd compared to normal glasses
- No correcttion for astigmatism possible
- The Adjustment takes a few seconds
- The glasses are less aesthetically pleasing compared tto normal glasses
- More reflections on the lens surface compared to normal glasses due to missing AR coatings and multiplle surfaces.
- More star bursts when used at night or halo effects
- Great price point (most cost less than 50$)
- Easy adjustments
As you can see the negative points outweigh the pros by far. But having these as a backup plan when your real glasses fail is definitely an option. The thing is are they an option for you? When your astigmatism is higher than 0.75 diopters they are not an option for you. Not even as spare glasses.
Your optician adjusts the height of the optical center individually for each eye so prismatic effects do not disturb the way how your eyes play together. This is not possible with adjustable focus lenses as they are not custom-made for you. In most cases, you can tolerate them if your eyes have a very similar prescription.
How Do Adjustable Focus Glasses Work?
Adjustable focuses glasses work with two lenses in front of each eye. On each side of the temple, you will find a little nob or a regulator. By using this nob you can adjust the diopters in most cases in a range from +3.00D up to -6.00D. When the nob is turned or the regulator moved on the temple one of the lenses in front of your eyes shifts vertically. This way the adjustable focus glasses are able to switch between multiple prescriptions.
But the glasses only work when each eye gets adjusted individually before use. So in order to make the adjustable focus glasses work for you focus on a certain distance you want to see clearly in with one eye at a time and adjust the glasses with the nob until you see clearly.
When you wear bifocals or progressive glasses usually and you want to switch from the reading distance to the driving distance you need to readjust the lenses. Because they can be adjusted to one distance only.
Here in the video below you can see how fast this type of glasses can be adjusted. It really just takes a couple of seconds.
Adjustable Focus Eyeglasses Where Buy?
Adjustable focus eyeglasses are available online and oftentimes in grocery stores. Here in the list below. I will list the differences in regards to the adjsutable prescritptions depending on the manufacturer:
- EnzoDate Adlens -4.0D to +5.0D (Amazon)
- ZZSNT Reading Glasses -6D to +3D (Amazon)
- SEEPlus -4.00 to +5.00D (SeePlus Website)
An important thing to note here is when you have reading glasses and you want to use the adjustable focus glasses for reading too. You need to consider your Add value in your prescription. Let us look at a simple example.
|OD (Right eye)||+2.25||-0.50||0||+2.00|
|OS (Leftt eye)||+2.75||+2.00|
Here in the table above you can see the column with the letters SPH. This is the amount of prescription you need to see clearly in the distance. But when it comes to reading the Add value needs to be added to the SPH value so you know which glasses to buy as they have different ranges for the adjustment. In this case the needed power for reading adds up to 4.25 Diopters of the right and 4.75 diopters for the left eye.
In such a case only the EnzoDate and the Seeplus mentioned above would work for you. The ZZSNT would not give you a clear vision in the reading distance. The example above was targeted to hyperopes. Now lets make an example for myopes as well.
|OD (Right eye)||-3.00||-0.75||90||2.50|
|OS (Leftt eye)||-2.50||2.50|
Just check if the SPH value fits the range of the glasses you want to buy. And as with the examplle above you need to check if the range also fits when you add the Add value to the SPH and in this case we have +0,50 for the right eye and 0 for the left eye.So in this case you could buy every one option listed above.
Butt what you keep in mind those adjusttable focus glasses will not correct the astigmatism which is described by the CYL value. The right eye would have a little less clear vision. But for some spare glasses this would work well.
This is my short take on the glasses you can adjust yourself. They are not really a replacement for your normal glasses but a really good back up solution. If your CYL value is higher than 1.00D you will experience more bluriness with the glasses llisted above. In such a case it would be better to have cheap custom glasses in case your normal glasses break.