In this article, you will learn about what frames can be fit with prescription lenses and where the limitations are. You will see a few examples of extreme cases and what influences a lens lab to say yes or no to an order. Generally speaking most of the frames today can be fitted with prescription lenses.
I do not talk about clip-in solutions you can behind the curved lenses of sunglasses. That is of course also an option but all the information in this article is targeted to build the prescription directly into the frame no matter if the frame I wrapped-around your head or not.
Typical no-goes are frames with just one lens. They are also called shield sunglasses. In case there is an RXable version of the shield (like RX DIRECT from Rudy Project) with a cutout to pop in your prescription lens you will be able to get your prescription in those glasses.
If not you would have to switch to another pair of glasses to get the prescription built-in. But when the two lenses are used in the glasses you wish to buy chances are pretty high even curved lenses can be fitted.
As a rule of thumb with a prescription value of higher than plus or minus six lens labs start to have real problems with the manufacturing of the lenses. Oftentimes a few can exceed even those lens powers while others start to decline order higher than three diopters.
So it is very dependent on the manufacturer. When the lens power gets increased the lenses get extremely thick when curved. First, we talk about the limitations you can run into when prescription lenses need to be fitted into a frame.
Diameter of the Lenses
prescription lenses need to be produced in a certain diameter in order to be fitted in glasses frames. The needed diameter is determined by the centration of the optical center. This optical center needs to be positioned in front of the eye. Bigger lenses are oftentimes in are just available in lower lens powers.
Usually, very high lens powers like -10D are available in a 65mm diameter. When the diameter needs to be bigger than that the available ranges of prescription are dramatically reduced. Especially when you need to go in size of the diameter like 90mm and more. Reasons therefore lie in the manufacturing processes as well as optimizations for the clear field of view and lens design choices made by the manufacturer.
The illustrations above sum up the rules behind the needed diameter of the prescription lens in combination with the centration. In this case the thickness of the lens in the middle is also illustrated. When centration is suboptimal the lens becomes extremely thick.
Manufactures can counter the thickness with different lens designs like lenticular lenses but this concept usually does not makes sense when your lens power is lower than 10 diopters.
Needed Curvature of the Prescription Lenses
The manufacturer can produce a certain lens power only in specific curvatures. Usually the lower the lens power the more options you have. In the example below you can see very curved prescription lenses with a lens power of two diopters plus.
To be more specific the exact curve of the front surface is eight. A lot of wrapped around glasses frames have a curve of six and lower than that are normal prescription lenses. A curve of 0 in this case describes simply a flat surface.
Sometimes when the lens gets too big the manufacturer of the frame can provide special adapters to make the needed lens diameter smaller. With those techniques a lot more extremely wrapped around frames can be fitted with prescription lenses. The question is always are you willing to take the cut. And by the cut I speak about a loss in peripheral vision. Because a piece of the lens will be replaced by a plastic adapter.
Limits of Prescription Lenses
With a lot of limitations in regards to the lens design manufactures are able to produce extreme lens powers today. For example Essilor was able to produce lenses with a lens power of -108 diopters. Here below you can see a video of the man wearing the glasses. of course most people never need this much lens power. But if you have a closer look at the produced lenses they have an extremely small diameter.
And if you are willing to accept the downsides of certain lens designs or even adapters like the one shown in the video you can practically build prescription lenses in every frame you can buy.
But your optician will probably not encourage you to do so if he or she can produce an easier solution for you which works better in your daily activities. Key here is to know the wishes of the customer and align them with what is technically possible. When you are not satisfied with the lens designs that are available for your frame in combination with your needed prescription check out other frames first with different centration.
And if this does not work look for clip in solutions to get your prescription lenses into the frame or adapters. Some more specialized shops have a variety of options for you. For some customers we even 3D printed solutions (adapters) but we will not do this anymore for custom parts as it gets too time consuming.
It is possible to fit prescription lenses in nearly every frame. The centration is one of the key factors that needs to be factored in if the order can be completed or not. Visit an experienced optician if you have a needed lens power higher than five. Asking more than one lens lab may be valuable as technical knowledge and capabilities may differ from manufacturer to manufacturer.