Let’s say you are shopping for prescription sunglasses. A good way to do it is to use a “normal” pair of sunglasses and replace the lenses with your prescription. Ideally you want the final product to look as close as possible to the original pair you selected when they still had non-prescription lenses in them. We have already discussed the basic requirements that prescription sunglasses should fulfill. That includes a good coverage, good glare protection and certainly good UV protection. We are very fortunate at the moment that the sunglasses fashion is big, beautiful and many of them even wrap around the face nicely. But can we fit all prescription lenses into frames like that?

The answer here is “within reason”. What exactly does this mean? Well, it actually depends a lot on your prescription. When manufacturing a lens for a highly curved frame such as a fashion sunglasses frame, lenses end up being thicker either on the outside or inside edge depending on your prescription. So, if your current “normal” lenses are very powerful and already reasonably thick in your “normal” frames, then they will be even thicker in a large wrap-around frame.

When manufacturing prescription lenses for sunglasses, we always try to find a good balance between the best possible cosmetic, optical and fitting quality. Unfortunately that disqualifies certain prescriptions from going into certain frames. Imagine this: the more wrap-around your sunglasses frame is, the steeper the curve of the lens has to be to follow the wrap of the frame. When talking about lens curves, an important one is what’s called the “base curve”. This is usually the flattest curve of a lens. If you have a minus lens (lens thin in the centre and thicker on the outside), the base curve is on the front of the lens, if you have a plus lens (lens thicker in the middle and thinner on the outside), the base curve is on the inside of the lens.

“Normal” lenses usually have a base curve between 2 and 4, whereas lenses for wrap-around frames require base curves of between 6 and 8 (the higher the base curve, the more curved the lens). Have a look at the 3 examples below to see the required difference in base curve, depending on the wrap of the frame they go into.

It must also be noted, that the optical quality of a prescription lens is different when manufactured with different base curves. As a rule of thumb, the flatter the lens, the better the optical quality. So, if you have a high prescription, you are definitely better off selecting a reasonably flat frame design (example 1). If you have a low prescription, you can select from higher curved models as well (examples 2 and 3).

As a guideline, one could say that most lens prescription can be fitted into frames as in example 1, prescriptions between + and – 4.00 can most likely be fitted into frames as in example 2 and prescriptions between +6 and -2 can most likely be fitted into frames as in example 3.

I suggest you always ask your eyecare professional if a frame is suitable for your prescription before you go out and purchase sunglasses that you want to use for your new prescription sunglasses. Ideally you want to purchase your sunglasses frame from your optician rather than from the local pharmacy or fashion shop. However, if you see a nice pair somewhere else and you think that they may be suitable for prescription sunglass lenses, make sure you can return them for a full refund, just in case your optician decides that it is technically not possible or advisable to put your prescription into that $1000 pair of Louis Vuitton sunglasses or the $20 copy .

Most opticians cary a good range of fashion sunglasses that are suitable for many prescriptions. We have made sure for example that more than 90% of our sunglasses are indeed suitable for prescription lenses.Whatever you do, make sure that you get good quality frames. Some cheap copies are made from inferiour materials and after you have spent good money for your new prescription sunglass lenses, you don’t want the frame to break or the colour to fade or peel after a week or so. When choosing plastic frames, try and find one made from high quality acetate or another optical quality plastic material. When choosing a metal frame, make sure that it also is made from high quality materials and finishes. Usually you get what you pay for. So, do shop around, but don’t save at the wrong end. You’ll regret it if you do.