It seems more and more that I get questions about prescription sunglasses.
Some of you may remember Hidalgos, a popular website with lots of information about sunglasses and prescription sunglasses.
Since Hidalgos went out of business we have been trying to fill that gap, and are making progress I'm glad to say.
We now use the same optical supply company that Hidalgos used.
We continue to offer prescription lenses both for Randolph Engineering frames that we sell, as well as any of your own frames you have and want new lenses made for.
Over the next few weeks I will provide more information on what we offer, but to begin with lets talk about prescription sunglass lenses.
How Are Prescription Lenses Made?
Eyeglass lenses begin their life in large, hockey-puck-like large pieces called “blanks” which about four inches in diameter and about half an inch thick.
These lens blanks come with one side flat and the other side with a curvature.
A technician then selects a lens blank with the correct amount of existing curvature that corresponds to your prescription.
Using a lensometer the blanks have the optical center marked which refers to the exact point that will be over your pupil.
The lens blank is then placed in a generator (a grinding machine) and the flat side of the lens is ground into the correct shape.
Once the correct curve is created it will go through the process of polishing, beveling and steralization. This is done with another machine and several other tools like soft sandpaper.
At this point in the process the lenses have any tints or UV treatments applied just prior to being placed in your frame.
The final step is to edge the lens with an edge grinder so that each lens will fit snuggly into your frame.
Prescription lenses basically come in 3 versions:
- Single vision;
Single vision lenses are very simple, and as you can see in the image above require only basic grinding of the lens puck.
But both bi-focal and tri-focal lenses are more complex and can be made with or without a line.
Multi-focal lenses without any lines are known as progressive lenses.
Progressive lenses can be bi-focal without a line, or tri-focals, which are more complicated, can be progressive lenses as well.
Once the lenses have been properly ground, treated and edged they are placed into your frame and delivered to you.
There are a number of lens materials that are used in making prescription lenses.
In the early days glass was used which offer exceptional optics. However, they are heavy and can easily break potentially causing serious injury to your eyes.
However, modern glass lenses are made to sustain high impact damage and are often used in high quality sunglasses because of their exceptional optical qualities.
Glass lenses can be heavy depending upon your prescription.
CR-39SR plastic lenses are very popular alternative to glass lenses because they are 50% lighter than glass, are inexpensive and have excellent optical qualities. They are also more impact resistant than glass lenses.
Polycarbonate lenses are lighter than plastic eyeglass lenses and are significantly more impact resistant. Polycarbonate lenses are great for safety and sports shooting eyewear like Randolph Ranger shooting glasses.
Trivex is a newer lightweight and impact-resistant eyeglass material but with slightly different optical and impact resistance qualities.
Trivex lenses are made of a urethane-based monomer. The liquid lens material is baked until it sets which gives it sharper optics that polycarbonate lenses.
Aviator-Sunglasses Prescription Lenses
We offer a number of options for both eyeglass and sunglass prescription lenses in either Randolph Prescription frames or frames you provide to us.
If you are a former Hidalgos customer, or just looking for reasonably priced prescription frames and lenses, then consider us for your next set of prescription lenses.
While you can find purchase options here on our website often times the best option is to contact us by email or telephone and let us walk you through the process to achieve the best result.
Over the next few weeks watch our blog for more information on prescription lenses.
Until next time, keep your wings straight and level Hersch!
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