How Are Eyeglass Lenses Made?
By Essilor News
What goes into making prescription lenses? It's a combination of technology, science, and art. And an old art at that—eleventh-century scholars first noted that a convex piece of glass would magnify letters on a page. Now, there is a great deal of technology that goes into creating the lens shape and edge of the bevel to fit into the chosen frame, and, of course, the varying optical correction in the prescription makes for differing lens curvature.
So, how are lenses actually made? After your eye prescription order is sent on to the laboratory, the clerk in the stock picking department chooses the appropriate semi-finished lens blanks. Then, the back side of your lenses is cut according to the parameters of your prescription. After your lenses are polished and engraved, they go through inspection and any lens deemed flawed will have to be redone.
Lenses that require it are tinted, and each lens is compared to the sample to ensure a perfect match. They are then dipped in a number of baths until they are perfectly cleaned. Some lenses, such as Crizal®, go through an additional step like adding a no-glare coating or a treatment to resist scratches. Then, a technician applies yellow markings so the eyecare professional can verify the lens order was applied. Finally, your lenses are blocked and edged and assembled with the frame. They are cleaned and checked one last time and sent to your eyecare professional.
There's a great deal of automation that goes into such a high-demand, high-output market. Computer specifications drive extraordinarily precise machines to shape and surface lenses to the exact prescriptions. This video gives a good sense of how Essilor lenses are made. It also reveals that the size of the original optical blank raw material -which can be derived from highly heated and treated plastic or resin pellets, is surprisingly large.
As you might expect, the range and type of correction needed for the broad array of prescription requirements and conditions is vast. Thus, there are many types of lenses to best address specific needs. Besides the typical conditions of nearsightedness, farsightedness, and astigmatism that need correcting (and correction by different lens materials), specialty Transitions® lenses are available that are clear indoors, but tint outdoors according to the amount of ambient sunlight.
The degree of scientific refinement in the lens process has spawned innovative and even futuristic applications of lens technology that aids glasses wearers with issues like glare, smudges, protection from damaging ultraviolet light, and more. While Crizal lenses can be a solid solution for such issues, progressive lenses such as Varilux® can help with sharper vision and smoother transitions at any distance. You can learn more about both from your eyecare professional.
Our eyes are engineering marvels, and work in tandem with our brains to deliver the wonders of the world to our minds. But sometimes they need a little help. Science (and a good optical lab) to the rescue!