How Are Eyeglass Lenses Made?
By Essilor News
What goes into making the miracle known as a prescription lens? 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.
Plastic, polycarbonate and high index lenses dominate the market now, but for many years lenses made of glass were the most common option. Plastic, polycarbonate, high index and glass lenses are made in successive stages of grinding, using a base piece of plastic polycarbonate and high index that is further refined in prescription and lens shape. 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.
There's a great deal of automation that goes into such a high-demand, high-output market. Computer specifications drive extraordinarily precise machines toshape and surface lenses to the exact prescriptions. This video gives a good sense of the process. It also reveals that the size of the original optical blank raw material -that 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 manytypes 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.
As this podcast from NPR explains, advances in lens technology include lenses that will allow up to 14 percent more light into your eye, which translates into better sight. Of course, some specialty prescriptions require adjustments even after they are returned from the lab, which optometrists and opticians are happy to do for you.
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!