Changes in fashion happen so quickly that it is sometimes no easy feat to keep up with them. If brightly-colored clothes are the latest trend one year, it is not long before the very same clothes are attracting disdainful looks. But it is not only jeans, dresses, blouses, shirts and shoes that are affected by fashion trends. Eyeglass frames are another accessory for which new trends are constantly emerging. And so it naturally happens again and again that you suddenly don't like your current model of eyeglass frames as much anymore. But does that necessarily mean that you need a brand new pair of glasses? "Under certain conditions, it is possible to put old eyeglass lenses into new eyeglass frames," says Heike Rudolph, an optician at Niemand Optik in Berlin.
Certain data, referred to as centering data, plays a significant role in such cases. In order to optimize the performance of modern eyeglass lenses, the exact perspective point must be determined with great accuracy. More and more, such accuracy demands the implementation of state-of-the-art technology, such as high-precision measuring systems, for example the modern centering systems or the revolutionary i.Profiler system from ZEISS.
Examples of modern eyeglass lenses include individually measured and customized lenses, such as the ZEISS single vision lens or the ZEISS Individual 2 progressive lens.
In order to optimize the optical performance of customized eyeglass lenses, the eye care professional makes a record of the following centering data: the distance between the center of the pupil and the center of the frame, the distance between the lower edge of the frame and the center of the pupil, the distance between the rear glass surface and the foremost point of the cornea, the angle between the lens surface and the vertical line of vision (technical term: inclination) as well as the angle between the lens surface and the horizontal line of vision (referred to as the curvature). This extensive list of centering data alone illustrates the highly sensitive functionality of modern eyeglass lenses and demonstrates the importance of the interaction between the eyes, eyeglass lenses and suitable eyeglass frames. It is therefore only possible in very few cases that "old" customized lenses can be put into new frames. The option of fitting used eyeglass lenses into new eyeglass frames is most likely to work in the case of standard single vision lenses, because only the inter-pupillary distance has to be identical. In the case of standard single vision lenses, the remaining centering data is not generally needed. "Of course, the strength of the eyeglass lenses also plays a decisive role," says Mr. Rudolph. "The higher the optical effect of an eyeglass lens, the narrower the tolerances in the production of the glasses."
Progressive lenses are even more problematic. "In this case, the tolerances are unfortunately even more restricted, because in spite of being very small, the lenses should enable precise distance vision, near vision and intermediate vision," says Mr. Rudolph. The eyeglass lens must therefore be a technical masterpiece, because not only must it simultaneously correct nearsightedness, farsightedness and presbyopia, it must also enable clear vision at all of the distances in between. "In this instance, there are only very few cases in which it is possible to put old eyeglass lenses into new eyeglass frames," says the Berlin-based eye care professional.
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