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. Spectacle frames are another accessory for which there are constantly new trends emerging. And so it naturally happens again and again, that you suddenly don't like your current model of spectacle 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 spectacle lenses into new spectacle frames", says Heike Rudolph, an optician at the Niemand Optik in Berlin Charlottenburg.
Certain data, referred to as centering data, plays a significant role in such cases. In order to optimally utilise the performance of modern spectacle lenses, the exact perspective point must be determined accurately. With increasing frequency, 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 spectacle lenses are individually measured and customised lenses, such as the single vision lens Clarlet Individual or the progressive lens ZEISS Progressive Individual2 with EyeFit technology from ZEISS.
In order to optimally utilize the optical performance of customised spectacle lenses, the optician 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 bears evidence of the highly sensitive functionality of modern spectacle lenses and demonstrates the importance of the interaction between the eyes, spectacle lenses and suitable spectacle frames. It is therefore only possible in very few cases that "old" customised lenses can be put into new frames. The option of fitting used spectacle lenses into new spectacle frames is most likely to work in the case of standard single vision lenses, because only the interpupillary distance is required to be identical. In the case of standard single vision lenses, the remaining centering data is not generally requested. "Of course, the strength of the spectacle lenses also plays a decisive role", says the expert Heike Rudolph. "The higher the optical effect of an spectacle lens is, the narrower are 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 Heike Rudolph. The spectacle 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 spectacle lenses into new spectacle frames", says the Berlin-based optician.
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