Désirée Niendorf

The optician does this to mark the optical center of the lenses. In other words, the optical center always has to be precisely in front of the eye because this the point where our vision is optimal. The process itself is called centration. Making a mark with a pen is a very traditional approach that can be used also for follow-up checks to see whether the optical center is really in front of the eye. And opticians today often like to complement this with modern measuring technology.

Generally speaking, there might be a number of reasons for this. The most important thing, of course, is to always check whether the prescription is correct. Do I really have the right lens power to correct the optical error? If you do have the right prescription, it might be that the lenses aren’t positioned correctly in the frame. In this case, the optical center won't be directly in front of your eye. This is always extremely important because this is the point where our vision is optimal. And this factor is particularly crucial if you have high diopters or if you have complex eyeglass lenses such as progressive lenses that integrate multiple lens power for different distances in the lenses. And this can actually lead to significant problems if the position isn’t correct. If this has happened, the only option is to remake the lens.

Thanks to modern measuring technology, centration is a very fast and comfortable process for consumers today. This involves taking one or a number of images of the person wearing the glasses. These are then evaluated using software. The centration parameters can then be generated automatically from this data. Another advantage of this is that the head and body posture can be evaluated at the same time to ensure they are exactly the same as in the wearer’s day-to-day life. The software can then be used to compensate for errors caused by incorrect head posture or turning the head when the measurement was taken. In this way, modern devices support opticians in their work.

In principle, yes; but it goes without saying that it’s especially important to pay close attention to the size of the frames in this case to make sure they are really a good fit for the wearer afterwards. ZEISS offers a solution for this that involves having a so-called avatar of yourself created at the optician’s store. The avatar is a 3D image of your face that is created to scale. Using this avatar, it’s then completely flexible and convenient to try on eyeglass frames at home. A high-precision 3D scan is also created of the frames themselves. And this makes it possible to really ensure that the process is highly realistic and, above all, is scaled correctly in relation to your face. Plus, you can even project tints and anti-reflection coatings into the frames so you can see the combination as a whole. If you’ve selected your frames online you can order them directly from the optician where you previously had your avatar created.