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 as well as the angle between the lens surface and the horizontal line of vision. 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. The strength of the spectacle lenses also plays a decisive role.The higher the optical effect of an spectacle lens is, the narrower are the tolerances in the production of the glasses.
