Many individual parameters or measuring points are important when fitting lenses into a spectacle frame. They determine how natural the wearer's vision will be and how fast he or she can adapt to their new lenses. These parameters include, for example, the back vertex distance, the distance between the pupils, the viewing height, the tilt of the lenses in the frame, and the wrap or curvature of the frame. However, there is one point in the eye that is not directly measured by your optician. The eye's centre of rotation is a further parameter that is taken into account in the production of ZEISS precision lenses.
At ZEISS this value is calculated using a complex algorithm. It was first incorporated in the production of spectacle lenses in 1970 and has been constantly enhanced and optimised in ZEISS lens designs ever since. This is only possible by collecting a large volume of datasets from wearers – more than 500,000 in all! The eye's centre of rotation indicates at what point the eye rotates behind the lens during the visual process!