The sphere value provides information about the respective strength of the spectacle lens, measured in diopters. It indicates whether you are farsighted (+) or nearsighted (-). Both phenomena result from a disproportion between the physiological length of your eye and the refractive power of your lens. If the light reflected from an object falls on your eye, it is refracted in the lens in order to combine the individual rays in a point on the retina, so that a sharp image of the object is created. In the case of spherical ametropia, the refracted light in front of or behind the retina is combined in one point. The problem with such a shift in distance is that if you are nearsighted you can only see more distant objects out of focus, whereas if you are far-sighted you have problems focusing on closer objects. By specifying this value, you let us know what degree of curvature we need to grind into your glasses so that your ametropia can be corrected appropriately. With the right strength, the bundled light moves to the right place on the retina and creates sharp images. more less