Disc designed to be attached to a concave curved surface of an optical component to modify an optical power of said component, the disc comprising a Fresnel lens made up of a series of Fresnel regions of spherical general shape, in which the changes of height between successive Fresnel regions are located on a concave face of the disc, and in which said Fresnel regions are made out in a special distribution. A disc of this kind maintains the dioptric quality without introducing distortions.