A Method implemented by computer means for determining a lens blank intended to be used for the manufacturing of a finished optical article, the method comprises: - a virtual volume data determining step, during which virtual volume data are determined based at least on finished optical article data representative of the volume of the finished optical article and over-thickness data representative of over-thickness requirements, the virtual volume data are determined so that the virtual volume defined by the virtual volume data includes the volume of the finished optical article volume of the finished optical article and the over-thickness, the virtual volume comprises a first surface, a second surface opposed to the first surface and a first peripheral edge surface linking the first surface to the second surface, the finished optical article comprises a third surface, a fourth surface opposed to the third surface and a second peripheral edge surface linking the third surface to the fourth surface, the over-thickness data comprises a machining over-thickness value corresponding to the minimum distance between each point of a first set of surfaces consisting in the first and second surfaces of the virtual volume and each point of a second set of surfaces consisting in the third and the fourth surfaces of the finished optical article, - a lens blank determining step, during which a lens blank is determined based on said virtual volume data so as to include the virtual volume defined by the virtual volume data, and wherein the machining over-thickness value is greater than or equal to 0.5 mm. - a virtual volume data determining step, during which virtual volume data are determined based at least on finished optical article data representative of the volume of the finished optical article and over-thickness data representative of over-thickness requirements, the virtual volume data are determined so that the virtual volume defined by the virtual volume data includes the volume of the finished optical article volume of the finished optical article and the over-thickness, the virtual volume comprises a first surface, a second surface opposed to the first surface and a first peripheral edge surface linking the first surface to the second surface, the finished optical article comprises a third surface, a fourth surface opposed to the third surface and a second peripheral edge surface linking the third surface to the fourth surface, the over-thickness data comprises a machining over-thickness value corresponding to the minimum distance between each point of a first set of surfaces consisting in the first and second surfaces of the virtual volume and each point of a second set of surfaces consisting in the third and the fourth surfaces of the finished optical article, the virtual volume comprises a first surface, a second surface opposed to the first surface and a first peripheral edge surface linking the first surface to the second surface, the finished optical article comprises a third surface, a fourth surface opposed to the third surface and a second peripheral edge surface linking the third surface to the fourth surface, the over-thickness data comprises a machining over-thickness value corresponding to the minimum distance between each point of a first set of surfaces consisting in the first and second surfaces of the virtual volume and each point of a second set of surfaces consisting in the third and the fourth surfaces of the finished optical article, - a lens blank determining step, during which a lens blank is determined based on said virtual volume data so as to include the virtual volume defined by the virtual volume data, and wherein the machining over-thickness value is greater than or equal to 0.5 mm.