A method for minimizing the difference in thickness between two ophthalmic lenses for the same spectacles, wherein each of the two ophthalmic lenses is an uncut finished spectacle lens having a periphery having the form of a circle or an ellipse, and wherein the spectacles have a frame into which the two ophthalmic lenses are to be inserted after edging along a frame line, the method comprising the following steps: A) providing , for each ophthalmic lens , an original lens shape satisfying predetermined optical properties over the complete back surface and a modified lens shape having a front surface and a back surface, wherein the modified lens shape comprises a predetermined shape of the front surface and a predetermined shape of the back surface within a prescription zone of the back surface bordered by a first boundary line , such that the ophthalmic lens satisfies the predetermined optical properties within the prescription zone , and an extension of the back surface radially outwards of the prescription zone by carrier lines (30-37); B) adapting the extension of the back surface of the modified lens shape of the ophthalmic lens having a smaller maximum thickness by replacing the back surface by a combination of the original lens shape and the modified lens shape according to CS = OS + A ⋅ MS − OS wherein CS is the sagittal height of the combined back surface, OS is the sagittal height of the back surface of the original lens shape, MS is the sagittal height of the back surface of the modified lens shape and A is a value from and including 0 to and including 1, wherein the sagittal height of the combined back surface, the sagittal height of the original lens shape and the sagittal height of the modified lens shape are each determined within the same reference system, and C) optimizing A so that the difference in maximum thickness between the two ophthalmic lenses along the frame line is minimized. A) providing , for each ophthalmic lens , an original lens shape satisfying predetermined optical properties over the complete back surface and a modified lens shape having a front surface and a back surface, wherein the modified lens shape comprises a predetermined shape of the front surface and a predetermined shape of the back surface within a prescription zone of the back surface bordered by a first boundary line , such that the ophthalmic lens satisfies the predetermined optical properties within the prescription zone , and an extension of the back surface radially outwards of the prescription zone by carrier lines (30-37); B) adapting the extension of the back surface of the modified lens shape of the ophthalmic lens having a smaller maximum thickness by replacing the back surface by a combination of the original lens shape and the modified lens shape according to CS = OS + A ⋅ MS − OS wherein CS is the sagittal height of the combined back surface, OS is the sagittal height of the back surface of the original lens shape, MS is the sagittal height of the back surface of the modified lens shape and A is a value from and including 0 to and including 1, wherein the sagittal height of the combined back surface, the sagittal height of the original lens shape and the sagittal height of the modified lens shape are each determined within the same reference system, and C) optimizing A so that the difference in maximum thickness between the two ophthalmic lenses along the frame line is minimized. <EOS>