Method for determining at least one optical parameter of a spectacle lens , wherein the optical parameter denotes a value for a property of the spectacle lens which is set during the production of the spectacle lens in order to achieve an intended correction of ametropia of at least one eye of a user of the spectacle lens , wherein the method comprises the following steps: a) Recording at least one image using a spectacle lens , wherein the at least one image comprises an eye portion including at least one eye of a user of the spectacle lens , wherein a variation of a region of the eye portion of the user of the spectacle lens that is visible through the spectacle lens is effected by the recording of the at least one image using the spectacle lens ; and b) Ascertaining at least one optical parameter of the spectacle lens by means of image processing of the image, characterized in that the at least one optical parameter of the spectacle lens is ascertained on the basis of the variation V E of the visible region of the eye portion of the user in accordance with equation : V E = 1 1 − d n D 1 ⋅ 1 1 − e + e ′ S ′ , wherein for d = 0.0005 m in the case of the negative lens and d = 0.001 m in the case of the positive lens , n a refractive index of a material of the spectacle lens of 1.5 or 1.52 or 1.6 or 1.67 or 1.74 or a combination thereof, e = 0.012 m and e' = 0.013348 m are used, and wherein S' corresponds to the vertex power of the spectacle lens and D 1 corresponds to the power of the front lens surface of the spectacle lens , wherein the variation V E concerns a geometric dimension of the at least one eye , wherein the geometric dimension of the at least one eye is selected from: - a common diameter of pupil and iris ; - a horizontal distance between a right eye angle and a left eye angle ; or - a vertical distance between an upper lid and a lower lid . a) Recording at least one image using a spectacle lens , wherein the at least one image comprises an eye portion including at least one eye of a user of the spectacle lens , wherein a variation of a region of the eye portion of the user of the spectacle lens that is visible through the spectacle lens is effected by the recording of the at least one image using the spectacle lens ; and b) Ascertaining at least one optical parameter of the spectacle lens by means of image processing of the image, in that the at least one optical parameter of the spectacle lens is ascertained on the basis of the variation V E of the visible region of the eye portion of the user in accordance with equation : V E = 1 1 − d n D 1 ⋅ 1 1 − e + e ′ S ′ , wherein for d = 0.0005 m in the case of the negative lens and d = 0.001 m in the case of the positive lens , n a refractive index of a material of the spectacle lens of 1.5 or 1.52 or 1.6 or 1.67 or 1.74 or a combination thereof, e = 0.012 m and e' = 0.013348 m are used, and wherein S' corresponds to the vertex power of the spectacle lens and D 1 corresponds to the power of the front lens surface of the spectacle lens , wherein the variation V E concerns a geometric dimension of the at least one eye , wherein the geometric dimension of the at least one eye is selected from: - a common diameter of pupil and iris ; - a horizontal distance between a right eye angle and a left eye angle ; or - a vertical distance between an upper lid and a lower lid . - a common diameter of pupil and iris ; - a horizontal distance between a right eye angle and a left eye angle ; or - a vertical distance between an upper lid and a lower lid . <EOS>