Fig. 7

A virtual prism with a prism diopter of |PD0|, depicting the power profile with a color-coded map [a] and a graphical display [b] of the power PDφ. |PD0|: nominal value of the prism diopter (∆), corresponding to the prismatic power in the principal section (φ = 0 and 180 degrees), φ: angle between the principal section and an oblique section of the prism.