Method for determining geometrical parameters of a soft contact lens

Method for determining geometrical parameters of a soft contact lens (CL), the method comprising the steps of

• providing an OCT imaging device comprising an OCT light source;
• providing a soft contact lens (CL) having a back surface (BS) and a front surface (FS);
• arranging the soft contact lens (CL) relative to the OCT imaging device such that light coming from the OCT light source impinges on the back surface (BS) of the soft contact lens (CL);
• irradiating the soft contact lens (CL) with light from the OCT light source and generating a three-dimensional OCT image of the soft contact lens (CL) using the OCT imaging device;
• from the three-dimensional OCT image determining a plurality of edge points (Ei) located on the edge (E) of the soft contact lens (CL);
• connecting adjacent ones (Ei,E2;
• E2,E3) of the edge points in a circumferential direction by individual straight lines, each of the individual straight lines having a length (Ui), to form an approximated circumference of the soft contact lens (CL);
• summing up the lengths (Ui) of all individual straight lines, the sum of the lengths of all individual straight lines representing a length U of the approximated circumference of the soft contact lens (CL);
• from the so determined length U of the approximated circumference of the soft contact lens (CL) determining a diameter D of the soft contact lens (CL) according to the equation D=U/Tr.