US Patent 11555758 Method and system of measuring toric lens axis angle

A method of measuring an axis angle of a toric contact lens including a posterior toric central zone having a cylindrical axis, and an anterior lens surface forming a ballast that has an axis of orientation offset from the cylindrical axis at a selected rotational angle is disclosed. The method involves (a) providing anterior and posterior mold sections including respective anterior and posterior mold cavity defining surfaces, wherein the posterior mold cavity defining surface includes a toric central zone and the anterior mold cavity defining surface is shaped to provide the ballast, the mold sections being alignable at multiple rotational positions; (b) providing a detectable feature on each of the anterior and posterior mold sections at a predetermined angular location with respect to the tonic and ballast axes thereof, respectively; (c) rotating the detectable feature of the posterior mold section relative to the detectable feature of the anterior mold section, wherein the detectable feature of the anterior mold section is a zero reference; and (d) measuring the axis angle between the detectable feature of the posterior mold section relative to the detectable feature of the anterior mold section after rotational displacement of the mold sections during toric contact lens formation.