Abstract: A pair of cylinder lenses have a combined power of zero when their cylinder axes are parallel and a small cross cylinder power when one lens is rotated until its axis is perpendicular to the cylinder axis of the other lens. Cross-cylinder lenses are used to determine the accuracy of the cylinder power and cylinder axis selected by the practitioner. By mounting one cylinder lens in a motor-driven ring-like lens mount having a member which engages another ring-like lens mount, a single motor can be used to drive both lenses; select between parallel cylinder axes and crossed cylinder axes; and rotate the crossed axis lenses as an assembly to the desired position.

Abstract: An optical alignment system having a movable portion which contains a centering reticle and range finder, the movable portion is optically coupled to a stationary portion including a field lens to permit the precise positioning of a member relative to an object observed at the field lens. A zone parallel light and an image on the field lens permit adjustment of the member and movable portion without corresponding movement of the operator's head. The system is readily combined with an optometer to provide precision positioning of an optometer eyepiece relative to a patient's eye.