Abstract: A device is provided for use with a lensometer which will adjustably hold a ground lens as it is moved until its optical center coincides with the line of sight of the lensometer. The device is provided with two spaced apart, fixed markers and a line passing therethrough will indicate a horizontal line passing through the optical center of the lenses when they are fitted into the frames of the eye spectacle. The device is also provided with a movable marker, movable precise amounts in accordance with the prescription of an individual patient for a particular spectacle frame to indicate the geometric center of that lens when mounted in that spectacle frame and for that particular patient.