Convenience, visualization, easy operation and accuracy make it
indispensable during the Optometry.

1) Clip this measurer on the frame, aim the center point at the 
     intermediate position of the bridge.
2) Adjust the measuring pieces by the knobs on both sides. When 
    the upper edge of the measuring pieces aligned with the pupil 
    center, the pupil height can be read at the lower edge of the frame.