The mirror frame controls the function of the lens

When choosing a frame, consideration should be given to the mutual influence with the lens: the larger the frame size, the larger the effective diameter of the frame, the larger the minimum required lens blank, and the thicker and heavier the lens after edge cutting. Therefore, height lenses and non spherical lenses require small-sized, symmetrical, circular or square frames, and frames with a meridian that is too long are not suitable. The gradient mirror requires a frame of appropriate height, with a vertical distance of at least 22 millimeters from the center of the pupil to the bottom of the inner groove of the mirror ring.
For highly astigmatic lenses, it is necessary to consider the meridian direction with the highest refractive power. For lenses with a size of+6.00/-4.00 * 180, it is necessary to choose a narrow and high frame with a relatively large height, so that the thickness of the top and bottom edges is not too thick. For lenses with a size of+6.00/-4.00 * 90, a wider and shallower frame should be selected.