Variable Lenses Minus Mode

Lens power is adjusted by sliding two lenses left or right relative to each other. These lenses are not pure convex or concave, but rather a "wave". The front lens has the convex plus curve towards the nose, and a small concave minus curve on the outside. The back lens is the opposite, with the small convex plus curve on the outside.

 

Here the glasses are in minus power, concave mode, with the back lens pushed outside so that the plus area is shifted further outside, enabling the minus areas of both lenses to overlap towards the middle. While the minus area does not completely cover the larger plus area, the concave power greatly exceeds the convex, producing a maximum net power of -6.

 

The center of the lens is used by the wearer to focus for distance vision. The ring around the edge looks just like the plus carrier portion of a myodisc lens, since it has the same convex lens shape used to thin the lens edge on a high minus lens. But here, we now have myodiscs mass produced in a mere -6 power.

Done