The glasses work on the principle that the more liquid pumped into a thin sac in the plastic lenses, the stronger the correction.
[Joshua Silver] has attached plastic syringes filled with silicone oil on each bow of the glasses; the wearer adds or subtracts the clear liquid with a little dial on the pump until the focus is right. After that adjustment, the syringes are removed and the “adaptive glasses” are ready to go.
Currently, Silver said, a pair costs about $19, but his hope is to cut that to a few dollars.
This is interesting for several reasons:
- It increases the flexibility of a single pair of eyeglasses for different situations.
- It allows the entire field of view to be the same focal length, unlike a bifocal or multifocal lens that has only a small region at the required focus and everything else off-focus.
- It decreases the long-term cost by allowing eyeglasses to adapt to changing eye-lens powers over many years (assuming the glasses last that long).
- It’s a clever emulation of what nature does for the eye-lenses of most species: make them fluid-filled and change their shape with muscle tension.
Overall, seems like a design that solves several problems simultaneously. Quite impressive.