ADAPTIVE EYE CARE ⋅ JOSHUA SILVER ⋅ 1996
In the Adaptive Eyecare glasses the lenses are built as flexible membranes filled with liquid that can change shape easily. The change in the shape, that implies a change in the power of the lenses themselves, is controlled by a small pump so that the user has complete control on it and can adjust his / her own glasses according to the need. These glasses can correct myopia, presbyopia but not astigmatism.
These glasses represent an easy way to increase accessibility by distributing glasses without prescription (initially thought for developing countries), or for example, to keep them even when the need is changing over a period of time.
More info and image source: adaptive-eyecare.org