Inventor's 2020 vision: to help 1bn of the world's poorest see better | Society | The Guardian: "Silver has devised a pair of glasses which rely on the principle that the fatter a lens the more powerful it becomes. Inside the device's tough plastic lenses are two clear circular sacs filled with fluid, each of which is connected to a small syringe attached to either arm of the spectacles.
The wearer adjusts a dial on the syringe to add or reduce amount of fluid in the membrane, thus changing the power of the lens. When the wearer is happy with the strength of each lens the membrane is sealed by twisting a small screw, and the syringes removed. The principle is so simple, the team has discovered, that with very little guidance people are perfectly capable of creating glasses to their own prescription.
Silver calls his flash of insight a 'tremendous glimpse of the obvious' - namely that opticians weren't necessary to provide glasses. This is a crucial factor in the developing world where trained specialists are desperately in demand: in Britain there is one optometrist for every 4,500 people, in sub-Saharan Africa the ratio is 1:1,000,000."