British inventor Josh Silver began working on eyeglasses that can be tuned by the wearer in 1985. His goal is to bring better vision to a billion people worldwide who cannot afford, or don't have access to, an optometrist. He 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's goal is to distribute a billion pairs of his adaptive glasses to poor people by 2020 .

Already, 30,000 pairs have been given out in 15 countries. Her hope is to get the cost of manufacturing each pair down to a dollar each.