Professor John Silver is on a quest to deliver affordable glasses to 1 billion of the world’s poorest people. His invention is readily adjusted by individual wearers and does not rely on opticians or expensive specialized equipment:

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. [via The Guardian]