© Science Museum / Science & Society Picture Library
A pair of adaptive spectacles invented by Joshua D Silver, profesor of physics at Oxford University. Spectacles have been in use in the West for at least 700 years. The earliest had convex lenses, and were designed to beworn by people with long sight, to help them focus on nearby objects. Later, concave spectacle lenses were made for people with short sight. In 1784 Benjamin Franklin (1706-1790) invented 'bifocals' - spectacles split into two parts, each with a different focal length. Adaptive spectacles are designed to allow the wearer to manually adjust the power of each lens to their own requirements.