Spectacles (glasses) are pairs of lenses used in front of the eyes. They may be made of glass, but modern spectacles are almost entirely made from plastic.

The lenses are designed to help eyes where the normal eye muscles are weak and cannot pull the eyeball into shape to give natural focus. This is especially common in people as they get older.

Lenses are different shapes depending on whether people are long-sighted (and have convex lenses) or short-sighted (and who need concave lenses). Long-sighted people can see about them normally, but cannot read things close up. Short-sighted people can read a book without glasses but need glasses to see the world around them.