Eyeglasses are remedial lenses mounted in frames that help those with vision problems see clearly. The lenses are shaped in order to bend light rays so that they will focus at the back of the eye, the retina. Some people whom can see distant objects clearly but to who near objects look blurry suffer from hyperopic or farsightedness. Some people suffer from myopia or nearsightedness, in which the image is focused in front of the retina so that only near objects can be seen clearly. Concave lenses can be worn to diverge the light rays and permit light from far away objects to focus directly on the retina. A condition called presbyopia occurs when the lens of the eye loses it elasticity and it can no longer change shape. The condition is usually associated with age and becomes evident after 40. Presbyopia causes people to be somewhat farsighted. Sometimes this is corrected by wearing bifocals, or eyeglasses that have a second lens below the top lens. A person with presbyopia can look through the bottom lens while reading and use the top lens for distant objects. The invention of eyeglasses has a long and colorful history. It is said that during the days of the Roman Empire, the emperor Nero watched exhibitions in the Coliseum holding a jewel with curved facets up to one eye, but this cannot be verified. However, Roger Bacon, an English scholar, is said to have suggested the use of eyeglasses in the 1200s. An Italian physicist, Salvino degliArmati probably invented eyeglasses in around 1285. He shared the design of his new device with an Italian monk, Allesandro Della Spina, who made public the invention and is often given credit for inventing eyeglasses.