When Were Spectacles Invented?
If you look around you, you’ll notice that an amazing number of people wear spectacles. We are so used to seeing people wear glasses that it’s hard for us to imagine a time when there was no such thing. People with poor eyesight simply had to get along as best they could.
Nobody is really sure when spectacles were invented. In the year 1266, Roger Bacon, an English monk who made many interesting experiments, found a way to make the letters in a book larger and easier to read. He simply put a piece from a ball of glass on the book. Of course, this wasn’t the same as having spectacles to help him.
The first evidence we have of someone actually wearing spectacles is a portrait of a cardinal painted in 1352 in Italy. He wears two framed lenses with their handles riveted together and attracted over the eyes.
When printed books began to appear, spectacles became a real necessity for many people and the use of them began to spread. During the sixteenth century, they were being made in large quantities in northern Italy and southern Germany. In 1784, Benjamin Franklin invented bifocals, which are two different kinds of lenses in the same pair of spectacles.
To understand how spectacles can help a person see better, you must know something about the eye. The eye is shaped like a ball, with a slight bulge at the front. At the centre of this bulge is the pupil, which lets the light into the dark inside of the eye. Light passes through the pupil to the lens. The lens focuses the light, forming a picture at the back of the eyeball. Here there is a screen of light-sensitive cells called the retina.
Some people have eyeballs that are a little longer than normal, front to back; with others the eyeball may be too short, and the lens may not be able to focus a sharp picture on the retina. Spectacles provide the eye with an extra lens. The extra lens corrects what your own lens does, so that there is a sharp picture focused on the retina and you can see later.