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Seeing double 
Poor eyesight is not a problem for today. But imagine what it must have been like long ago. 
In ancient times, people tried to find ways to magnify things  and make them appear bigger. 
In ancient Rome, for example,  scholars with bad eyes looked through a glass bowl  water to read.  The water magnified the words.
Polished glass
The development of high-quality glass led to the creation of glasses.  A  scholar in Spain in the ninth century was the first person to  use glass to magnify things.  
He discovered that if the glass was polished into a half sphere, it magnified things. People called these 'reading stones'. They put the flat side of the stone on something they wanted to read and looked through the stone. 
It was still a further 400 years before eyeglasses were invented. 
A man called Salvino D'Armate  in Florence, Italy, is said to be the first person to have made eyeglasses. But this is not certain. 
What we do know is that eyeglasses for reading started to be used in Europe around 1280.
Near and far
The earliest 'reading stones' and glasses were for people who are farsighted. If you are farsighted, you can see things that are far away. But things that are close to you - for example, words on a page - look blurry. 
It was probably not until nearly 200 years later that someone figured out how to correct the eyesight of people who were nearsighted. 
Nearsighted is the opposite of farsighted. Nearsighted people can see things that are close clearly. But they have problems seeing things that are far away. 
Fixing the different problems requires  different lenses. Magnifying things close up requires a convex lens. A convex lens bulges. 
To see things  farther away requires a concave lens. A concave lens is polished so that it has a hollow in it.
now do this
1 The earliest 'glasses' were called ...
a. 'water bowls'. 
b. 'reading stones'.
c. 'spectacles'. 
 2 Glasses like the ones we use today were invented around ...
a. 1280 
b. 1340 
c.  the ninth century 
 3 A convex lens can help someone who is ...
a. nearsighted. 
b. myopic.
c. farsighted.



The invention of glasses