If you can’t see clearly without glasses, you might need them. Or when you get to be about 45 and your eyes lose some of their ability to focus, you might need glasses then.
There are three common eye problems that require glasses: nearsightedness, farsightedness, and astigmatism.
Nearsighted people see things clearly only if these objects are very near. Anything at a distance will be blurry. Nearsightedness occurs when a person’s eyeball is too long, causing the image of a picture to focus in front of the retina, rather than directly on it.
Farsighted people see things clearly only if these objects are far away. What happens is that the eyeball is too short, and the image of a picture focuses behind the retina.
People who have astigmatism find things blurry whether these images are near or far. Here, some of the images of a picture focus on the retina, while other images of the same picture focus in front or behind it.
All of these problems can be corrected with glasses.
Legends tell of people wearing glasses in China as far back as 500 B.C.!