It is smaller than the real version of the chart that is used to test how well you can see. It was first developed in 1863. This means that you must be 20 feet from the chart to see what most people can see at 200 feet.
People wear glasses for several reasons.
In these people, the image is focused in front of the retina. The lens of glasses needed to correct vision in nearsighted people is concave. In farsighted people, objects are focused behind the retina. The lens of glasses needed to correct vision in farsighted people is convex. Astigmatism is another reason that you might have to wear glasses.