Neuroscience for Kids

DoYou Wear Glasses?
(Here'sWhy)

Looking Good!

Have you ever seen this "eye chart" before? It is smaller than the real version of the chart that isused to test how well you can see. It was first developed in 1863. If you have 20/20 vision, it means that at a distance of 20 feet, you can read a certain line (labeled 20) on the chart and that your vision is normal. If you can only see the top line clearly (the one labeled 200), then you have 20/200 vision. This means that you must be 20 feet from the chart to see what most people can see at 200 feet. By the way, ifsomeone's vision is 20/200 or worse, then they are legallyblind.

People wear glasses for several reasons. People who have "fuzzy" vision when they look at distant objects arecalled nearsighted (myopic). In these people, the image is focused infront of the retina. The lens of glasses needed to correct vision innearsighted people is concave. People who need glasses for reading andwho have "fuzzy" vision for objects close to them are called farsighted(hyperopia). In farsighted people, objects are focused behind the retina.The lens of glasses needed to correct vision in farsighted people isconvex. Astigmatism is another reason that you might have to wearglasses.