Science | Science Experiment of the Week 12 | 329 - Astigmatism

Eye Glasses, Nearsighted, Farsighted - This week's experiment has to do with your eyes. Do you wear glasses? If not, you probably know someone that does. There are different reasons for wearing glasses.

This Week's Experiment - #329 Astigmatism

These experiments are from Robert Krampf - The Happy Scientist

This week's experiment has to do with your eyes. Do you wear glasses? If not, you probably know someone that does. There are different reasons for wearing glasses. I am nearsighted, which means that I can see things up close, but need glasses to let me see things far away. Other people are farsighted, which is just the opposite. They can see distant objects, but need glasses to see up close.

You can take a quick glance at a pair of glasses and tell whether they are for someone that is nearsighted or farsighted. Hold the glasses in your hand, a few inches above a page with some writing. Looking through the lens, if the writing looks smaller, the glasses are for someone that is nearsighted. If the writing looks larger, then they are for someone that is farsighted.

While you have the glasses in your hand, you can also check for astigmatism. To do that, rotate the glasses as you look through them. If the writing is distorted as you rotate the glasses, then the glasses are for someone with astigmatism.

What is astigmatism? Ideally, the shape of your eye is nice and round. If it is not, then it causes a distortion. Besides looking at glasses, you can also detect an astigmatism by using your eyes. Go to either of these websites:

(Note: the websites Mr. Krampf linked to no longer exist. A search for astigmatism images will provide many images for this purpose.)

If you have astigmatism, some of the lines will look darker and bolder than others. If you turn your head, you will find that different lines now look bolder. The difference is not on the page. It is in your eyes.

(Note: The following experiment requires a graphic created by Robert Krampf that does not appear to be online anymore. It's possible that the experiment can be done with the graphics from the above search, but I haven't tested them.)

If you do not have astigmatism, you can still see what it is like. You just need glasses to do it. Not eye glasses, but drinking glasses. You will need:

the graphic from the website
a straight sided, clear, drinking glass
water

Fill the glass with water and hold it in front of the graphic. Look through the glass and you will see that the horizontal lines look darker than the vertical ones. This is what happens with astigmatism. Of course, the distortion in a person's eyes is not nearly as much as you get through the glass, but it should give you an idea of what an astigmatism is.

Have a marvelous week.

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