How to tell if someone is wearing non prescription glasses?

[Phoebe]

Now, there are so many people wearing eyeglasses. But i heard that there are some people wearing non prescription glasses. How can i judge that they are wearing non prescription glasses or prescription glasses?

[Lilliana]

You can put the glasses in the place about 30 centimeters away from you. Then you see the object through the glasses, if the object does not seem bigger or smaller, the glasses is non prescription glasses. Otherwise, the glasses are prescription. However, if the prescription degree is not heavy, it will be hard to tell the difference between prescription glasses and not prescription glasses.