 Another type of glasses for which we can easily calculate the diopters needed are reading glasses. Reading glasses are for people that have hyperopia or are foresighted. So what is the problem in this case? The problem in this case is that they cannot see anything close up sharply. So if they try to read a book like this, either it's just not sharp or it gives a very quickly a headache because they have to really, really squeeze their muscles. However, if the object is a bit further away, they see extremely clearly. So what we need in this case, we need some kind of glasses that will out of the object that is close up. So let's see. I want to read a text at a distance of, let's say, 25 centimeters. My text needs to be created, an image of it, that is further away. And how far away? It needs to be just so far away that it starts getting sharp. So the point where if you're too close, you're blurry. And if you're too far, it's clear. It's called the near point. So when you want to calculate the glasses or the diopters of reading glasses, for somebody with hyperopia, you have to ask them, okay, so how far away do you have to hold the text until it becomes clear? Pay attention that there is often also a far point where it can get blurry again. It can be that somebody has hyperopia and myopia at the same time. Like watch the other videos for glasses with the far point. If somebody has only the near point issue here, it's actually quite easy. We need an image at the near point distance. So Q, let's assume somebody was testing it. And once the book is, let's say, 60 centimeters away, 0.60 meters, they see clear. Again, I'm creating a virtual image. So here must be a minus in front of it. The image is not a real image. It's a virtual image. Now let's put this in the equation. So 1 over object distance plus 1 over image distance is 1 over the focal distance, always equal to the power in diopters. So 1 over in the example, 0.25 meters, plus 1 over minus 0.60 meters. You see my diopters. So my diopters are equal to, 1 over 25 is 4, minus 1 over 0.6, plus 2.3 diopters. What does the plus mean? The plus means they actually need the converging lens. So reading glasses are converging lenses. So just to recap how you figure it out, what diopters somebody needs reading glasses will have to get. You ask them how far away, if you start from where it's blurry, you have to hold the book until it gets clear. That is your near point. And then you ask them where you actually want to hold the book when you usually read. You plug where they want the book or the object as the object distance and where it starts getting clear as the image distance and you get your diopters.