# Single and double angle plots interpretation for Astigmatism Analysis

There are two ways of representing the results of astigmatism analysis The first way is the most common way that everyone knows because it is the way That is more common or more familiar with the real location around the eye It is the Single Angle representation. In this kind of Single Angle representation We have a polar plot from 0 to 360 degrees and we know that the zero is the same location that the 360 degrees and that are coincident with the locations in the eye. Anyway when we work with astigmatism analysis the most common and the most adequate could be to work in a double angle even though we can show all the results in a single angle plot. All our calculations are going to be performed in a double angle plot and in the next lesson We will explain what is the reason of this kind of analysis based on the double angle. The most important here in order to interpret correctly the result is that if we are working with a single angle if our results are representing in a 360 degrees plot, our results are going to be classified in with-the-rule astigmatism in the vertical orientation. You can see here that the blue area is the area that contains all the cases that are with-the-rule cases with-the-rule astigmatism and we have the against-the-rule in the horizontal location Also we have this kind of oblique locations in yellow. Anyway, This is very familiar for the surgeon because you see exactly what are the locations of the astigmatism in the same way that are located in the real eye. Anyway if you have a double angle plot you have to see first What is the number of angles you have in the plot You can see here that you have from 0 to 180 So the data are going to be represented in a different way. All your with-the-rule cases are going to be located at the left side of the plot and all there against-the-rule cases are going to be located at the right side. So in the vertical locations you are going to have the oblique positions So you have to know before to interpret the results If you are working with that single angle or if you are working in a double angle plot. Even though you can represent in both sides you can see here exactly what is the corneal topography for the different kinds of astigmatism. E ven though you can use both plots. Always the calculations are going to be conducted in a double angle plot and later you have to transform the location of the points to a single angle if you want to represent a single angle and usually If you are going to represent in a single angle you are going to represent only the upper side of the plot. Not all the plot like in the double angle because here you have one hundred and eighty degrees and here You have also one hundred and eighty degrees.