I am going to start this series of posts about graphics for showing results of refractive surgery with basic descriptive graphics. The data used for all the graphics of the series consists of 100 simulated observations, you can find the table here, it is very basic data, just id, sex, age, eye (right or left) and subjective refraction pre and post-operative. Some graphics will be more suitable for the public while others can be used just for yourself to get a better insight of what is going on.

You might just want to know that the mean age of the patients is 39.96 years with a standard deviation (sd) of 12.48 and a mean spherical equivalent (SE) of -3.13 D with a sd of 3.39 and be happy with it, or you might want to know more, to begin with, their distributions:



The age distribution is quite uniform, the SE distribution too but there is a peak between -6 D and -7 D, that SE doubles the amount of patients approximatly than lower SE and myopes higher that -7 are very few. We can have a look at the distribution for people older or younger than 40:




It seems above 40 patients are less myope in our data. Another way to see this is with a boxplot:




Here the white dot is the mean and the vertical line next to it is the median. We can also see the distributions including the sex of the patient:




The bars are stacked, that means that a whole vertical bar shows the total patients for that SE interval and the color within the bar shows if it is for males or females, in cases where there are both colours it shows the amount of each one, for example above 40 years old for SE between -6 and -7 there are 8 patients, 2 females and 6 males.

We can do the same for the postoperative SE and we will get this:




The range now goes between -1.50 D and +1.50 D and is much more normally distributed around -0.25. We will now look at the cumulative percentage of patiens within a given range:

description6This graphic tells us that 35% of the patients ended with a SE between +0.25 D and -0.25 D, that 58% are within +0.50 D and -0.50 D and so on.

All this descriptive graphics can be done by any factor you are interested in, like surgery type, operation room, discharged patients at 3 months (yes or no?) and also instead of SE you could see the cumulative percentages within a given visus.

Now we know what we have before and after the surgery, in the next post we will relate one to the other in different ways.