In the study A Multicenter Prospective Cohort Study on Refractive Surgery in 15011 Eyes by Kamiya et al there is a table for demographics. I will show that table in graphics for easier comparation between procedures. The first one is gender by procedure:

 

kamiya3

 

Then all the other characteristics for the whole population:

 

kamiya2

 

And then the same characteristics per procedure, you can click on the image to enlarge it:

 

kamiya1

 

With this graphic is much easier to compare every characteristic between procedures.