In the last update for RSG I have included the SIA consistency. Up to now you could get your SIA but there was no measure about its consistency, you got an ellipse with the standard deviation (sd) of x and y in the graphic but it was not quantified and when subdividing per factor not even the ellipse. Now you got to the left the mean SIA for the cornea and the SIA sd, if you choose to separate the graphics by factor you get within each graphic the number of eyes, mean and sd of the SIA for each factor. That SIA sd represents the radius in diopters of the circle with the same area as the ellipse in diopters which is easier for interpretation.

The update is online and you can try it here.

SIA.SD