1 topography images as they appear prior to contour line and reference plane analysis 2 the same topography images as 1 but with the entire space within the boundary of the 1st and 2nd contour lines color coded to indicate the region of the nrr analyzed and 3 the same topography images as 1 but with color coding confined to the 30 u00b0 nrr sectors that have met the criterion for significant and repeatable change this provides a comprehensive pictorial depiction of the nrr with respect to the graphical analysis at each time point in a way that allows the longitudinal data to be weighed both quantitatively and qualitatively the examiner can also thus verify if the quantitative analysis of change agrees with the appearance of the nrr as seen in the images the converse of an increase in the size of the nrr is sometimes observed after glaucoma treatment in the analysis described such an occurrence is manifest as an elevation in the position of parts or all of a rim area profile relative to time points prior to treatment to determine if such elevation represents a significant increase in rim area sequential rim area profiles are analyzed with respect to their upper instead of lower limits of variability these upper limits are calculated as described in equation 5 if the upper limits are exceeded to meet the criterion for repeatable change then the change observed is attributed to the effect of treatment a concomitant change in cup size accompanies any change in the size.