Fig. 8.

Measured PISA distance for the 11 clinical patients, as measured by experts and observers instructed to measure either the radius of a hemisphere, r_h, or the urchinoid distance, d_u. The distance was consistently smaller when operators were measuring r_h than either when they measured d_u or when experts measured PISA distance according to their usual clinical practice. In addition the spread of values for each individual patient for each of the measurement techniques was smaller when observers measured d_u than for the other groups. Lines represent 95% confidence intervals.