My IOP varied more than 5 mmHg within a short amount of time!

I am using 7CR and collecting at least 3 readings in each eye each time. The data shown here were in left eye.

This does not happen every time but it did happen. Here is one example. My IOP varied from 13.0 to 18.6 mmHg within 1 min, a 6.6 mmHg difference! 

           time             IOPcc    IOPg    IOPdiff  Score

07/22 19:37:52      18.6      16.4      2.2       9.1
07/22 19:37:27      13.0      12.6      0.4       9.0
07/22 19:37:19      13.7      12.3      1.4       8.6