1) Close the caliper and press the zero button to calibrate the caliper.
2) Make sure that the reading on the caliper screen is in millimeters (mm). If it is not in mm then press the blue button above the caliper screen to cycle between the different measurements until mm appears on the screen.
3) Open the caliper wider than the width of the slit lamp ocular.
4) Use the caliper to pinch the widest part of the slit lamp ocular.
5) Enter the first measurement into the field below labeled ocular measurement #1.
6) Go back to step 3 and repeat the instructions to take 2 more measurements and enter them into the measurement #2 and measurement #3 fields.