CALIBRATION OF THE KERATOMETER

Measuring the Calibration Balls

Once the unit is mounted on the headrest, 
swing the instrument side-to-side to 
locate the ball and adjust the vertical 
height so that the crosshair is in the 
center of the center ring mire.  Focus the 
instrument such that the mires are in 
sharp focus.  Next rotate the drums until 
the mires are properly overlapped (plus 
sign over the plus sign and minus over 
the minus).  The above procedure is just 
as you would do on the eye.  There should not be any toricity.

Read the dioptric (or millimeter) values from the drums.  Repeat the above procedure for the other two balls if you are using the three ball set.  They should read the same value as indicatedon the calibration balls.  If the readings are the same your instrument is in proper calibration.

If the readings are different you must make additional adjustments.