KERATOMETER MEASURING 
                 TECHNIQUE

Focusing the Mires

Usually the mires are not in sharp focus 
when you first locate them.  They are 
focused by moving the body of the 
instrument forward or backward using 
the highest knob directly in front of the 
examiner.  The center ring will appear 
double when it is out-of-focus.

If the end of the 
focusing range is 
reached and the 
mires are still not in
focus, the position 
of the patient's 
head must be 
changed (see next 
screen).