KERATOMETER MEASURING TECHNIQUE


Modification of the Mires

The mire can be modified to make it easier 
to determine when the mires are properly 
overlapped and give better repeatability.  
The center of the one plus sign can be 
blacked out and the extent of the other 
one decreased on the mire object plate
(on the front of the instrument).  This 
allows the plus signs to be aligned using 
vernier acuity which is more accurate than 
just overlapping the plus signs.  The mires 
are moved until a full plus sign is formed. 
Likewise, the center of one minus sign can 
be blacked out and the other one shortened.