KERATOMETER MEASURING TECHNIQUE

           Converting from Diopters to Radii

Some keratometers have the power drums marked in diopters 
only while others will give both dioptric and radius values.  
Often in contact lens fitting you want to know the radius of 
the cornea.

If your keratometer is only marked with dioptric values, you 
can convert the dioptric value to radius by using the 
following formula:

		    	                                  (1.3375-1.00)
	            radius (meters)=  -------------
			                                           diopters

Usually you want the value in millimeters, to obtain the 
millimeter value you can multiply the above result by 1000 
or more easily use the following formula:

			                                337.5
	           radius (mm)= --------
			                             diopters
Most contact lens textbooks and manuals that come with the keratometer provide tables that have conversion tables  
Contact lens laboratories often supply them.