OPHTHALMOMETER MEASURING TECHNIQUE

Converting from Diopters to Radii

The ophthalmometer power drums marked with both dioptric and radius values and has a range from 35 D. (9.64 mm) to 60 D. (5.62 mm).

The dioptric value  is converted 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 have conversion tables 
                        Contact lens laboratories often supply them.