Immersion vs Optical
I have heard in the seminars to not input the immersion numbers in the US box, and just use the optical biometry box when I am using Hicsoap software. Is this correct?
Optical Biometry was calibrated to be the same as Immersion ASCAN. For large groups the average axial length will be the same, although for a specific patient it can be different. The difference in the Lens Constant is due to the difference in the Keratometers. Immersion Ascan used the manual keratometer which uses a 3.2 mm ring and optical biometry like the IOL Master uses 2.5 mm ring and LenStar 2.0 mm ring. The smaller the zone the steeper the K-reading, so Optical biometry is about 0.3 D higher Aconstant the Immersion Ascan BECAUSE THE KERATOMETERS WERE DIFFERENT.
So, if you use IMMERSION ASCAN and measure the Ks with Optical Biometry you should put the AL in the Optical Biometry Box, if you use the Manual Keratometer you should put it in the US Box.