The A-Constant in IOL Calculations

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USCTrojan11

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I realize there's few people who can answer this question but I am quite frustrated so I'll take a shot at this.

I'm currently inputing post-surgical data (MR, BCVA and K1 and K2) in the Holladay IOL consultant to create a personalized A-constant for the Tecnis One Piece lens (ZCB00). The manufacturer published A-con is 118.8 but the HIC has calculated the personalized A-constant to be 120.005 - extraordinarily high. Now the reason the A-con value is so high I believe is that we are using K1 and K2 values that were determined pre-op as a baseline and comparing the ORBscan changes and adding those to K1 and K2.

Ex:
Pre-OP IOL Master K1: 41 @91 K2: 43@1
Pre-OP Orbscan: Mean K 44.2
Post-Op Orbscan: Mean K 44.8
Since pre and post orb differ by 0.6, we add that change to K1 and K2 so
Post-OP IOL Master K1: 41.6@91 and K2: 43.6@1

Is this correct? Could this be why our A-con is sky high? Any advice is greatly appreciated.
 
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