CataractCoach™ 2573: How to adjust IOL calcs for the 2nd eye cataract surgery

This is a question that I am commonly asked: the patient had a refractive surprise with the cataract surgery of the first eye, so now how should we adjust the IOL calculations for the second eye in order to hit our refractive target? The key point to remember is that even with great measurements, we are always making an estimation of the effective lens position (ELP) of the IOL optic. We are removing a human lens (cataract) with a thickness of 4 to 5 mm and replacing it with a man-made IOL that is about 1 mm thin. When the capsular bag shrink-wraps down, where exactly the optic sits is not always precisely known. This is why typically 80% of our patients end up between +/- 0.5 diopters of the intended target. In this case shown here, I explain how to use an adjusted A-constant to help apply this adjustment to the second eye. There are other methods as well, but I find this is the simplest and most easily explained. How do you make an adjustment for the second eye if the first eye was a refractive surprise? Please comment below.