The three main factors in IOL calculations are corneal power, axial length, and effective lens position. Prior LASIK makes this more challenging because it will affect the corneal power, making dioptric measurements more challenging. The prior LASIK may also affect the calculation of the effect lens position (ELP) since some formulae will use the keratometry value in determining ELP.
IOL calculations are, in fact, estimations and this is particularly true in eyes with prior kerato-refractive surgery such as LASIK. We can get reasonably close to achieving our post-op goal of plano for this patient, but the spread of the results bell curve is wider than for virgin eyes.
Click below for the video to understand the process of IOL calcs after LASIK: