Both classical and modern formulas have been used for the power calculation of regular IOL or accommodative IOL in aphakic, pseudophakic and phakic eyes. The modern formulas include that of Haigis, Hoffer, Q, Holladay, Olson, SRK/T, SRK I and II, and the more recent formulas by Odenthal et al, Aramberri et al, Rosa et al and Jin et al. Most of these efforts were to improve the prediction of IOL-power by a better prediction of the postoperative anterior chamber depth or the effective lens position defined by ACDpre, corneal height and curvature, lens thickness and axial length. All the existing IOL-power calculations are based on the classical vergence formulas of Fyodorov, and van der Heijde or their revision, the Hoffer Q formula. The CVFs assume a thin-lens and are all based on a 2-optics system which, strictly speaking, can only apply to aphakic eyes. For pseudophakic or phakic eyes, the 3-optics systems are much more complex and the over-simplified 2-optics CVF suffers the following possible drawbacks. It excludes the effects of IOL thickness and shape and the role of natural lens or primary IOL. Major error may result from the use of the keratometric power rather than the true postoperative corneal power which requires accurate measurement of both the anterior and posterior radius. In addition, the CVF assumes paraxial ray and spherical surface for the cornea and IOL. Therefore, it also excludes the effects due to corneal surface asphericity change after refractive surgery. One of the major pitfalls of the existing IOL power calculations is the ignoring of individual true corneal power and using a mean-zero error for the postoperative refraction. Except the Haigis formula and the Lin Z2-formula, all other optimization formulas are based on one-constant like the surgeon factor, the A-constant, the ACDpost or the ELP. The mean-zero error might be the result of the balanced errors of short and long eyes. Therefore, the validity range of axial length for various existing formulas under a linear empirical-fit could not justify their accuracy when they are applied to individual eyes. A true personalized IOL power prediction, in our opinion, should at least individualize the following parameters: the postoperative ELP, axial length, corneal anterior and posterior surface, and the IOL types. In this chapter an up-date of the IOL formulas are presented and critical issues of following four topics are covered: IOL-power, Corneal power after refractive surgery, Piggyback IOL power, and Accommodating IOL.