Holladay Formulas

The Holladay formulas are thin-lens vergence formulas designed to calculate the intraocular lens (IOL) power. In this chapter, the general formulation of this type of formula is described. The Holladay 1 formula was the first theoretical formula that used two variables to predict the position of the IOL (effective lens position, ELP). The Holladay 2 formula increased the number of variables involved in the ELP prediction. Recently, an axial length adjustment has improved the performance of these formulas in long and short eyes. The refractive outcomes published in the most relevant studies are discussed. The Holladay IOL Consultant software contains these formulas and offers many useful tools to the cataract surgeon.