Outcomes Review of Intraocular Lens Power Calculation Formulas

This chapter analizes the published outcomes of intraocular lens (IOL) power calculation formulas. A modified version of the formula performance index (PI) proposed by Prof. Haigis is presented. This index ranks formulas accuracy based on several parameters, including the standard deviation (SD) of the prediction error, the median absolute error (MedAE) , the relationship between the prediction error (PE) and axial length (AL) and the percentage of eyes with a prediction error within ±1.00 D. Modifications include the mean absolute error, (MAE) the percentage of eyes with a prediction error within ±0.50 D, and the relationship between the prediction error and keratometry (K). A further version of the PI, specifically designed for subgroup analysis, is also presented. The data of 17 studies (including eyes with any AL) are presented, and formulas are compared by means of the PI. A similar analysis is presented separately for short, medium, and long eyes, as well as for eyes with flat and steep corneas, shallow and deep anterior chambers (ACD) and for eyes with a target refraction other than emmetropia.