Multiple published clinical studies have demonstrated that the Kane formula is more accurate than all currently available IOL formulas (including Hill-RBF 2.0, Barrett Universal 2, Olsen, Haigis, Hoffer Q, Holladay 1, SRK/T, EVO and Holladay 2).

The Kane formula maintains its accuracy at the extremes of axial length, resulting in a 25.1% reduction in absolute error in long eyes (≥26.0 mm), compared with the SRK/T; and a 25.5% reduction in absolute error in short eyes (≤22.0 mm), compared with the Hoffer Q formula.


The Kane formula was developed in September 2017 using ~30,000 highly accurate cases. The formula is based on theoretical optics and incorporates both regression and artificial intelligence components to further refine its predictions. The formula was created using high-performance cloud-based computing which is a way to leverage the power of the cloud to create a virtual supercomputer capable of performing many decades worth of calculations in a few days. A focus of the formula was to reduce the errors seen at the extremes of the various ocular dimensions which is where the current formulas display larger errors. Variables used in the formula are axial length, keratometry, anterior chamber depth, lens thickness, central corneal thickness and patient gender.


Compulsory fields for the calculator are the A-constant, gender, axial length, corneal power and anterior chamber depth. Although adding lens thickness and central corneal thickness improves the prediction they are optional variables. This allows owners of older biometers to use the formula.

Index relates to the K-index of the instrument used to measure the corneal curvature. A default value of 1.3375 has been selected, if your device uses a different K-index please select the appropriate option from the drop-down menu.

The formula has been developed to have an A-constant very similar to the SRK/T A-constant. If the surgeon has an optimised A-constant, then that is recommended for use. Otherwise, we recommend the ULIB SRK/T A-constant for any particular IOL. The “Constants” page has information about the appropriate constant for different IOLs.