Power of Intraocular lens is determined by?

The most common method of determining IOL power uses a regression formula called 'SRK (Sanders, Retzlaff and Kraff) formula'. The formula is P = A - 2.5L - 0.9K, where: P is the power of IOL,
A is a constant which is specific for each lens type.
L is the axial length of the eyeball in mm, which is determined by A-scan ultrasonography.
K is average corneal curvature, which is determined by keratometry.