I measure the eyes carefully — including length and corneal shape — and use sophisticated formulae to select the power that suits your goals. I currently employ the Barrett formula and associated Lens Factor (LF) constants, which provide reliably predicted refractive outcomes in my practice.

For the technically minded: Optical low‑coherence interferometry provides micron‑level axial length measurements, while corneal tomography informs anterior and posterior corneal power. Effective lens position prediction using Barrett Universal II with optimised constants reduces refractive surprise across a wide range of axial lengths.