Calculators

IOL Power

SRK/T, Hoffer Q and SRK II with target refraction

Axial lengthmmA-constantK1DK2D

Target refractionDSpectacle plane, e.g. −0.25 for plano-ish, −2.50 for monovision near eye

Enter values to calculate

Reference

Formula choice by axial length: short (<22 mm) → Hoffer Q; average (22–24.5 mm) → any modern formula; long (>24.5 mm) → SRK/T. Fourth-generation and AI formulas (Barrett Universal II, Kane, EVO) are preferred where available.

Optimised A-constants are lens- and biometer-specific (e.g. ULIB / IOLCon). SRK II is historical and shown for teaching.

Hoffer Q pACD is derived from A (pACD = 0.58357·A − 63.896).