IOL Power (SRK II)
Intraocular-lens power by the SRK II regression formula with the axial-length adjustment band (Sanders / Retzlaff / Kraff 1988).
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Lens A-constant
- 118.4
- Axial length
- 23.5 mm
- Average keratometry
- 44 D
- Target refraction
- 0 D
Result: Emmetropic IOL power 20.05 D for AL 23.5 mm (A-constant adjustment 0).
The tool opens with these values already filled in. Replace them with your own.
What the result means
- Caveat
- A regression formula superseded by optical/theoretical formulas (SRK/T, Barrett); does not replace device biometry. Target refraction applies the SRK refractive factor ≈ 1.25 D/D.
What you enter
- Lens A-constant
- Axial length
- Average keratometry
- Target refraction (0 for emmetropia)
How this is calculated
- Formula
- P = A1 − 0.9·K − 2.5·AL; A1 = A-constant adjusted for axial length (AL<20 +3, 20–21 +2, 21–22 +1, 22–24.5 0, ≥24.5 −0.5).
Sanders DR, Retzlaff J, Kraff MC. Comparison of the SRK II formula and other second-generation formulas. J Cataract Refract Surg. 1988;14(2):136-141. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.